This file contains information about GCC releases which has been generated automatically from the online release notes. It covers releases of GCC (and the former EGCS project) since EGCS 1.0, on the line of development that led to GCC 3. For information on GCC 2.8.1 and older releases of GCC 2, see ONEWS. ====================================================================== http://gcc.gnu.org/gcc-12/index.html GCC 12 Release Series Jun 20, 2024 The GCC developers are pleased to announce the release of GCC 12.4. This release is a bug-fix release, containing fixes for regressions in GCC 12.3 relative to previous releases of GCC. Release History GCC 12.4 Jun 20, 2024 ([1]changes, [2]documentation) GCC 12.3 May 8, 2023 ([3]changes, [4]documentation) GCC 12.2 Aug 19, 2022 ([5]changes, [6]documentation) GCC 12.1 May 6, 2022 ([7]changes, [8]documentation) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [9]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [10]GCC project web site or contact the [11]GCC development mailing list. To obtain GCC please use [12]our mirror sites or [13]our version control system. For questions related to the use of GCC, please consult these web pages and the [14]GCC manuals. If that fails, the [15]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [16]gcc@gcc.gnu.org. All of [17]our lists have public archives. Copyright (C) [18]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [19]maintained by the GCC team. Last modified 2024-06-20. References 1. https://gcc.gnu.org/gcc-12/changes.html 2. https://gcc.gnu.org/onlinedocs/12.4.0/ 3. https://gcc.gnu.org/gcc-12/changes.html 4. https://gcc.gnu.org/onlinedocs/12.3.0/ 5. https://gcc.gnu.org/gcc-12/changes.html 6. https://gcc.gnu.org/onlinedocs/12.2.0/ 7. https://gcc.gnu.org/gcc-12/changes.html 8. https://gcc.gnu.org/onlinedocs/12.1.0/ 9. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Contributors.html 10. https://gcc.gnu.org/index.html 11. mailto:gcc@gcc.gnu.org 12. https://gcc.gnu.org/mirrors.html 13. https://gcc.gnu.org/git.html 14. https://gcc.gnu.org/onlinedocs/ 15. mailto:gcc-help@gcc.gnu.org 16. mailto:gcc@gcc.gnu.org 17. https://gcc.gnu.org/lists.html 18. https://www.fsf.org/ 19. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-12/changes.html GCC 12 Release Series Changes, New Features, and Fixes This page is a "brief" summary of some of the huge number of improvements in GCC 12. You may also want to check out our [1]Porting to GCC 12 page and the [2]full GCC documentation. Caveats * An ABI incompatibility between C and C++ when passing or returning by value certain aggregates containing zero width bit-fields has been discovered on various targets. As mentioned in [3]PR102024, since the [4]PR42217 fix in GCC 4.5 the C++ front-end has been removing zero width bit-fields from the internal representation of the aggregates after the layout of those aggregates, but the C front-end kept them, so passing e.g. struct S { float a; int : 0; float b; } or struct T { float c; int : 0; } by value could differ between C and C++. Starting with GCC 12 the C++ front-end no longer removes those bit-fields from the internal representation and per clarified psABI some targets have been changed, so that they either ignore those bit-fields in the argument passing by value decisions in both C and C++, or they always take them into account. x86-64, ARM and AArch64 will always ignore them (so there is a C ABI incompatibility between GCC 11 and earlier with GCC 12 or later), PowerPC64 ELFv2 and S/390 always take them into account (so there is a C++ ABI incompatibility, GCC 4.4 and earlier compatible with GCC 12 or later, incompatible with GCC 4.5 through GCC 11). RISC-V has changed the handling of these already starting with GCC 10. As the ABI requires, MIPS takes them into account handling function return values so there is a C++ ABI incompatibility with GCC 4.5 through 11. For function arguments on MIPS, refer to [5]the MIPS specific entry. GCC 12 on the above targets will report such incompatibilities as warnings or other diagnostics unless -Wno-psabi is used. * C: Computed gotos require a pointer type now. * C++: Two non-standard std::pair constructors have been deprecated. These allowed the use of an rvalue and a literal 0 to construct a pair containing a move-only type and a pointer. The nullptr keyword should be used to initialize the pointer member instead of a literal 0, as this is portable to other C++ implementations. * The configuration option --enable-libstdcxx-allocator no longer supports the bitmap, mt, and pool arguments. Those configurations had been broken for some time. * D: Building and bootstrapping GDC, the D compiler, now requires a working GDC compiler (GCC version 9.1 or later) and D runtime library, libphobos, as the D front end is written in D. On some targets, libphobos isn't enabled by default, but compiles and works if --enable-libphobos is used. Other targets may require a more recent minimum version of GCC to bootstrap. Specifics are documented for affected targets in the [6]manual for installing GCC. * Fortran: OpenMP code using the omp_lib.h include file can no longer be compiled with -std=f95 but now requires at least -std=f2003. Alternatively, use the omp_lib module, which still supports -std=f95 and is recommended to be used instead in general. * OpenMP offloading to Intel MIC has been deprecated and will be removed in a future release. * The cr16 target with the cr16-*-* configuration has been obsoleted and will be removed in a future release. * The hppa[12]*-*-hpux10* and hppa[12]*-*-hpux11* configurations targeting 32-bit PA-RISC with HP-UX have been obsoleted and will be removed in a future release. * The m32c*-*-rtems* configuration has been obsoleted and will be removed in a future release. * The support for the m32r-*-linux*, m32rle-*-linux*, m68k*-*-openbsd* and vax-*-openbsd* configurations has been removed. * STABS: Support for emitting the STABS debugging format is deprecated and will be removed in the next release. All ports now default to emit DWARF (version 2 or later) debugging info or are obsoleted. * The optimization level -Ofast now implies -fno-semantic-interposition. General Improvements * Vectorization is enabled at -O2 which is now equivalent to what would have been -O2 -ftree-vectorize -fvect-cost-model=very-cheap in the past. Note that the default vectorizer cost model has been changed; it used to behave as if -fvect-cost-model=cheap had been specified. * GCC now supports the [7]ShadowCallStack sanitizer, which can be enabled using the command-line option [8]-fsanitize=shadow-call-stack. This sanitizer currently only works on AArch64 targets and it requires an environment in which all code has been compiled with -ffixed-r18. Its primary initial user is the Linux kernel. New Languages and Language specific improvements * OpenMP + OpenMP 5.0 support has been extended: The close map modifier and the affinity clause are now supported. In addition, Fortran gained the following features which were available in C and C++ before: declare variant is now available, depobj, mutexinoutset and iterator can now also be used with the depend clause, defaultmap has been updated for OpenMP 5.0, and the loop directive and combined directives involving the master directive have been added. + The following OpenMP 5.1 features have been added: support for expressing OpenMP directives as C++ 11 attributes, the masked and scope constructs, the nothing and error directives, and using primary with the proc_bind clause and OMP_PROC_BIND environment variable, the reproducible and unconstrained modifiers to the order clause, and, for C/C++ only, the align and allocator modifiers to the allocate clause and the atomic extensions are now available. The OMP_PLACE environment variable supports the OpenMP 5.1 features. In addition, the OMP_NUM_TEAMS and OMP_TEAMS_THREAD_LIMIT environment variables and their associated API routines are now supported as well as the memory-allocation routines added for Fortran and extended for C/C++ in OpenMP 5.1. In Fortran code, strictly structured blocks can be used. + The [9]OpenMP Implementation Status can be found in the libgomp manual. * Version 2.6 of the [10]OpenACC specification continues to be maintained and improved in the C, C++ and Fortran compilers. See the [11]implementation status section on the OpenACC wiki page and the [12]run-time library documentation for further information. In addition to general performance tuning and bug fixing, new features include: + OpenACC worker parallelism for [13]AMD GPUs (already for a long time supported for [14]Nvidia GPUs). + Data privatization/sharing at the OpenACC gang level. + Considerable improvements for the experimental OpenACC 'kernels' decomposition ([15]--param openacc-kernels=decompose). + A new warning flag [16]-Wopenacc-parallelism to warn about potentially suboptimal choices related to OpenACC parallelism. * The offload target code generation for OpenMP and OpenACC can now be better adjusted using the new [17]-foffload-options= flag and the pre-existing but now documented [18]-foffload= flag. Ada * Ada 2022 + Added the -gnat2022 flag to indicate strict Ada 2022 compliance. The old -gnat2020 flag is now deprecated. + Support for Big Numbers (Annex G) has seen continuous improvements. It is now considered complete. It is compatible with SPARK, i.e. can be used from SPARK code. + Continuous improvements to the Ada 2022 standard since GCC 11. + Greatly improved compile time support. More functions can now have the with Static aspect and can be used in more contexts. * Ada 2022 extensions. The use of the -gnatX flag is necessary to access these features as they are not considered stable or standard. + Fixed lower bound for unconstrained arrays. o type Matrix is array (Natural range 0 .. <>, Natural range 0 .. <>) of Integer; is now valid. o Subtypes can also specify a lower bound: subtype String_1 is String (1 .. <>);. Boundaries from slices will "slide" to the correct lower bound of the subtype. + Generalized Object.Operand notation. The following code is now valid V.Add_Element(42);, with V being a vector, for example. + Additional when constructs. Keywords return, goto and raise can now use when in addition to the existing exit when. The following expression is therefore now valid raise Constraint_Error with "Element is null" when Element = null; + Pattern matching o The case statement has been extended to cover records and arrays as well as finer grained casing on scalar types. In the future it is expected to provide more compile time guarantees when accessing discriminated fields. Case exhaustion is supported for pattern matching. An example would be type Sign is (Neg, Zero, Pos); function Multiply (S1, S2 : Sign) return Sign is (case (S1, S2) is when (Neg, Neg) | (Pos, Pos) => Pos, when (Zero, <>) | (<>, Zero) => Zero, when (Neg, Pos) | (Pos, Neg) => Neg); * gnatfind and gnatxref, which were already deprecated, have been removed. * Greatly expanded code covered by contracts. Thanks to this work, there are now several Ada standard libraries fully proven in SPARK which means they have no runtime nor logical errors. They are mostly numeric and string handling libraries. * Enable return-slot optimization for Pure functions. * General optimizations, improvements and additions to the standard library. Performance, correctness and in some cases stability was improved. Memory pools have also seen some minor enhancements. * Improvements to embedded-RTOS targets such as RTEMS, VxWorks and QNX. Older targets were removed or cleaned. * Added some [19]hardening features. C family * Support for __builtin_shufflevector compatible with the clang language extension was added. * Support for attribute unavailable was added. * A new built-in function, __builtin_assoc_barrier, was added. It can be used to inhibit re-association of floating-point expressions. * Support for __builtin_dynamic_object_size compatible with the clang language extension was added. * New warnings: + [20]-Wbidi-chars warns about potentially misleading UTF-8 bidirectional control characters. The default is -Wbidi-chars=unpaired ([21]PR103026) + [22]-Warray-compare warns about comparisons between two operands of array type ([23]PR97573) * Enhancements to existing warnings: + [24]-Wattributes has been extended so that it's possible to use -Wno-attributes=ns::attr or -Wno-attributes=ns:: to suppress warnings about unknown scoped attributes (in C++11 and C2X). Similarly, #pragma GCC diagnostic ignored_attributes "vendor::attr" can be used to achieve the same effect ([25]PR101940) C * Some new features from the upcoming C2X revision of the ISO C standard are supported with -std=c2x and -std=gnu2x. Some of these features are also supported as extensions when compiling for older language versions. In addition to the features listed, some features previously supported as extensions and now added to the C standard are enabled by default in C2X mode and not diagnosed with -std=c2x -Wpedantic. + Digit separators (as in C++) are supported for C2X. + The #elifdef and #elifndef preprocessing directives are now supported. + The printf and scanf format checking with [26]-Wformat now supports the %b format specified by C2X for binary integers, and the %B format recommended by C2X for printf. C++ * Several C++23 features have been implemented: + [27]P1938R3, if consteval ([28]PR100974) + [29]P0849R8, auto(x): decay-copy in the language ([30]PR103049) + [31]P2242R3, Non-literal variables (and labels and gotos) in constexpr functions ([32]PR102612) + [33]P2334R1, Support for preprocessing directives elifdef and elifndef ([34]PR102616) + [35]P2360R0, Extend init-statement to allow alias-declaration ([36]PR102617) + [37]P2128R6, Multidimensional subscript operator + [38]DR 2397, auto specifier for pointers and references to arrays ([39]PR100975) * Several C++ Defect Reports have been resolved, e.g.: + [40]DR 960, Covariant functions and lvalue/rvalue references + [41]DR 1227, Mixing immediate and non-immediate contexts in deduction failure + [42]DR 1315, Restrictions on non-type template arguments in partial specializations + [43]DR 2082, Referring to parameters in unevaluated operands of default arguments + [44]DR 2351, void{} + [45]DR 2374, Overly permissive specification of enum direct-list-initialization + [46]DR 2397, auto specifier for pointers and references to arrays + [47]DR 2446, Questionable type-dependency of concept-ids * New command-line option -fimplicit-constexpr can be used to make inline functions implicitly constexpr ([48]git) * New command-line option -ffold-simple-inlines can be used to fold calls to certain trivial inline functions (currently std::move, std::forward, std::addressof and std::as_const). In contrast to inlining such calls, folding means that no intermediate code or debug information will be generated for them; this minimizes the abstraction penalty incurred for using these functions versus using the fundamental operations from which they're defined (e.g. std::move versus static_cast). This flag is enabled by default when -fno-inline is not active. * Deduction guides can be declared at class scope ([49]PR79501) * [50]-Wuninitialized warns about using uninitialized variables in member initializer lists ([51]PR19808) * [52]-Wint-in-bool-context is now disabled when instantiating a template ([53]git) * Stricter checking of attributes on friend declarations: if a friend declaration has an attribute, that declaration must be a definition. Moreover, a C++11 attribute cannot appear in the middle of the decl-specifier-seq. ([54]PR99032) * New warning options for C++ language mismatches: -Wc++11-extensions, -Wc++14-extensions, -Wc++17-extensions, -Wc++20-extensions, and -Wc++23-extensions. They are enabled by default and can be used to control existing pedwarns about occurrences of new C++ constructs in code using an old C++ standard dialect. * New warning [55]-Wmissing-requires warns about missing requires ([56]git) * The existing std::is_constant_evaluated in if warning was extended to warn in more cases ([57]PR100995) * [58]-Waddress has been enhanced so that it now warns about, for instance, comparing the address of a nonstatic member function to null ([59]PR102103) * Errors about narrowing are no longer hidden if they occur in system headers * Ordered comparison of null pointers is now rejected ([60]PR99701) * Anonymous structs with bases are now rejected ([61]git) * The compiler rejects taking the address of an immediate member function ([62]PR102753) * The compiler has support for C++20 __cpp_lib_is_pointer_interconvertible and __cpp_lib_is_layout_compatible to help the C++ library implement [63]P0466, Layout-compatibility and Pointer-interconvertibility Traits ([64]PR101539) * Memory usage of constraint subsumption has been improved ([65]PR100828) * constinit thread_local variables are optimized better ([66]PR101786) * Support for C++17 std::hardware_destructive_interference_size was added, along with the [67]-Winterference-size warning ([68]git) * Many bugs in the CTAD handling have been fixed ([69]PR101344, [70]PR101883, [71]PR89062, [72]PR101233, [73]PR88252, [74]PR86439, [75]PR98832, [76]PR102933 ...) * Two-stage name lookup for dependent operator expressions has been corrected ([77]PR51577) * Several issues with constrained variable templates have been fixed ([78]PR98486) * The compiler performs less instantiating when doing speculative constant evaluation ([79]git) * Various diagnostic improvements; e.g., a more precise caret location for pointer-to-member expressions * The new -fconstexpr-fp-except flag allows IEC559 floating point exceptions in constant-expressions. Runtime Library (libstdc++) * Improved experimental C++20 support, including: + std::vector, std::basic_string, std::optional, and std::variant can be used in constexpr functions. + std::make_shared for arrays with default initialization, and std::atomic>. + Layout-compatibility and pointer-interconvertibility traits. * Improved experimental C++23 support, including: + Monadic operations for std::optional. + std::expected + std::move_only_function + + std::basic_string::resize_and_overwrite + std::unique_ptr can be used in constexpr functions. + (not built by default, requires linking to an extra library). + + std::invoke_r + constexpr std::type_info::operator== D * New features: + Support for the D programming language has been updated to version 2.100.1 of the language and run-time library. Full changelog for this release and previous releases can be found on the [80]dlang.org website. + On supported targets, the __traits(compiles) expression can now be used to determine whether a target-specific built-in is available without error during CTFE ([81]PR101127). + Functions annotated with pragma(inline, true) are now compiled into every module where they are used from ([82]PR106563). + Partial support for directly importing C99 sources into a D compilation ([83]ImportC) has been added to the language. A notable missing feature is support for preprocessing C imports, which can be worked around by preprocessing all C sources used for importing ahead of time. * New language options: + -fcheck=, enables or disables the code generation of specific run-time contract checks. + -fcheckaction=, controls the run-time behavior on an assert, array bounds check, or final switch contract failure. The default is -fcheckaction=throw. + -fdump-c++-spec=, dumps all compiled extern(C++) declarations as C++ code to the given file. The supplementary option -fdump-c++-spec-verbose turns on emission of comments for ignored declarations in the generated spec. + -fextern-std=, controls which C++ standard extern(C++) declarations are compiled to be compatible with. The default is -fextern-std=c++17. + -fpreview=, added to enable upcoming D language features in the compiler. + -frevert=, added to revert D language changes to support older D codebases that need more time to transition. + -fsave-mixins=, saves mixins expanded at compile-time to a file. * Deprecated and removed features: + The -Wtemplates compiler switch has been removed, as it had been superceded by -ftransition=templates, which more accurately reports on which templates have been instantiated. + The -ftransition=dip25 and -ftransition=dip1000 compiler switches have been renamed to -fpreview=dip25 and -fpreview=dip1000. Fortran * WG5/N1942, "TS 29113 Further Interoperability of Fortran with C", is now fully supported. In addition to implementing previously missing functionality, such as support for character arguments of length greater than one in functions marked bind(c) and gaps in the handling for assumed-rank arrays, numerous other bugs have been fixed, and an extensive set of new conformance test cases has been added. * GCC 12 now uses OPERATION as the name of the function to the CO_REDUCE intrinsic for the pairwise reduction, thus conforming to the Fortran 2018 standard. Previous versions used OPERATOR which conforms to TS 18508. * On POWER systems which support it, the -mabi=ieeelongdouble option now selects the IEEE 128-bit floating point format for REAL(KIND=16). R16_IBM and R16_IEEE have been added to the -fconvert option, the CONVERT specifier of the OPEN statement and the GFORTRAN_CONVERT_UNIT environment variable. Go * GCC 12 provides a complete implementation of the Go 1.18 user packages. * Although Go 1.18 includes support for generic programming, that support is not yet available in GCC. libgccjit * The libgccjit API gained 30 new entry points: + 17 new "reflection" entry points for querying functions and types ([84]LIBGCCJIT_ABI_16) + [85]gcc_jit_lvalue_set_tls_model for supporting thread-local variables ([86]LIBGCCJIT_ABI_17) + [87]gcc_jit_lvalue_set_link_section for setting the link section of global variables, analogous to [88]__attribute__((section(".section"))) ([89]LIBGCCJIT_ABI_18) + 4 new entry points for initializing global variables and creating constructors for rvalues ([90]LIBGCCJIT_ABI_19) + Support for sized integer types, including 128-bit integers and helper functions for such types ([91]LIBGCCJIT_ABI_20) + [92]gcc_jit_context_new_bitcast for reinterpreting the bits of an rvalue as a different type ([93]LIBGCCJIT_ABI_21) + [94]gcc_jit_lvalue_set_register_name for setting a specific register for a variable ([95]LIBGCCJIT_ABI_22) + [96]gcc_jit_context_set_bool_print_errors_to_stderr ([97]LIBGCCJIT_ABI_23) + 2 new entry points for setting the alignment of a variable ([98]LIBGCCJIT_ABI_24) * libgccjit has gained support for the use of various atomic builtins ([99]PR96066, [100]PR96067) * [101]gcc_jit_context_new_cast is now able to handle truncation and extension between different integer types ([102]PR95498) New Targets and Target Specific Improvements AArch64 & arm * Newer revisions of the Arm Architecture are supported as arguments to the -march option: armv8.7-a, armv8.8-a, armv9-a. * The Arm Cortex-A510 CPU is now supported through the cortex-a510 argument to the -mcpu and -mtune options. * GCC can now auto-vectorize operations performing sign-differing dot-product operations, taking advantage of instructions in the Advanced SIMD (AArch64/AArch32) and SVE (AArch64) instruction sets. AArch64 * A number of new CPUs are supported through the -mcpu and -mtune options (GCC identifiers in parentheses). + Ampere-1 (ampere1). + Arm Cortex-A710 (cortex-a710). + Arm Cortex-X2 (cortex-x2). * The 64-byte atomic load/store intrinsics to accelerator memory from the [103]2020 Arm Architecture extensions are supported through the +ls64 option extension. * Initial code generation support is supported for hardware instructions used to accelerate the memcpy,memmove and memset standard functions. These instructions can be generated when compiling with the +mopsoption extension. * The ACLE Advanced SIMD intrinsics accessible through the arm_neon.h header have been significantly reimplemented and generate higher-performing code than previous GCC versions. * The option -mtune=neoverse-512tvb is added to tune for Arm Neoverse cores that have a total vector bandwidth of 512 bits. Please refer to the documentation for more details. AMD Radeon (GCN) * Debug experience with ROCGDB has been improved. * Support for the type __int128_t/integer(kind=16) was added. * For offloading, the limitation of using only one wavefront per compute unit (CU) has been lifted. Up to 40 workgroups per CU and 16 wavefronts per workgroup are supported (up to a limit of 40 wavefronts in total, per CU). Additionally, the number of used wavefronts and workgroups was tuned for performance. arm * Support is added for accessing the stack canary value via the TLS register through the -fstack-protector-guard=tls and -mstack-protector-guard-offset= options. This intended for use in Linux kernel development. Please refer to the documentation for more details. BPF * Support for CO-RE (compile-once, run-everywhere) has been added to the BPF back end. CO-RE allows to compile portable BPF programs that are able to run among different versions of the Linux kernel. IA-32/x86-64 * New ISA extension support for Intel AVX512-FP16 was added. AVX512-FP16 intrinsics are available via the -mavx512fp16 compiler switch. * For both C and C++ the _Float16 type is supported on x86 systems with SSE2 enabled. Without {-mavx512fp16}, all operations will be emulated in software and float instructions. * Mitigation against straight line speculation (SLS) for function return and indirect jump is supported via -mharden-sls=[none|all|return|indirect-jmp]. * Add CS prefix to call and jmp to indirect thunk with branch target in r8-r15 registers via -mindirect-branch-cs-prefix. * Always use global offset table (GOT) to access external data and function symbols when the new -mno-direct-extern-access command-line option is specified. LoongArch * Support for the LoongArch architecture instruction set has been added. * The Loongson CPU codename LA464 and LoongArch 64-bit generic CPU codename loongarch64 are supported through the -march= and -mtune= options (GCC identifiers in parentheses). + Loongson LA464 core (la464). + LoongArch 64-bit generic core (loongarch64). MIPS * The ABI passing arguments containing zero-width fields (for example, C/C++ zero-width bit-fields, GNU C/C++ zero-length arrays, and GNU C empty structs) has changed. Now a zero-width field will not prevent an aligned 64-bit floating-point field next to it from being passed through FPR. This is compatible with LLVM, but incompatible with previous GCC releases. GCC 12 on MIPS will report such incompatibilities as an inform unless -Wno-psabi is used. * The ABI returning values containing C++17 empty bases has changed. Now an empty base will not prevent an aggregate containing only one or two floating-point fields from being returned through FPR. This is compatible with GCC 6 and earlier, but incompatible with GCC 7 through 11. GCC 12 on MIPS will report such incompatibilities as an inform unless -Wno-psabi is used. NVPTX * The -march flag has been added. The -misa flag is now considered an alias of the -march flag. * Support for PTX ISA target architectures sm_53, sm_70, sm_75 and sm_80 has been added. These can be specified using the -march flag. * The default PTX ISA target architecture has been set back to sm_30, to fix support for sm_30 boards. * The -march-map flag has been added. The -march-map value will be mapped to an valid -march flag value. For instance, -march-map=sm_50 maps to -march=sm_35. This can be used to specify that generated code is to be executed on a board with at least some specific compute capability, without having to know the valid values for the -march flag. * The -mptx flag has been added to specify the PTX ISA version for the generated code; permitted values are 3.1 (matches previous GCC versions), 6.0, 6.3, and 7.0. If not specified, the used version is the minimal version required for -march but at least 6.0. * An mptx-3.1 multilib was added. This allows using older drivers which do not support PTX ISA version 6.0. * The new __PTX_SM__ predefined macro allows code to check the PTX ISA target architecture being targeted by the compiler. * The new __PTX_ISA_VERSION_MAJOR__ and __PTX_ISA_VERSION_MINOR__ predefined macros allows code to check the PTX ISA version being targeted by the compiler. PowerPC / PowerPC64 / RS6000 * The internal implementation of Power's target-specific built-in functions has been rewritten to be easier and less error-prone to maintain. Every attempt has been made to ensure that the new behavior matches the old behavior, but inevitably some bugs can be expected. Please [104]report any problems. * The built-in functions __builtin_get_texasr, __builtin_get_texasru, __builtin_get_tfhar, __builtin_get_tfiar, __builtin_set_texasr, __builtin_set_texasru, __builtin_set_tfhar, and __builtin_set_tfiar now behave as documented in all supported configurations. On prior releases, the arguments and return values of these functions were treated as unsigned long long instead of as unsigned long, when the options -m32 -mpowerpc64 were in effect. * The overloaded built-in functions vec_cntlz_lsbb and vec_cnttz_lsbb now behave as documented. On prior releases, these built-in functions had incorrect semantics on little-endian targets. PRU * The [105]__regio_symbol variable qualifier has been added. It allows easier access in C programs to the __R30 and __R31 CPU I/O registers. RISC-V * Default ISA spec version was bump to 20191213, more detail see this [106]announcement * New ISA extension support for zba, zbb, zbc, zbs was added. * New ISA extension support for vector and scalar crypto was added, only support architecture testing macro and -march= parsing. * The option -mtune=thead-c906 is added to tune for T-HEAD c906 cores. * libstdc++ no longer attempts to detect built-in atomics. Distributions that have out-of-tree workarounds for -latomic should check their ABIs again. Operating Systems Improvements to Static Analyzer * The analyzer has gained a [107]-Wanalyzer-use-of-uninitialized-value warning, similar to [108]-Wuninitialized and [109]-Wmaybe-uninitialized, but based on an interprocedural path-sensitive analysis ([110]PR95006). Such warnings are not disabled by the new [111]-ftrivial-auto-var-init (see below), as the latter is considered a mitigation option. * [112]-Wanalyzer-write-to-const and [113]-Wanalyzer-write-to-string-literal will now check for [114]__attribute__ ((access, ....)) on calls to externally-defined functions, and complain about read-only regions pointed to by arguments marked with a write_only or read_write attribute ([115]PR104793). * The analyzer's "taint" mode, activated by [116]-fanalyzer-checker=taint (in addition to [117]-fanalyzer), has gained four new taint-based warnings: + [118]-Wanalyzer-tainted-allocation-size for e.g. attacker-controlled malloc and alloca, + [119]-Wanalyzer-tainted-divisor for detecting where an attacker can inject a divide-by-zero, + [120]-Wanalyzer-tainted-offset for attacker-controlled pointer offsets, + [121]-Wanalyzer-tainted-size for attacker-controlled values being used as a size parameter to calls to memset or to functions marked with [122]__attribute__ ((access, ....)). The existing [123]-Wanalyzer-tainted-array-index has been reworded to talk about "attacker-controlled" rather than "tainted" values, for consistency with the new warnings. A new [124]__attribute__ ((tainted_args)) has been added to the C and C++ front ends, usable on functions, and on function pointer callback fields in structs. The analyzer's taint mode will treat all parameters and buffers pointed to by parameters of such functions as being attacker-controlled, such as for annotating system calls in an operating system kernel as being an "attack surface". * The analyzer now respects [125]__attribute__((const)): it will treat such functions as returning the same value when given the same inputs ([126]PR104434), and as having no side effects ([127]PR104576). * The analyzer is now able to split its analysis into multiple execution paths in places where there isn't a split in the control flow graph. For example, it now handles realloc calls by splitting the execution path into three possible outcomes for the call: + failure, returning NULL + success, growing the buffer in-place without moving it + success, allocating a new buffer, copying the content of the old buffer to it, and freeing the old buffer * The analyzer's interprocedural path exploration logic is now able to track calls through function pointers. * The analyzer now makes the assumption that if we know PTR is non-NULL, then (PTR + OFFSET) is also non-NULL. This isn't strictly true, but eliminates false positives in practice ([128]PR101962). * The analyzer has gained some initial support for inline assembler code. This is extremely limited, and is purely to help suppress false positives when analyzing the Linux kernel, which makes heavy use of inline assembler ([129]PR101570). * The way the analyzer tracks the state of memory along an execution path has been improved in various ways for GCC 12: + An optimization for representing bulk updates to memory (e.g. zero fills) has been removed as it never worked well. In GCC 12 it has been replaced with a simpler and more accurate approach, eliminating many false positives ([130]PR95006). + Various optimizations have been added, speeding up the analysis on a particularly problematic source file from 4 minutes down to 17 seconds ([131]PR104943, [132]PR104954, and [133]PR104955). + The analyzer now tracks the sizes of dynamically-allocated regions, both on the heap (via malloc etc) and stack (via alloca), though none of the analyzer warnings make use of this yet in GCC 12. * The analyzer's handling of switch statements has been rewritten, fixing various bugs. Other significant improvements Eliminating uninitialized variables * GCC can now [134]initialize all stack variables implicitly, including padding. This is intended to eliminate all classes of uninitialized stack variable flaws. Lack of explicit initialization will still warn when [135]-Wuninitialized is active. For best debugging, use of the new command-line option [136]-ftrivial-auto-var-init=pattern can be used to fill variables with a repeated 0xFE pattern, which tends to illuminate many bugs (e.g. pointers receive invalid addresses, sizes and indices are very large). For best production results, the new command-line option [137]-ftrivial-auto-var-init=zero can be used to fill variables with 0x00, which tends to provide a safer state for bugs (e.g. pointers are NULL, strings are NUL filled, and sizes and indices are 0). Debugging formats * GCC can now generate debugging information in [138]CTF, a lightweight debugging format that provides information about C types and the association between functions and data symbols and types. This format is designed to be embedded in ELF files and to be very compact and simple. A new command-line option -gctf enables the generation of CTF. * GCC can now generate debugging information in BTF. This is a debugging format mainly used in BPF programs and the Linux kernel. The compiler can generate BTF for any target, when enabled with the command-line option -gbtf GCC 12.1 This is the [139]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 12.1 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 12.2 This is the [140]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 12.2 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Target Specific Changes LoongArch * The default setting of -m[check|no-check]-zero-division is changed for optimized code. Now -mno-check-zero-division is the default for all optimization levels but -O0 and -Og. The old behavior can be obtained by explicitly passing -mcheck-zero-division to GCC. GCC 12.3 Target Specific Changes x86-64 * GCC now supports AMD CPUs based on the znver4 core via -march=znver4. The switch makes GCC consider using 512-bit vectors when auto-vectorizing. This is the [141]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 12.3 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 12.4 This is the [142]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 12.4 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). For questions related to the use of GCC, please consult these web pages and the [143]GCC manuals. If that fails, the [144]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [145]gcc@gcc.gnu.org. All of [146]our lists have public archives. Copyright (C) [147]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [148]maintained by the GCC team. Last modified 2024-06-20. 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https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Warning-Options.html#index-Waddress 59. https://gcc.gnu.org/PR102103 60. https://gcc.gnu.org/PR99701 61. https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=3ead06c1 62. https://gcc.gnu.org/PR102753 63. https://wg21.link/p0466 64. https://gcc.gnu.org/PR101539 65. https://gcc.gnu.org/PR100828 66. https://gcc.gnu.org/PR101786 67. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Warning-Options.html#index-Winterference-size 68. https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=76b75018 69. https://gcc.gnu.org/PR101344 70. https://gcc.gnu.org/PR101883 71. https://gcc.gnu.org/PR89062 72. https://gcc.gnu.org/PR101233 73. https://gcc.gnu.org/PR88252 74. https://gcc.gnu.org/PR86439 75. https://gcc.gnu.org/PR98832 76. https://gcc.gnu.org/PR102933 77. https://gcc.gnu.org/PR51577 78. https://gcc.gnu.org/PR98486 79. https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=1595fe44 80. https://dlang.org/changelog/2.100.1.html 81. https://gcc.gnu.org/PR101127 82. https://gcc.gnu.org/PR106563 83. https://dlang.org/spec/importc.html 84. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/jit/topics/compatibility.html#libgccjit-abi-16 85. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/jit/topics/expressions.html#c.gcc_jit_lvalue_set_tls_model 86. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/jit/topics/compatibility.html#libgccjit-abi-17 87. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/jit/topics/expressions.html#c.gcc_jit_lvalue_set_link_section 88. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Common-Variable-Attributes.html#index-section-variable-attribute 89. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/jit/topics/compatibility.html#libgccjit-abi-18 90. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/jit/topics/compatibility.html#libgccjit-abi-19 91. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/jit/topics/compatibility.html#libgccjit-abi-20 92. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/jit/topics/expressions.html#c.gcc_jit_context_new_bitcast 93. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/jit/topics/compatibility.html#libgccjit-abi-21 94. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/jit/topics/expressions.html#c.gcc_jit_lvalue_set_register_name 95. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/jit/topics/compatibility.html#libgccjit-abi-22 96. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/jit/topics/contexts.html#c.gcc_jit_context_set_bool_print_errors_to_stderr 97. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/jit/topics/compatibility.html#libgccjit-abi-23 98. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/jit/topics/compatibility.html#libgccjit-abi-24 99. https://gcc.gnu.org/PR96066 100. https://gcc.gnu.org/PR96067 101. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/jit/topics/expressions.html#c.gcc_jit_context_new_cast 102. https://gcc.gnu.org/PR95498 103. https://community.arm.com/arm-community-blogs/b/architectures-and-processors-blog/posts/arm-a-profile-architecture-developments-2020 104. https://gcc.gnu.org/bugs/ 105. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Named-Address-Spaces.html#PRU-Named-Address-Spaces 106. https://groups.google.com/a/groups.riscv.org/g/sw-dev/c/aE1ZeHHCYf4 107. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Static-Analyzer-Options.html#index-Wanalyzer-use-of-uninitialized-value 108. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Warning-Options.html#index-Wuninitialized 109. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Warning-Options.html#index-Wmaybe-uninitialized 110. https://gcc.gnu.org/PR95006 111. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Optimize-Options.html#index-ftrivial-auto-var-init 112. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Static-Analyzer-Options.html#index-Wanalyzer-write-to-const 113. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Static-Analyzer-Options.html#index-Wanalyzer-write-to-string-literal 114. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Common-Function-Attributes.html 115. https://gcc.gnu.org/PR104793 116. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Static-Analyzer-Options.html#index-fanalyzer-checker 117. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Static-Analyzer-Options.html#index-fanalyzer 118. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Static-Analyzer-Options.html#index-Wanalyzer-tainted-allocation-size 119. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Static-Analyzer-Options.html#index-Wanalyzer-tainted-divisor 120. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Static-Analyzer-Options.html#index-Wanalyzer-tainted-offset 121. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Static-Analyzer-Options.html#index-Wanalyzer-tainted-size 122. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Common-Function-Attributes.html 123. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Static-Analyzer-Options.html#index-Wanalyzer-tainted-array-index 124. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Common-Function-Attributes.html#index-tainted_005fargs-function-attribute 125. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Common-Function-Attributes.html#index-const-function-attribute 126. https://gcc.gnu.org/PR104434 127. https://gcc.gnu.org/PR104576 128. https://gcc.gnu.org/PR101962 129. https://gcc.gnu.org/PR101570 130. https://gcc.gnu.org/PR95006 131. https://gcc.gnu.org/PR104943 132. https://gcc.gnu.org/PR104954 133. https://gcc.gnu.org/PR104955 134. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Optimize-Options.html#index-ftrivial-auto-var-init 135. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Warning-Options.html#index-Wuninitialized 136. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Optimize-Options.html#index-ftrivial-auto-var-init 137. https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc/Optimize-Options.html#index-ftrivial-auto-var-init 138. https://ctfstd.org/ 139. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=12.0 140. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=12.2 141. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=12.3 142. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=12.4 143. https://gcc.gnu.org/onlinedocs/ 144. mailto:gcc-help@gcc.gnu.org 145. mailto:gcc@gcc.gnu.org 146. https://gcc.gnu.org/lists.html 147. https://www.fsf.org/ 148. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-11/index.html GCC 11 Release Series May 29, 2023 The GCC developers are pleased to announce the release of GCC 11.4. This release is a bug-fix release, containing fixes for regressions in GCC 11.3 relative to previous releases of GCC. Release History GCC 11.4 May 29, 2023 ([1]changes, [2]documentation) GCC 11.3 April 21, 2022 ([3]changes, [4]documentation) GCC 11.2 July 28, 2021 ([5]changes, [6]documentation) GCC 11.1 April 27, 2021 ([7]changes, [8]documentation) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [9]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [10]GCC project web site or contact the [11]GCC development mailing list. To obtain GCC please use [12]our mirror sites or [13]our version control system. For questions related to the use of GCC, please consult these web pages and the [14]GCC manuals. If that fails, the [15]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [16]gcc@gcc.gnu.org. All of [17]our lists have public archives. Copyright (C) [18]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [19]maintained by the GCC team. Last modified 2024-05-30. References 1. https://gcc.gnu.org/gcc-11/changes.html 2. https://gcc.gnu.org/onlinedocs/11.4.0/ 3. https://gcc.gnu.org/gcc-11/changes.html 4. https://gcc.gnu.org/onlinedocs/11.3.0/ 5. https://gcc.gnu.org/gcc-11/changes.html 6. https://gcc.gnu.org/onlinedocs/11.2.0/ 7. https://gcc.gnu.org/gcc-11/changes.html 8. https://gcc.gnu.org/onlinedocs/11.1.0/ 9. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Contributors.html 10. https://gcc.gnu.org/index.html 11. mailto:gcc@gcc.gnu.org 12. https://gcc.gnu.org/mirrors.html 13. https://gcc.gnu.org/git.html 14. https://gcc.gnu.org/onlinedocs/ 15. mailto:gcc-help@gcc.gnu.org 16. mailto:gcc@gcc.gnu.org 17. https://gcc.gnu.org/lists.html 18. https://www.fsf.org/ 19. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-11/changes.html GCC 11 Release Series Changes, New Features, and Fixes This page is a "brief" summary of some of the huge number of improvements in GCC 11. You may also want to check out our [1]Porting to GCC 11 page and the [2]full GCC documentation. Caveats * The default mode for C++ is now -std=gnu++17 instead of -std=gnu++14. Note that [3]C++17 changes to template template parameter matching can be disabled independently of other features with -fno-new-ttp-matching. * When building GCC itself, the host compiler must now support C++11, rather than C++98. In particular bootstrapping GCC 11 using an older version of GCC requires a binary of GCC 4.8 or later, rather than of GCC 3.4 or later as was the case for bootstrapping GCC 10. * Naming and location of auxiliary and dump output files changed. If you compile multiple input files in a single command, if you enable Link Time Optimization, or if you use -dumpbase, -dumpdir, -save-temps=*, and you expect any file other than the primary output file(s) to be created as a side effect, watch out for improvements and a few surprises. See [4]the patch, particularly its textual description, for more details about the changes. * -gsplit-dwarf no longer enables debug info generation on its own but requires a separate -g for this. * The libstdc++ configure option --enable-cheaders=c_std is deprecated and will be removed in a future release. It should be possible to use --enable-cheaders=c_global (the default) with no change in behaviour. * The front end for compiling BRIG format of Heterogeneous System Architecture Intermediate Language (HSAIL) has been deprecated and will likely be removed in a future release. * Some short options of the gcov tool have been renamed: -i to -j and -j to -H. General Improvements * [5]ThreadSanitizer improvements to support alternative runtimes and environments. The [6]Linux Kernel Concurrency Sanitizer (KCSAN) is now supported. + Add --param tsan-distinguish-volatile to optionally emit instrumentation distinguishing volatile accesses. + Add --param tsan-instrument-func-entry-exit to optionally control if function entries and exits should be instrumented. * In previous releases of GCC, the "column numbers" emitted in diagnostics were actually a count of bytes from the start of the source line. This could be problematic, both because of: + multibyte characters (requiring more than one byte to encode), and + multicolumn characters (requiring more than one column to display in a monospace font) For example, the character π ("GREEK SMALL LETTER PI (U+03C0)") occupies one column, and its UTF-8 encoding requires two bytes; the character 🙂 ("SLIGHTLY SMILING FACE (U+1F642)") occupies two columns, and its UTF-8 encoding requires four bytes. In GCC 11 the column numbers default to being column numbers, respecting multi-column characters. The old behavior can be restored using a new option [7]-fdiagnostics-column-unit=byte. There is also a new option [8]-fdiagnostics-column-origin=, allowing the pre-existing default of the left-hand column being column 1 to be overridden if desired (e.g. for 0-based columns). The output of [9]-fdiagnostics-format=json has been extended to supply both byte counts and column numbers for all source locations. Additionally, in previous releases of GCC, tab characters in the source would be emitted verbatim when quoting source code, but be prefixed with whitespace or line number information, leading to misalignments in the resulting output when compared with the actual source. Tab characters are now printed as an appropriate number of spaces, using the [10]-ftabstop option (which defaults to 8 spaces per tab stop). * Introduce [11]Hardware-assisted AddressSanitizer support. This sanitizer currently only works for the AArch64 target. It helps debug address problems similarly to [12]AddressSanitizer but is based on partial hardware assistance and provides probabilistic protection to use less RAM at run time. [13]Hardware-assisted AddressSanitizer is not production-ready for user space, and is provided mainly for use compiling the Linux Kernel. To use this sanitizer the command line arguments are: + -fsanitize=hwaddress to instrument userspace code. + -fsanitize=kernel-hwaddress to instrument kernel code. * For targets that produce DWARF debugging information GCC now defaults to [14]DWARF version 5 (with the exception of VxWorks and Darwin/Mac OS X which default to version 2 and AIX which defaults to version 4). This can produce up to 25% more compact debug information compared to earlier versions. To take full advantage of DWARF version 5 GCC needs to be built against binutils version 2.35.2 or higher. When GCC is built against earlier versions of binutils GCC will still emit DWARF version 5 for most debuginfo data, but will generate version 4 debug line tables (even when explicitly given -gdwarf-5). The following debug information consumers can process DWARF version 5: + GDB 8.0, or higher + valgrind 3.17.0 + elfutils 0.172, or higher (for use with systemtap, dwarves/pahole, perf and libabigail) + dwz 0.14 Programs embedding libbacktrace are urged to upgrade to the version shipping with GCC 11. To make GCC 11 generate an older DWARF version use -g together with -gdwarf-2, -gdwarf-3 or -gdwarf-4. * Vectorizer improvements: + The straight-line code vectorizer now considers the whole function when vectorizing and can handle opportunities crossing CFG merges and backedges. * A series of conditional expressions that compare the same variable can be transformed into a switch statement if each of them contains a comparison expression. Example: int IsHTMLWhitespace(int aChar) { return aChar == 0x0009 || aChar == 0x000A || aChar == 0x000C || aChar == 0x000D || aChar == 0x0020; } This statement can be transformed into a switch statement and then expanded into a bit-test. * New command-line options: + [15]-fbit-tests, enabled by default, can be used to enable or disable switch expansion using bit-tests. * Inter-procedural optimization improvements: + A new IPA-modref pass was added to track side effects of function calls and improve precision of points-to-analysis. The pass can be controlled by the [16]-fipa-modref option. + The identical code folding pass (controlled by [17]-fipa-icf) was significantly improved to increase the number of unified functions and to reduce compile-time memory use. + IPA-CP (Interprocedural constant propagation) heuristics improved its estimation of potential usefulness of known loop bounds and strides by taking the estimated frequency of these loops into account. * Link-time optimization improvements: + The LTO bytecode format was optimized for smaller object files and faster streaming. + Memory allocation of the linking stage was improved to reduce peak memory use. * Profile driven optimization improvements: + Using [18]-fprofile-values, was improved by tracking more target values for e.g. indirect calls. + GCOV data file format outputs smaller files by representing zero counters in a more compact way. New Languages and Language specific improvements * GCC 11 adds support for non-rectangular loop nests in OpenMP constructs and the allocator routines of [19]OpenMP 5.0, including initial allocate clause support in C/C++. The OMP_TARGET_OFFLOAD environment variable and the active-levels routines are now supported. For C/C++, the declare variant and map support has been extended. For Fortran, OpenMP 4.5 is now fully supported and OpenMP 5.0 support has been extended, including the following features which were before only available in C and C++: order(concurrent), device_type, memorder-clauses for flush, lastprivate with conditional modifier, atomic construct and reduction clause extensions of OpenMP 5.0, if clause with simd and cancel modifiers, target data without map clause, and limited support for the requires construct. * Version 2.6 of the [20]OpenACC specification continues to be maintained and improved in the C, C++ and Fortran compilers. See the [21]implementation status section on the OpenACC wiki page and the [22]run-time library documentation for further information. C family * New attributes: + The [23]no_stack_protector attribute has been added to mark functions which should not be instrumented with stack protection (-fstack-protector). + The existing [24]malloc attribute has been extended so that it can be used to identify allocator/deallocator API pairs. A pair of new [25]-Wmismatched-dealloc and [26]-Wmismatched-new-delete warnings will complain about mismatched calls, and [27]-Wfree-nonheap-object about deallocation calls with pointers not obtained from allocation functions. Additionally, the static analyzer will use these attributes when checking for leaks, double-frees, use-after-frees, and similar issues. * New warnings: + [28]-Wmismatched-dealloc, enabled by default, warns about calls to deallocation functions with pointers returned from mismatched allocation functions. + [29]-Wsizeof-array-div, enabled by -Wall, warns about divisions of two sizeof operators when the first one is applied to an array and the divisor does not equal the size of the array element. + [30]-Wstringop-overread, enabled by default, warns about calls to string functions reading past the end of the arrays passed to them as arguments. In prior GCC releases most instances of his warning are diagnosed by -Wstringop-overflow. + [31]-Wtsan, enabled by default, warns about unsupported features in ThreadSanitizer (currently std::atomic_thread_fence). * Enhancements to existing warnings: + [32]-Wfree-nonheap-object detects many more instances of calls to deallocation functions with pointers not returned from a dynamic memory allocation function. + [33]-Wmaybe-uninitialized diagnoses passing pointers or references to uninitialized memory to functions taking const-qualified arguments. + [34]-Wuninitialized detects reads from uninitialized dynamically allocated memory. * For ELF targets that support the GNU or FreeBSD OSABIs, the used attribute will now save the symbol declaration it is applied to from linker garbage collection. To support this behavior, used symbols that have not been placed in specific sections (e.g. with the section attribute, or the -f{function,data}-sections options) will be placed in new, unique sections. This functionality requires Binutils version 2.36 or later. C * Several new features from the upcoming C2X revision of the ISO C standard are supported with -std=c2x and -std=gnu2x. Some of these features are also supported as extensions when compiling for older language versions. In addition to the features listed, some features previously supported as extensions and now added to the C standard are enabled by default in C2X mode and not diagnosed with -std=c2x -Wpedantic. + The BOOL_MAX and BOOL_WIDTH macros are provided in . + As in C++, function definitions no longer need to give names for unused function parameters. + The expansions of the true and false macros in have changed so that they have type bool. + The [[nodiscard]] standard attribute is now supported. + The __has_c_attribute preprocessor operator is now supported. + Macros INFINITY, NAN, FLT_SNAN, DBL_SNAN, LDBL_SNAN, DEC_INFINITY, DEC_NAN, and corresponding signaling NaN macros for _FloatN, _FloatNx and _DecimalN types, are provided in . There are also corresponding built-in functions __builtin_nansdN for decimal signaling NaNs. + Macros FLT_IS_IEC_60559, DBL_IS_IEC_60559 and LDBL_IS_IEC_60559 are provided in . + The feature test macro __STDC_WANT_IEC_60559_EXT__ is supported by . + Labels may appear before declarations and at the end of a compound statement. * New warnings: + [35]-Warray-parameter, enabled by -Wall, warns about redeclarations of functions with ordinary array arguments declared using inconsistent forms. The warning also enables the detection of the likely out of bounds accesses in calls to such functions with smaller arrays. + [36]-Wvla-parameter, enabled by -Wall, warns redeclarations of functions with variable length array arguments declared using inconsistent forms or with mismatched bounds. The warning also enables the detection of the likely out of bounds accesses in calls to such functions with smaller arrays. C++ * The default mode has been changed to -std=gnu++17. * Several C++20 features have been implemented: + the compiler now supports consteval virtual functions + P2082R1, Fixing CTAD for aggregates + P0593R6, Pseudo-destructors end object lifetimes + P1907R1, Inconsistencies with non-type template parameters (complete implementation) + P1975R0, Fixing the wording of parenthesized aggregate-initialization + P1009R2, Array size deduction in new-expressions + P1099R5, using enum + Modules, Requires -fmodules-ts and some aspects are incomplete. Refer to [37]C++ 20 Status * The C++ front end has experimental support for some of the upcoming C++23 draft features with the -std=c++23, -std=gnu++23, -std=c++2b or -std=gnu++2b flags, including + P0330R8, Literal Suffix for (signed) size_t. For a full list of new features, see [38]the C++ status page. * Several C++ Defect Reports have been resolved, e.g.: + DR 625, Use of auto as a template-argument + DR 1512, Pointer comparison vs qualification conversions + DR 1722, Should lambda to function pointer conversion function be noexcept? + DR 1914, Duplicate standard attributes + DR 2032, Default template-arguments of variable templates + DR 2289, Uniqueness of decomposition declaration names + DR 2237, Can a template-id name a constructor? + DR 2303, Partial ordering and recursive variadic inheritance + DR 2369, Ordering between constraints and substitution + DR 2450, braced-init-list as a template-argument * G++ now performs better access checking in templates ([39]PR41437). * reinterpret_casts in constexpr evaluation are now checked more completely ([40]PR95307). * The diagnostic for static_assert has been improved: the compiler now shows the expression including its template arguments (if there were any), and can point to the failing clause if the condition comprised of any logical AND operators ([41]PR97518). * New warnings: + [42]-Wctad-maybe-unsupported, disabled by default, warns about performing class template argument deduction on a type with no deduction guides. + [43]-Wrange-loop-construct, enabled by -Wall, warns when a range-based for-loop is creating unnecessary and expensive copies. + [44]-Wdeprecated-enum-enum-conversion, enabled by default in C++20, warns about deprecated arithmetic conversions on operands of enumeration types, as outlined in [depr.arith.conv.enum]. + [45]-Wdeprecated-enum-float-conversion, enabled by default in C++20, warns about deprecated arithmetic conversions on operands where one is of enumeration type and the other is of a floating-point type, as outlined in [depr.arith.conv.enum]. + [46]-Wmismatched-new-delete, enabled by -Wall, warns about calls to C++ operator delete with pointers returned from mismatched forms of operator new or from other mismatched allocation functions. + [47]-Wvexing-parse, enabled by default, warns about the most vexing parse rule: the cases when a declaration looks like a variable definition, but the C++ language requires it to be interpreted as a function declaration. * Enhancements to existing warnings: + [48]-Wnonnull considers the implicit this argument of every C++ nonstatic member function to have been implicitly declared with attribute nonnull and triggers warnings for calls where the pointer is null. Runtime Library (libstdc++) * Improved C++17 support, including: + std::from_chars and std::to_chars for floating-point types. * Improved experimental C++20 support, including: + Calendar additions to . Thanks to Cassio Neri for optimizations. + std::bit_cast + std::source_location + Atomic wait and notify operations. + , , and + + Efficient access to basic_stringbuf's buffer. + Heterogeneous lookup in unordered containers. * Experimental C++23 support, including: + contains member functions for strings, thanks to Paul Fee. + std::to_underlying, std::is_scoped_enum * Experimental support for Data-Parallel Types (simd) from the Parallelism 2 TS, thanks to Matthias Kretz. * Faster std::uniform_int_distribution, thanks to Daniel Lemire. D * New features: + A new bottom type typeof(*null) has been added to represent run-time errors and non-terminating functions. This also introduces a new standard alias for the type named noreturn, and is implicitly imported into every module. + Printf-like and scanf-like functions are now detected by prefixing them with pragma(printf) for printf-like functions or pragma(scanf) for scanf-like functions. + The __traits() expression now supports the extensions isDeprecated, isDisabled, isFuture, isModule, isPackage, child, isReturnOnStack, isZeroInit, getTargetInfo, getLocation, hasPostblit, isCopyable, getVisibility, and totype. + An expression-based contract syntax has been added to the language. + Function literals can now return a value by reference with the ref keyword. + A new syntax is available to declare aliases to function types using the alias syntax based on the assignment operator. + New types __c_complex_float, __c_complex_double, __c_complex_real, and __c_wchar_t have been added for interfacing with C and C++ code, and are available from the core.stdc.config module. + User-defined attributes can now be used to annotate enum members, alias declarations, and function parameters. + Template alias parameters can now be instantiated with basic types such as int or void function(). + The mixin construct can now be used as types in the form mixin(string) var. + The mixin construct can now take an argument list, same as pragma(msg). * New intrinsics: + Bitwise rotate intrinsics core.bitop.rol and core.bitop.ror have been added. + Byte swap intrinsic core.bitop.byteswap for swapping bytes in a 2-byte ushort has been added. + Math intrinsics available from core.math now have overloads for float and double types. + Volatile intrinsics core.volatile.volatileLoad and core.volatile.volatileStore have been moved from the core.bitop module. * New attributes: + The following GCC attributes are now recognized and available from the gcc.attributes module with short-hand aliases for convenience: o @attribute("alloc_size", arguments) or @alloc_size(arguments). o @attribute("always_inline") or @always_inline. o @attribute("used") or @used. o @attribute("optimize", arguments) or @optimize(arguments). o @attribute("cold") or @cold. o @attribute("noplt") or @noplt. o @attribute("target_clones", arguments) or @target_clones(arguments). o @attribute("no_icf") or @no_icf. o @attribute("noipa") or @noipa. o @attribute("symver", arguments) or @symver(arguments). + New aliases have been added to gcc.attributes for compatibility with ldc.attributes. o The @allocSize(arguments) attribute is the same as @alloc_size(arguments), but uses a 0-based index for function arguments. o The @assumeUsed attribute is an alias for @attribute("used"). o The @fastmath attribute is an alias for @optimize("Ofast"). o The @naked attribute is an alias for @attribute("naked"). This attribute may not be available on all targets. o The @restrict attribute has been added to specify that a function parameter is to be restrict-qualified in the C99 sense of the term. o The @optStrategy(strategy) attribute is an alias for @optimize("O0") when the strategy is "none", otherwise @optimize("Os") for the "optsize" and "minsize" strategies. o The @polly attribute is an alias for @optimize("loop-parallelize-all"). o The @section(name) attribute is an alias for @attribute("section", name). o The @target(arguments) attribute is an alias for attribute("target", arguments). o The @weak attribute is an alias for @attribute("weak"). * New language options: + -fweak-templates, added to control whether declarations that can be defined in multiple objects should be emitted as weak symbols. The default is to emit all symbols with extern linkage as weak, unless the target lacks support for weak symbols. + -Wdeprecated, this option is now enabled by default. + -Wextra, this option now turns on all warnings that are not part of the core D language front-end - -Waddress, -Wcast-result, -Wunknown-pragmas. + -Wvarargs, added to turn on warnings about questionable usage of the va_start intrinsic. * Deprecated and removed features: + Compiler-recognized attributes are now made available from the gcc.attributes module, the former module gcc.attribute has been deprecated and will be removed in a future release. + The @attribute("alias") attribute has been removed, as it had been superseded by pragma(mangle). + The @attribute("forceinline") attribute has been removed and renamed to @always_inline. + __vector types that are not supported in hardware are now rejected at compile-time. Previously all vector types were accepted by the compiler and emulated when target support was absent. + The extern(Pascal) linkage attribute has been removed. + The deprecation phase for -ftransition=import and -ftransition=checkimports is finished. These switches no longer have an effect and are now removed. Symbols that are not visible in a particular scope will no longer be found by the compiler. + It is now an error to use private variables selectively imported from other modules. Due to a bug, some imported private members were visible from other modules, violating the specification. + The -fweak compiler switch has been removed, as it existed only for testing. Fortran * Added DEPRECATED to !GCC$'s attributes directive. Go * GCC 11 provides a complete implementation of the Go 1.16.3 user packages. libgccjit * libgccjit was marked as merely "Alpha" quality when [49]originally added in GCC 5. Given that we have maintained [50]API and ABI compatibility since then and it is in use by various projects, we have removed that caveat. * libgccjit can now be built for MinGW * The libgccjit API gained 10 new entry points: + [51]gcc_jit_global_set_initializer + 9 entrypoints for [52]directly embedding asm statements into a compile, analogous to inline asm in the C front end New Targets and Target Specific Improvements AArch64 & arm * A number of new CPUs are supported through arguments to the -mcpu and -mtune options in both the arm and aarch64 back ends (GCC identifiers in parentheses): + Arm Cortex-A78 (cortex-a78). + Arm Cortex-A78AE (cortex-a78ae). + Arm Cortex-A78C (cortex-a78c). + Arm Cortex-X1 (cortex-x1). + Arm Neoverse V1 (neoverse-v1). + Arm Neoverse N2 (neoverse-n2). * GCC can now auto-vectorize operations performing addition, subtraction, multiplication and the accumulate/subtract variants on complex numbers, taking advantage of the Advanced SIMD instructions in the Armv8.3-a (AArch64/AArch32), SVE (AArch64), SVE2 (AArch64) and MVE (AArch32 M-profile) instruction sets. AArch64 * In addition to the above, the following AArch64-only CPUs are now supported: + Fujitsu A64FX (a64fx). + Arm Cortex-R82 (cortex-r82). * The AArch64 Armv8-R architecture is now supported through the -march=armv8-r option. * Mitigation against the [53]Straight-line Speculation vulnerability is supported with the -mharden-sls= option. Please refer to the documentation for usage instructions. * The availability of Advanced SIMD intrinsics available through the arm_neon.h header is improved and GCC 11 supports the full set of intrinsics defined by ACLE Q3 2020. AMD Radeon (GCN) * Initial support for gfx908 GPUs has been added. arm * Initial auto-vectorization is now available when targeting the MVE instruction set. * GCC can now make use of the Low Overhead Branch instruction in Armv8.1-M to optimize loop counters and checks. * The -mcpu=cortex-m55 option now supports the extensions +nomve and +nomve.fp to control generation of MVE and MVE floating-point instructions. IA-32/x86-64 * New ISA extension support for Intel TSXLDTRK was added to GCC. TSXLDTRK intrinsics are available via the -mtsxldtrk compiler switch. * New ISA extension support for Intel SERIALIZE was added to GCC. SERIALIZE intrinsics are available via the -mserialize compiler switch. * New ISA extension support for Intel HRESET was added to GCC. HRESET intrinsics are available via the -mhreset compiler switch. * New ISA extension support for Intel UINTR was added to GCC. UINTR intrinsics are available via the -muintr compiler switch. * New ISA extension support for Intel KEYLOCKER was added to GCC. KEYLOCKER intrinsics are available via the -mkeylocker compiler switch. * New ISA extension support for Intel AMX-TILE, AMX-INT8, AMX-BF16 was added to GCC. AMX-TILE, AMX-INT8, AMX-BF16 intrinsics are available via the -mamx-tile, -mamx-int8, -mamx-bf16 compiler switches. * New ISA extension support for Intel AVX-VNNI was added to GCC. AVX-VNNI intrinsics are available via the -mavxvnni compiler switch. * GCC now supports the Intel CPU named Sapphire Rapids through -march=sapphirerapids. The switch enables the MOVDIRI, MOVDIR64B, AVX512VP2INTERSECT, ENQCMD, CLDEMOTE, SERIALIZE, PTWRITE, WAITPKG, TSXLDTRK, AMT-TILE, AMX-INT8, AMX-BF16, and AVX-VNNI ISA extensions. * GCC now supports the Intel CPU named Alderlake through -march=alderlake. The switch enables the CLDEMOTE, PTWRITE, WAITPKG, SERIALIZE, KEYLOCKER, AVX-VNNI, and HRESET ISA extensions. * GCC now supports the Intel CPU named Rocketlake through -march=rocketlake. Rocket Lake is based on Icelake client and minus SGX. * GCC now supports AMD CPUs based on the znver3 core via -march=znver3. * GCC now supports micro-architecture levels defined in the x86-64 psABI via -march=x86-64-v2, -march=x86-64-v3 and -march=x86-64-v4. Nios II * The options -mcustom-insn=N no longer produce compiler warnings if the custom instruction is not generated due to missing optimization options such as -fno-math-errno, -ffinite-math-only, or -funsafe-math-optimizations. These warnings were not consistently emitted for all custom instructions. * The -mcustom-fpu-cfg=fph2 option has been added to enable the custom instructions supported by the Nios II Floating Point Hardware 2 Component. NVPTX * The -misa default has changed from sm_30 to sm_35. * The -m32 compiler switch has been removed. * The -msoft-stack-reserve-local format has been fixed. Previously, it accepted -msoft-stack-reserve-local. It now accepts -msoft-stack-reserve-local=. S/390, System z, IBM Z Systems * The behavior when compiling with -fexcess-precision=standard (e.g., implied by -std=c99) on s390(x) targets can now be controlled at configure time with the flag --enable-s390-excess-float-precision. When enabled, GCC will maintain previous behavior and evaluate float expressions in double precision, which aligns with the definition of float_t as double. With the flag disabled, GCC will always evaluate float expressions in single precision. In native builds and cross compiles that have target libc headers, GCC will by default match the definition of float_t in the installed glibc. RISC-V * Support address sanitizer for RISC-V. * Support big-endian for RISC-V, thanks to Marcus Comstedt. * Implement new style of architecture extension test macros: each architecture extension has a corresponding feature test macro, which can be used to test its existence and version information. * Legacy architecture extension test macros like __riscv_atomic are deprecated, but will still be supported for at least 2 release cycles. * Support IFUNC for riscv*-*-linux*. * Add new option -misa-spec=* to control ISA spec version. This controls the default version of each extensions. It defaults to 2.2. * Introduce the --with-multilib-generator configure time option. This allows for flexible config multi-lib settings. Its syntax is the same as RISC-V's multilib-generator. * Extend the sytax for multilib-generator, support expansion operator * to reduce the complexity of complicated multi-lib re-use rules. * Support -mcpu=* option aligned with RISC-V clang/LLVM. It sets the pipeline model and architecture extensions, like -mtune=* plus -march=*. * Support for TLS stack protector canary access, thanks to Cooper Qu. * Support __builtin_thread_pointer for RISC-V. * Introduce shorten_memrefs optimization, which reduces the code size for memory access, thanks to Craig Blackmore. Operating Systems AIX * GCC for AIX can be built as a 64-bit application and the runtime is built as FAT libraries containing both 32-bit and 64-bit objects. * Support AIX Vector Extended ABI with -mabi=vec-extabi. * Thread-Local uninitiated data placed in local common section. * Use thread-safe access in ctype. * Link with libc128.a when long-double-128 enabled. Improvements to Static Analyzer * The implementation of how program state is tracked within [54]-fanalyzer has been completely rewritten for GCC 11, fixing numerous bugs, and allowing for the analyzer to scale to larger C source files. * The analysis of allocations and deallocations has been generalized beyond malloc and free. + As preliminary work towards eventually supporting C++, the malloc/free checking will also check new/delete and new[]/delete[]. However, C++ is not yet properly supported by [55]-fanalyzer (for example, exception-handling is unimplemented). + As noted above, the existing [56]malloc attribute has been extended so that it can be used to identify allocator/deallocator API pairs. The analyzer will use these attributes when checking for leaks, double-frees, use-after-frees, and similar issues. + A new [57]-Wanalyzer-mismatching-deallocation warning has been added, covering such mismatches as using scalar delete rather vector delete[]. * The analyzer has gained warnings [58]-Wanalyzer-shift-count-negative, [59]-Wanalyzer-shift-count-overflow, [60]-Wanalyzer-write-to-const, and [61]-Wanalyzer-write-to-string-literal, all enabled by default when [62]-fanalyzer is enabled. * The analyzer can now be extended by GCC plugins, allowing for domain-specific path-sensitive warnings. An example of using a [63]GCC plugin to check for misuses of CPython's global interpreter lock can be seen in the test suite * The analyzer has gained new debugging options [64]-fdump-analyzer-json and [65]-fno-analyzer-feasibility. Other significant improvements * GCC has gained a new environment variable [66]GCC_EXTRA_DIAGNOSTIC_OUTPUT which can be used by IDEs to request machine-readable fix-it hints without needing to adjust build flags. GCC 11.1 This is the [67]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 11.1 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 11.2 This is the [68]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 11.2 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 11.3 This is the [69]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 11.3 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 11.4 This is the [70]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 11.4 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Target Specific Changes x86-64 * The x86-64 ABI of passing and returning structure with a 64-bit single precision vector changed in GCC 11.1 when 3DNOW is disabled. Disabling 3DNOW no longer changes how they are passed nor returned. This ABI change is now diagnosed with -Wpsabi. * Mitigation against straight line speculation (SLS) for function return and indirect jump is supported via -mharden-sls=[none|all|return|indirect-jmp]. * Add CS prefix to call and jmp to indirect thunk with branch target in r8-r15 registers via -mindirect-branch-cs-prefix. For questions related to the use of GCC, please consult these web pages and the [71]GCC manuals. If that fails, the [72]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [73]gcc@gcc.gnu.org. All of [74]our lists have public archives. Copyright (C) [75]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [76]maintained by the GCC team. Last modified 2024-06-14. 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https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Warning-Options.html#index-Warray-parameter 36. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Warning-Options.html#index-Wvla-parameter 37. https://gcc.gnu.org/projects/cxx-status.html#cxx20 38. https://gcc.gnu.org/projects/cxx-status.html#cxx23 39. https://gcc.gnu.org/PR41437 40. https://gcc.gnu.org/PR95307 41. https://gcc.gnu.org/PR97518 42. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/C_002b_002b-Dialect-Options.html#index-Wctad-maybe-unsupported 43. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/C_002b_002b-Dialect-Options.html#index-Wrange-loop-construct 44. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/C_002b_002b-Dialect-Options.html#index-Wdeprecated-enum-enum-conversion 45. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/C_002b_002b-Dialect-Options.html#index-Wdeprecated-enum-float-conversion 46. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/C_002b_002b-Dialect-Options.html#index-Wmismatched-new-delete 47. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/C_002b_002b-Dialect-Options.html#index-Wvexing-parse 48. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Warning-Options.html#index-Wnonnull 49. https://gcc.gnu.org/gcc-5/changes.html#jit 50. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/jit/topics/compatibility.html 51. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/jit/topics/expressions.html#c.gcc_jit_global_set_initializer 52. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/jit/topics/asm.html 53. https://developer.arm.com/documentation/102587/0102/Straight-line-speculation-frequently-asked-questions 54. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Static-Analyzer-Options.html 55. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Static-Analyzer-Options.html 56. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 57. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Static-Analyzer-Options.html#index-Wanalyzer-mismatching-deallocation 58. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Static-Analyzer-Options.html#index-Wanalyzer-shift-count-negative 59. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Static-Analyzer-Options.html#index-Wanalyzer-shift-count-overflow 60. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Static-Analyzer-Options.html#index-Wanalyzer-write-to-const 61. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Static-Analyzer-Options.html#index-Wanalyzer-write-to-string-literal 62. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Static-Analyzer-Options.html 63. https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=66dde7bc64b75d4a338266333c9c490b12d49825 64. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Static-Analyzer-Options.html#index-fdump-analyzer-json 65. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Static-Analyzer-Options.html#index-fno-analyzer-feasibility 66. https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Environment-Variables.html#index-GCC_005fEXTRA_005fDIAGNOSTIC_005fOUTPUT 67. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=11.0 68. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=11.2 69. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=11.3 70. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=11.4 71. https://gcc.gnu.org/onlinedocs/ 72. mailto:gcc-help@gcc.gnu.org 73. mailto:gcc@gcc.gnu.org 74. https://gcc.gnu.org/lists.html 75. https://www.fsf.org/ 76. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-10/index.html GCC 10 Release Series (This release series is no longer supported.) July, 7, 2023 The [1]GNU project and the GCC developers are pleased to announce the release of GCC 10.5. This release is a bug-fix release, containing fixes for regressions in GCC 10.4 relative to previous releases of GCC. Release History GCC 10.5 July 7, 2023 ([2]changes, [3]documentation) GCC 10.4 June 28, 2022 ([4]changes, [5]documentation) GCC 10.3 April 8, 2021 ([6]changes, [7]documentation) GCC 10.2 July 23, 2020 ([8]changes, [9]documentation) GCC 10.1 May 7, 2020 ([10]changes, [11]documentation) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [12]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [13]GCC project web site or contact the [14]GCC development mailing list. To obtain GCC please use [15]our mirror sites or [16]our version control system. For questions related to the use of GCC, please consult these web pages and the [17]GCC manuals. If that fails, the [18]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [19]gcc@gcc.gnu.org. All of [20]our lists have public archives. Copyright (C) [21]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [22]maintained by the GCC team. Last modified 2024-05-30. References 1. http://www.gnu.org/ 2. https://gcc.gnu.org/gcc-10/changes.html 3. https://gcc.gnu.org/onlinedocs/10.5.0/ 4. https://gcc.gnu.org/gcc-10/changes.html 5. https://gcc.gnu.org/onlinedocs/10.4.0/ 6. https://gcc.gnu.org/gcc-10/changes.html 7. https://gcc.gnu.org/onlinedocs/10.3.0/ 8. https://gcc.gnu.org/gcc-10/changes.html 9. https://gcc.gnu.org/onlinedocs/10.2.0/ 10. https://gcc.gnu.org/gcc-10/changes.html 11. https://gcc.gnu.org/onlinedocs/10.1.0/ 12. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Contributors.html 13. https://gcc.gnu.org/index.html 14. mailto:gcc@gcc.gnu.org 15. https://gcc.gnu.org/mirrors.html 16. https://gcc.gnu.org/git.html 17. https://gcc.gnu.org/onlinedocs/ 18. mailto:gcc-help@gcc.gnu.org 19. mailto:gcc@gcc.gnu.org 20. https://gcc.gnu.org/lists.html 21. https://www.fsf.org/ 22. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-10/changes.html GCC 10 Release Series Changes, New Features, and Fixes This page is a "brief" summary of some of the huge number of improvements in GCC 10. You may also want to check out our [1]Porting to GCC 10 page and the [2]full GCC documentation. Caveats * An ABI incompatibility between C++14 and C++17 has been fixed. On some targets a class with a zero-sized subobject would be passed incorrectly when compiled as C++17 or C++20. See the [3]C++ notes below for more details. * The deprecated Profile Mode and array_allocator extensions have been removed from libstdc++. * The non-standard std::__is_nullptr_t type trait is deprecated and will be removed from libstdc++ in a future release. The standard trait std::is_null_pointer should be instead. * The minimum version of the [4]MPFR library required for building GCC has been increased to version 3.1.0 (released 2011-10-03). * The automatic template instantiation at link time (-frepo) has been removed. * The --param allow-store-data-races internal parameter has been removed in favor of a new official option -fallow-store-data-races. While default behavior is unchanged and the new option allows to correctly maintain a per compilation unit setting across link-time optimization, alteration of the default via --param allow-store-data-races will now be diagnosed and build systems have to be adjusted accordingly. * Offloading to Heterogeneous System Architecture Intermediate Language (HSAIL) has been deprecated and will likely be removed in a future release. * The type of the std::iterator base class of std::istreambuf_iterator was changed in C++98 mode to be consistent with C++11 and later standards. See the [5]libstdc++ notes below for more details. General Improvements * New built-in functions: + The [6]__has_builtin built-in preprocessor operator can be used to query support for built-in functions provided by GCC and other compilers that support it. + __builtin_roundeven for the corresponding function from ISO/IEC TS 18661. * New command-line options: + [7]-fallocation-dce removes unneeded pairs of new and delete operators. + [8]-fprofile-partial-training can now be used to inform the compiler that code paths not covered by the training run should not be optimized for size. + [9]-fprofile-reproducible controls level of reproducibility of profile gathered by [10]-fprofile-generate. This makes it possible to rebuild program with same outcome which is useful, for example, for distribution packages. + [11]-fprofile-prefix-path can be used in combination with -fprofile-generate=profile_dir and -fprofile-use=profile_dir to inform GCC where the base directory of build source tree is in case it differs between instrumentation and optimized builds. + [12]-fanalyzer enables a new static analysis pass and associated warnings. This pass performs a time-consuming exploration of paths through the code in the hope of detecting various common errors, such as double-free bugs. This option should be regarded as experimental in this release. In particular, analysis of non-C code is unlikely to work. * Inter-procedural optimization improvements: + The inter-procedural scalar replacement of aggregates (IPA-SRA) pass was re-implemented to work at link-time and can now also remove computing and returning unused return values. + [13]-finline-functions is now enabled at -O2 and was retuned for better code size versus runtime performance trade-offs. Inliner heuristics was also significantly sped up to avoid negative impact to -flto -O2 compile times. + Inliner heuristics and function cloning can now use value-range information to predict effectivity of individual transformations. + During link-time optimization the C++ One Definition Rule is used to increase precision of type based alias analysis. * Link-time optimization improvements: + A new binary [14]lto-dump has been added. It dumps various information about LTO bytecode object files. + The parallel phase of the LTO can automatically detect a running make's jobserver or fall back to number of available cores. + The LTO bytecode can be compressed with the [15]zstd algorithm. The configure script automatically detects zstd support. + Most --param values can now be specified at translation unit granularity. This includes all parameters controlling the inliner and other inter-procedural optimizations. Unlike earlier releases, GCC 10 will ignore parameters controlling optimizations specified at link-time and apply parameters specified at compile-time in the same manner as done for optimization flags. * Profile driven optimization improvements: + Profile maintenance during compilation and hot/cold code partitioning have been improved. + Using [16]-fprofile-values, an instrumented binary can track multiple values (up to 4) for e.g. indirect calls and provide more precise profile information. New Languages and Language-Specific Improvements * Version 2.6 of the [17]OpenACC specification is now supported by the C, C++ and Fortran compilers. See the [18]implementation status section on the OpenACC wiki page and the [19]run-time library documentation for further information. * GCC 10 adds a number of newly implemented [20]OpenMP 5.0 features such as conditional lastprivate clause, scan and loop directives, order(concurrent) and use_device_addr clauses support, if clause on simd construct, and partial support for the declare variant directive, getting closer to full support of the OpenMP 5.0 standard. * OpenMP and OpenACC now support [21]offloading to AMD Radeon (GCN) GPUs; supported are the third-generation Fiji (fiji) and the fifth-generation VEGA 10/VEGA 20 (gfx900 or gfx906). C family * New attributes: + The access function and type attribute has been added to describe how a function accesses objects passed to it by pointer or reference, and to associate such arguments with integer arguments denoting the objects' sizes. The attribute is used to enable the detection of invalid accesses by user-defined functions, such as those diagnosed by -Wstringop-overflow. + The symver attribute can be used to bind symbols to specific version nodes on ELF platforms. This is preferred to using inline assembly with GNU as symver directive because the latter is not compatible with link-time optimizations. * New warnings: + [22]-Wstring-compare, enabled by -Wextra, warns about equality and inequality expressions between zero and the result of a call to either strcmp and strncmp that evaluate to a constant as a result of the length of one argument being greater than the size of the array pointed to by the other. + [23]-Wzero-length-bounds, enabled by -Warray-bounds, warns about accesses to elements of zero-length arrays that might overlap other members of the same object. * Enhancements to existing warnings: + [24]-Warray-bounds detects more out-of-bounds accesses to member arrays as well as accesses to elements of zero-length arrays. + [25]-Wformat-overflow makes full use of string length information computed by the strlen optimization pass. + [26]-Wrestrict detects overlapping accesses to dynamically allocated objects. + [27]-Wreturn-local-addr diagnoses more instances of return statements returning addresses of automatic variables. + [28]-Wstringop-overflow detects more out-of-bounds stores to member arrays including zero-length arrays, dynamically allocated objects and variable length arrays, as well as more instances of reads of unterminated character arrays by string built-in functions. The warning also detects out-of-bounds accesses by calls to user-defined functions declared with the new attribute access. + [29]-Warith-conversion re-enables warnings from -Wconversion, -Wfloat-conversion, and -Wsign-conversion that are now off by default for an expression where the result of an arithmetic operation will not fit in the target type due to promotion, but the operands of the expression do fit in the target type. * Extended characters in identifiers may now be specified directly in the input encoding (UTF-8, by default), in addition to the UCN syntax (\uNNNN or \UNNNNNNNN) that is already supported: static const int π = 3; int get_naïve_pi() { return π; } C * Several new features from the upcoming C2X revision of the ISO C standard are supported with -std=c2x and -std=gnu2x. Some of these features are also supported as extensions when compiling for older language versions. In addition to the features listed, some features previously supported as extensions and now added to the C standard are enabled by default in C2X mode and not diagnosed with -std=c2x -Wpedantic. + The [[]] attribute syntax is supported, as in C++. Existing attributes can be used with this syntax in forms such as [[gnu::const]]. The standard attributes [[deprecated]], [[fallthrough]] and [[maybe_unused]] are supported. + UTF-8 character constants using the u8'' syntax are supported. + defines macros FLT_NORM_MAX, DBL_NORM_MAX and LDBL_NORM_MAX. + When decimal floating-point arithmetic is supported, defines macros DEC32_TRUE_MIN, DEC64_TRUE_MIN and DEC128_TRUE_MIN, in addition to the macros that were previously only defined if __STDC_WANT_DEC_FP__ was defined before including . + In C2X mode, empty parentheses in a function definition give that function a type with a prototype for subsequent calls; other old-style function definitions are diagnosed by default in C2X mode. + The strftime format checking supports the %OB and %Ob formats. + In C2X mode, -fno-fp-int-builtin-inexact is enabled by default. * GCC now defaults to -fno-common. As a result, global variable accesses are more efficient on various targets. In C, global variables with multiple tentative definitions now result in linker errors. With -fcommon such definitions are silently merged during linking. C++ * Several C++20 features have been implemented: + Concepts, including P0734R0, P0857R0, P1084R2, P1141R2, P0848R3, P1616R1, P1452R2 + P1668R1, Permitting Unevaluated inline-assembly in constexpr Functions + P1161R3, Deprecate a[b,c] + P0848R3, Conditionally Trivial Special Member Functions + P1091R3, Extending structured bindings + P1143R2, Adding the constinit keyword + P1152R4, Deprecating volatile + P0388R4, Permit conversions to arrays of unknown bound + P0784R7, constexpr new + P1301R4, [[nodiscard("with reason")]] + P1814R0, class template argument deduction for alias templates + P1816R0, class template argument deduction for aggregates + P0960R3, Parenthesized initialization of aggregates + P1331R2, Allow trivial default initialization in constexpr contexts + P1327R1, Allowing dynamic_cast and polymorphic typeid in constexpr contexts + P0912R5, Coroutines (requires -fcoroutines) * Several C++ Defect Reports have been resolved, e.g.: + DR 1560, lvalue-to-rvalue conversion in ?: + DR 1813, __is_standard_layout for a class with repeated bases + DR 2094, volatile scalars are trivially copyable, + DR 2096, constraints on literal unions + DR 2413, typename in conversion-function-ids + DR 2352, Similar types and reference binding + DR 1601, Promotion of enumeration with fixed underlying type + DR 330, Qualification conversions and pointers to arrays of pointers + DR 1307, Overload resolution based on size of array initializer-list + DR 1710, Missing template keyword in class-or-decltype * New warnings: + [30]-Wmismatched-tags, disabled by default, warns about declarations of structs, classes, and class templates and their specializations with a class-key that does not match either the definition or the first declaration if no definition is provided. The option is provided to ease portability to Windows-based compilers. + [31]-Wredundant-tags, disabled by default, warns about redundant class-key and enum-key in contexts where the key can be eliminated without causing an syntactic ambiguity. * G++ can now detect modifying constant objects in constexpr evaluation (which is undefined behavior). * G++ no longer emits bogus -Wsign-conversion warnings with explicit casts. * Narrowing is now detected in more contexts (e.g., case values). * Memory consumption of the compiler has been reduced in constexpr evaluation. * The noexcept-specifier is now properly treated as a complete-class context as per [class.mem]. * The attribute deprecated can now be used on namespaces too. * The ABI of passing and returning certain C++ classes by value changed on several targets in GCC 10, including [32]AArch64, [33]ARM, [34]PowerPC ELFv2, [35]S/390 and [36]Itanium. These changes affect classes with a zero-sized subobject (an empty base class, or data member with the [[no_unique_address]] attribute) where all other non-static data members have the same type (this is called a "homogeneous aggregate" in some ABI specifications, or if there is only one such member, a "single element"). In -std=c++17 and -std=c++20 modes, classes with an empty base class were not considered to have a single element or to be a homogeneous aggregate, and so could be passed differently (in the wrong registers or at the wrong stack address). This could make code compiled with -std=c++17 and -std=c++14 ABI incompatible. This has been corrected and the empty bases are ignored in those ABI decisions, so functions compiled with -std=c++14 and -std=c++17 are now ABI compatible again. Example: struct empty {}; struct S : empty { float f; }; void f(S);. Similarly, in classes containing non-static data members with empty class types using the C++20 [[no_unique_address]] attribute, those members weren't ignored in the ABI argument passing decisions as they should be. Both of these ABI changes are now diagnosed with -Wpsabi. Runtime Library (libstdc++) * Improved experimental C++2a support, including: + Library concepts in and . + Constrained algorithms in , , and (thanks to Patrick Palka). + New algorithms shift_left and shift_right (thanks to Patrick Palka). + std::span (thanks to JeanHeyd Meneide). + Three-way comparisons in and throughout the library. + Constexpr support in and elsewhere (thanks to Edward Smith-Rowland). + and std::jthread (thanks to Thomas Rodgers). + std::atomic_ref and std::atomic. + Integer comparison functions (cmp_equal, cmp_less etc.). + std::ssize, std::to_array. + std::construct_at, std::destroy, constexpr std::allocator. + Mathematical constants in . * Support for RDSEED in std::random_device. * Reduced header dependencies, leading to faster compilation for some code. * The std::iterator base class of std::istreambuf_iterator was changed in C++98 mode to be consistent with C++11 and later standards. This is expected to have no noticeable effect except in the unlikely case of a class which has potentially overlapping subobjects of type std::istreambuf_iterator and another iterator type with a std::iterator base class. The layout of such a type might change when compiled as C++98. [37]Bug 92285 has more details and concrete examples. D * Support for static foreach has been implemented. * Aliases can now be created directly from any __traits that return symbols or tuples. Previously, an AliasSeq was necessary in order to alias their return. * It is now possible to detect the language ABI specified for a struct, class, or interface using __traits(getLinkage, ...). * Support for core.math.toPrec intrinsics has been added. These intrinsics guarantee the rounding to specific floating-point precisions at specified points in the code. * Support for pragma(inline) has been implemented. Previously the pragma was recognized, but had no effect on the compilation. * Optional parentheses in asm operands are deprecated and will be removed in a future release. * All content imported files are now included in the make dependency list when compiling with -M. * Compiler recognized attributes provided by the gcc.attribute module will now take effect when applied to function prototypes as well as when applied to full function declarations. * Added a --enable-libphobos-checking configure option to control whether run-time checks are compiled into the D runtime library. * Added a --with-libphobos-druntime-only configure option to indicate whether to build only the core D runtime library, or both the core and standard libraries into libphobos. Fortran * use_device_addr of version 5.0 of the [38]OpenMP specification is now supported. Note that otherwise OpenMP 4.5 is partially supported in the Fortran compiler; the largest missing item is structure element mapping. * The default buffer size for I/O using unformatted files has been increased to 1048576. The buffer size for can now be set at runtime via the environment variables GFORTRAN_FORMATTED_BUFFER_SIZE and GFORTRAN_UNFORMATTED_BUFFER_SIZE for formatted and unformatted files, respectively. * Mismatches between actual and dummy argument lists in a single file are now rejected with an error. Use the new option -fallow-argument-mismatch to turn these errors into warnings; this option is implied with -std=legacy. -Wargument-mismatch has been removed. * The handling of a BOZ literal constant has been reworked to provide better conformance to the Fortran 2008 and 2018 standards. In these Fortran standards, a BOZ literal constant is a typeless and kindless entity. As a part of the rework, documented and undocumented extensions to the Fortran standard now emit errors during compilation. Some of these extensions are permitted with the -fallow-invalid-boz option, which degrades the error to a warning and the code is compiled as with older gfortran. * At any optimization level except-Os, gfortran now uses inline packing for arguments instead of calling a library routine. If the source contains a large number of arguments that need to be repacked, code size or time for compilation can become excessive. If that is the case, -fno-inline-arg-packing can be used to disable inline argument packing. * Legacy extensions: + For formatted input/output, if the explicit widths after the data-edit descriptors I, F and G have been omitted, default widths are used. + A blank format item at the end of a format specification, i.e. nothing following the final comma, is allowed. Use the option -fdec-blank-format-item; this option is implied with -fdec. + The existing support for AUTOMATIC and STATIC attributes has been extended to allow variables with the AUTOMATIC attribute to be used in EQUIVALENCE statements. Use -fdec-static; this option is implied by -fdec. + Allow character literals in assignments and DATA statements for numeric (INTEGER, REAL, or COMPLEX) or LOGICAL variables. Use the option -fdec-char-conversions; this option is implied with -fdec. + DEC comparisons, i.e. allow Hollerith constants to be used in comparisons with INTEGER, REAL, COMPLEX and CHARACTER expressions. Use the option -fdec. * Character type names in errors and warnings now include len in addition to kind; * is used for assumed length. The kind is omitted if it is the default kind. Examples: CHARACTER(12), CHARACTER(6,4). * CO_BROADCAST now supports derived type variables including objects with allocatable components. In this case, the optional arguments STAT= and ERRMSG= are currently ignored. * The handling of module and submodule names has been reworked to allow the full 63-character length mandated by the standard. Previously symbol names were truncated if the combined length of module, submodule, and function name exceeded 126 characters. This change therefore breaks the ABI, but only for cases where this 126 character limit was exceeded. Go * GCC 10 provides a complete implementation of the Go 1.14.6 user packages. libgccjit * The libgccjit API gained four new entry points: + [39]gcc_jit_version_major, [40]gcc_jit_version_minor, and [41]gcc_jit_version_patchlevel for programmatically checking the libgccjit version from client code, and + [42]gcc_jit_context_new_bitfield New Targets and Target Specific Improvements AArch64 & arm * The AArch64 and arm ports now support condition flag output constraints in inline assembly, as indicated by the __GCC_ASM_FLAG_OUTPUTS__. On arm this feature is only available for A32 and T32 targets. Please refer to the documentation for more details. AArch64 * There have been several improvements related to the Scalable Vector Extension (SVE): + The SVE ACLE types and intrinsics are now supported. They can be accessed using the header file arm_sve.h. + It is now possible to create fixed-length SVE types using the arm_sve_vector_bits attribute. For example: #if __ARM_FEATURE_SVE_BITS==512 typedef svint32_t vec512 __attribute__((arm_sve_vector_bits(512))); typedef svbool_t pred512 __attribute__((arm_sve_vector_bits(512))); #endif + -mlow-precision-div, -mlow-precision-sqrt and -mlow-precision-recip-sqrt now work for SVE. + -msve-vector-bits=128 now generates vector-length-specific code for little-endian targets. It continues to generate vector-length-agnostic code for big-endian targets, just as previous releases did for all targets. + The vectorizer is now able to use extending loads and truncating stores, including gather loads and scatter stores. + The vectorizer now compares the cost of vectorizing with SVE and vectorizing with Advanced SIMD and tries to pick the best one. Previously it would always use SVE if possible. + If a vector loop uses Advanced SIMD rather than SVE, the vectorizer now considers using SVE to vectorize the left-over elements (the “scalar tail” or “epilog”). + Besides these specific points, there have been many general improvements to the way that the vectorizer uses SVE. * The -mbranch-protection=pac-ret option now accepts the optional argument +b-key extension to perform return address signing with the B-key instead of the A-key. * The option -moutline-atomics has been added to aid deployment of the Large System Extensions (LSE) on GNU/Linux systems built with a baseline architecture targeting Armv8-A. When the option is specified code is emitted to detect the presence of LSE instructions at runtime and use them for standard atomic operations. For more information please refer to the documentation. * The Transactional Memory Extension is now supported through ACLE intrinsics. It can be enabled through the +tme option extension (for example, -march=armv8.5-a+tme). * A number of features from Armv8.5-A are now supported through ACLE intrinsics. These include: + The random number instructions that can be enabled through the (already present in GCC 9.1) +rng option extension. + Floating-point intrinsics to round to integer instructions from Armv8.5-A when targeting -march=armv8.5-a or later. + Memory Tagging Extension intrinsics enabled through the +memtag option extension. * Similarly, the following Armv8.6-A features are now supported through ACLE intrinsics: + The bfloat16 extension. This extension is enabled automatically when Armv8.6-A is selected (such as by -march=armv8.6-a). It can also be enabled for Armv8.2-A and later using the +bf16 option extension. + The Matrix Multiply extension. This extension is split into three parts, one for each supported data type: o Support for 8-bit integer matrix multiply instructions. This extension is enabled automatically when Armv8.6-A is selected. It can also be enabled for Armv8.2-A and later using the +i8mm option extension. o Support for 32-bit floating-point matrix multiply instructions. This extension can be enabled using the +f32mm option extension, which also has the effect of enabling SVE. o Support for 64-bit floating-point matrix multiply instructions. This extension can be enabled using the +f64mm option extension, which likewise has the effect of enabling SVE. * SVE2 is now supported through ACLE intrinsics and (to a limited extent) through autovectorization. It can be enabled through the +sve2 option extension (for example, -march=armv8.5-a+sve2). Additional extensions can be enabled through +sve2-sm4, +sve2-aes, +sve2-sha3 and +sve2-bitperm. * Support has been added for the following processors (GCC identifiers in parentheses): + Arm Cortex-A77 (cortex-a77). + Arm Cortex-A76AE (cortex-a76ae). + Arm Cortex-A65 (cortex-a65). + Arm Cortex-A65AE (cortex-a65ae). + Arm Cortex-A34 (cortex-a34). + Marvell ThunderX3 (thunderx3t110). The GCC identifiers can be used as arguments to the -mcpu or -mtune options, for example: -mcpu=cortex-a77 or -mtune=cortex-a65ae or as arguments to the equivalent target attributes and pragmas. arm * Support for the FDPIC ABI has been added. It uses 64-bit function descriptors to represent pointers to functions, and enables code sharing on MMU-less systems. The corresponding target triple is arm-uclinuxfdpiceabi, and the C library is uclibc-ng. * Support has been added for the Arm EABI on NetBSD through the arm*-*-netbsdelf-*eabi* triplet. * The handling of 64-bit integer operations has been significantly reworked and improved leading to improved performance and reduced stack usage when using 64-bit integral data types. The option -mneon-for-64bits is now deprecated and will be removed in a future release. * Support has been added for the following processors (GCC identifiers in parentheses): + Arm Cortex-A77 (cortex-a77). + Arm Cortex-A76AE (cortex-a76ae). + Arm Cortex-M35P (cortex-m35p). + Arm Cortex-M55 (cortex-m55). The GCC identifiers can be used as arguments to the -mcpu or -mtune options, for example: -mcpu=cortex-a77 or -mtune=cortex-m35p. * Support has been extended for the ACLE [43]data-processing intrinsics to include 32-bit SIMD, saturating arithmetic, 16-bit multiplication and other related intrinsics aimed at DSP algorithm optimization. * Support for -mpure-code in Thumb-1 (v6m) has been added: this M-profile feature is no longer restricted to targets with MOVT. For example, -mcpu=cortex-m0 now supports this option. * Support for the [44]Armv8.1-M Mainline Architecture has been added. + Armv8.1-M Mainline can be enabled by using the -march=armv8.1-m.main command-line option. * Support for the [45]MVE beta ACLE intrinsics has been added. These intrinsics can be enabled by including the arm_mve.h header file and passing the +mve or +mve.fp option extensions (for example: -march=armv8.1-m.main+mve). * Support for the Custom Datapath Extension beta ACLE [46]intrinsics has been added. * Support for Armv8.1-M Mainline Security Extensions architecture has been added. The -mcmse option, when used in combination with an Armv8.1-M Mainline architecture (for example: -march=armv8.1-m.main -mcmse), now leads to the generation of improved code sequences when changing security states. AMD Radeon (GCN) * Code generation and in particular vectorization support have been much improved. ARC * The interrupt service routine functions save all used registers, including extension registers and auxiliary registers used by Zero Overhead Loops. * Improve code size by using multiple short instructions instead of a single long mov or ior instruction when its long immediate constant is known. * Fix usage of the accumulator register for ARC600. * Fix issues with uncached attribute. * Remove -mq-class option. * Improve 64-bit integer addition and subtraction operations. AVR * Support for the XMEGA-like devices ATtiny202, ATtiny204, ATtiny402, ATtiny404, ATtiny406, ATtiny804, ATtiny806, ATtiny807, ATtiny1604, ATtiny1606, ATtiny1607, ATmega808, ATmega809, ATmega1608, ATmega1609, ATmega3208, ATmega3209, ATmega4808, ATmega4809 has been added. * A new command-line option -nodevicespecs has been added. It allows to provide a custom device-specs file by means of avr-gcc -nodevicespecs -specs=my-spec-file and without the need to provide options -B and -mmcu=. See [47]AVR command-line options for details. This feature is also available in GCC 9.3+ and GCC 8.4+. * New command-line options -mdouble=[32,64] and -mlong-double=[32,64] have been added. They allow to choose the size (in bits) of the double and long double types, respectively. Whether or not the mentioned layouts are available, whether the options act as a multilib option, and the default for either option are controlled by the new [48]AVR configure options --with-double= and --with-long-double=. * A new configure option --with-libf7= has been added. It controls to which level avr-libgcc provides 64-bit floating point support by means of [49]Libf7. * A new configure option --with-double-comparison= has been added. It's unlikely you need to set this option by hand. IA-32/x86-64 * Support to expand __builtin_roundeven into the appropriate SSE 4.1 instruction has been added. * New ISA extension support for Intel ENQCMD was added to GCC. ENQCMD intrinsics are available via the -menqcmd compiler switch. * GCC now supports the Intel CPU named Cooperlake through -march=cooperlake. The switch enables the AVX512BF16 ISA extensions. * GCC now supports the Intel CPU named Tigerlake through -march=tigerlake. The switch enables the MOVDIRI MOVDIR64B AVX512VP2INTERSECT ISA extensions. MIPS * The mips*-*-linux* targets now mark object files with appropriate GNU-stack note, facilitating use of non-executable stack hardening on GNU/Linux. The soft-float targets have this feature enabled by default, while for hard-float targets it is required for GCC to be configured with --with-glibc-version=2.31 against glibc 2.31 or later. PowerPC / PowerPC64 / RS6000 * Many vector builtins have been listed as deprecated in the [50]64-Bit ELF V2 ABI Specification for quite a number of years. The vector builtins listed in Tables A.8 through A.10 are now deprecated for GCC 10, and will likely be removed from support in GCC 11. Note that this does not result in any loss of function. These deprecated builtins generally provide somewhat nonsensical argument lists (for example, mixing signed, unsigned, and bool vector arguments arbitrarily), or are duplicate builtins that are inconsistent with the expected naming scheme. We expect that this will be unlikely to affect much if any code, and any required code changes will be trivial. PRU * A new back end targeting TI PRU I/O processors has been contributed to GCC. RISC-V * The riscv*-*-* targets now require GNU binutils version 2.30 or later, to support new assembly instructions produced by GCC. V850 * The ABI for V850 nested functions has been changed. Previously the V850 port used %r20 for the static chain pointer, now the port uses %r19. This corrects a long standing latent bug in the v850 port where a call to a nested function would unexpectedly change the value in %r20. Operating Systems Improvements for plugin authors * GCC diagnostics can now have a chain of events associated with them, describing a path through the code that triggers the problem. These can be printed by the diagnostics subsystem in various ways, controlled by the [51]-fdiagnostics-path-format option, or captured in JSON form via [52]-fdiagnostics-format=json. * GCC diagnostics can now be associated with [53]CWE weakness identifiers, which will appear on the standard error stream, and in the JSON output from [54]-fdiagnostics-format=json. Other significant improvements * To allow inline expansion of both memcpy and memmove, the existing movmem instruction patterns used for non-overlapping memory copies have been renamed to cpymem. The movmem name is now used for overlapping memory moves, consistent with the library functions memcpy and memmove. * For many releases, when GCC emits a warning it prints the option controlling that warning. As of GCC 10, that option text is now a clickable hyperlink for the documentation of that option (assuming a [55]sufficiently capable terminal). This behavior can be controlled via a new [56]-fdiagnostics-urls option (along with various environment variables and heuristics documented with that option). GCC 10.1 This is the [57]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 10.1 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 10.2 This is the [58]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 10.2 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 10.3 This is the [59]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 10.3 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Target Specific Changes AArch64 * A bug with the Random Number intrinsics in the arm_acle.h header that resulted in an incorrect status result being returned has been fixed. * GCC now supports the Fujitsu A64FX. The associated -mcpu and -mtune options are -mcpu=a64fx and -mtune=a64fx respectively. In particular, -mcpu=a64fx generates code for Armv8.2-A with SVE and tunes the code for the A64FX. This includes tuning the SVE code, although by default the code is still length-agnostic and so works for all SVE implementations. Adding -msve-vector-bits=512 makes the code specific to 512-bit SVE. x86-64 * GCC 10.3 supports AMD CPUs based on the znver3 core via -march=znver3. GCC 10.4 This is the [60]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 10.4 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Target Specific Changes x86-64 * The x86-64 ABI of passing and returning structures with a 64-bit integer vector changed in GCC 10.1 when MMX is disabled. Disabling MMX no longer changes how they are passed nor returned. This ABI change is now diagnosed with -Wpsabi. GCC 10.5 This is the [61]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 10.5 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). For questions related to the use of GCC, please consult these web pages and the [62]GCC manuals. If that fails, the [63]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [64]gcc@gcc.gnu.org. All of [65]our lists have public archives. Copyright (C) [66]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [67]maintained by the GCC team. Last modified 2023-07-07. 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https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Optimize-Options.html#index-finline-functions 14. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/lto-dump.html 15. https://facebook.github.io/zstd/ 16. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Optimize-Options.html#index-fprofile-values 17. https://www.openacc.org/ 18. https://gcc.gnu.org/wiki/OpenACC/Implementation Status#status-10 19. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/libgomp/#toc-Enabling-OpenACC-1 20. https://www.openmp.org/specifications/ 21. https://gcc.gnu.org/wiki/Offloading 22. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Warning-Options.html#index-Wstring-compare 23. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Warning-Options.html#index-Wzero-length-bounds 24. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Warning-Options.html#index-Warray-bounds 25. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Warning-Options.html#index-Wformat-overflow 26. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Warning-Options.html#index-Wrestrict 27. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Warning-Options.html#index-Wreturn-local-addr 28. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Warning-Options.html#index-Wstringop-overflow 29. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Warning-Options.html#index-Warith-conversion 30. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/C_002b_002b-Dialect-Options.html#index-Wmismatched-tags 31. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/C_002b_002b-Dialect-Options.html#index-Wredundant-tags 32. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94383 33. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94711 34. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94707 35. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94704 36. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94706 37. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92285 38. https://www.openmp.org/specifications/ 39. https://gcc.gnu.org/onlinedocs/jit/topics/compatibility.html#c.gcc_jit_version_major 40. https://gcc.gnu.org/onlinedocs/jit/topics/compatibility.html#c.gcc_jit_version_minor 41. https://gcc.gnu.org/onlinedocs/jit/topics/compatibility.html#c.gcc_jit_version_patchlevel 42. https://gcc.gnu.org/onlinedocs/jit/topics/types.html#c.gcc_jit_context_new_bitfield 43. https://developer.arm.com/documentation/101028/0009/Data-processing-intrinsics 44. https://developer.arm.com/Architectures/M-Profile Architecture 45. https://developer.arm.com/architectures/instruction-sets/intrinsics/ 46. https://developer.arm.com/documentation/101028/0010/Custom-Datapath-Extension 47. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/AVR-Options.html#index-nodevicespecs 48. https://gcc.gnu.org/install/configure.html#avr 49. https://gcc.gnu.org/wiki/avr-gcc#Libf7 50. https://openpowerfoundation.org/?resource_lib=64-bit-elf-v2-abi-specification-power-architecture 51. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-path-format 52. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-format 53. https://cwe.mitre.org/ 54. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-format 55. https://gist.github.com/egmontkob/eb114294efbcd5adb1944c9f3cb5feda 56. https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-urls 57. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=10.0 58. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=10.2 59. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=10.3 60. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=10.4 61. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=10.5 62. https://gcc.gnu.org/onlinedocs/ 63. mailto:gcc-help@gcc.gnu.org 64. mailto:gcc@gcc.gnu.org 65. https://gcc.gnu.org/lists.html 66. https://www.fsf.org/ 67. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-9/index.html GCC 9 Release Series (This release series is no longer supported.) May 27, 2022 The [1]GNU project and the GCC developers are pleased to announce the release of GCC 9.5. This release is a bug-fix release, containing fixes for regressions in GCC 9.4 relative to previous releases of GCC. Release History GCC 9.5 May 27, 2022 ([2]changes, [3]documentation) GCC 9.4 June 1, 2021 ([4]changes, [5]documentation) GCC 9.3 Mar 12, 2020 ([6]changes, [7]documentation) GCC 9.2 Aug 12, 2019 ([8]changes, [9]documentation) GCC 9.1 May 3, 2019 ([10]changes, [11]documentation) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [12]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [13]GCC project web site or contact the [14]GCC development mailing list. To obtain GCC please use [15]our mirror sites or [16]our version control system. For questions related to the use of GCC, please consult these web pages and the [17]GCC manuals. If that fails, the [18]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [19]gcc@gcc.gnu.org. All of [20]our lists have public archives. Copyright (C) [21]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [22]maintained by the GCC team. Last modified 2024-05-30. References 1. http://www.gnu.org/ 2. https://gcc.gnu.org/gcc-9/changes.html 3. https://gcc.gnu.org/onlinedocs/9.5.0/ 4. https://gcc.gnu.org/gcc-9/changes.html 5. https://gcc.gnu.org/onlinedocs/9.4.0/ 6. https://gcc.gnu.org/gcc-9/changes.html 7. https://gcc.gnu.org/onlinedocs/9.3.0/ 8. https://gcc.gnu.org/gcc-9/changes.html 9. https://gcc.gnu.org/onlinedocs/9.2.0/ 10. https://gcc.gnu.org/gcc-9/changes.html 11. https://gcc.gnu.org/onlinedocs/9.1.0/ 12. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Contributors.html 13. https://gcc.gnu.org/index.html 14. mailto:gcc@gcc.gnu.org 15. https://gcc.gnu.org/mirrors.html 16. https://gcc.gnu.org/git.html 17. https://gcc.gnu.org/onlinedocs/ 18. mailto:gcc-help@gcc.gnu.org 19. mailto:gcc@gcc.gnu.org 20. https://gcc.gnu.org/lists.html 21. https://www.fsf.org/ 22. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-9/changes.html GCC 9 Release Series Changes, New Features, and Fixes This page is a "brief" summary of some of the huge number of improvements in GCC 9. You may also want to check out our [1]Porting to GCC 9 page and the [2]full GCC documentation. Caveats * On Arm targets (arm*-*-*), [3]a bug in the implementation of the procedure call standard (AAPCS) in the GCC 6, 7 and 8 releases has been fixed: a structure containing a bit-field based on a 64-bit integral type and where no other element in a structure required 64-bit alignment could be passed incorrectly to functions. This is an ABI change. If the option -Wpsabi is enabled (on by default) the compiler will emit a diagnostic note for code that might be affected. * Support for a number of older systems and recently unmaintained or untested target ports of GCC has been declared obsolete in GCC 9. Unless there is activity to revive them, the next release of GCC will have their sources permanently removed. The following ports for individual systems on particular architectures have been obsoleted: + Solaris 10 (*-*-solaris2.10). Details can be found in the [4]announcement. + Cell Broadband Engine SPU (spu*-*-*). Details can be found in the [5]announcement. * A change to the C++ std::rotate algorithm in GCC 9.1.0 can cause ABI incompatibilities with object files compiled with other versions of GCC. If the std::rotate algorithm is called with an empty range then it might cause a divide-by-zero error (as a SIGFPE signal) and crash. The change has been reverted for GCC 9.2.0 and future releases. For more details see [6]Bug 90920. The problem can be avoided by recompiling any objects that might call std::rotate with an empty range, so that the GCC 9.1.0 definition of std::rotate is not used. * The automatic template instantiation at link time ([7]-frepo) has been deprecated and will be removed in a future release. * The --with-default-libstdcxx-abi=gcc4-compatible configure option is broken in the 9.1 and 9.2 releases, producing a shared library with missing symbols (see [8]Bug 90361). As a workaround, configure without that option and build GCC as normal, then edit the installed headers to define the _GLIBCXX_USE_CXX11_ABI macro to 0. General Improvements The following GCC command line options have been introduced or improved. * All command line options that take a byte-size argument accept 64-bit integers as well as standard SI and IEC suffixes such as kb and KiB, MB and MiB, or GB and GiB denoting the corresponding multiples of bytes. See [9]Invoking GCC for more. * A new option [10]-flive-patching=[inline-only-static|inline-clone] generates code suitable for live patching. At the same time it provides multiple-level control over IPA optimizations. See the user guide for more details. * A new option, --completion, has been added to provide more fine option completion in a shell. It is intended to be used by Bash-completion. * GCC's diagnostics now print source code with a left margin showing line numbers, configurable with [11]-fno-diagnostics-show-line-numbers. GCC's diagnostics can also now label regions of the source code to show pertinent information, such as the types within an expression. $ g++ t.cc t.cc: In function 'int test(const shape&, const shape&)': t.cc:15:4: error: no match for 'operator+' (operand types are 'boxed_value' and 'boxed_value') 14 | return (width(s1) * height(s1) | ~~~~~~~~~~~~~~~~~~~~~~ | | | boxed_value<[...]> 15 | + width(s2) * height(s2)); | ^ ~~~~~~~~~~~~~~~~~~~~~~ | | | boxed_value<[...]> These labels can be disabled via [12]-fno-diagnostics-show-labels. * A new option [13]-fdiagnostics-format=json has been introduced for emitting diagnostics in a machine-readable format. * The alignment-related options [14]-falign-functions, [15]-falign-labels, [16]-falign-loops, and [17]-falign-jumps received support for a secondary alignment (e.g. -falign-loops=n:m:n2:m2). * New pair of profiling options ([18]-fprofile-filter-files and [19]-fprofile-exclude-files) has been added. The options help to filter which source files are instrumented. * AddressSanitizer generates more compact redzones for automatic variables. That helps to reduce memory footprint of a sanitized binary. * Numerous improvements have been made to the output of [20]-fopt-info. Messages are now prefixed with optimized, missed, or note, rather than the old behavior of all being prefixed with note. The output from -fopt-info can now contain information on inlining decisions: $ g++ -c inline.cc -O2 -fopt-info-inline-all inline.cc:24:11: note: Considering inline candidate void foreach(T, T, void (*)( E)) [with T = char**; E = char*]/2. inline.cc:24:11: optimized: Inlining void foreach(T, T, void (*)(E)) [with T = char**; E = char*]/2 into int main(int, char**)/1. inline.cc:19:12: missed: not inlinable: void inline_me(char*)/0 -> int std::pu ts(const char*)/3, function body not available inline.cc:13:8: optimized: Inlined void inline_me(char*)/4 into int main(int, c har**)/1 which now has time 127.363637 and size 11, net change of +0. Unit growth for small function inlining: 16->16 (0%) Inlined 2 calls, eliminated 1 functions The output from the vectorizer has been rationalized so that failed attempts to vectorize a loop are displayed in the form [LOOP-LOCATION]: couldn't vectorize this loop [PROBLEM-LOCATION]: because of [REASON] rather than an exhaustive log of all decisions made by the vectorizer. For example: $ gcc -c v.c -O3 -fopt-info-all-vec v.c:7:3: missed: couldn't vectorize loop v.c:10:7: missed: statement clobbers memory: __asm__ __volatile__("" : : : "me mory"); v.c:3:6: note: vectorized 0 loops in function. v.c:10:7: missed: statement clobbers memory: __asm__ __volatile__("" : : : "me mory"); The old behavior can be obtained via a new -internals suboption of -fopt-info. * A new option, [21]-fsave-optimization-record has been added, which writes a SRCFILE.opt-record.json.gz file describing the optimization decisions made by GCC. This is similar to the output of -fopt-info, but with additional metadata such as the inlining chain, and profile information (if available). * Inter-procedural propagation of stack alignment can now be controlled by [22]-fipa-stack-alignment. * Propagation of addressability, readonly, and writeonly flags on static variables can now be controlled by [23]-fipa-reference-addressable. The following built-in functions have been introduced. * [24]__builtin_expect_with_probability to provide branch prediction probability hints to the optimizer. * [25]__builtin_has_attribute determines whether a function, type, or variable has been declared with some attribute. * [26]__builtin_speculation_safe_value can be used to help mitigate against unsafe speculative execution. The following attributes have been introduced. * The [27]copy function attribute has been added. The attribute can also be applied to type definitions and to variable declarations. A large number of improvements to code generation have been made, including but not limited to the following. * Switch expansion has been improved by using a different strategy (jump table, bit test, decision tree) for a subset of switch cases. * A linear function expression defined as a switch statement can be transformed by [28]-ftree-switch-conversion. For example: int foo (int how) { switch (how) { case 2: how = 205; break; case 3: how = 305; break; case 4: how = 405; break; case 5: how = 505; break; case 6: how = 605; break; } return how; } can be transformed into 100 * how + 5 (for values defined in the switch statement). * Inter-procedural optimization improvements: + Inliner defaults were tuned to better suit modern C++ codebases, especially when built with link time-optimizations. New parameters max-inline-insns-small, max-inline-insns-size, uninlined-function-insns, uninlined-function-time, uninlined-thunk-insns, and uninlined-thunk-time were added. + Hot/cold partitioning is now more precise and aggressive. + Improved scalability for very large translation units (especially when link-time optimizing large programs). * Profile driven optimization improvements: + [29]-fprofile-use now enables [30]-fversion-loops-for-strides, [31]-floop-interchange, [32]-floop-unroll-and-jam, [33]-ftree-loop-distribution. + Streaming of counter histograms was removed, which reduces the size of profile files. Histograms are computed on the fly with link-time optimization. + The parameter hot-bb-count-ws-permille was reduced from 999 to 990 to account for more precise histograms. * Link-time optimization improvements: + Types are now simplified prior to streaming resulting in significant reductions of LTO object file sizes and link-time memory use as well as improvements of link-time parallelism. + The default number of partitions (--param lto-partitions) was increased from 32 to 128 enabling effective use of CPUs with more than 32 hyperthreads. --param lto-max-streaming-parallelism can now be used to control the number of streaming processes. + Warnings on C++ One Decl Rule violations (-Wodr) are now more informative and produce fewer redundant results. Overall compile time of Firefox 66 and LibreOffice 6.2.3 on an 8-core machine was reduced by about 5% compared to GCC 8.3, and the size of LTO object files by 7%. LTO link time improves by 11% on an 8-core machine and scales significantly better for more parallel build environments. The serial stage of the link-time optimization is 28% faster consuming 20% less memory. The parallel stage now scales to up to 128 partitions rather than 32 and reduces memory use for every worker by 30%. The following improvements to the gcov command-line utility have been made. * The gcov tool received a new option [34]--use-hotness-colors (-q) that can provide perf-like coloring of hot functions. * The gcov tool has changed its intermediate format to a new JSON format. New Languages and Language specific improvements [35]OpenACC support in C, C++, and Fortran continues to be maintained and improved. Most of the OpenACC 2.5 specification is implemented. See the [36]implementation status section on the OpenACC wiki page for further information. C family * Version 5.0 of the [37]OpenMP specification is now partially supported in the C and C++ compilers. For details which features of OpenMP 5.0 are and which are not supported in the GCC 9 release see [38]this mail. * New extensions: + [39]__builtin_convertvector built-in for vector conversions has been added. * New warnings: + [40]-Waddress-of-packed-member, enabled by default, warns about an unaligned pointer value from the address of a packed member of a struct or union. * Enhancements to existing warnings: + [41]-Warray-bounds detects more instances of out-of-bounds indices. + [42]-Wattribute-alias also detects attribute mismatches between alias declarations and their targets, in addition to mismatches between their types. + [43]-Wformat-overflow and [44]-Wformat-truncation have been extended to all formatted input/output functions (where applicable) and enhanced to detect a subset of instances of reading past the end of unterminated constant character arrays in %s directives. + [45]-Wmissing-attributes detects instances of missing function attributes on declarations of aliases and weak references. + [46]-Wstringop-truncation also detects a subset of instances of reading past the end of unterminated constant character arrays, * If a macro is used with the wrong argument count, the C and C++ front ends now show the definition of that macro via a note. * The spelling corrector now considers transposed letters, and the threshold for similarity has been tightened, to avoid nonsensical suggestions. C * There is now experimental support for -std=c2x, to select support for the upcoming C2X revision of the ISO C standard. This standard is in the early stages of development and the only feature supported in GCC 9 is _Static_assert with a single argument (support for _Static_assert with two arguments was added in C11 and GCC 4.6). There are also new options -std=gnu2x, for C2X with GNU extensions, and -Wc11-c2x-compat, to warn for uses of features added in C2X (such warnings are also enabled by use of -Wpedantic if not using -std=c2x or -std=gnu2x). * New warnings: + [47]-Wabsolute-value warns for calls to standard functions that compute the absolute value of an argument when a more appropriate standard function is available. For example, calling abs(3.14) triggers the warning because the appropriate function to call to compute the absolute value of a double argument is fabs. The option also triggers warnings when the argument in a call to such a function has an unsigned type. This warning can be suppressed with an explicit type cast and it is also enabled by -Wextra. C++ * New warnings: + [48]-Wdeprecated-copy, implied by -Wextra, warns about the C++11 deprecation of implicitly declared copy constructor and assignment operator if one of them is user-provided. -Wdeprecated-copy-dtor also warns if the destructor is user-provided, as specified in C++11. + [49]-Winit-list-lifetime, on by default, warns about uses of std::initializer_list that are likely to result in a dangling pointer, such as returning or assigning from a temporary list. + [50]-Wredundant-move, implied by -Wextra, warns about redundant calls to std::move. + [51]-Wpessimizing-move, implied by -Wall, warns when a call to std::move prevents copy elision. + [52]-Wclass-conversion, on by default, warns when a conversion function will never be called due to the type it converts to. * The C++ front end has experimental support for some of the upcoming C++2a draft features with the -std=c++2a or -std=gnu++2a flags, including range-based for statements with initializer, default constructible and assignable stateless lambdas, lambdas in unevaluated contexts, language support for empty data members, allowing pack expansion in lambda init-capture, likely and unlikely attributes, class types in non-type template parameters, allowing virtual function calls in constant expressions, explicit(bool), std::is_constant_evaluated, nested inline namespaces, etc. For a full list of new features, see [53]the C++ status page. * The C++ front end now preserves source locations for literals, id-expression, and mem-initializer for longer. For example it is now able to pin-point the pertinent locations for bad initializations such as these $ g++ -c bad-inits.cc bad-inits.cc:10:14: error: cannot convert 'json' to 'int' in initialization 10 | { 3, json::object }, | ~~~~~~^~~~~~ | | | json bad-inits.cc:14:31: error: initializer-string for array of chars is too long [-f permissive] 14 | char buffers[3][5] = { "red", "green", "blue" }; | ^~~~~~~ bad-inits.cc: In constructor 'X::X()': bad-inits.cc:17:13: error: invalid conversion from 'int' to 'void*' [-fpermissiv e] 17 | X() : one(42), two(42), three(42) | ^~ | | | int rather than emitting the error at the final closing parenthesis or brace. * Error-reporting of overload resolution has been special-cased to make the case of a single failed candidate easier to read. For example: $ g++ param-type-mismatch.cc param-type-mismatch.cc: In function 'int test(int, const char*, float)': param-type-mismatch.cc:8:32: error: cannot convert 'const char*' to 'const char* *' 8 | return foo::member_1 (first, second, third); | ^~~~~~ | | | const char* param-type-mismatch.cc:3:46: note: initializing argument 2 of 'static int foo: :member_1(int, const char**, float)' 3 | static int member_1 (int one, const char **two, float three); | ~~~~~~~~~~~~~^~~ highlights both the problematic argument, and the parameter that it can't be converted to. * Diagnostics involving binary operators now use color to distinguish the two operands, and label them separately (as per the example of source labelling above). * Diagnostics involving function calls now highlight the pertinent parameter of the declaration in more places. $ g++ bad-conversion.cc bad-conversion.cc: In function 'void caller()': bad-conversion.cc:9:14: error: cannot convert 'bool' to 'void*' 9 | callee (0, false, 2); | ^~~~~ | | | bool bad-conversion.cc:3:19: note: initializing argument 2 of 'void callee(int, voi d*, int)' 3 | void callee (int, void *, int) | ^~~~~~ * The C++ front end's implementation of [54]-Wformat now shows precise locations within string literals, and underlines the pertinent arguments at bogus call sites (the C front end has been doing this since GCC 7). For example: $ g++ -c bad-printf.cc -Wall bad-printf.cc: In function 'void print_field(const char*, float, long int, long int)': bad-printf.cc:6:17: warning: field width specifier '*' expects argument of type 'int', but argument 3 has type 'long int' [-Wformat=] 6 | printf ("%s: %*ld ", fieldname, column - width, value); | ~^~~ ~~~~~~~~~~~~~~ | | | | int long int bad-printf.cc:6:19: warning: format '%ld' expects argument of type 'long int', b ut argument 4 has type 'double' [-Wformat=] 6 | printf ("%s: %*ld ", fieldname, column - width, value); | ~~~^ ~~~~~ | | | | long int double | %*f * The C++ front end has gained new fix-it hints for forgetting the return *this; needed by various C++ operators: $ g++ -c operator.cc operator.cc: In member function 'boxed_ptr& boxed_ptr::operator=(const boxed_ptr &)': operator.cc:7:3: warning: no return statement in function returning non-void [-W return-type] 6 | m_ptr = other.m_ptr; +++ |+ return *this; 7 | } | ^ for when the compiler needs a typename: $ g++ -c template.cc template.cc:3:3: error: need 'typename' before 'Traits::type' because 'Traits' i s a dependent scope 3 | Traits::type type; | ^~~~~~ | typename when trying to use an accessor member as if it were a data member: $ g++ -c fncall.cc fncall.cc: In function 'void hangman(const mystring&)': fncall.cc:12:11: error: invalid use of member function 'int mystring::get_length () const' (did you forget the '()' ?) 12 | if (str.get_length > 0) | ~~~~^~~~~~~~~~ | () for C++11's scoped enums: $ g++ -c enums.cc enums.cc: In function 'void json::test(const json::value&)': enums.cc:12:26: error: 'STRING' was not declared in this scope; did you mean 'js on::kind::STRING'? 12 | if (v.get_kind () == STRING) | ^~~~~~ | json::kind::STRING enums.cc:3:44: note: 'json::kind::STRING' declared here 3 | enum class kind { OBJECT, ARRAY, NUMBER, STRING, TRUE, FALSE, NULL_ }; | ^~~~~~ and a tweak to integrate the suggestions about misspelled members with that for accessors: $ g++ -c accessor-fixit.cc accessor-fixit.cc: In function 'int test(t*)': accessor-fixit.cc:17:15: error: 'class t' has no member named 'ratio'; did you m ean 'int t::m_ratio'? (accessible via 'int t::get_ratio() const') 17 | return ptr->ratio; | ^~~~~ | get_ratio() In addition, various diagnostics in the C++ front-end have been streamlined by consolidating the suggestion into the initial error, rather than emitting a follow-up note: $ g++ typo.cc typo.cc:5:13: error: 'BUFSIZE' was not declared in this scope; did you mean 'BUF _SIZE'? 5 | uint8_t buf[BUFSIZE]; | ^~~~~~~ | BUF_SIZE Runtime Library (libstdc++) * Improved support for C++17, including: + The C++17 implementation is no longer experimental. + Parallel algorithms and (requires [55]Thread Building Blocks 2018 or newer). + . + Using the types and functions in does not require linking with -lstdc++fs now. * Improved experimental support for C++2a, including: + Type traits std::remove_cvref, std::unwrap_reference, std::unwrap_decay_ref, std::is_nothrow_convertible, and std::type_identity. + Headers and . + Uniform container erasure (std::erase_if). + contains member of maps and sets. + String prefix and suffix checking (starts_with, ends_with). + Functions std::midpoint and std::lerp for interpolation. + std::bind_front. + std::visit. + std::assume_aligned. + Uses-allocator construction utilities. + std::pmr::polymorphic_allocator. + Library support for char8_t type. + Destroying delete. + std::is_constant_evaluated() function. * Support for opening file streams with wide character paths on Windows * Incomplete support for the C++17 Filesystem library and the Filesystem TS on Windows. * Incomplete, experimental support for the Networking TS. D * Support for the D programming language has been added to GCC, implementing version 2.076 of the language and run-time library. Fortran * Asynchronous I/O is now fully supported. The program needs to be linked against the pthreads library to use it, otherwise the I/O is done synchronously. For systems which do not support POSIX condition variables, such as AIX, all I/O is still done synchronously. * The BACK argument for MINLOC and MAXLOC has been implemented. * The FINDLOC intrinsic function has been implemented. * The IS_CONTIGUOUS intrinsic function has been implemented. * Direct access to the real and imaginary parts of a complex variable via c%re and c%im has been implemented. * Type parameter inquiry via str%len and a%kind has been implemented. * C descriptors and the ISO_Fortran_binding.h source file have been implemented. * The MAX and MIN intrinsics are no longer guaranteed to return any particular value in case one of the arguments is a NaN. Note that this conforms to the Fortran standard and to what other Fortran compilers do. If there is a need to handle that case in some specific way, one needs to explicitly check for NaN's before calling MAX or MIN, e.g. by using the IEEE_IS_NAN function from the intrinsic module IEEE_ARITHMETIC. * A new command-line option [56]-fdec-include, set also by the [57]-fdec option, has been added to increase compatibility with legacy code. With this option, an INCLUDE directive is also parsed as a statement, which allows the directive to be spread across multiple source lines with line continuations. * A new [58]BUILTIN directive, has been added. The purpose of the directive is to provide an API between the GCC compiler and the GNU C Library which would define vector implementations of math routines. Go * GCC 9 provides a complete implementation of the Go 1.12.2 user packages. libgccjit * The libgccjit API gained a new entry point: [59]gcc_jit_context_add_driver_option. New Targets and Target Specific Improvements AArch64 & Arm * Support has been added for the following processors (GCC identifiers in parentheses): + Arm Cortex-A76 (cortex-a76). + Arm Cortex-A55/Cortex-A76 DynamIQ big.LITTLE (cortex-a76.cortex-a55). + Arm Neoverse N1 (neoverse-n1). The GCC identifiers can be used as arguments to the -mcpu or -mtune options, for example: -mcpu=cortex-a76 or -mtune=cortex-a76.cortex-a55 or as arguments to the equivalent target attributes and pragmas. * The Armv8.3-A complex number instructions are now supported via intrinsics when the option -march=armv8.3-a or equivalent is specified. For the half-precision floating-point variants of these instructions use the architecture extension flag +fp16, e.g. -march=armv8.3-a+fp16. The intrinsics are defined by the ACLE specification. * The Armv8.5-A architecture is now supported through the -march=armv8.5-a option. * The Armv8.5-A architecture also adds some security features that are optional to all older architecture versions. These are now supported and only affect the assembler. + Speculation Barrier instruction through the -march=armv8-a+sb option. + Execution and Data Prediction Restriction instructions through the -march=armv8-a+predres option. + Speculative Store Bypass Safe instruction through the -march=armv8-a+ssbs option. This does not require a compiler option for Arm and thus -march=armv8-a+ssbs is an AArch64-specific option. AArch64 specific * Support has been added for the Arm Neoverse E1 processor (-mcpu=neoverse-e1). * The AArch64 port now has support for stack clash protection using the [60]-fstack-clash-protection option. The probing interval/guard size can be set by using --param stack-clash-protection-guard-size=12|16. The value of this parameter must be in bytes represented as a power of two. The two supported values for this parameter are 12 (for a 4KiB size, 2^12) and 16 (for a 64KiB size, 2^16). The default value is 16 (64Kb) and can be changed at configure time using the flag --with-stack-clash-protection-guard-size=12|16. * The option -msign-return-address= has been deprecated. This has been replaced by the new -mbranch-protection= option. This new option can now be used to enable the return address signing as well as the new Branch Target Identification feature of Armv8.5-A architecture. For more information on the arguments accepted by this option, please refer to [61]AArch64-Options. * The following optional extensions to Armv8.5-A architecture are now supported and only affect the assembler. + Random Number Generation instructions through the -march=armv8.5-a+rng option. + Memory Tagging Extension through the -march=armv8.5-a+memtag option. Arm specific * Support for the deprecated Armv2 and Armv3 architectures and their variants has been removed. Their corresponding -march values and the -mcpu options that used these architectures have been removed. * Support for the Armv5 and Armv5E architectures (which have no known implementations) has been removed. Note that Armv5T, Armv5TE and Armv5TEJ architectures remain supported. * Corrected FPU configurations for Cortex-R7 and Cortex-R8 when using their respective -mcpu options. AMD GCN * A new back end targeting AMD GCN GPUs has been contributed to GCC. The implementation is currently limited to compiling single-threaded, stand-alone programs. Future versions will add support for offloading multi-threaded kernels via OpenMP and OpenACC. The following devices are supported (GCC identifiers in parentheses): + Fiji (fiji). + Vega 10 (gfx900). ARC * LRA is now on by default for the ARC target. This can be controlled by -mlra. * Add support for frame code-density and branch-and-index instructions. C-SKY * A new back end targeting C-SKY V2 processors has been contributed to GCC. IA-32/x86-64 * Support of Intel MPX (Memory Protection Extensions) has been removed. * New ISA extension support for Intel PTWRITE was added to GCC. PTWRITE intrinsics are available via the -mptwrite compiler switch. * GCC now supports the Intel CPU named Cascade Lake with AVX512 extensions through -march=cascadelake. The switch enables the following ISA extensions: AVX512F, AVX512VL, AVX512CD, AVX512BW, AVX512DQ, AVX512VNNI. MIPS * The Loongson loongson-mmi and loongson-ext extensions have been split from loongson3a: + loongson-mmi contains the Loongson MMI (MultiMedia extensions Instructions). + loongson-ext contains the Loongson EXT (EXTensions instructions). * The Loongson EXT2 (EXTensions R2 instructions) are now supported. + loongson-ext2 contains the Loongson EXT2 instructions. Command-line options-m[no-]loongson-mmi, -m[no-]loongson-ext, and -m[no-]loongson-ext2 enable or disable those extensions. * Support has been added for the following processors (GCC identifiers in parentheses): + Loongson 3A1000 (gs464) which enables loongson-mmi, loongson-ext by default. + Loongson 3A2000/3A3000 (gs464e) which enables loongson-mmi, loongson-ext, loongson-ext2 by default. + Loongson 2K1000 (gs264e) which enables loongson-ext, loongson-ext2, msa by default. The GCC identifiers can be used as arguments to the -mcpu and -mtune options (as in -mcpu=gs464 or -mtune=gs464e) or as arguments to the equivalent target attributes and pragmas. OpenRISC * A new back end targeting OpenRISC processors has been contributed to GCC. S/390, System z, IBM z Systems * Support for the arch13 architecture has been added. When using the -march=arch13 option, the compiler will generate code making use of the new instructions introduced with the vector enhancement facility 2 and the miscellaneous instruction extension facility 2. The -mtune=arch13 option enables arch13 specific instruction scheduling without making use of new instructions. * Builtins for the new vector instructions have been added and can be enabled using the -mzvector option. * Support for ESA architecture machines g5 and g6 is deprecated since GCC 6.1.0 and has been removed now. * When compiling with -march=z14 or higher GCC emits alignments hints on the vector load/store instructions (8 or 16 byte). * Functions now have a default alignment of 16 bytes. This helps with branch prediction effects. * -mfentry is now supported. As well as the mcount mechanism the __fentry__ is called before the function prologue. However, since just a single instruction is required to call __fentry__ the call sequence imposes a smaller overhead than mcount (4 instructions). The produced code is compatible only with newer glibc versions, which provide the __fentry__ symbol and do not clobber r0 when resolving lazily bound functions. -mfentry is only supported when generating 64-bit code and does not work with nested C functions. * The -mnop-mcount option can be used to emit NOP instructions instead of an mcount or fentry call stub. * With the -mrecord-mcount option a __mcount_loc section is generated containing pointers to each profiling call stub. This is useful for automatically patching in and out calls. Operating Systems Solaris * g++ now unconditionally enables large file support when compiling 32-bit code. * Support for the AddressSanitizer and UndefinedBehaviorSanitizer has been merged from LLVM. For the moment, this only works for 32-bit code on both SPARC and x86. * An initial port of the D runtime library has been completed on Solaris 11/x86. It requires the use of GNU as. Solaris 11/SPARC support is still work-in-progress. Windows * A C++ Microsoft ABI bitfield layout bug, [62]PR87137 has been fixed. A non-field declaration could cause the current bitfield allocation unit to be completed, incorrectly placing a following bitfield into a new allocation unit. The Microsoft ABI is selected for: + Mingw targets + PowerPC, IA-32 or x86-64 targets when the -mms-bitfields option is specified, or __attribute__((ms_struct)) is used + SuperH targets when the -mhitachi option is specified, or __attribute__((renesas)) is used Improvements for plugin authors * GCC's diagnostic subsystem now has a way to logically group together related diagnostics, auto_diagnostic_group. Such diagnostics will be nested by the output of [63]-fdiagnostics-format=json. * GCC now has a set of [64]user experience guidelines for GCC, with information and advice on implementing new diagnostics. Other significant improvements * GCC's internal "selftest" suite now runs for C++ as well as C (in debug builds of the compiler). GCC 9.1 This is the [65]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 9.1 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 9.2 This is the [66]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 9.2 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 9.3 This is the [67]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 9.3 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 9.4 This is the [68]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 9.4 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Target Specific Changes AArch64 * The option -moutline-atomics has been added to aid deployment of the Large System Extensions (LSE) on GNU/Linux systems built with a baseline architecture targeting Armv8-A. When the option is specified code is emitted to detect the presence of LSE instructions at run time and use them for standard atomic operations. For more information please refer to the documentation. * GCC now supports the Fujitsu A64FX. The associated -mcpu and -mtune options are -mcpu=a64fx and -mtune=a64fx respectively. In particular, -mcpu=a64fx generates code for Armv8.2-A with SVE and tunes the code for the A64FX. This includes tuning the SVE code, although by default the code is still length-agnostic and so works for all SVE implementations. Adding -msve-vector-bits=512 makes the code specific to 512-bit SVE. GCC 9.5 This is the [69]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 9.5 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). For questions related to the use of GCC, please consult these web pages and the [70]GCC manuals. If that fails, the [71]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [72]gcc@gcc.gnu.org. All of [73]our lists have public archives. Copyright (C) [74]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [75]maintained by the GCC team. Last modified 2024-05-09. References 1. https://gcc.gnu.org/gcc-9/porting_to.html 2. https://gcc.gnu.org/onlinedocs/index.html#current 3. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88469 4. https://gcc.gnu.org/ml/gcc/2018-10/msg00139.html 5. https://gcc.gnu.org/ml/gcc/2019-04/msg00023.html 6. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90920 7. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/C_002b_002b-Dialect-Options.html#index-frepo 8. https://gcc.gnu.org/PR90361 9. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Invoking-GCC.html#Invoking-GCC 10. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-flive-patching 11. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Diagnostic-Message-Formatting-Options.html#index-fno-diagnostics-show-line-numbers 12. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Diagnostic-Message-Formatting-Options.html#index-fno-diagnostics-show-labels 13. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-format 14. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-falign-functions 15. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-falign-labels 16. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-falign-loops 17. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-falign-jumps 18. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Instrumentation-Options.html#index-fprofile-filter-files 19. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Instrumentation-Options.html#index-fprofile-exclude-files 20. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Developer-Options.html#index-fopt-info 21. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Developer-Options.html#index-fsave-optimization-record 22. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-fipa-stack-alignment 23. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-fipa-reference-addressable 24. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Other-Builtins.html#index-_005f_005fbuiltin_005fexpect_005fwith_005fprobability 25. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Other-Builtins.html#index-_005f_005fbuiltin_005fhas_005fattribute-1 26. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Other-Builtins.html#index-_005f_005fbuiltin_005fspeculation_005fsafe_005fvalue-1 27. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Common-Function-Attributes.html#index-copy-function-attribute 28. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-ftree-switch-conversion 29. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-fprofile-use 30. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-fversion-loops-for-strides 31. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-floop-interchange 32. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-floop-unroll-and-jam 33. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-ftree-loop-distribution 34. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Invoking-Gcov.html#Invoking-Gcov 35. https://www.openacc.org/ 36. https://gcc.gnu.org/wiki/OpenACC/Implementation Status#status-9 37. https://www.openmp.org/specifications/ 38. https://gcc.gnu.org/ml/gcc-patches/2018-11/msg00628.html 39. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Vector-Extensions.html#index-_005f_005fbuiltin_005fconvertvector 40. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Warning-Options.html#index-Waddress-of-packed-member 41. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Warning-Options.html#index-Warray-bounds 42. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Warning-Options.html#index-Wattribute-alias 43. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Warning-Options.html#index-Wformat-overflow 44. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Warning-Options.html#index-Wformat-truncation 45. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Warning-Options.html#index-Wmissing-attributes 46. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Warning-Options.html#index-Wstringop-truncation 47. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Warning-Options.html#index-Wabsolute-value 48. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/C_002b_002b-Dialect-Options.html#index-Wdeprecated-copy 49. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/C_002b_002b-Dialect-Options.html#index-Winit-list-lifetime 50. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/C_002b_002b-Dialect-Options.html#index-Wredundant-move 51. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/C_002b_002b-Dialect-Options.html#index-Wpessimizing-move 52. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/C_002b_002b-Dialect-Options.html#index-Wclass-conversion 53. https://gcc.gnu.org/projects/cxx-status.html#cxx2a 54. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Warning-Options.html#index-Wformat 55. https://github.com/oneapi-src/oneTBB 56. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gfortran/Fortran-Dialect-Options.html#index-fdec-include 57. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gfortran/Fortran-Dialect-Options.html#index-fdec 58. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gfortran/BUILTIN-directive.html#BUILTIN-directive 59. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/jit/topics/contexts.html#gcc_jit_context_add_driver_option 60. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Instrumentation-Options.html#index-fstack-protector 61. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/AArch64-Options.html#AArch64-Options 62. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87137 63. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-format 64. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gccint/User-Experience-Guidelines.html 65. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=9.0 66. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=9.2 67. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=9.3 68. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=9.4 69. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=9.5 70. https://gcc.gnu.org/onlinedocs/ 71. mailto:gcc-help@gcc.gnu.org 72. mailto:gcc@gcc.gnu.org 73. https://gcc.gnu.org/lists.html 74. https://www.fsf.org/ 75. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-8/index.html GCC 8 Release Series (This release series is no longer supported.) May 14, 2021 The [1]GNU project and the GCC developers are pleased to announce the release of GCC 8.5. This release is a bug-fix release, containing fixes for regressions in GCC 8.4 relative to previous releases of GCC. Release History GCC 8.5 May 14, 2021 ([2]changes, [3]documentation) GCC 8.4 Mar 4, 2020 ([4]changes, [5]documentation) GCC 8.3 Feb 22, 2019 ([6]changes, [7]documentation) GCC 8.2 Jul 26, 2018 ([8]changes, [9]documentation) GCC 8.1 May 2, 2018 ([10]changes, [11]documentation) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. A list of [12]successful builds is updated as new information becomes available. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [13]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [14]GCC project web site or contact the [15]GCC development mailing list. To obtain GCC please use [16]our mirror sites or [17]our version control system. For questions related to the use of GCC, please consult these web pages and the [18]GCC manuals. If that fails, the [19]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [20]gcc@gcc.gnu.org. All of [21]our lists have public archives. Copyright (C) [22]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [23]maintained by the GCC team. Last modified 2024-05-30. References 1. http://www.gnu.org/ 2. https://gcc.gnu.org/gcc-8/changes.html 3. https://gcc.gnu.org/onlinedocs/8.5.0/ 4. https://gcc.gnu.org/gcc-8/changes.html 5. https://gcc.gnu.org/onlinedocs/8.4.0/ 6. https://gcc.gnu.org/gcc-8/changes.html 7. https://gcc.gnu.org/onlinedocs/8.3.0/ 8. https://gcc.gnu.org/gcc-8/changes.html 9. https://gcc.gnu.org/onlinedocs/8.2.0/ 10. https://gcc.gnu.org/gcc-8/changes.html 11. https://gcc.gnu.org/onlinedocs/8.1.0/ 12. https://gcc.gnu.org/gcc-8/buildstat.html 13. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/Contributors.html 14. https://gcc.gnu.org/index.html 15. mailto:gcc@gcc.gnu.org 16. https://gcc.gnu.org/mirrors.html 17. https://gcc.gnu.org/git.html 18. https://gcc.gnu.org/onlinedocs/ 19. mailto:gcc-help@gcc.gnu.org 20. mailto:gcc@gcc.gnu.org 21. https://gcc.gnu.org/lists.html 22. https://www.fsf.org/ 23. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-8/changes.html GCC 8 Release Series Changes, New Features, and Fixes This page is a "brief" summary of some of the huge number of improvements in GCC 8. You may also want to check out our [1]Porting to GCC 8 page and the [2]full GCC documentation. Caveats * Support for the obsolete SDB/coff debug info format has been removed. The option -gcoff no longer does anything. * The Cilk+ extensions to the C and C++ languages have been removed. * The MPX extensions to the C and C++ languages have been deprecated and will be removed in a future release. * The extension allowing arithmetic on std::atomic and types like std::atomic has been deprecated. * The non-standard C++0x std::copy_exception function was removed. std::make_exception_ptr should be used instead. * Support for the powerpc*-*-*spe* target ports which have been recently unmaintained and untested in GCC has been declared obsolete in GCC 8 as [3]announced. Unless there is activity to revive them, the next release of GCC will have their sources permanently removed. General Improvements * Inter-procedural optimization improvements: + Reworked run-time estimation metrics leading to more realistic guesses driving inliner and cloning heuristics. + The ipa-pure-const pass is extended to propagate the malloc attribute, and the corresponding warning option -Wsuggest-attribute=malloc emits a diagnostic for functions which can be annotated with the malloc attribute. * Profile driven optimization improvements: + New infrastructure for representing profiles (both statically guessed and profile feedback) which allows propagation of additional information about the reliability of the profile. + A number of improvements in the profile updating code solving problems found by new verification code. + Static detection of code which is not executed in a valid run of the program. This includes paths which trigger undefined behavior as well as calls to functions declared with the cold attribute. Newly the noreturn attribute does not imply all effects of cold to differentiate between exit (which is noreturn) and abort (which is in addition not executed in valid runs). + -freorder-blocks-and-partition, a pass splitting function bodies into hot and cold regions, is now enabled by default at -O2 and higher for x86 and x86-64. * Link-time optimization improvements: + We have significantly improved debug information on ELF targets using DWARF by properly preserving language-specific information. This allows for example the libstdc++ pretty-printers to work with LTO optimized executables. * A new option -fcf-protection=[full|branch|return|none] is introduced to perform code instrumentation to increase program security by checking that target addresses of control-flow transfer instructions (such as indirect function call, function return, indirect jump) are valid. Currently the instrumentation is supported on x86 GNU/Linux targets only. See the user guide for further information about the option syntax and section "New Targets and Target Specific Improvements" for IA-32/x86-64 for more details. * The -gcolumn-info option is now enabled by default. It includes column information in addition to just filenames and line numbers in DWARF debugging information. * The polyhedral-based loop nest optimization pass -floop-nest-optimize has been overhauled. It's still considered experimental and may not result in any runtime improvements. * Two new classical loop nest optimization passes have been added. -floop-unroll-and-jam performs outer loop unrolling and fusing of the inner loop copies. -floop-interchange exchanges loops in a loop nest to improve data locality. Both passes are enabled by default at -O3 and above. * The classic loop nest optimization pass -ftree-loop-distribution has been improved and enabled by default at -O3 and above. It supports loop nest distribution in some restricted scenarios; it also supports cancellable innermost loop distribution with loop versioning under run-time alias checks. * The new option -fstack-clash-protection causes the compiler to insert probes whenever stack space is allocated statically or dynamically to reliably detect stack overflows and thus mitigate the attack vector that relies on jumping over a stack guard page as provided by the operating system. * A new pragma GCC unroll has been implemented in the C family of languages, as well as Fortran and Ada, so as to make it possible for the user to have a finer-grained control over the loop unrolling optimization. * GCC has been enhanced to detect more instances of meaningless or mutually exclusive attribute specifications and handle such conflicts more consistently. Mutually exclusive attribute specifications are ignored with a warning regardless of whether they appear on the same declaration or on distinct declarations of the same entity. For example, because the noreturn attribute on the second declaration below is mutually exclusive with the malloc attribute on the first, it is ignored and a warning is issued. > void* __attribute__ ((malloc)) f (unsigned); void* __attribute__ ((noreturn)) f (unsigned); warning: ignoring attribute 'noreturn' because it conflicts with attribute 'malloc' [-Wattributes] * The gcov tool can distinguish functions that begin on a same line in a source file. This can be a different template instantiation or a class constructor: File 'ins.C' Lines executed:100.00% of 8 Creating 'ins.C.gcov' -: 0:Source:ins.C -: 0:Graph:ins.gcno -: 0:Data:ins.gcda -: 0:Runs:1 -: 0:Programs:1 -: 1:template -: 2:class Foo -: 3:{ -: 4: public: 2: 5: Foo(): b (1000) {} ------------------ Foo::Foo(): 1: 5: Foo(): b (1000) {} ------------------ Foo::Foo(): 1: 5: Foo(): b (1000) {} ------------------ 2: 6: void inc () { b++; } ------------------ Foo::inc(): 1: 6: void inc () { b++; } ------------------ Foo::inc(): 1: 6: void inc () { b++; } ------------------ -: 7: -: 8: private: -: 9: int b; -: 10:}; -: 11: 1: 12:int main(int argc, char **argv) -: 13:{ 1: 14: Foo a; 1: 15: Foo b; -: 16: 1: 17: a.inc (); 1: 18: b.inc (); 1: 19:} * The gcov tool has more accurate numbers for execution of lines in a source file. * The gcov tool can use TERM colors to provide more readable output. * AddressSanitizer gained a new pair of sanitization options, -fsanitize=pointer-compare and -fsanitize=pointer-subtract, which warn about subtraction (or comparison) of pointers that point to a different memory object: int main () { /* Heap allocated memory. */ char *heap1 = (char *)__builtin_malloc (42); char *heap2 = (char *)__builtin_malloc (42); if (heap1 > heap2) return 1; return 0; } ==17465==ERROR: AddressSanitizer: invalid-pointer-pair: 0x604000000010 0x6040000 00050 #0 0x40070f in main /tmp/pointer-compare.c:7 #1 0x7ffff6a72a86 in __libc_start_main (/lib64/libc.so.6+0x21a86) #2 0x400629 in _start (/tmp/a.out+0x400629) 0x604000000010 is located 0 bytes inside of 42-byte region [0x604000000010,0x604 00000003a) allocated by thread T0 here: #0 0x7ffff6efb390 in __interceptor_malloc ../../../../libsanitizer/asan/asan _malloc_linux.cc:86 #1 0x4006ea in main /tmp/pointer-compare.c:5 #2 0x7ffff6a72a86 in __libc_start_main (/lib64/libc.so.6+0x21a86) 0x604000000050 is located 0 bytes inside of 42-byte region [0x604000000050,0x604 00000007a) allocated by thread T0 here: #0 0x7ffff6efb390 in __interceptor_malloc ../../../../libsanitizer/asan/asan _malloc_linux.cc:86 #1 0x4006f8 in main /tmp/pointer-compare.c:6 #2 0x7ffff6a72a86 in __libc_start_main (/lib64/libc.so.6+0x21a86) SUMMARY: AddressSanitizer: invalid-pointer-pair /tmp/pointer-compare.c:7 in main * The store merging pass has been enhanced to handle bit-fields and not just constant stores, but also data copying from adjacent memory locations into other adjacent memory locations, including bitwise logical operations on the data. The pass can also handle byte swapping into memory locations. * The undefined behavior sanitizer gained two new options included in -fsanitize=undefined: -fsanitize=builtin which diagnoses at run time invalid arguments to __builtin_clz or __builtin_ctz prefixed builtins, and -fsanitize=pointer-overflow which performs cheap run time tests for pointer wrapping. * A new attribute no_sanitize can be applied to functions to instruct the compiler not to do sanitization of the options provided as arguments to the attribute. Acceptable values for no_sanitize match those acceptable by the -fsanitize command-line option. void __attribute__ ((no_sanitize ("alignment", "object-size"))) f () { /* Do something. */; } New Languages and Language specific improvements Ada * For its internal exception handling used on the host for error recovery in the front-end, the compiler now relies on the native exception handling mechanism of the host platform, which should be more efficient than the former mechanism. BRIG (HSAIL) In this release cycle, the focus for the BRIGFE was on stabilization and performance improvements. Also a couple of completely new features were added. * Improved support for function and module scope group segment variables. PRM specs define function and module scope group segment variables as an experimental feature. However, PRM test suite uses them. Now group segment is handled by separate book keeping of module scope and function (kernel) offsets. Each function has a "frame" in the group segment offset to which is given as an argument, similar to traditional call stack frame handling. * Reduce the number of type conversions due to the untyped HSAIL registers. Instead of always representing the HSAIL's untyped registers as unsigned int, the gccbrig now pre-analyzes the BRIG code and builds the register variables as a type used the most when storing or reading data to/from each register. This reduces the number of total casts which cannot be always optimized away. * Support for BRIG_KIND_NONE directives. * Made -O3 the default optimization level for BRIGFE. * Fixed illegal addresses generated from address expressions which refer only to offset 0. * Fixed a bug with reg+offset addressing on 32b segments. In 'large' mode, the offset is treated as 32-bit unless it's in global, read-only or kernarg address space. * Fixed a crash caused sometimes by calls with more than 4 arguments. * Fixed a mis-execution issue with kernels that have both unexpanded ID functions and calls to subfunctions. * Treat HSAIL barrier builtins as setjmp/longjump style functions to avoid illegal optimizations. * Ensure per WI copies of private variables are aligned correctly. * libhsail-rt: Assume the host runtime allocates the work group memory. C family * New command-line options have been added for the C and C++ compilers: + [4]-Wmultistatement-macros warns about unsafe macros expanding to multiple statements used as a body of a statement such as if, else, while, switch, or for. + [5]-Wstringop-truncation warns for calls to bounded string manipulation functions such as strncat, strncpy, and stpncpy that might either truncate the copied string or leave the destination unchanged. For example, the following call to strncat is diagnosed because it appends just three of the four characters from the source string. void append (char *buf, size_t bufsize) { strncat (buf, ".txt", 3); } warning: 'strncat' output truncated copying 3 bytes from a string of length 4 [- Wstringop-truncation] Similarly, in the following example, the call to strncpy specifies the size of the destination buffer as the bound. If the length of the source string is equal to or greater than this size the result of the copy will not be NUL-terminated. Therefore, the call is also diagnosed. To avoid the warning, specify sizeof buf - 1 as the bound and set the last element of the buffer to NUL. void copy (const char *s) { char buf[80]; strncpy (buf, s, sizeof buf); … } warning: 'strncpy' specified bound 80 equals destination size [-Wstringop-trunca tion] The -Wstringop-truncation option is included in -Wall. Note that due to GCC bug [6]82944, defining strncat, strncpy, or stpncpy as a macro in a system header as some implementations do, suppresses the warning. + [7]-Wif-not-aligned controls warnings issued in response to invalid uses of objects declared with attribute [8]warn_if_not_aligned. The -Wif-not-aligned option is included in -Wall. + [9]-Wmissing-attributes warns when a declaration of a function is missing one or more attributes that a related function is declared with and whose absence may adversely affect the correctness or efficiency of generated code. For example, in C++, the warning is issued when an explicit specialization of a primary template declared with attribute alloc_align, alloc_size, assume_aligned, format, format_arg, malloc, or nonnull is declared without it. Attributes deprecated, error, and warning suppress the warning. The -Wmissing-attributes option is included in -Wall. + [10]-Wpacked-not-aligned warns when a struct or union declared with attribute packed defines a member with an explicitly specified alignment greater than 1. Such a member will wind up under-aligned. For example, a warning will be issued for the definition of struct A in the following: struct __attribute__ ((aligned (8))) S8 { char a[8]; }; struct __attribute__ ((packed)) A { struct S8 s8; }; warning: alignment 1 of 'struct S' is less than 8 [-Wpacked-not-aligned] The -Wpacked-not-aligned option is included in -Wall. + -Wcast-function-type warns when a function pointer is cast to an incompatible function pointer. This warning is enabled by -Wextra. + -Wsizeof-pointer-div warns for suspicious divisions of the size of a pointer by the size of the elements it points to, which looks like the usual way to compute the array size but won't work out correctly with pointers. This warning is enabled by -Wall. + -Wcast-align=strict warns whenever a pointer is cast such that the required alignment of the target is increased. For example, warn if a char * is cast to an int * regardless of the target machine. + -fprofile-abs-path creates absolute path names in the .gcno files. This allows gcov to find the correct sources in projects where compilations occur with different working directories. * -fno-strict-overflow is now mapped to -fwrapv -fwrapv-pointer and signed integer overflow is now undefined by default at all optimization levels. Using -fsanitize=signed-integer-overflow is now the preferred way to audit code, -Wstrict-overflow is deprecated. * The [11]-Warray-bounds option has been improved to detect more instances of out-of-bounds array indices and pointer offsets. For example, negative or excessive indices into flexible array members and string literals are detected. * The [12]-Wrestrict option introduced in GCC 7 has been enhanced to detect many more instances of overlapping accesses to objects via restrict-qualified arguments to standard memory and string manipulation functions such as memcpy and strcpy. For example, the strcpy call in the function below attempts to truncate the string by replacing its initial characters with the last four. However, because the function writes the terminating NUL into a[4], the copies overlap and the call is diagnosed. void f (void) { char a[] = "abcd1234"; strcpy (a, a + 4); … } warning: 'strcpy' accessing 5 bytes at offsets 0 and 4 overlaps 1 byte at offset 4 [-Wrestrict] The -Wrestrict option is included in -Wall. * Several optimizer enhancements have enabled improvements to the [13]-Wformat-overflow and [14]-Wformat-truncation options. The warnings detect more instances of buffer overflow and truncation than in GCC 7 and are better at avoiding certain kinds of false positives. * When reporting mismatching argument types at a function call, the C and C++ compilers now underline both the argument and the pertinent parameter in the declaration. $ gcc arg-type-mismatch.cc arg-type-mismatch.cc: In function 'int caller(int, int, float)': arg-type-mismatch.cc:5:24: error: invalid conversion from 'int' to 'const char*' [-fpermissive] return callee(first, second, third); ^~~~~~ arg-type-mismatch.cc:1:40: note: initializing argument 2 of 'int callee(int, c onst char*, float)' extern int callee(int one, const char *two, float three); ~~~~~~~~~~~~^~~ * When reporting on unrecognized identifiers, the C and C++ compilers will now emit fix-it hints suggesting #include directives for various headers in the C and C++ standard libraries. $ gcc incomplete.c incomplete.c: In function 'test': incomplete.c:3:10: error: 'NULL' undeclared (first use in this function) return NULL; ^~~~ incomplete.c:3:10: note: 'NULL' is defined in header ''; did you forge t to '#include '? incomplete.c:1:1: +#include const char *test(void) incomplete.c:3:10: return NULL; ^~~~ incomplete.c:3:10: note: each undeclared identifier is reported only once for ea ch function it appears in $ gcc incomplete.cc incomplete.cc:1:6: error: 'string' in namespace 'std' does not name a type std::string s("hello world"); ^~~~~~ incomplete.cc:1:1: note: 'std::string' is defined in header ''; did you forget to '#include '? +#include std::string s("hello world"); ^~~ * The C and C++ compilers now use more intuitive locations when reporting on missing semicolons, and offer fix-it hints: $ gcc t.c t.c: In function 'test': t.c:3:12: error: expected ';' before '}' token return 42 ^ ; } ~ * When reporting on missing '}' and ')' tokens, the C and C++ compilers will now highlight the corresponding '{' and '(' token, issuing a 'note' if it's on a separate line: $ gcc unclosed.c unclosed.c: In function 'log_when_out_of_range': unclosed.c:12:50: error: expected ')' before '{' token && (temperature < MIN || temperature > MAX) { ^~ ) unclosed.c:11:6: note: to match this '(' if (logging_enabled && check_range () ^ or highlighting it directly if it's on the same line: $ gcc unclosed-2.c unclosed-2.c: In function 'test': unclosed-2.c:8:45: error: expected ')' before '{' token if (temperature < MIN || temperature > MAX { ~ ^~ ) They will also emit fix-it hints. C++ * GCC 8 (-fabi-version=12) has a couple of corrections to the calling convention, which changes the ABI for some uncommon code: + Passing an empty class as an argument now takes up no space on x86_64, as required by the psABI. + Passing or returning a class with only deleted copy and move constructors now uses the same calling convention as a class with a non-trivial copy or move constructor. This only affects C++17 mode, as in earlier standards passing or returning such a class was impossible. + WARNING: In GCC 8.1 the second change mistakenly also affects classes with a deleted copy constructor and defaulted trivial move constructor (bug [15]c++/86094). This issue is fixed in GCC 8.2 (-fabi-version=13). You can test whether these changes affect your code with -Wabi=11 (or -Wabi=12 in GCC 8.2 for the third issue); if these changes are problematic for your project, the GCC 7 ABI can be selected with -fabi-version=11. * The value of the C++11 alignof operator has been corrected to match C _Alignof (minimum alignment) rather than GNU __alignof__ (preferred alignment); on ia32 targets this means that alignof(double) is now 4 rather than 8. Code that wants the preferred alignment should use __alignof__ instead. * New command-line options have been added for the C++ compiler to control warnings: + [16]-Wclass-memaccess warns when objects of non-trivial class types are manipulated in potentially unsafe ways by raw memory functions such as memcpy, or realloc. The warning helps detect calls that bypass user-defined constructors or copy-assignment operators, corrupt virtual table pointers, data members of const-qualified types or references, or member pointers. The warning also detects calls that would bypass access controls to data members. For example, a call such as: memcpy (&std::cout, &std::cerr, sizeof std::cout); results in warning: 'void* memcpy(void*, const void*, long unsigned int)' writing t o an object of type 'std::ostream' {aka 'class std::basic_ostream'} with n o trivial copy-assignment [-Wclass-memaccess] The -Wclass-memaccess option is included in -Wall. * The C++ front end has experimental support for some of the upcoming C++2a draft features with the -std=c++2a or -std=gnu++2a flags, including designated initializers, default member initializers for bit-fields, __VA_OPT__ (except that #__VA_OPT__ is unsupported), lambda [=, this] captures, etc. For a full list of new features, see [17]the C++ status page. * When reporting on attempts to access private fields of a class or struct, the C++ compiler will now offer fix-it hints showing how to use an accessor function to get at the field in question, if one exists. $ gcc accessor.cc accessor.cc: In function 'void test(foo*)': accessor.cc:12:12: error: 'double foo::m_ratio' is private within this context if (ptr->m_ratio >= 0.5) ^~~~~~~ accessor.cc:7:10: note: declared private here double m_ratio; ^~~~~~~ accessor.cc:12:12: note: field 'double foo::m_ratio' can be accessed via 'double foo::get_ratio() const' if (ptr->m_ratio >= 0.5) ^~~~~~~ get_ratio() * The C++ compiler can now give you a hint if you use a macro before it was defined (e.g. if you mess up the order of your #include directives): $ gcc ordering.cc ordering.cc:2:24: error: expected ';' at end of member declaration virtual void clone() const OVERRIDE { } ^~~~~ ; ordering.cc:2:30: error: 'OVERRIDE' does not name a type virtual void clone() const OVERRIDE { } ^~~~~~~~ ordering.cc:2:30: note: the macro 'OVERRIDE' had not yet been defined In file included from ordering.cc:5: c++11-compat.h:2: note: it was later defined here #define OVERRIDE override * The -Wold-style-cast diagnostic can now emit fix-it hints telling you when you can use a static_cast, const_cast, or reinterpret_cast. $ gcc -c old-style-cast-fixits.cc -Wold-style-cast old-style-cast-fixits.cc: In function 'void test(void*)': old-style-cast-fixits.cc:5:19: warning: use of old-style cast to 'struct foo*' [ -Wold-style-cast] foo *f = (foo *)ptr; ^~~ ---------- static_cast (ptr) * When reporting on problems within extern "C" linkage specifications, the C++ compiler will now display the location of the start of the extern "C". $ gcc -c extern-c.cc extern-c.cc:3:1: error: template with C linkage template void test (void); ^~~~~~~~ In file included from extern-c.cc:1: unclosed.h:1:1: note: 'extern "C"' linkage started here extern "C" { ^~~~~~~~~~ extern-c.cc:3:39: error: expected '}' at end of input template void test (void); ^ In file included from extern-c.cc:1: unclosed.h:1:12: note: to match this '{' extern "C" { ^ * When reporting on mismatching template types, the C++ compiler will now use color to highlight the mismatching parts of the template, and will elide the parameters that are common between two mismatching templates, printing [...] instead: $ gcc templates.cc templates.cc: In function 'void test()': templates.cc:9:8: error: could not convert 'vector()' from 'vector' to 'vector' fn_1(vector ()); ^~~~~~~~~~~~~~~~~ templates.cc:10:8: error: could not convert 'map()' from 'map<[...] ,double>' to 'map<[...],int>' fn_2(map()); ^~~~~~~~~~~~~~~~~~ Those [...] elided parameters can be seen using -fno-elide-type: $ gcc templates.cc -fno-elide-type templates.cc: In function 'void test()': templates.cc:9:8: error: could not convert 'vector()' from 'vector' to 'vector' fn_1(vector ()); ^~~~~~~~~~~~~~~~~ templates.cc:10:8: error: could not convert 'map()' from 'map' to 'map' fn_2(map()); ^~~~~~~~~~~~~~~~~~ The C++ compiler has also gained an option -fdiagnostics-show-template-tree which visualizes such mismatching templates in a hierarchical form: $ gcc templates-2.cc -fdiagnostics-show-template-tree templates-2.cc: In function 'void test()': templates-2.cc:9:8: error: could not convert 'vector()' from 'vector' to 'vector' vector< [double != int]> fn_1(vector ()); ^~~~~~~~~~~~~~~~~ templates-2.cc:10:8: error: could not convert 'map >, ve ctor >()' from 'map>,vector>' to 'map>,vector>' map< map< [...], vector< [double != float]>>, vector< [double != float]>> fn_2(map>, vector> ()); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ which again works with -fno-elide-type: $ gcc templates-2.cc -fdiagnostics-show-template-tree -fno-elide-type templates-2.cc: In function 'void test()': templates-2.cc:9:8: error: could not convert 'vector()' from 'vector' to 'vector' vector< [double != int]> fn_1(vector ()); ^~~~~~~~~~~~~~~~~ templates-2.cc:10:8: error: could not convert 'map >, ve ctor >()' from 'map>,vector>' to 'map>,vector>' map< map< int, vector< [double != float]>>, vector< [double != float]>> fn_2(map>, vector> ()); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ * Flowing off the end of a non-void function is considered unreachable and may be subject to optimization on that basis. As a result of this change, -Wreturn-type warnings are enabled by default for C++. Runtime Library (libstdc++) * Improved experimental support for C++17, including the following features: + Deduction guides to support class template argument deduction. + std::filesystem implementation. + std::char_traits and std::char_traits are usable in constant expressions. + std::to_chars and std::from_chars (for integers only, not for floating point types). * Experimental support for C++2a: std::to_address (thanks to Glen Fernandes) and std::endian. * On GNU/Linux, std::random_device::entropy() accesses the kernel's entropy count for the random device, if known (thanks to Xi Ruoyao). * Support for std::experimental::source_location. * AddressSanitizer integration for std::vector, detecting out-of-range accesses to the unused capacity of a vector. * Extensions __gnu_cxx::airy_ai and __gnu_cxx::airy_bi added to the Mathematical Special Functions. Fortran * The main version of libfortran has been changed to 5. * Parameterized derived types, a major feature of Fortran 2003, have been implemented. * Partial support is provided for Fortran 2018 teams, which are hierarchical subsets of images that execute independently of other image subsets. * The maximum rank for arrays has been increased to 15, conforming to the Fortran 2008 standard. * Transformational intrinsics are now fully supported in initialization expressions. * New flag -fc-prototypes to write C prototypes for BIND(C) procedures and variables. * If -fmax-stack-var-size is honored if given together with -Ofast, -fstack-arrays is no longer set in that case. * New options -fdefault-real-16 and -fdefault-real-10 to control the default kind of REAL variables. * A warning is now issued if an array subscript inside a DO loop could lead to an out-of-bounds-access. The new option -Wdo-subscript, enabled by -Wextra, warns about this even if the compiler can not prove that the code will be executed. * The Fortran front end now attempts to interchange loops if it is deemed profitable. So far, this is restricted to FORALL and DO CONCURRENT statements with multiple indices. This behavior be controlled with the new flag -ffrontend-loop-interchange, which is enabled with optimization by default. The -Wfrontend-loop-interchange option warns about such occurrences. * When an actual argument contains too few elements for a dummy argument, an error is now issued. The -std=legacy option can be used to still compile such code. * The RECL= argument to OPEN and INQUIRE statements now allows 64-bit integers, making records larger than 2GiB possible. * The GFORTRAN_DEFAULT_RECL environment variable no longer has any effect. The record length for preconnected units is now larger than any practical limit, same as for sequential access units opened without an explicit RECL= specifier. * Character variables longer than HUGE(0) elements are now possible on 64-bit targets. Note that this changes the procedure call ABI for all procedures with character arguments on 64-bit targets, as the type of the hidden character length argument has changed. The hidden character length argument is now of type INTEGER(C_SIZE_T). * Partial support is provided for Fortran 2018 teams, which are hierarchical subsets of images that execute independently of other image subsets. Go * GCC 8 provides a complete implementation of the Go 1.10.1 user packages. * The garbage collector is now fully concurrent. As before, values stored on the stack are scanned conservatively, but value stored in the heap are scanned precisely. * Escape analysis is fully implemented and enabled by default in the Go front end. This significantly reduces the number of heap allocations by allocating values on the stack instead. libgccjit The libgccjit API gained four new entry points: * [18]gcc_jit_type_get_vector and * [19]gcc_jit_context_new_rvalue_from_vector for working with vectors, * [20]gcc_jit_type_get_aligned * [21]gcc_jit_function_get_address The C code generated by [22]gcc_jit_context_dump_reproducer_to_file is now easier-to-read. New Targets and Target Specific Improvements AArch64 * The Armv8.4-A architecture is now supported. It can be used by specifying the -march=armv8.4-a option. * The Dot Product instructions are now supported as an optional extension to the Armv8.2-A architecture and newer and are mandatory on Armv8.4-A. The extension can be used by specifying the +dotprod architecture extension. E.g. -march=armv8.2-a+dotprod. * The Armv8-A +crypto extension has now been split into two extensions for finer grained control: + +aes which contains the Armv8-A AES crytographic instructions. + +sha2 which contains the Armv8-A SHA2 and SHA1 cryptographic instructions. Using +crypto will now enable these two extensions. * New Armv8.4-A FP16 Floating Point Multiplication Variant instructions have been added. These instructions are mandatory in Armv8.4-A but available as an optional extension to Armv8.2-A and Armv8.3-A. The new extension can be used by specifying the +fp16fml architectural extension on Armv8.2-A and Armv8.3-A. On Armv8.4-A the instructions can be enabled by specifying +fp16. * New cryptographic instructions have been added as optional extensions to Armv8.2-A and newer. These instructions can be enabled with: + +sha3 New SHA3 and SHA2 instructions from Armv8.4-A. This implies +sha2. + +sm4 New SM3 and SM4 instructions from Armv8.4-A. * The Scalable Vector Extension (SVE) is now supported as an optional extension to the Armv8.2-A architecture and newer. This support includes automatic vectorization with SVE instructions, but it does not yet include the SVE Arm C Language Extensions (ACLE). It can be enabled by specifying the +sve architecture extension (for example, -march=armv8.2-a+sve). By default, the generated code works with all vector lengths, but it can be made specific to N-bit vectors using -msve-vector-bits=N. * Support has been added for the following processors (GCC identifiers in parentheses): + Arm Cortex-A75 (cortex-a75). + Arm Cortex-A55 (cortex-a55). + Arm Cortex-A55/Cortex-A75 DynamIQ big.LITTLE (cortex-a75.cortex-a55). The GCC identifiers can be used as arguments to the -mcpu or -mtune options, for example: -mcpu=cortex-a75 or -mtune=cortex-a75 or as arguments to the equivalent target attributes and pragmas. ARC * Added support for: + Fast interrupts. + Naked functions. + aux variable attributes. + uncached type qualifier. + Secure functions via sjli instruction. * New exception handling implementation. * Revamped trampoline implementation. * Refactored small data feature implementation, controlled via the -G command-line option. * New support for reduced register set ARC architecture configurations, controlled via the -mrf16 command-line option. * Refurbished and improved support for zero overhead loops. Introduced -mlpc-width command-line option to control the width of the lp_count register. ARM * The -mfpu option now takes a new option setting of -mfpu=auto. When set to this the floating-point and SIMD settings are derived from the settings of the -mcpu or -march options. The internal CPU configurations have been updated with information about the permitted floating-point configurations supported. See the user guide for further information about the extended option syntax for controlling architectural extensions via the -march option. -mfpu=auto is now the default setting unless the compiler has been configured with an explicit --with-fpu option. * The -march and -mcpu options now accept optional extensions to the architecture or CPU option, allowing the user to enable or disable any such extensions supported by that architecture or CPU such as (but not limited to) floating-point and AdvancedSIMD. For example: the option -mcpu=cortex-a53+nofp will generate code for the Cortex-A53 processor with no floating-point support. This, in combination with the new -mfpu=auto option, provides a straightforward way of specifying a valid build target through a single -mcpu or -march option. The -mtune option accepts the same arguments as -mcpu but only the CPU name has an effect on tuning. The architecture extensions do not have any effect. For details of what extensions a particular architecture or CPU option supports please refer to the [23]documentation. * The -mstructure-size-boundary option has been deprecated and will be removed in a future release. * The default link behavior for Armv6 and Armv7-R targets has been changed to produce BE8 format when generating big-endian images. A new flag -mbe32 can be used to force the linker to produce legacy BE32 format images. There is no change of behavior for Armv6-M and other Armv7 or later targets: these already defaulted to BE8 format. This change brings GCC into alignment with other compilers for the ARM architecture. * The Armv8-R architecture is now supported. It can be used by specifying the -march=armv8-r option. * The Armv8.3-A architecture is now supported. It can be used by specifying the -march=armv8.3-a option. * The Armv8.4-A architecture is now supported. It can be used by specifying the -march=armv8.4-a option. * The Dot Product instructions are now supported as an optional extension to the Armv8.2-A architecture and newer and are mandatory on Armv8.4-A. The extension can be used by specifying the +dotprod architecture extension. E.g. -march=armv8.2-a+dotprod. * Support for setting extensions and architectures using the GCC target pragma and attribute has been added. It can be used by specifying #pragma GCC target ("arch=..."), #pragma GCC target ("+extension"), __attribute__((target("arch=..."))) or __attribute__((target("+extension"))). * New Armv8.4-A FP16 Floating Point Multiplication Variant instructions have been added. These instructions are mandatory in Armv8.4-A but available as an optional extension to Armv8.2-A and Armv8.3-A. The new extension can be used by specifying the +fp16fml architectural extension on Armv8.2-A and Armv8.3-A. On Armv8.4-A the instructions can be enabled by specifying +fp16. * Support has been added for the following processors (GCC identifiers in parentheses): + Arm Cortex-A75 (cortex-a75). + Arm Cortex-A55 (cortex-a55). + Arm Cortex-A55/Cortex-A75 DynamIQ big.LITTLE (cortex-a75.cortex-a55). + Arm Cortex-R52 for Armv8-R (cortex-r52). The GCC identifiers can be used as arguments to the -mcpu or -mtune options, for example: -mcpu=cortex-a75 or -mtune=cortex-r52 or as arguments to the equivalent target attributes and pragmas. AVR * The AVR port now supports the following XMEGA-like devices: ATtiny212, ATtiny214, ATtiny412, ATtiny414, ATtiny416, ATtiny417, ATtiny814, ATtiny816, ATtiny817, ATtiny1614, ATtiny1616, ATtiny1617, ATtiny3214, ATtiny3216, ATtiny3217 The new devices are listed under [24]-mmcu=avrxmega3. + These devices see flash memory in the RAM address space, so that features like PROGMEM and __flash are not needed any more (as opposed to other AVR families for which read-only data will be located in RAM except special, non-standard features are used to locate and access such data). This requires that the compiler is used with Binutils 2.29 or newer so that [25]read-only data will be located in flash memory. + A new command-line option -mshort-calls is supported. This option is used internally for multilib selection of the avrxmega3 variants. It is not an optimization option. Do not set it by hand. * The compiler now generates [26]efficient interrupt service routine (ISR) prologues and epilogues. This is achieved by using the new [27]AVR pseudo instruction __gcc_isr which is supported and resolved by the GNU assembler. + As the __gcc_isr pseudo-instruction will be resolved by the assembler, inline assembly is transparent to the process. This means that when inline assembly uses an instruction like INC that clobbers the condition code, then the assembler will detect this and generate an appropriate ISR prologue / epilogue chunk to save / restore SREG as needed. + A new command-line option -mno-gas-isr-prologues disables the generation of the __gcc_isr pseudo instruction. Any non-naked ISR will save and restore SREG, tmp_reg and zero_reg, no matter whether the respective register is clobbered or used. + The feature is turned on per default for all optimization levels except for -O0 and -Og. It is explicitly enabled by means of option -mgas-isr-prologues. + Support has been added for a new [28]AVR function attribute no_gccisr. It can be used to disable __gcc_isr pseudo instruction generation for individual ISRs. + This optimization is only available if GCC is configured with GNU Binutils 2.29 or newer; or at least with a version of Binutils that implements feature [29]PR21683. * The compiler no more saves / restores registers in main; the effect is the same as if attribute OS_task was specified for main. This optimization can be switched off by the new command-line option -mno-main-is-OS_task. IA-32/x86-64 * The x86 port now supports the naked function attribute. * Better tuning for znver1 and Intel Core based CPUs. * Vectorization cost metrics has been reworked leading to significant improvements on some benchmarks. * GCC now supports the Intel CPU named Cannonlake through -march=cannonlake. The switch enables the AVX512VBMI, AVX512IFMA and SHA ISA extensions. * GCC now supports the Intel CPU named Icelake through -march=icelake. The switch enables the AVX512VNNI, GFNI, VAES, AVX512VBMI2, VPCLMULQDQ, AVX512BITALG, RDPID and AVX512VPOPCNTDQ ISA extensions. * GCC now supports the Intel Control-flow Enforcement Technology (CET) extension through -fcf-protection option. NDS32 * New command-line options -mext-perf, -mext-perf2, and -mext-string have been added for performance extension instructions. Nios II * The Nios II back end has been improved to generate better-optimized code. Changes include switching to LRA, more accurate cost models, and more compact code for addressing static variables. * New command-line options -mgprel-sec= and -mr0rel-sec= have been added. * The stack-smashing protection options are now enabled on Nios II. PA-RISC * The default call ABI on 32-bit linux has been changed from callee copies to caller copies. This affects objects larger than eight bytes passed by value. The goal is to improve compatibility with x86 and resolve issues with OpenMP. * Other PA-RISC targets are unchanged. PowerPC / PowerPC64 / RS6000 * The PowerPC SPE support is split off to a separate powerpcspe port. The separate port is deprecated and might be removed in a future release. * The Paired Single support (as used on some PPC750 CPUs, -mpaired, powerpc*-*-linux*paired*) is deprecated and will be removed in a future release. * The Xilinx floating point support (-mxilinx-fpu, powerpc-xilinx-eabi*) is deprecated and will be removed in a future release. * Support for using big-endian AltiVec intrinsics on a little-endian target (-maltivec=be) is deprecated and will be removed in a future release. Tile * The TILE-Gx port is deprecated and will be removed in a future release. Operating Systems Windows * GCC on Microsoft Windows can now be configured via --enable-mingw-wildcard or --disable-mingw-wildcard to force a specific behavior for GCC itself with regards to supporting the wildcard character. Prior versions of GCC would follow the configuration of the MinGW runtime. This behavior can still be obtained by not using the above options or by using --enable-mingw-wildcard=platform. Improvements for plugin authors * Plugins can now register a callback hook for when comments are encountered by the C and C++ compilers, e.g. allowing for plugins to handle documentation markup in code comments. * The gdbinit support script for debugging GCC now has a break-on-diagnostic command, providing an easy way to trigger a breakpoint whenever a diagnostic is emitted. * The API for creating fix-it hints now supports newlines, and for emitting mutually incompatible fix-it hints for one diagnostic. GCC 8.1 This is the [30]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 8.1 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 8.2 This is the [31]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 8.2 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). General Improvements * Fixed LTO link-time performance problems caused by an overflow in the partitioning algorithm while building large binaries. Language Specific Changes C++ GCC 8.2 fixed a bug introduced in GCC 8.1 affecting passing or returning of classes with a deleted copy constructor and defaulted trivial move constructor (bug [32]c++/86094). GCC 8.2 introduces -fabi-version=13 and makes it the default, ABI incompatibilities between GCC 8.1 and 8.2 can be reported with -Wabi=12. See [33]C++ changes for more details. Target Specific Changes IA-32/x86-64 * -mtune=native performance regression [34]PR84413 on Intel Skylake processors has been fixed. GCC 8.3 This is the [35]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 8.3 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Windows * A C++ Microsoft ABI bitfield layout bug, [36]PR87137 has been fixed. A non-field declaration could cause the current bitfield allocation unit to be completed, incorrectly placing a following bitfield into a new allocation unit. The Microsoft ABI is selected for: + Mingw targets + PowerPC, IA-32 or x86-64 targets when the -mms-bitfields option is specified, or __attribute__((ms_struct)) is used + SuperH targets when the -mhitachi option is specified, or __attribute__((renesas)) is used GCC 8 introduced additional cases of this defect, but rather than resolve only those regressions, we decided to resolve all the cases of this defect in single change. GCC 8.4 This is the [37]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 8.4 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 8.5 This is the [38]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 8.5 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Target Specific Changes AArch64 * The option -moutline-atomics has been added to aid deployment of the Large System Extensions (LSE) on GNU/Linux systems built with a baseline architecture targeting Armv8-A. When the option is specified code is emitted to detect the presence of LSE instructions at run time and use them for standard atomic operations. For more information please refer to the documentation. For questions related to the use of GCC, please consult these web pages and the [39]GCC manuals. If that fails, the [40]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [41]gcc@gcc.gnu.org. All of [42]our lists have public archives. Copyright (C) [43]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [44]maintained by the GCC team. Last modified 2023-01-11. References 1. https://gcc.gnu.org/gcc-8/porting_to.html 2. https://gcc.gnu.org/onlinedocs/index.html#current 3. https://gcc.gnu.org/ml/gcc/2018-04/msg00102.html 4. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/Warning-Options.html#index-Wmultistatement-macros 5. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/Warning-Options.html#index-Wstringop-truncation 6. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82944 7. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/Warning-Options.html#index-Wif-not-aligned 8. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/Common-Variable-Attributes.html#index-warn_005fif_005fnot_005faligned-variable-attribute 9. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/Warning-Options.html#index-Wmissing-attributes 10. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/Warning-Options.html#index-Wpacked-not-aligned 11. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/Warning-Options.html#index-Warray-bounds 12. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/Warning-Options.html#index-Wrestrict 13. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/Warning-Options.html#index-Wformat-overflow 14. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/Warning-Options.html#index-Wformat-truncation 15. https://gcc.gnu.org/PR86094 16. https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Dialect-Options.html#index-Wclass-memaccess 17. https://gcc.gnu.org/projects/cxx-status.html#cxx2a 18. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/jit/topics/types.html#gcc_jit_type_get_vector 19. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/jit/topics/expressions.html#gcc_jit_context_new_rvalue_from_vector 20. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/jit/topics/types.html#gcc_jit_type_get_aligned 21. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/jit/topics/function-pointers.html#gcc_jit_function_get_address 22. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/jit/topics/contexts.html#gcc_jit_context_dump_reproducer_to_file 23. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/ARM-Options.html#ARM-Options 24. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/AVR-Options.html 25. https://sourceware.org/PR21472 26. https://gcc.gnu.org/PR20296 27. https://sourceware.org/binutils/docs-2.29/as/AVR-Pseudo-Instructions.html 28. https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/AVR-Function-Attributes.html 29. https://sourceware.org/PR21683 30. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=8.0 31. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=8.2 32. https://gcc.gnu.org/PR86094 33. https://gcc.gnu.org/gcc-8/changes.html#cxx 34. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84413 35. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=8.3 36. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87137 37. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=8.4 38. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=8.5 39. https://gcc.gnu.org/onlinedocs/ 40. mailto:gcc-help@gcc.gnu.org 41. mailto:gcc@gcc.gnu.org 42. https://gcc.gnu.org/lists.html 43. https://www.fsf.org/ 44. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-7/index.html GCC 7 Release Series (This release series is no longer supported.) Nov 14, 2019 The [1]GNU project and the GCC developers are pleased to announce the release of GCC 7.5. This release is a bug-fix release, containing fixes for regressions in GCC 7.4 relative to previous releases of GCC. Release History GCC 7.5 Nov 14, 2019 ([2]changes, [3]documentation) GCC 7.4 Dec 6, 2018 ([4]changes, [5]documentation) GCC 7.3 Jan 25, 2018 ([6]changes, [7]documentation) GCC 7.2 Aug 14, 2017 ([8]changes, [9]documentation) GCC 7.1 May 2, 2017 ([10]changes, [11]documentation) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. A list of [12]successful builds is updated as new information becomes available. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [13]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [14]GCC project web site or contact the [15]GCC development mailing list. To obtain GCC please use [16]our mirror sites or [17]our version control system. For questions related to the use of GCC, please consult these web pages and the [18]GCC manuals. If that fails, the [19]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [20]gcc@gcc.gnu.org. All of [21]our lists have public archives. Copyright (C) [22]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [23]maintained by the GCC team. Last modified 2024-05-30. References 1. http://www.gnu.org/ 2. https://gcc.gnu.org/gcc-7/changes.html 3. https://gcc.gnu.org/onlinedocs/7.5.0/ 4. https://gcc.gnu.org/gcc-7/changes.html 5. https://gcc.gnu.org/onlinedocs/7.4.0/ 6. https://gcc.gnu.org/gcc-7/changes.html 7. https://gcc.gnu.org/onlinedocs/7.3.0/ 8. https://gcc.gnu.org/gcc-7/changes.html 9. https://gcc.gnu.org/onlinedocs/7.2.0/ 10. https://gcc.gnu.org/gcc-7/changes.html 11. https://gcc.gnu.org/onlinedocs/7.1.0/ 12. https://gcc.gnu.org/gcc-7/buildstat.html 13. https://gcc.gnu.org/onlinedocs/gcc/Contributors.html 14. https://gcc.gnu.org/index.html 15. mailto:gcc@gcc.gnu.org 16. https://gcc.gnu.org/mirrors.html 17. https://gcc.gnu.org/git.html 18. https://gcc.gnu.org/onlinedocs/ 19. mailto:gcc-help@gcc.gnu.org 20. mailto:gcc@gcc.gnu.org 21. https://gcc.gnu.org/lists.html 22. https://www.fsf.org/ 23. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-7/changes.html GCC 7 Release Series Changes, New Features, and Fixes This page is a brief summary of some of the huge number of improvements in GCC 7. For more information, see the [1]Porting to GCC 7 page and the [2]full GCC documentation. Caveats * GCC now uses [3]LRA (a new local register allocator) by default for new targets. * The non-standard C++0x type traits has_trivial_default_constructor, has_trivial_copy_constructor and has_trivial_copy_assign have been removed. * The libstdc++ [4]Profile Mode has been deprecated and will be removed in a future version. * The Cilk+ extensions to the C and C++ languages have been deprecated. * On ARM targets (arm*-*-*), [5]a bug introduced in GCC 5 that affects conformance to the procedure call standard (AAPCS) has been fixed. The bug affects some C++ code where class objects are passed by value to functions and could result in incorrect or inconsistent code being generated. This is an ABI change. If the option -Wpsabi is enabled (on by default) the compiler will emit a diagnostic note for code that might be affected. General Optimizer Improvements * GCC 7 can determine the return value or range of return values of some calls to the sprintf family of functions and make it available to other optimization passes. Some calls to the snprintf function with a zero size argument can be folded into constants. This optimization is included in -O1 and can be selectively controlled by the -fprintf-return-value option. * A new store merging pass has been added. It merges constant stores to adjacent memory locations into fewer, wider, stores. It is enabled by the -fstore-merging option and at the -O2 optimization level or higher (and -Os). * A new code hoisting optimization has been added to the partial redundancy elimination pass. It attempts to move evaluation of expressions executed on all paths to the function exit as early as possible. This primarily helps improve code size, but can improve the speed of the generated code as well. It is enabled by the -fcode-hoisting option and at the -O2 optimization level or higher (and -Os). * A new interprocedural bitwise constant propagation optimization has been added, which propagates knowledge about which bits of variables are known to be zero (including pointer alignment information) across the call graph. It is enabled by the -fipa-bit-cp option if -fipa-cp is enabled as well, and is enabled at the -O2 optimization level and higher (and -Os). This optimization supersedes interprocedural alignment propagation of GCC 6, and therefore the option -fipa-cp-alignment is now deprecated and ignored. * A new interprocedural value range propagation optimization has been added, which propagates integral range information across the call graph when variable values can be proven to be within those ranges. It is enabled by the -fipa-vrp option and at the -O2 optimization level and higher (and -Os). * A new loop splitting optimization pass has been added. Certain loops which contain a condition that is always true on one side of the iteration space and always false on the other are split into two loops, such that each of the two new loops iterates on just one side of the iteration space and the condition does not need to be checked inside of the loop. It is enabled by the -fsplit-loops option and at the -O3 optimization level or higher. * The shrink-wrapping optimization can now separate portions of prologues and epilogues to improve performance if some of the work done traditionally by prologues and epilogues is not needed on certain paths. This is controlled by the -fshrink-wrap-separate option, enabled by default. It requires target support, which is currently only implemented in the PowerPC and AArch64 ports. * AddressSanitizer gained a new sanitization option, -fsanitize-address-use-after-scope, which enables sanitization of variables whose address is taken and used after a scope where the variable is defined: int main (int argc, char **argv) { char *ptr; { char my_char; ptr = &my_char; } *ptr = 123; return *ptr; } ==28882==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7fffb8dba99 0 at pc 0x0000004006d5 bp 0x7fffb8dba960 sp 0x7fffb8dba958 WRITE of size 1 at 0x7fffb8dba990 thread T0 #0 0x4006d4 in main /tmp/use-after-scope-1.c:10 #1 0x7f9c71943290 in __libc_start_main (/lib64/libc.so.6+0x20290) #2 0x400739 in _start (/tmp/a.out+0x400739) Address 0x7fffb8dba990 is located in stack of thread T0 at offset 32 in frame #0 0x40067f in main /tmp/use-after-scope-1.c:3 This frame has 1 object(s): [32, 33) 'my_char' <== Memory access at offset 32 is inside this variable The option is enabled by default with -fsanitize=address and disabled by default with -fsanitize=kernel-address. Compared to the LLVM compiler, where the option already exists, the implementation in the GCC compiler has some improvements and advantages: + Complex uses of gotos and case labels are properly handled and should not report any false positive or false negatives. + C++ temporaries are sanitized. + Sanitization can handle invalid memory stores that are optimized out by the LLVM compiler when optimization is enabled. * The -fsanitize=signed-integer-overflow suboption of the UndefinedBehavior Sanitizer now diagnoses arithmetic overflows even on arithmetic operations with generic vectors. * Version 5 of the DWARF debugging information standard is supported through the -gdwarf-5 option. The DWARF version 4 debugging information remains the default until consumers of debugging information are adjusted. New Languages and Language specific improvements OpenACC support in C, C++, and Fortran continues to be maintained and improved. See the [6]OpenACC and [7]Offloading wiki pages for further information. Ada * On mainstream native platforms, Ada programs no longer require the stack to be made executable in order to run properly. BRIG (HSAIL) Support for processing BRIG 1.0 files was added in this release. BRIG is a binary format for HSAIL (Heterogeneous System Architecture Intermediate Language). The BRIG front end can be used for implementing HSAIL "finalizers" (compilation of HSAIL to a native ISA) for GCC-supported targets. An implementation of an HSAIL runtime library, libhsail-rt is also included. C family * New command-line options have been added for the C and C++ compilers: + -Wimplicit-fallthrough warns when a switch case falls through. This warning has five different levels. The compiler is able to parse a wide range of fallthrough comments, depending on the level. It also handles control-flow statements, such as ifs. It's possible to suppress the warning by either adding a fallthrough comment, or by using a null statement: __attribute__ ((fallthrough)); (C, C++), or [[fallthrough]]; (C++17), or [[gnu::fallthrough]]; (C++11/C++14). This warning is enabled by -Wextra. + -Wpointer-compare warns when a pointer is compared with a zero character constant. Such code is now invalid in C++11 and GCC rejects it. This warning is enabled by default. + -Wduplicated-branches warns when an if-else has identical branches. + -Wrestrict warns when an argument passed to a restrict-qualified parameter aliases with another argument. + -Wmemset-elt-size warns for memset calls, when the first argument references an array, and the third argument is a number equal to the number of elements of the array, but not the size of the array. This warning is enabled by -Wall. + -Wint-in-bool-context warns about suspicious uses of integer values where boolean values are expected. This warning is enabled by -Wall. + -Wswitch-unreachable warns when a switch statement has statements between the controlling expression and the first case label which will never be executed. This warning is enabled by default. + -Wexpansion-to-defined warns when defined is used outside #if. This warning is enabled by -Wextra or -Wpedantic. + -Wregister warns about uses of the register storage specifier. In C++17 this keyword has been removed and for C++17 this is a pedantic warning enabled by default. The warning is not emitted for the GNU Explicit Register Variables extension. + -Wvla-larger-than=N warns about unbounded uses of variable-length arrays, and about bounded uses of variable-length arrays whose bound can be larger than N bytes. + -Wduplicate-decl-specifier warns when a declaration has duplicate const, volatile, restrict or _Atomic specifier. This warning is enabled by -Wall. * GCC 6's C and C++ front ends were able to offer suggestions for misspelled field names: spellcheck-fields.cc:52:13: error: 'struct s' has no member named 'colour'; did you mean 'color'? return ptr->colour; ^~~~~~ GCC 7 greatly expands the scope of these suggestions. Firstly, it adds fix-it hints to such suggestions: spellcheck-fields.cc:52:13: error: 'struct s' has no member named 'colour'; did you mean 'color'? return ptr->colour; ^~~~~~ color The suggestions now cover many other things, such as misspelled function names: spellcheck-identifiers.c:11:3: warning: implicit declaration of function 'gtk_wi dget_showall'; did you mean 'gtk_widget_show_all'? [-Wimplicit-function-declarat ion] gtk_widget_showall (w); ^~~~~~~~~~~~~~~~~~ gtk_widget_show_all misspelled macro names and enum values: spellcheck-identifiers.cc:85:11: error: 'MAX_ITEM' undeclared here (not in a fun ction); did you mean 'MAX_ITEMS'? int array[MAX_ITEM]; ^~~~~~~~ MAX_ITEMS misspelled type names: spellcheck-typenames.c:7:14: error: unknown type name 'singed'; did you mean 'si gned'? void test (singed char e); ^~~~~~ signed and, in the C front end, named initializers: test.c:7:20: error: 'struct s' has no member named 'colour'; did you mean 'color '? struct s test = { .colour = 3 }; ^~~~~~ color * The preprocessor can now offer suggestions for misspelled directives, e.g.: test.c:5:2: error:invalid preprocessing directive #endfi; did you mean #endif? #endfi ^~~~~ endif * Warnings about format strings now underline the pertinent part of the string, and can offer suggested fixes. In some cases, the pertinent argument is underlined. test.c:51:29: warning: format '%s' expects argument of type 'char *', but argume nt 3 has type 'int' [-Wformat=] printf ("foo: %d bar: %s baz: %d", 100, i + j, 102); ~^ ~~~~~ %d * The new -Wdangling-else command-line option has been split out of -Wparentheses and warns about dangling else. * The -Wshadow warning has been split into three variants. -Wshadow=global warns for any shadowing. This is the default when using -Wshadow without any argument. -Wshadow=local only warns for a local variable shadowing another local variable or parameter. -Wshadow=compatible-local only warns for a local variable shadowing another local variable or parameter whose type is compatible (in C++ compatible means that the type of the shadowing variable can be converted to that of the shadowed variable). The following example shows the different kinds of shadow warnings: enum operation { add, count }; struct container { int nr; }; int container_count (struct container c, int count) { int r = 0; for (int count = 0; count > 0; count--) { struct container count = c; r += count.nr; } return r; } -Wshadow=compatible-local will warn for the parameter being shadowed with the same type: warn-test.c:8:12: warning: declaration of 'count' shadows a parameter [-Wshadow= compatible-local] for (int count = 0; count > 0; count--) ^~~~~ warn-test.c:5:42: note: shadowed declaration is here container_count (struct container c, int count) ^~~~~ -Wshadow=local will warn for the above and for the shadowed declaration with incompatible type: warn-test.c:10:24: warning: declaration of 'count' shadows a previous local [-Ws hadow=local] struct container count = c; ^~~~~ warn-test.c:8:12: note: shadowed declaration is here for (int count = 0; count > 0; count--) ^~~~~ -Wshadow=global will warn for all of the above and the shadowing of the global declaration: warn-test.c:5:42: warning: declaration of 'count' shadows a global declaration [ -Wshadow] container_count (struct container c, int count) ^~~~~ warn-test.c:1:23: note: shadowed declaration is here enum operation { add, count }; ^~~~~ * GCC 7 contains a number of enhancements that help detect buffer overflow and other forms of invalid memory accesses. + The -Walloc-size-larger-than=size option detects calls to standard and user-defined memory allocation functions decorated with attribute alloc_size whose argument exceeds the specified size (PTRDIFF_MAX by default). The option also detects arithmetic overflow in the computation of the size in two-argument allocation functions like calloc where the total size is the product of the two arguments. Since calls with an excessive size cannot succeed they are typically the result of programming errors. Such bugs have been known to be the source of security vulnerabilities and a target of exploits. -Walloc-size-larger-than=PTRDIFF_MAX is included in -Wall. For example, the following call to malloc incorrectly tries to avoid passing a negative argument to the function and instead ends up unconditionally invoking it with an argument less than or equal to zero. Since after conversion to the type of the argument of the function (size_t) a negative argument results in a value in excess of the maximum PTRDIFF_MAX the call is diagnosed. void* f (int n) { return malloc (n > 0 ? 0 : n); } warning: argument 1 range [2147483648, 4294967295] exceeds maximum object size 2 147483647 [-Walloc-size-larger-than=] + The -Walloc-zero option detects calls to standard and user-defined memory allocation functions decorated with attribute alloc_size with a zero argument. -Walloc-zero is not included in either -Wall or -Wextra and must be explicitly enabled. + The -Walloca option detects all calls to the alloca function in the program. -Walloca is not included in either -Wall or -Wextra and must be explicitly enabled. + The -Walloca-larger-than=size option detects calls to the alloca function whose argument either may exceed the specified size, or that is not known to be sufficiently constrained to avoid exceeding it. -Walloca-larger-than is not included in either -Wall or -Wextra and must be explicitly enabled. For example, compiling the following snippet with -Walloca-larger-than=1024 results in a warning because even though the code appears to call alloca only with sizes of 1kb and less, since n is signed, a negative value would result in a call to the function well in excess of the limit. void f (int n) { char *d; if (n < 1025) d = alloca (n); else d = malloc (n); … } warning: argument to 'alloca may be too large due to conversion from 'int' to 'l ong unsigned int' [-Walloca-larger-than=] In contrast, a call to alloca that isn't bounded at all such as in the following function will elicit the warning below regardless of the size argument to the option. void f (size_t n) { char *d = alloca (n); … } warning: unbounded use of 'alloca' [-Walloca-larger-than=] + The -Wformat-overflow=level option detects certain and likely buffer overflow in calls to the sprintf family of formatted output functions. Although the option is enabled even without optimization it works best with -O2 and higher. For example, in the following snippet the call to sprintf is diagnosed because even though its output has been constrained using the modulo operation it could result in as many as three bytes if mday were negative. The solution is to either allocate a larger buffer or make sure the argument is not negative, for example by changing mday's type to unsigned or by making the type of the second operand of the modulo expression unsigned: 100U. void* f (int mday) { char *buf = malloc (3); sprintf (buf, "%02i", mday % 100); return buf; } warning: 'sprintf may write a terminating nul past the end of the destination [- Wformat-overflow=] note: 'sprintf' output between 3 and 4 bytes into a destination of size 3 + The -Wformat-truncation=level option detects certain and likely output truncation in calls to the snprintf family of formatted output functions. -Wformat-truncation=1 is included in -Wall and enabled without optimization but works best with -O2 and higher. For example, the following function attempts to format an integer between 0 and 255 in hexadecimal, including the 0x prefix, into a buffer of four characters. But since the function must always terminate output by the null character ('\0') such a buffer is only big enough to fit just one digit plus the prefix. Therefore the snprintf call is diagnosed. To avoid the warning either use a bigger buffer or handle the function's return value which indicates whether or not its output has been truncated. void f (unsigned x) { char d[4]; snprintf (d, sizeof d, "%#02x", x & 0xff); … } warning: 'snprintf' output may be truncated before the last format character [-W format-truncation=] note: 'snprintf' output between 3 and 5 bytes into a destination of size 4 + The -Wnonnull option has been enhanced to detect a broader set of cases of passing null pointers to functions that expect a non-null argument (those decorated with attribute nonnull). By taking advantage of optimizations the option can detect many more cases of the problem than in prior GCC versions. + The -Wstringop-overflow=type option detects buffer overflow in calls to string handling functions like memcpy and strcpy. The option relies on [8]Object Size Checking and has an effect similar to defining the _FORTIFY_SOURCE macro. -Wstringop-overflow=2 is enabled by default. For example, in the following snippet, because the call to strncat specifies a maximum that allows the function to write past the end of the destination, it is diagnosed. To correct the problem and avoid the overflow the function should be called with a size of at most sizeof d - strlen(d) - 1. void f (const char *fname) { char d[8]; strncpy (d, "/tmp/", sizeof d); strncat (d, fname, sizeof d); … } warning: specified bound 8 equals the size of the destination [-Wstringop-overfl ow=] * The header provided by GCC defines macros such as INT_WIDTH for the width in bits of integer types, if __STDC_WANT_IEC_60559_BFP_EXT__ is defined before the header is included. The header defines such macros as SIZE_WIDTH and INTMAX_WIDTH for the width of some standard typedef names for integer types, again if __STDC_WANT_IEC_60559_BFP_EXT__ is defined before the header is included; note that GCC's implementation of this header is only used for freestanding compilations, not hosted compilations, on most systems. These macros come from ISO/IEC TS 18661-1:2014. * The header provided by GCC defines the macro CR_DECIMAL_DIG, from ISO/IEC TS 18661-1:2014, if __STDC_WANT_IEC_60559_BFP_EXT__ is defined before the header is included. This represents the number of decimal digits for which conversions between decimal character strings and binary formats, in both directions, are correctly rounded, and currently has the value of UINTMAX_MAX on all systems, reflecting that GCC's compile-time conversions are correctly rounded for any number of digits. * New __builtin_add_overflow_p, __builtin_sub_overflow_p, __builtin_mul_overflow_p built-in functions have been added. These work similarly to their siblings without the _p suffix, but do not actually store the result of the arithmetics anywhere, just return whether the operation would overflow. Calls to these built-ins with integer constant arguments evaluate to integer constants expressions. For example, in the following, c is assigned the result of a * b only if the multiplication does not overflow, otherwise it is assigned the value zero. The multiplication is performed at compile-time and without triggering a -Woverflow warning. enum { a = 12345678, b = 87654321, c = __builtin_mul_overflow_p (a, b, a) ? 0 : a * b }; C * The C front end now supports type names _FloatN for floating-point types with IEEE interchange formats and _FloatNx for floating-point types with IEEE extended formats. These type names come from ISO/IEC TS 18661-3:2015. The set of types supported depends on the target for which GCC is configured. Most targets support _Float32, _Float32x and _Float64. _Float128 is supported on targets where IEEE binary128 encoding was already supported as long double or __float128. _Float64x is supported on targets where a type with either binary128 or Intel extended precision format is available. Constants with these types are supported using suffixes fN, FN, fNx and FNx (e.g., 1.2f128 or 2.3F64x). Macros such as FLT128_MAX are defined in if __STDC_WANT_IEC_60559_TYPES_EXT__ is defined before it is included. These new types are always distinct from each other and from float, double and long double, even if they have the same encoding. Complex types such as _Complex _Float128 are also supported. Type-generic built-in functions such as __builtin_isinf support the new types, and the following type-specific built-in functions have versions (suffixed fN or fNx) for the new types: __builtin_copysign, __builtin_fabs, __builtin_huge_val, __builtin_inf, __builtin_nan, __builtin_nans. * Compilation with -fopenmp is now compatible with the C11 _Atomic keyword. C++ * The C++ front end has experimental support for all of the current C++17 draft with the -std=c++1z or -std=gnu++1z flags, including if constexpr, class template argument deduction, auto template parameters, and structured bindings. For a full list of new features, see [9]the C++ status page. * C++17 support for new of over-aligned types can be enabled in other modes with the -faligned-new flag. * The C++17 evaluation order requirements can be selected in other modes with the -fstrong-eval-order flag, or disabled in C++17 mode with -fno-strong-eval-order. * The default semantics of inherited constructors has changed in all modes, following [10]P0136. Essentially, overload resolution happens as if calling the inherited constructor directly, and the compiler fills in construction of the other bases and members as needed. Most uses should not need any changes. The old behavior can be restored with -fno-new-inheriting-ctors, or -fabi-version less than 11. * The resolution of DR 150 on matching of template template parameters, allowing default template arguments to make a template match a parameter, is currently enabled by default in C++17 mode only. The default can be overridden with -f{no-,}new-ttp-matching. * The C++ front end will now provide fix-it hints for some missing semicolons, allowing for automatic fixes by IDEs: test.cc:4:11: error: expected ';' after class definition class a {} ^ ; * -Waligned-new has been added to the C++ front end. It warns about new of type with extended alignment without -faligned-new. Runtime Library (libstdc++) * The type of exception thrown by iostreams, std::ios_base::failure, now uses the [11]cxx11 ABI. * Experimental support for C++17, including the following new features: + std::string_view; + std::any, std::optional, and std::variant; + std::invoke, std::is_invocable, std::is_nothrow_invocable, and invoke_result; + std::is_swappable, and std::is_nothrow_swappable; + std::apply, and std::make_from_tuple; + std::void_t, std::bool_constant, std::conjunction, std::disjunction, and std::negation; + Variable templates for type traits; + Mathematical Special Functions; + std::chrono::floor, std::chrono::ceil, std::chrono::round, and std::chrono::abs; + std::clamp, std::gcd, std::lcm, 3-dimensional std::hypot; + std::scoped_lock, std::shared_mutex, std::atomic::is_always_lock_free; + std::sample, std::default_searcher, std::boyer_moore_searcher and std::boyer_moore_horspool_searcher; + Extraction and re-insertion of map and set nodes, try_emplace members for maps, and functions for accessing containers std::size, std::empty, and std::data; + std::shared_ptr support for arrays, std::shared_ptr::weak_type, std::enable_shared_from_this::weak_from_this(), and std::owner_less; + std::byte; + std::as_const, std::not_fn, std::has_unique_object_representations, constexpr std::addressof. Thanks to Daniel Krügler, Tim Shen, Edward Smith-Rowland, and Ville Voutilainen for work on the C++17 support. * A new power-of-two rehashing policy for use with the _Hashtable internals, thanks to François Dumont. Fortran * Support for a number of extensions for compatibility with legacy code with new flags: + -fdec-structure Support for DEC STRUCTURE and UNION + -fdec-intrinsic-ints Support for new integer intrinsics with B/I/J/K prefixes such as BABS, JIAND... + -fdec-math Support for additional math intrinsics, including COTAN and degree-valued trigonometric functions such as TAND, ASIND... + -fdec Enable the -fdec-* family of extensions. * New flag -finit-derived to allow default initialization of derived-type variables. * Improved DO loops with step equal to 1 or -1, generates faster code without a loop preheader. A new warning, -Wundefined-do-loop, warns when a loop iterates either to HUGE(i) (with step equal to 1), or to -HUGE(i) (with step equal to -1). Invalid behavior can be caught at run time with -fcheck=do enabled: program test implicit none integer(1) :: i do i = -HUGE(i)+10, -HUGE(i)-1, -1 print *, i end do end program test At line 8 of file do_check_12.f90 Fortran runtime error: Loop iterates infinitely * Version 4.5 of the [12]OpenMP specification is now partially supported in the Fortran compiler; the largest missing item is structure element mapping. * User-defined derived-type input/output (UDTIO) is added. * Derived type coarrays with allocatable and pointer components are partially supported. * Non-constant stop codes and error stop codes (Fortran 2015 feature). * Derived types with allocatable components of recursive type. * Intrinsic assignment to polymorphic variables. * Improved submodule support. * Improved diagnostics (polymorphic results in pure functions). * Coarray: Support for failed images (Fortan 2015 feature). Go * GCC 7 provides a complete implementation of the Go 1.8.1 user packages. * Compared to the Go 1.8.1 toolchain, the garbage collector is more conservative and less concurrent. * Escape analysis is available for experimental use via the -fgo-optimize-allocs option. The -fgo-debug-escape prints information useful for debugging escape analysis choices. Java (GCJ) The GCC Java front end and associated libjava runtime library have been removed from GCC. libgccjit The libgccjit API gained support for marking calls as requiring tail-call optimization via a new entry point: [13]gcc_jit_rvalue_set_bool_require_tail_call. libgccjit performs numerous checks at the API boundary, but if these succeed, it previously ignored errors and other diagnostics emitted within the core of GCC, and treated the compile of a gcc_jit_context as having succeeded. As of GCC 7 it now ensures that if any diagnostics are emitted, they are visible from the libgccjit API, and that the the context is flagged as having failed. New Targets and Target Specific Improvements AArch64 * GCC has been updated to the latest revision of the procedure call standard (AAPCS64) to provide support for parameter passing when data types have been over-aligned. * The ARMv8.3-A architecture is now supported. It can be used by specifying the -march=armv8.3-a option. * The option -msign-return-address= is supported to enable return address protection using ARMv8.3-A Pointer Authentication Extensions. For more information on the arguments accepted by this option, please refer to [14]AArch64-Options. * The ARMv8.2-A architecture and the ARMv8.2-A 16-bit Floating-Point Extensions are now supported. They can be used by specifying the -march=armv8.2-a or -march=armv8.2-a+fp16 options. The 16-bit Floating-Point Extensions introduce new half-precision data processing floating-point instructions. * Support has been added for the following processors (GCC identifiers in parentheses): ARM Cortex-A73 (cortex-a73), Broadcom Vulcan (vulcan), Cavium ThunderX CN81xx (thunderxt81), Cavium ThunderX CN83xx (thunderxt83), Cavium ThunderX CN88xx (thunderxt88), Cavium ThunderX CN88xx pass 1.x (thunderxt88p1), Cavium ThunderX 2 CN99xx (thunderx2t99), Qualcomm Falkor (falkor). The GCC identifiers can be used as arguments to the -mcpu or -mtune options, for example: -mcpu=cortex-a73 or -mtune=vulcan or as arguments to the equivalent target attributes and pragmas. ARC * Added support for ARC HS and ARC EM processors. * Added support for ARC EM variation found in Intel QuarkSE SoCs. * Added support for NPS400 ARC700 based CPUs. * Thread Local Storage is now supported by ARC CPUs. * Fixed errors for ARC600 when using 32x16 multiplier option. * Fixed PIE for ARC CPUs. * New CPU templates are supported via multilib. ARM * Support for the ARMv5 and ARMv5E architectures has been deprecated (which have no known implementations) and will be removed in a future GCC release. Note that ARMv5T, ARMv5TE and ARMv5TEJ architectures remain supported. The values armv5 and armv5e of -march are thus deprecated. * The ARMv8.2-A architecture and the ARMv8.2-A 16-bit Floating-Point Extensions are now supported. They can be used by specifying the -march=armv8.2-a or -march=armv8.2-a+fp16 options. The 16-bit Floating-Point Extensions introduce new half-precision data processing floating-point instructions. * The ARMv8-M architecture is now supported in its two architecture profiles: ARMv8-M Baseline and ARMv8-M Mainline with its DSP and Floating-Point Extensions. They can be used by specifying the -march=armv8-m.base, armv8-m.main or armv8-m.main+dsp options. * Support has been added for the following processors (GCC identifiers in parentheses): ARM Cortex-A73 (cortex-a73), ARM Cortex-M23 (cortex-m23) and ARM Cortex-M33 (cortex-m33). The GCC identifiers can be used as arguments to the -mcpu or -mtune options, for example: -mcpu=cortex-a73 or -mtune=cortex-m33. * A new command-line option -mpure-code has been added. It does not allow constant data to be placed in code sections. This option is only available when generating non-PIC code for ARMv7-M targets. * Support for the ACLE Coprocessor Intrinsics has been added. This enables the generation of coprocessor instructions through the use of intrinsics such as cdp, ldc, and others. * The configure option --with-multilib-list now accepts the value rmprofile to build multilib libraries for a range of embedded targets. See our [15]installation instructions for details. AVR * On the reduced Tiny cores, the progmem [16]variable attribute is now properly supported. Respective read-only variables are located in flash memory in section .progmem.data. No special code is needed to access such variables; the compiler automatically adds an offset of 0x4000 to all addresses, which is needed to access variables in flash memory. As opposed to ordinary cores where it is sufficient to specify the progmem attribute with definitions, on the reduced Tiny cores the attribute also has to be specified with (external) declarations: extern const int array[] __attribute__((__progmem__)); int get_value2 (void) { /* Access via addresses array + 0x4004 and array + 0x4005. */ return array[2]; } const int* get_address (unsigned idx) { /* Returns array + 0x4000 + 2 * idx. */ return &array[idx]; } * A new command-line option -Wmisspelled-isr has been added. It turns off — or turns into errors — warnings that are reported for interrupt service routines (ISRs) which don't follow AVR-LibC's naming convention of prefixing ISR names with __vector. * __builtin_avr_nops(n) is a new [17]built-in function that inserts n NOP instructions into the instruction stream. n must be a value known at compile time. IA-32/x86-64 * Support for the AVX-512 Fused Multiply Accumulation Packed Single precision (4FMAPS), AVX-512 Vector Neural Network Instructions Word variable precision (4VNNIW), AVX-512 Vector Population Count (VPOPCNTDQ) and Software Guard Extensions (SGX) ISA extensions has been added. NVPTX * OpenMP target regions can now be offloaded to NVidia PTX GPGPUs. See the [18]Offloading Wiki on how to configure it. PowerPC / PowerPC64 / RS6000 * The PowerPC port now uses LRA by default. * GCC now diagnoses inline assembly that clobbers register r2. This has always been invalid code, and is no longer quietly tolerated. * The PowerPC port's support for ISA 3.0 (-mcpu=power9) has been enhanced to generate more of the new instructions by default, and to provide more built-in functions to generate code for other new instructions. * The configuration option --enable-gnu-indirect-function is now enabled by default on PowerPC GNU/Linux builds. * The PowerPC port will now allow 64-bit and 32-bit integer types to be allocated to the VSX vector registers (ISA 2.06 and above). In addition, on ISA 3.0, 16-bit and 8-bit integer types can be allocated in the vector registers. Previously, only 64-bit integer types were allowed in the traditional floating point registers. * New options -mstack-protector-guard=global, -mstack-protector-guard=tls, -mstack-protector-guard-reg=, and -mstack-protector-guard-offset= change how the stack protector gets the value to use as canary. S/390, System z, IBM z Systems, IBM Z * Support for the IBM z14 processor has been added. When using the -march=z14 option, the compiler will generate code making use of the new instructions introduced with the vector enhancement facility and the miscellaneous instruction extension facility 2. The -mtune=z14 option enables z14 specific instruction scheduling without making use of new instructions. * Builtins for the new vector instructions have been added and can be enabled using the -mzvector option. RISC-V * Support for the RISC-V instruction set has been added. RX Basic support for atomic built-in function has been added. It is currently implemented by flipping interrupts off and on as needed. SH * Support for SH5/SH64 has been removed. * Improved utilization of delay slots on SH2A. * Improved utilization of zero-displacement conditional branches. * The following deprecated options have been removed + -mcbranchdi + -mcmpeqdi + -minvalid-symbols + -msoft-atomic + -mspace + -madjust-unroll * Support for the following SH2A instructions has been added + mov.b @-Rm,R0 + mov.w @-Rm,R0 + mov.l @-Rm,R0 + mov.b R0,@Rn+ + mov.w R0,@Rn+ + mov.l R0,@Rn+ SPARC * The SPARC port now uses LRA by default. * Support for the new Subtract-Extended-with-Carry instruction available in SPARC M7 (Niagara 7) has been added. Operating Systems AIX * Visibility support has been enabled for AIX 7.1 and above. Fuchsia * Support has been added for the [19]Fuchsia OS. RTEMS * The ABI changes on ARM so that no short enums are used by default. Other significant improvements * -fverbose-asm previously emitted information on the meanings of assembly expressions. This has been extended so that it now also prints comments showing the source lines that correspond to the assembly, making it easier to read the generated assembly (especially with larger functions). For example, given this C source file: int test (int n) { int i; int total = 0; for (i = 0; i < n; i++) total += i * i; return total; } -fverbose-asm now gives output similar to this for the function body (when compiling for x86_64, with -Os): .text .globl test .type test, @@function test: .LFB0: .cfi_startproc # example.c:4: int total = 0; xorl %eax, %eax # # example.c:6: for (i = 0; i < n; i++) xorl %edx, %edx # i .L2: # example.c:6: for (i = 0; i < n; i++) cmpl %edi, %edx # n, i jge .L5 #, # example.c:7: total += i * i; movl %edx, %ecx # i, tmp92 imull %edx, %ecx # i, tmp92 # example.c:6: for (i = 0; i < n; i++) incl %edx # i # example.c:7: total += i * i; addl %ecx, %eax # tmp92, jmp .L2 # .L5: # example.c:10: } ret .cfi_endproc * Two new options have been added for printing fix-it hints: + -fdiagnostics-parseable-fixits allows for fix-it hints to be emitted in a machine-readable form, suitable for consumption by IDEs. For example, given: spellcheck-fields.cc:52:13: error: 'struct s' has no member named 'colour'; did you mean 'color'? return ptr->colour; ^~~~~~ color it will emit: fix-it:"spellcheck-fields.cc":{52:13-52:19}:"color" + -fdiagnostics-generate-patch will print a patch in "unified" format after any diagnostics are printed, showing the result of applying all fix-it hints. For the above example it would emit: --- spellcheck-fields.cc +++ spellcheck-fields.cc @@ -49,5 +49,5 @@ color get_color(struct s *ptr) { - return ptr->colour; + return ptr->color; } * The gcc and g++ driver programs will now provide suggestions for misspelled arguments to command-line options. $ gcc -c test.c -ftls-model=global-dinamic gcc: error: unknown TLS model 'global-dinamic' gcc: note: valid arguments to '-ftls-model=' are: global-dynamic initial-exec lo cal-dynamic local-exec; did you mean 'global-dynamic'? * The compiler will now provide suggestions for misspelled parameters. $ gcc -c test.c --param max-early-inliner-iteration=3 cc1: error: invalid --param name 'max-early-inliner-iteration'; did you mean 'ma x-early-inliner-iterations'? * Profile-guided optimization (PGO) instrumentation, as well as test coverage (GCOV), can newly instrument constructors (functions marks with __attribute__((constructor))), destructors and C++ constructors (and destructors) of classes that are used as the type of a global variable. * A new option -fprofile-update=atomic prevents creation of corrupted profiles created during an instrumentation run (-fprofile=generate) of an application. The downside of the option is a speed penalty. Providing -pthread on the command line selects atomic profile updating (when supported by the target). * GCC's already extensive testsuite has gained some new capabilities, to further improve the reliability of the compiler: + GCC now has an internal unit-testing API and a suite of tests for programmatic self-testing of subsystems. + GCC's C front end has been extended so that it can parse dumps of GCC's internal representations, allowing for DejaGnu tests that more directly exercise specific optimization passes. This covers both the [20]GIMPLE representation (for testing higher-level optimizations) and the [21]RTL representation, allowing for more direct testing of lower-level details, such as register allocation and instruction selection. GCC 7.1 This is the [22]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 7.1 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 7.2 This is the [23]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 7.2 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Target Specific Changes SPARC * Support for the SPARC M8 processor has been added. * The switches -mfix-ut700 and -mfix-gr712rc have been added to work around an erratum in LEON3FT processors. * Use of the Floating-point Multiply Single to Double (FsMULd) instruction can now be controlled by the -mfsmuld and -fno-fsmuld options. Operating Systems RTEMS * The Ada run-time support uses now thread-local storage (TLS). * Support for RISC-V has been added. * Support for 64-bit PowerPC using the ELFv2 ABI with 64-bit long double has been added. GCC 7.3 This is the [24]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 7.3 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Target Specific Changes SPARC * Workarounds for the four [25]LEON3FT errata GRLIB-TN-0010..0013 have been added. Relevant errata are activated by the target specific -mfix-ut699, -mfix-ut700 and -mfix-gr712rc switches. Operating Systems RTEMS * Support has been added for Epiphany target. GCC 7.4 This is the [26]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 7.4 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 7.5 This is the [27]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 7.5 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). For questions related to the use of GCC, please consult these web pages and the [28]GCC manuals. If that fails, the [29]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [30]gcc@gcc.gnu.org. All of [31]our lists have public archives. Copyright (C) [32]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [33]maintained by the GCC team. Last modified 2022-10-26. References 1. https://gcc.gnu.org/gcc-7/porting_to.html 2. https://gcc.gnu.org/onlinedocs/index.html#current 3. https://gcc.gnu.org/wiki/LRAIsDefault 4. https://gcc.gnu.org/onlinedocs/gcc-7.1.0/libstdc++/manual/manual/profile_mode.html 5. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77728 6. https://gcc.gnu.org/wiki/OpenACC 7. https://gcc.gnu.org/wiki/Offloading 8. https://gcc.gnu.org/onlinedocs/gcc-7.1.0/gcc/Object-Size-Checking.html 9. https://gcc.gnu.org/projects/cxx-status.html#cxx1z 10. https://wg21.link/p0136 11. https://gcc.gnu.org/onlinedocs/gcc-7.1.0/libstdc++/manual/using_dual_abi.html 12. https://www.openmp.org/specifications/ 13. https://gcc.gnu.org/onlinedocs/gcc-7.1.0/jit/topics/expressions.html#gcc_jit_rvalue_set_bool_require_tail_call 14. https://gcc.gnu.org/onlinedocs/gcc-7.1.0/gcc/AArch64-Options.html#AArch64-Options 15. https://gcc.gnu.org/install/configure.html 16. https://gcc.gnu.org/onlinedocs/gcc-7.1.0/gcc/AVR-Variable-Attributes.html 17. https://gcc.gnu.org/onlinedocs/gcc-7.1.0/gcc/AVR-Built-in-Functions.html 18. https://gcc.gnu.org/wiki/Offloading 19. https://fuchsia.googlesource.com/ 20. https://gcc.gnu.org/onlinedocs/gcc-7.1.0/gccint/GIMPLE-Tests.html 21. https://gcc.gnu.org/onlinedocs/gcc-7.1.0/gccint/RTL-Tests.html 22. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=7.0 23. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=7.2 24. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=7.3 25. https://www.gaisler.com/index.php/information/app-tech-notes 26. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=7.4 27. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=7.5 28. https://gcc.gnu.org/onlinedocs/ 29. mailto:gcc-help@gcc.gnu.org 30. mailto:gcc@gcc.gnu.org 31. https://gcc.gnu.org/lists.html 32. https://www.fsf.org/ 33. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-6/index.html GCC 6 Release Series (This release series is no longer supported.) October 26, 2018 The [1]GNU project and the GCC developers are pleased to announce the release of GCC 6.5. This release is a bug-fix release, containing fixes for regressions in GCC 6.4 relative to previous releases of GCC. Release History GCC 6.5 October 26, 2018 ([2]changes, [3]documentation) GCC 6.4 July 4, 2017 ([4]changes, [5]documentation) GCC 6.3 December 21, 2016 ([6]changes, [7]documentation) GCC 6.2 August 22, 2016 ([8]changes, [9]documentation) GCC 6.1 April 27, 2016 ([10]changes, [11]documentation) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. A list of [12]successful builds is updated as new information becomes available. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [13]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [14]GCC project web site or contact the [15]GCC development mailing list. To obtain GCC please use [16]our mirror sites or [17]our version control system. For questions related to the use of GCC, please consult these web pages and the [18]GCC manuals. If that fails, the [19]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [20]gcc@gcc.gnu.org. All of [21]our lists have public archives. Copyright (C) [22]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [23]maintained by the GCC team. Last modified 2024-05-30. References 1. http://www.gnu.org/ 2. https://gcc.gnu.org/gcc-6/changes.html 3. https://gcc.gnu.org/onlinedocs/6.5.0/ 4. https://gcc.gnu.org/gcc-6/changes.html 5. https://gcc.gnu.org/onlinedocs/6.4.0/ 6. https://gcc.gnu.org/gcc-6/changes.html 7. https://gcc.gnu.org/onlinedocs/6.3.0/ 8. https://gcc.gnu.org/gcc-6/changes.html 9. https://gcc.gnu.org/onlinedocs/6.2.0/ 10. https://gcc.gnu.org/gcc-6/changes.html 11. https://gcc.gnu.org/onlinedocs/6.1.0/ 12. https://gcc.gnu.org/gcc-6/buildstat.html 13. https://gcc.gnu.org/onlinedocs/gcc/Contributors.html 14. https://gcc.gnu.org/index.html 15. mailto:gcc@gcc.gnu.org 16. https://gcc.gnu.org/mirrors.html 17. https://gcc.gnu.org/git.html 18. https://gcc.gnu.org/onlinedocs/ 19. mailto:gcc-help@gcc.gnu.org 20. mailto:gcc@gcc.gnu.org 21. https://gcc.gnu.org/lists.html 22. https://www.fsf.org/ 23. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-6/changes.html GCC 6 Release Series Changes, New Features, and Fixes This page is a brief summary of some of the huge number of improvements in GCC 6. For more information, see the [1]Porting to GCC 6 page and the [2]full GCC documentation. Caveats * The default mode for C++ is now -std=gnu++14 instead of -std=gnu++98. * Support for a number of older systems and recently unmaintained or untested target ports of GCC has been declared obsolete in GCC 6. Unless there is activity to revive them, the next release of GCC will have their sources permanently removed. The following ports for individual systems on particular architectures have been obsoleted: + SH5 / SH64 (sh64-*-*) as announced [3]here. * The AVR port requires binutils version 2.26.1 or later for the fix for [4]PR71151 to work. * The GCC 6.5 release has an accidental ABI incompatibility for nested std::pair objects, for more details see [5]PR 87822. The bug causes a layout change for pairs where the first member is also a pair, e.g. std::pair, Z>. The GCC 6 release series is closed so the bug in GCC 6.5 will not be fixed upstream, but there is a patch in the bug report to allow it to be fixed by anybody packaging GCC 6.5 or installing it themselves. General Optimizer Improvements * UndefinedBehaviorSanitizer gained a new sanitization option, -fsanitize=bounds-strict, which enables strict checking of array bounds. In particular, it enables -fsanitize=bounds as well as instrumentation of flexible array member-like arrays. * Type-based alias analysis now disambiguates accesses to different pointers. This improves precision of the alias oracle by about 20-30% on higher-level C++ programs. Programs doing invalid type punning of pointer types may now need -fno-strict-aliasing to work correctly. * Alias analysis now correctly supports the weakref and alias attributes. This allows accessing both a variable and its alias in one translation unit which is common with link-time optimization. * Value range propagation now assumes that the this pointer in C++ member functions is non-null. This eliminates common null pointer checks but also breaks some non-conforming code-bases (such as Qt-5, Chromium, KDevelop). As a temporary work-around -fno-delete-null-pointer-checks can be used. Wrong code can be identified by using -fsanitize=undefined. * Link-time optimization improvements: + warning and error attributes are now correctly preserved by declaration linking and thus -D_FORTIFY_SOURCE=2 is now supported with -flto. + Type merging was fixed to handle C and Fortran interoperability rules as defined by the Fortran 2008 language standard. As an exception, CHARACTER(KIND=C_CHAR) is not inter-operable with char in all cases because it is an array while char is scalar. INTEGER(KIND=C_SIGNED_CHAR) should be used instead. In general, this inter-operability cannot be implemented, for example on targets where the argument passing convention for arrays differs from scalars. + More type information is now preserved at link time, reducing the loss of accuracy of the type-based alias analysis compared to builds without link-time optimization. + Invalid type punning on global variables and declarations is now reported with -Wodr-type-mismatch. + The size of LTO object files was reduced by about 11% (measured by compiling Firefox 46.0). + Link-time parallelization (enabled using -flto=n) was significantly improved by decreasing the size of streamed data when partitioning programs. The size of streamed IL while compiling Firefox 46.0 was reduced by 66%. + The linker plugin was extended to pass information about the type of binary produced to the GCC back end. (That can also be controlled manually by -flinker-output.) This makes it possible to properly configure the code generator and support incremental linking. Incremental linking of LTO objects by gcc -r is now supported for plugin-enabled setups. There are two ways to perform incremental linking: 1. Linking by ld -r will result in an object file with all sections from individual object files mechanically merged. This delays the actual link-time optimization to the final linking step and thus permits whole program optimization. Linking the final binary with such object files is however slower. 2. Linking by gcc -r will lead to link-time optimization and emit the final binary into the object file. Linking such an object file is fast but avoids any benefits from whole program optimization. GCC 7 will support incremental link-time optimization with gcc -r. * Inter-procedural optimization improvements: + Basic jump threading is now performed before profile construction and inline analysis, resulting in more realistic size and time estimates that drive the heuristics of the inliner and function cloning passes. + Function cloning now more aggressively eliminates unused function parameters. New Languages and Language specific improvements Compared to GCC 5, the GCC 6 release series includes a much improved implementation of the [6]OpenACC 2.0a specification. Highlights are: * In addition to single-threaded host-fallback execution, offloading is supported for nvptx (Nvidia GPUs) on x86_64 and PowerPC 64-bit little-endian GNU/Linux host systems. For nvptx offloading, with the OpenACC parallel construct, the execution model allows for an arbitrary number of gangs, up to 32 workers, and 32 vectors. * Initial support for parallelized execution of OpenACC kernels constructs: + Parallelization of a kernels region is switched on by -fopenacc combined with -O2 or higher. + Code is offloaded onto multiple gangs, but executes with just one worker, and a vector length of 1. + Directives inside a kernels region are not supported. + Loops with reductions can be parallelized. + Only kernels regions with one loop nest are parallelized. + Only the outer-most loop of a loop nest can be parallelized. + Loop nests containing sibling loops are not parallelized. Typically, using the OpenACC parallel construct gives much better performance, compared to the initial support of the OpenACC kernels construct. * The device_type clause is not supported. The bind and nohost clauses are not supported. The host_data directive is not supported in Fortran. * Nested parallelism (cf. CUDA dynamic parallelism) is not supported. * Usage of OpenACC constructs inside multithreaded contexts (such as created by OpenMP, or pthread programming) is not supported. * If a call to the acc_on_device function has a compile-time constant argument, the function call evaluates to a compile-time constant value only for C and C++ but not for Fortran. See the [7]OpenACC and [8]Offloading wiki pages for further information. C family * Version 4.5 of the [9]OpenMP specification is now supported in the C and C++ compilers. * The C and C++ compilers now support attributes on enumerators. For instance, it is now possible to mark enumerators as deprecated: enum { newval, oldval __attribute__ ((deprecated ("too old"))) }; * Source locations for the C and C++ compilers are now tracked as ranges, rather than just points, making it easier to identify the subexpression of interest within a complicated expression. For example: test.cc: In function 'int test(int, int, foo, int, int)': test.cc:5:16: error: no match for 'operator*' (operand types are 'int' and 'foo' ) return p + q * r * s + t; ~~^~~ In addition, there is now initial support for precise diagnostic locations within strings: format-strings.c:3:14: warning: field width specifier '*' expects a matching 'in t' argument [-Wformat=] printf("%*d"); ^ * Diagnostics can now contain "fix-it hints", which are displayed in context underneath the relevant source code. For example: fixits.c: In function 'bad_deref': fixits.c:11:13: error: 'ptr' is a pointer; did you mean to use '->'? return ptr.x; ^ -> * The C and C++ compilers now offer suggestions for misspelled field names: spellcheck-fields.cc:52:13: error: 'struct s' has no member named 'colour'; did you mean 'color'? return ptr->colour; ^~~~~~ * New command-line options have been added for the C and C++ compilers: + -Wshift-negative-value warns about left shifting a negative value. + -Wshift-overflow warns about left shift overflows. This warning is enabled by default. -Wshift-overflow=2 also warns about left-shifting 1 into the sign bit. + -Wtautological-compare warns if a self-comparison always evaluates to true or false. This warning is enabled by -Wall. + -Wnull-dereference warns if the compiler detects paths that trigger erroneous or undefined behavior due to dereferencing a null pointer. This option is only active when -fdelete-null-pointer-checks is active, which is enabled by optimizations in most targets. The precision of the warnings depends on the optimization options used. + -Wduplicated-cond warns about duplicated conditions in an if-else-if chain. + -Wmisleading-indentation warns about places where the indentation of the code gives a misleading idea of the block structure of the code to a human reader. For example, given [10]CVE-2014-1266: sslKeyExchange.c: In function 'SSLVerifySignedServerKeyExchange': sslKeyExchange.c:629:3: warning: this 'if' clause does not guard... [-Wmisleadin g-indentation] if ((err = SSLHashSHA1.update(&hashCtx, &signedParams)) != 0) ^~ sslKeyExchange.c:631:5: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if' goto fail; ^~~~ This warning is enabled by -Wall. * The C and C++ compilers now emit saner error messages if merge-conflict markers are present in a source file. test.c:3:1: error: version control conflict marker in file <<<<<<< HEAD ^~~~~~~ C * It is possible to disable warnings when an initialized field of a structure or a union with side effects is being overridden when using designated initializers via a new warning option -Woverride-init-side-effects. * A new type attribute scalar_storage_order applying to structures and unions has been introduced. It specifies the storage order (aka endianness) in memory of scalar fields in structures or unions. C++ * The default mode has been changed to -std=gnu++14. * [11]C++ Concepts are now supported when compiling with -fconcepts. * -flifetime-dse is more aggressive in dead-store elimination in situations where a memory store to a location precedes a constructor to that memory location. * G++ now supports [12]C++17 fold expressions, u8 character literals, extended static_assert, and nested namespace definitions. * G++ now allows constant evaluation for all non-type template arguments. * G++ now supports C++ Transactional Memory when compiling with -fgnu-tm. Runtime Library (libstdc++) * Extensions to the C++ Library to support mathematical special functions (ISO/IEC 29124:2010), thanks to Edward Smith-Rowland. * Experimental support for C++17, including the following new features: + std::uncaught_exceptions function (this is also available for -std=gnu++NN modes); + new member functions try_emplace and insert_or_assign for unique_key maps; + non-member functions std::size, std::empty, and std::data for accessing containers and arrays; + std::invoke; + std::shared_mutex; + std::void_t and std::bool_constant metaprogramming utilities. Thanks to Ville Voutilainen for contributing many of the C++17 features. * An experimental implementation of the File System TS. * Experimental support for most features of the second version of the Library Fundamentals TS. This includes polymorphic memory resources and array support in shared_ptr, thanks to Fan You. * Some assertions checked by Debug Mode can now also be enabled by _GLIBCXX_ASSERTIONS. The subset of checks enabled by the new macro have less run-time overhead than the full _GLIBCXX_DEBUG checks and don't affect the library ABI, so can be enabled per-translation unit. * Timed mutex types are supported on more targets, including Darwin. * Improved std::locale support for DragonFly and FreeBSD, thanks to John Marino and Andreas Tobler. Fortran * Fortran 2008 SUBMODULE support. * Fortran 2015 EVENT_TYPE, EVENT_POST, EVENT_WAIT, and EVENT_QUERY support. * Improved support for Fortran 2003 deferred-length character variables. * Improved support for OpenMP and OpenACC. * The MATMUL intrinsic is now inlined for straightforward cases if front-end optimization is active. The maximum size for inlining can be set to n with the -finline-matmul-limit=n option and turned off with -finline-matmul-limit=0. * The -Wconversion-extra option will warn about REAL constants which have excess precision for their kind. * The -Winteger-division option has been added, which warns about divisions of integer constants which are truncated. This option is included in -Wall by default. libgccjit * The driver code is now run in-process within libgccjit, providing a small speed-up of the compilation process. * The API has gained entrypoints for + [13]timing how long was spent in different parts of code, + [14]creating switch statements, + [15]allowing unreachable basic blocks in a function, and + [16]adding arbitrary command-line options to a compilation. New Targets and Target Specific Improvements AArch64 * A number of AArch64-specific options have been added. The most important ones are summarised in this section; for more detailed information please refer to the documentation. * The command-line options -march=native, -mcpu=native and -mtune=native are now available on native AArch64 GNU/Linux systems. Specifying these options causes GCC to auto-detect the host CPU and choose the optimal setting for that system. * -fpic is now supported when generating code for the small code model (-mcmodel=small). The size of the global offset table (GOT) is limited to 28KiB under the LP64 SysV ABI, and 15KiB under the ILP32 SysV ABI. * The AArch64 port now supports target attributes and pragmas. Please refer to the [17]documentation for details of available attributes and pragmas as well as usage instructions. * Link-time optimization across translation units with different target-specific options is now supported. * The option -mtls-size= is now supported. It can be used to specify the bit size of TLS offsets, allowing GCC to generate better TLS instruction sequences. * The option -fno-plt is now fully functional. * The ARMv8.1-A architecture and the Large System Extensions are now supported. They can be used by specifying the -march=armv8.1-a option. Additionally, the +lse option extension can be used in a similar fashion to other option extensions. The Large System Extensions introduce new instructions that are used in the implementation of atomic operations. * The ACLE half-precision floating-point type __fp16 is now supported in the C and C++ languages. * The ARM Cortex-A35 processor is now supported via the -mcpu=cortex-a35 and -mtune=cortex-a35 options as well as the equivalent target attributes and pragmas. * The Qualcomm QDF24xx processor is now supported via the -mcpu=qdf24xx and -mtune=qdf24xx options as well as the equivalent target attributes and pragmas. * Code generation for the ARM Cortex-A57 processor is improved. Among general code generation improvements, a better algorithm is added for allocating registers to floating-point multiply-accumulate instructions offering increased performance when compiling with -mcpu=cortex-a57 or -mtune=cortex-a57. * Code generation for the ARM Cortex-A53 processor is improved. A more accurate instruction scheduling model for the processor is now used, and a number of compiler tuning parameters have been set to offer increased performance when compiling with -mcpu=cortex-a53 or -mtune=cortex-a53. * Code generation for the Samsung Exynos M1 processor is improved. A more accurate instruction scheduling model for the processor is now used, and a number of compiler tuning parameters have been set to offer increased performance when compiling with -mcpu=exynos-m1 or -mtune=exynos-m1. * Improvements in the generation of conditional branches and literal pools allow the compiler to compile functions of a large size. Constant pools are now placed into separate rodata sections. The new option -mpc-relative-literal-loads generates per-function literal pools, limiting the maximum size of functions to 1MiB. * Several correctness issues generating Advanced SIMD instructions for big-endian targets have been fixed resulting in improved code generation for ACLE intrinsics with -mbig-endian. ARM * Support for revisions of the ARM architecture prior to ARMv4t has been deprecated and will be removed in a future GCC release. The -mcpu and -mtune values that are deprecated are: arm2, arm250, arm3, arm6, arm60, arm600, arm610, arm620, arm7, arm7d, arm7di, arm70, arm700, arm700i, arm710, arm720, arm710c, arm7100, arm7500, arm7500fe, arm7m, arm7dm, arm7dmi, arm8, arm810, strongarm, strongarm110, strongarm1100, strongarm1110, fa526, fa626. The value arm7tdmi is still supported. The values of -march that are deprecated are: armv2,armv2a,armv3,armv3m,armv4. * The ARM port now supports target attributes and pragmas. Please refer to the [18]documentation for details of available attributes and pragmas as well as usage instructions. * Support has been added for the following processors (GCC identifiers in parentheses): ARM Cortex-A32 (cortex-a32), ARM Cortex-A35 (cortex-a35) and ARM Cortex-R8 (cortex-r8). The GCC identifiers can be used as arguments to the -mcpu or -mtune options, for example: -mcpu=cortex-a32 or -mtune=cortex-a35. Heterogeneous Systems Architecture * GCC can now generate HSAIL (Heterogeneous System Architecture Intermediate Language) for simple OpenMP device constructs if configured with --enable-offload-targets=hsa. A new libgomp plugin then runs the HSA GPU kernels implementing these constructs on HSA capable GPUs via a standard HSA run time. If the HSA compilation back end determines it cannot output HSAIL for a particular input, it gives a warning by default. These warnings can be suppressed with -Wno-hsa. To give a few examples, the HSA back end does not implement compilation of code using function pointers, automatic allocation of variable sized arrays, functions with variadic arguments as well as a number of other less common programming constructs. When compilation for HSA is enabled, the compiler attempts to compile composite OpenMP constructs #pragma omp target teams distribute parallel for into parallel HSA GPU kernels. IA-32/x86-64 * GCC now supports the Intel CPU named Skylake with AVX-512 extensions through -march=skylake-avx512. The switch enables the following ISA extensions: AVX-512F, AVX512VL, AVX-512CD, AVX-512BW, AVX-512DQ. * Support for new AMD instructions monitorx and mwaitx has been added. This includes new intrinsic and built-in support. It is enabled through option -mmwaitx. The instructions monitorx and mwaitx implement the same functionality as the old monitor and mwait instructions. In addition, mwaitx adds a configurable timer. The timer value is received as third argument and stored in register %ebx. * x86-64 targets now allow stack realignment from a word-aligned stack pointer using the command-line option -mstackrealign or __attribute__ ((force_align_arg_pointer)). This allows functions compiled with a vector-aligned stack to be invoked from objects that keep only word-alignment. * Support for address spaces __seg_fs, __seg_gs, and __seg_tls. These can be used to access data via the %fs and %gs segments without having to resort to inline assembly. Please refer to the [19]documentation for usage instructions. * Support for AMD Zen (family 17h) processors is now available through the -march=znver1 and -mtune=znver1 options. MeP * Support for the MeP (mep-elf) architecture has been deprecated and will be removed in a future GCC release. MSP430 * The MSP430 compiler now has the ability to automatically distribute code and data between low memory (addresses below 64K) and high memory. This only applies to parts that actually have both memory regions and only if the linker script for the part has been specifically set up to support this feature. A new attribute of either can be applied to both functions and data, and this tells the compiler to place the object into low memory if there is room and into high memory otherwise. Two other new attributes - lower and upper - can be used to explicitly state that an object should be placed in the specified memory region. If there is not enough left in that region the compilation will fail. Two new command-line options - -mcode-region=[lower|upper|either] and -mdata-region=[lower|upper|either] - can be used to tell the compiler what to do with objects that do not have one of these new attributes. PowerPC / PowerPC64 / RS6000 * PowerPC64 now supports IEEE 128-bit floating-point using the __float128 data type. In GCC 6, this is not enabled by default, but you can enable it with -mfloat128. The IEEE 128-bit floating-point support requires the use of the VSX instruction set. IEEE 128-bit floating-point values are passed and returned as a single vector value. The software emulator for IEEE 128-bit floating-point support is only built on PowerPC GNU/Linux systems where the default CPU is at least power7. On future ISA 3.0 systems (POWER 9 and later), you will be able to use the -mfloat128-hardware option to use the ISA 3.0 instructions that support IEEE 128-bit floating-point. An additional type (__ibm128) has been added to refer to the IBM extended double type that normally implements long double. This will allow for a future transition to implementing long double with IEEE 128-bit floating-point. * Basic support has been added for POWER9 hardware that will use the recently published OpenPOWER ISA 3.0 instructions. The following new switches are available: + -mcpu=power9: Implement all of the ISA 3.0 instructions supported by the compiler. + -mtune=power9: In the future, apply tuning for POWER9 systems. Currently, POWER8 tunings are used. + -mmodulo: Generate code using the ISA 3.0 integer instructions (modulus, count trailing zeros, array index support, integer multiply/add). + -mpower9-fusion: Generate code to suitably fuse instruction sequences for a POWER9 system. + -mpower9-dform: Generate code to use the new D-form (register+offset) memory instructions for the vector registers. + -mpower9-vector: Generate code using the new ISA 3.0 vector (VSX or Altivec) instructions. + -mpower9-minmax: Reserved for future development. + -mtoc-fusion: Keep TOC entries together to provide more fusion opportunities. * New constraints have been added to support IEEE 128-bit floating-point and ISA 3.0 instructions: + wb: Altivec register if -mpower9-dform is enabled. + we: VSX register if -mpower9-vector is enabled for 64-bit code generation. + wo: VSX register if -mpower9-vector is enabled. + wp: Reserved for future use if long double is implemented with IEEE 128-bit floating-point instead of IBM extended double. + wq: VSX register if -mfloat128 is enabled. + wF: Memory operand suitable for POWER9 fusion load/store. + wG: Memory operand suitable for TOC fusion memory references. + wL: Integer constant identifying the element number mfvsrld accesses within a vector. * Support has been added for __builtin_cpu_is() and __builtin_cpu_supports(), allowing for very fast access to AT_PLATFORM, AT_HWCAP, and AT_HWCAP2 values. This requires use of glibc 2.23 or later. * All hardware transactional memory builtins now correctly behave as memory barriers. Programmers can use #ifdef __TM_FENCE__ to determine whether their "old" compiler treats the builtins as barriers. * Split-stack support has been added for gccgo on PowerPC64 for both big- and little-endian (but not for 32-bit). The gold linker from at least binutils 2.25.1 must be available in the PATH when configuring and building gccgo to enable split stack. (The requirement for binutils 2.25.1 applies to PowerPC64 only.) The split-stack feature allows a small initial stack size to be allocated for each goroutine, which increases as needed. * GCC on PowerPC now supports the standard lround function. * A new configuration option ---with-advance-toolchain=at was added for PowerPC 64-bit GNU/Linux systems to use the header files, library files, and the dynamic linker from a specific Advance Toolchain release instead of the default versions that are provided by the GNU/Linux distribution. In general, this option is intended for the developers of GCC, and it is not intended for general use. * The "q", "S", "T", and "t" asm-constraints have been removed. * The "b", "B", "m", "M", and "W" format modifiers have been removed. S/390, System z, IBM z Systems * Support for the IBM z13 processor has been added. When using the -march=z13 option, the compiler will generate code making use of the new instructions and registers introduced with the vector extension facility. The -mtune=z13 option enables z13 specific instruction scheduling without making use of new instructions. Compiling code with -march=z13 reduces the default alignment of vector types bigger than 8 bytes to 8. This is an ABI change and care must be taken when linking modules compiled with different arch levels which interchange variables containing vector type values. For newly compiled code the GNU linker will emit a warning. * The -mzvector option enables a C/C++ language extension. This extension provides a new keyword vector which can be used to define vector type variables. (Note: This is not available when enforcing strict standard compliance e.g. with -std=c99. Either enable GNU extensions with e.g. -std=gnu99 or use __vector instead of vector.) Additionally a set of overloaded builtins is provided which is partially compatible to the PowerPC Altivec builtins. In order to make use of these builtins the vecintrin.h header file needs to be included. * The new command-line options -march=native, and -mtune=native are now available on native IBM z Systems. Specifying these options causes GCC to auto-detect the host CPU and choose the optimal setting for that system. If GCC is unable to detect the host CPU these options have no effect. * The IBM z Systems port now supports target attributes and pragmas. Please refer to the [20]documentation for details of available attributes and pragmas as well as usage instructions. * -fsplit-stack is now supported as part of the IBM z Systems port. This feature requires a recent gold linker to be used. * Support for the g5 and g6 -march=/-mtune= CPU level switches has been deprecated and will be removed in a future GCC release. -m31 from now on defaults to -march=z900 if not specified otherwise. -march=native on a g5/g6 machine will default to -march=z900. SH * Support for SH5 / SH64 has been declared obsolete and will be removed in future releases. * Support for the FDPIC ABI has been added. It can be enabled using the new -mfdpic target option and --enable-fdpic configure option. SPARC * An ABI bug has been fixed in 64-bit mode. Unfortunately, this change will break binary compatibility with earlier releases for code it affects, but this should be pretty rare in practice. The conditions are: a 16-byte structure containing a double or a 8-byte vector in the second half is passed to a subprogram in slot #15, for example as 16th parameter if the first 15 ones have at most 8 bytes. The double or vector was wrongly passed in floating-point register %d32 in lieu of on the stack as per the SPARC calling conventions. Operating Systems AIX * DWARF debugging support for AIX 7.1 has been enabled as an optional debugging format. A more recent Technology Level (TL) and GCC built with that level are required for full exploitation of DWARF debugging capabilities. Linux * Support for the [21]musl C library was added for the AArch64, ARM, MicroBlaze, MIPS, MIPS64, PowerPC, PowerPC64, SH, i386, x32 and x86_64 targets. It can be selected using the new -mmusl option in case musl is not the default libc. GCC defaults to musl libc if it is built with a target triplet matching the *-linux-musl* pattern. RTEMS * The RTEMS thread model implementation changed. Mutexes now use self-contained objects defined in newlib instead of Classic API semaphores. The keys for thread specific data and the once function are directly defined via . Self-contained condition variables are provided via newlib . The RTEMS thread model also supports C++11 threads. * OpenMP support now uses self-contained objects provided by newlib and offers a significantly better performance compared to the POSIX configuration of libgomp. It is possible to configure thread pools for each scheduler instance via the environment variable GOMP_RTEMS_THREAD_POOLS. Solaris * Solaris 12 is now fully supported. Minimal support had already been present in GCC 5.3. * Solaris 12 provides a full set of startup files (crt1.o, crti.o, crtn.o), which GCC now prefers over its own ones. * Position independent executables (PIE) are now supported on Solaris 12. * Constructor priority is now supported on Solaris 12 with the system linker. * libvtv has been ported to Solaris 11 and up. Windows * The option -mstackrealign is now automatically activated in 32-bit mode whenever the use of SSE instructions is requested. Other significant improvements * The gcc and g++ driver programs will now provide suggestions for misspelled command-line options. $ gcc -static-libfortran test.f95 gcc: error: unrecognized command line option '-static-libfortran'; did you mean '-static-libgfortran'? * The --enable-default-pie configure option enables generation of PIE by default. GCC 6.2 This is the [22]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 6.2 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Target Specific Changes SPARC * Support for --with-cpu-32 and --with-cpu-64 configure options has been added on bi-architecture platforms. * Support for the SPARC M7 (Niagara 7) processor has been added. * Support for the VIS 4.0 instruction set has been added. GCC 6.3 This is the [23]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 6.3 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Target Specific Changes IA-32/x86-64 * Support for the [24]deprecated pcommit instruction has been removed. GCC 6.4 This is the [25]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 6.4 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Operating Systems RTEMS * The ABI changes on ARM so that no short enums are used by default. GCC 6.5 This is the [26]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 6.5 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). For questions related to the use of GCC, please consult these web pages and the [27]GCC manuals. If that fails, the [28]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [29]gcc@gcc.gnu.org. All of [30]our lists have public archives. Copyright (C) [31]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [32]maintained by the GCC team. Last modified 2023-02-20. References 1. https://gcc.gnu.org/gcc-6/porting_to.html 2. https://gcc.gnu.org/onlinedocs/index.html#current 3. https://gcc.gnu.org/ml/gcc/2015-08/msg00101.html 4. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71151 5. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87822 6. https://www.openacc.org/ 7. https://gcc.gnu.org/wiki/OpenACC 8. https://gcc.gnu.org/wiki/Offloading 9. https://www.openmp.org/specifications/ 10. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-1266 11. https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4377.pdf 12. https://gcc.gnu.org/projects/cxx-status.html#cxx1z 13. https://gcc.gnu.org/onlinedocs/gcc-6.1.0/jit/topics/performance.html 14. https://gcc.gnu.org/onlinedocs/gcc-6.1.0/jit/topics/functions.html#gcc_jit_block_end_with_switch 15. https://gcc.gnu.org/onlinedocs/gcc-6.1.0/jit/topics/contexts.html#gcc_jit_context_set_bool_allow_unreachable_blocks 16. https://gcc.gnu.org/onlinedocs/gcc-6.1.0/jit/topics/contexts.html#gcc_jit_context_add_command_line_option 17. https://gcc.gnu.org/onlinedocs/gcc-6.1.0/gcc/AArch64-Function-Attributes.html#AArch64-Function-Attributes 18. https://gcc.gnu.org/onlinedocs/gcc-6.1.0/gcc/ARM-Function-Attributes.html#ARM-Function-Attributes 19. https://gcc.gnu.org/onlinedocs/gcc-6.1.0/gcc/Named-Address-Spaces.html#Named-Address-Spaces 20. https://gcc.gnu.org/onlinedocs/gcc-6.1.0/gcc/S_002f390-Function-Attributes.html#S_002f390-Function-Attributes 21. http://www.musl-libc.org/ 22. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=6.2 23. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=6.3 24. https://www.intel.com/content/www/us/en/developer/articles/technical/deprecate-pcommit-instruction.html 25. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=6.4 26. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=6.5 27. https://gcc.gnu.org/onlinedocs/ 28. mailto:gcc-help@gcc.gnu.org 29. mailto:gcc@gcc.gnu.org 30. https://gcc.gnu.org/lists.html 31. https://www.fsf.org/ 32. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-5/index.html GCC 5 Release Series (This release series is no longer supported.) October 10, 2017 The [1]GNU project and the GCC developers are pleased to announce the release of GCC 5.5. This release is a bug-fix release, containing fixes for regressions in GCC 5.4 relative to previous releases of GCC. Release History GCC 5.5 October 10, 2017 ([2]changes, [3]documentation) GCC 5.4 June 3, 2016 ([4]changes, [5]documentation) GCC 5.3 December 4, 2015 ([6]changes, [7]documentation) GCC 5.2 July 16, 2015 ([8]changes, [9]documentation) GCC 5.1 April 22, 2015 ([10]changes, [11]documentation) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. A list of [12]successful builds is updated as new information becomes available. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [13]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [14]GCC project web site or contact the [15]GCC development mailing list. To obtain GCC please use [16]our mirror sites or [17]our version control system. For questions related to the use of GCC, please consult these web pages and the [18]GCC manuals. If that fails, the [19]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [20]gcc@gcc.gnu.org. All of [21]our lists have public archives. Copyright (C) [22]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [23]maintained by the GCC team. Last modified 2024-05-30. References 1. http://www.gnu.org/ 2. https://gcc.gnu.org/gcc-5/changes.html 3. https://gcc.gnu.org/onlinedocs/5.5.0/ 4. https://gcc.gnu.org/gcc-5/changes.html 5. https://gcc.gnu.org/onlinedocs/5.4.0/ 6. https://gcc.gnu.org/gcc-5/changes.html 7. https://gcc.gnu.org/onlinedocs/5.3.0/ 8. https://gcc.gnu.org/gcc-5/changes.html 9. https://gcc.gnu.org/onlinedocs/5.2.0/ 10. https://gcc.gnu.org/gcc-5/changes.html 11. https://gcc.gnu.org/onlinedocs/5.1.0/ 12. https://gcc.gnu.org/gcc-5/buildstat.html 13. https://gcc.gnu.org/onlinedocs/gcc/Contributors.html 14. https://gcc.gnu.org/index.html 15. mailto:gcc@gcc.gnu.org 16. https://gcc.gnu.org/mirrors.html 17. https://gcc.gnu.org/git.html 18. https://gcc.gnu.org/onlinedocs/ 19. mailto:gcc-help@gcc.gnu.org 20. mailto:gcc@gcc.gnu.org 21. https://gcc.gnu.org/lists.html 22. https://www.fsf.org/ 23. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-5/changes.html GCC 5 Release Series Changes, New Features, and Fixes Caveats * The default mode for C is now -std=gnu11 instead of -std=gnu89. * The C++ runtime library (libstdc++) uses a new ABI by default (see [1]below). * The Graphite framework for loop optimizations no longer requires the CLooG library, only ISL version 0.14 (recommended) or 0.12.2. The installation manual contains more information about requirements to build GCC. * The non-standard C++0x type traits has_trivial_default_constructor, has_trivial_copy_constructor and has_trivial_copy_assign have been deprecated and will be removed in a future version. The standard C++11 traits is_trivially_default_constructible, is_trivially_copy_constructible and is_trivially_copy_assignable should be used instead. * On AVR, support has been added for the devices ATtiny4/5/9/10/20/40. This requires Binutils 2.25 or newer. * The AVR port uses a new scheme to describe supported devices: For each supported device the compiler provides a device-specific [2]spec file. If the compiler is used together with AVR-LibC, this requires at least GCC 5.2 and a version of AVR-LibC which implements [3]feature #44574. General Optimizer Improvements * Inter-procedural optimization improvements: + An Identical Code Folding (ICF) pass (controlled via -fipa-icf) has been added. Compared to the identical code folding performed by the Gold linker this pass does not require function sections. It also performs merging before inlining, so inter-procedural optimizations are aware of the code re-use. On the other hand not all unifications performed by a linker are doable by GCC which must honor aliasing information. During link-time optimization of Firefox, this pass unifies about 31000 functions, that is 14% overall. + The devirtualization pass was significantly improved by adding better support for speculative devirtualization and dynamic type detection. About 50% of virtual calls in Firefox are now speculatively devirtualized during link-time optimization. + A new comdat localization pass allows the linker to eliminate more dead code in presence of C++ inline functions. + Virtual tables are now optimized. Local aliases are used to reduce dynamic linking time of C++ virtual tables on ELF targets and data alignment has been reduced to limit data segment bloat. + A new -fno-semantic-interposition option can be used to improve code quality of shared libraries where interposition of exported symbols is not allowed. + Write-only variables are now detected and optimized out. + With profile feedback the function inliner can now bypass --param inline-insns-auto and --param inline-insns-single limits for hot calls. + The IPA reference pass was significantly sped up making it feasible to enable -fipa-reference with -fprofile-generate. This also solves a bottleneck seen when building Chromium with link-time optimization. + The symbol table and call-graph API was reworked to C++ and simplified. + The interprocedural propagation of constants now also propagates alignments of pointer parameters. This for example means that the vectorizer often does not need to generate loop prologues and epilogues to make up for potential misalignments. * Link-time optimization improvements: + One Definition Rule based merging of C++ types has been implemented. Type merging enables better devirtualization and alias analysis. Streaming extra information needed to merge types adds about 2-6% of memory size and object size increase. This can be controlled by -flto-odr-type-merging. + Command-line optimization and target options are now streamed on a per-function basis and honored by the link-time optimizer. This change makes link-time optimization a more transparent replacement of per-file optimizations. It is now possible to build projects that require different optimization settings for different translation units (such as -ffast-math, -mavx, or -finline). Contrary to earlier GCC releases, the optimization and target options passed on the link command line are ignored. Note that this applies only to those command-line options that can be passed to optimize and target attributes. Command-line options affecting global code generation (such as -fpic), warnings (such as -Wodr), optimizations affecting the way static variables are optimized (such as -fcommon), debug output (such as -g), and --param parameters can be applied only to the whole link-time optimization unit. In these cases, it is recommended to consistently use the same options at both compile time and link time. + GCC bootstrap now uses slim LTO object files. + Memory usage and link times were improved. Tree merging was sped up, memory usage of GIMPLE declarations and types was reduced, and, support for on-demand streaming of variable constructors was added. * Feedback directed optimization improvements: + A new auto-FDO mode uses profiles collected by low overhead profiling tools (perf) instead of more expensive program instrumentation (via -fprofile-generate). SPEC2006 benchmarks on x86-64 improve by 4.7% with auto-FDO and by 7.3% with traditional feedback directed optimization. + Profile precision was improved in presence of C++ inline and extern inline functions. + The new gcov-tool utility allows manipulating profiles. + Profiles are now more tolerant to source file changes (this can be controlled by --param profile-func-internal-id). * Register allocation improvements: + A new local register allocator (LRA) sub-pass, controlled by -flra-remat, implements control-flow sensitive global register rematerialization. Instead of spilling and restoring a register value, it is recalculated if it is profitable. The sub-pass improved SPEC2000 generated code by 1% and 0.5% correspondingly on ARM and x86-64. + Reuse of the PIC hard register, instead of using a fixed register, was implemented on x86/x86-64 targets. This improves generated PIC code performance as more hard registers can be used. Shared libraries can significantly benefit from this optimization. Currently it is switched on only for x86/x86-64 targets. As RA infrastructure is already implemented for PIC register reuse, other targets might follow this in the future. + A simple form of inter-procedural RA was implemented. When it is known that a called function does not use caller-saved registers, save/restore code is not generated around the call for such registers. This optimization can be controlled by -fipa-ra + LRA is now much more effective at generating spills of general registers into vector registers instead of memory on architectures (e.g., modern Intel processors) where this is profitable. * UndefinedBehaviorSanitizer gained a few new sanitization options: + -fsanitize=float-divide-by-zero: detect floating-point division by zero; + -fsanitize=float-cast-overflow: check that the result of floating-point type to integer conversions do not overflow; + -fsanitize=bounds: enable instrumentation of array bounds and detect out-of-bounds accesses; + -fsanitize=alignment: enable alignment checking, detect various misaligned objects; + -fsanitize=object-size: enable object size checking, detect various out-of-bounds accesses. + -fsanitize=vptr: enable checking of C++ member function calls, member accesses and some conversions between pointers to base and derived classes, detect if the referenced object does not have the correct dynamic type. * Pointer Bounds Checker, a bounds violation detector, has been added and can be enabled via -fcheck-pointer-bounds. Memory accesses are instrumented with run-time checks of used pointers against their bounds to detect pointer bounds violations (overflows). The Pointer Bounds Checker is available on x86/x86-64 GNU/Linux targets with a new ISA extension Intel MPX support. See the Pointer Bounds Checker [4]Wiki page for more details. New Languages and Language specific improvements * [5]OpenMP 4.0 specification offloading features are now supported by the C, C++, and Fortran compilers. Generic changes: + Infrastructure (suitable for any vendor). + Testsuite which covers offloading from the [6]OpenMP 4.0 Examples document. Specific for upcoming Intel Xeon Phi products: + Run-time library. + Card emulator. * GCC 5 includes a preliminary implementation of the OpenACC 2.0a specification. OpenACC is intended for programming accelerator devices such as GPUs. See [7]the OpenACC wiki page for more information. C family * The default setting of the -fdiagnostics-color= command-line option is now [8]configurable when building GCC using configuration option --with-diagnostics-color=. The possible values are: never, always, auto and auto-if-env. The new default auto uses color only when the standard error is a terminal. The default in GCC 4.9 was auto-if-env, which is equivalent to auto if there is a non-empty GCC_COLORS environment variable, and never otherwise. As in GCC 4.9, an empty GCC_COLORS variable in the environment will always disable colors, no matter what the default is or what command-line options are used. * A new command-line option -Wswitch-bool has been added for the C and C++ compilers, which warns whenever a switch statement has an index of boolean type. * A new command-line option -Wlogical-not-parentheses has been added for the C and C++ compilers, which warns about "logical not" used on the left hand side operand of a comparison. * A new command-line option -Wsizeof-array-argument has been added for the C and C++ compilers, which warns when the sizeof operator is applied to a parameter that has been declared as an array in a function definition. * A new command-line option -Wbool-compare has been added for the C and C++ compilers, which warns about boolean expressions compared with an integer value different from true/false. * Full support for Cilk Plus has been added to the GCC compiler. Cilk Plus is an extension to the C and C++ languages to support data and task parallelism. * A new attribute no_reorder prevents reordering of selected symbols against other such symbols or inline assembler. This enables to link-time optimize the Linux kernel without having to resort to -fno-toplevel-reorder that disables several optimizations. * New preprocessor constructs, __has_include and __has_include_next, to test the availability of headers have been added. This demonstrates a way to include the header only if it is available: #ifdef __has_include # if __has_include() # include # define have_optional 1 # elif __has_include() # include # define have_optional 1 # define experimental_optional # else # define have_optional 0 # endif #endif The header search paths for __has_include and __has_include_next are equivalent to those of the standard directive #include and the extension #include_next respectively. * A new built-in function-like macro to determine the existence of an attribute, __has_attribute, has been added. The equivalent built-in macro __has_cpp_attribute was added to C++ to support [9]Feature-testing recommendations for C++. The macro __has_attribute is added to all C-like languages as an extension: int #ifdef __has_attribute # if __has_attribute(__noinline__) __attribute__((__noinline__)) # endif #endif foo(int x); If an attribute exists, a nonzero constant integer is returned. For standardized C++ attributes a date is returned, otherwise the constant returned is 1. Both __has_attribute and __has_cpp_attribute will add underscores to an attribute name if necessary to resolve the name. For C++11 and onwards the attribute may be scoped. * A new set of built-in functions for arithmetics with overflow checking has been added: __builtin_add_overflow, __builtin_sub_overflow and __builtin_mul_overflow and for compatibility with clang also other variants. These builtins have two integral arguments (which don't need to have the same type), the arguments are extended to infinite precision signed type, +, - or * is performed on those, and the result is stored in an integer variable pointed to by the last argument. If the stored value is equal to the infinite precision result, the built-in functions return false, otherwise true. The type of the integer variable that will hold the result can be different from the types of the first two arguments. The following snippet demonstrates how this can be used in computing the size for the calloc function: void * calloc (size_t x, size_t y) { size_t sz; if (__builtin_mul_overflow (x, y, &sz)) return NULL; void *ret = malloc (sz); if (ret) memset (res, 0, sz); return ret; } On e.g. i?86 or x86-64 the above will result in a mul instruction followed by a jump on overflow. * The option -fextended-identifiers is now enabled by default for C++, and for C99 and later C versions. Various bugs in the implementation of extended identifiers have been fixed. C * The default mode has been changed to -std=gnu11. * A new command-line option -Wc90-c99-compat has been added to warn about features not present in ISO C90, but present in ISO C99. * A new command-line option -Wc99-c11-compat has been added to warn about features not present in ISO C99, but present in ISO C11. * It is possible to disable warnings about conversions between pointers that have incompatible types via a new warning option -Wno-incompatible-pointer-types; warnings about implicit incompatible integer to pointer and pointer to integer conversions via a new warning option -Wno-int-conversion; and warnings about qualifiers on pointers being discarded via a new warning option -Wno-discarded-qualifiers. * To allow proper use of const qualifiers with multidimensional arrays, GCC will not warn about incompatible pointer types anymore for conversions between pointers to arrays with and without const qualifier (except when using -pedantic). Instead, a new warning is emitted only if the const qualifier is lost. This can be controlled with a new warning option -Wno-discarded-array-qualifiers. * The C front end now generates more precise caret diagnostics. * The -pg command-line option now only affects the current file in an LTO build. C++ * G++ now supports [10]C++14 variable templates. * -Wnon-virtual-dtor doesn't warn anymore for final classes. * Excessive template instantiation depth is now a fatal error. This prevents excessive diagnostics that usually do not help to identify the problem. * G++ and libstdc++ now implement the feature-testing macros from [11]Feature-testing recommendations for C++. * G++ now allows typename in a template template parameter. template typename X> struct D; // OK * G++ now supports [12]C++14 aggregates with non-static data member initializers. struct A { int i, j = i; }; A a = { 42 }; // a.j is also 42 * G++ now supports [13]C++14 extended constexpr. constexpr int f (int i) { int j = 0; for (; i > 0; --i) ++j; return j; } constexpr int i = f(42); // i is 42 * G++ now supports the [14]C++14 sized deallocation functions. void operator delete (void *, std::size_t) noexcept; void operator delete[] (void *, std::size_t) noexcept; * A new One Definition Rule violation warning (controlled by -Wodr) detects mismatches in type definitions and virtual table contents during link-time optimization. * New warnings -Wsuggest-final-types and -Wsuggest-final-methods help developers to annotate programs with final specifiers (or anonymous namespaces) to improve code generation. These warnings can be used at compile time, but they are more useful in combination with link-time optimization. * G++ no longer supports [15]N3639 variable length arrays, as they were removed from the C++14 working paper prior to ratification. GNU VLAs are still supported, so VLA support is now the same in C++14 mode as in C++98 and C++11 modes. * G++ now allows passing a non-trivially-copyable class via C varargs, which is conditionally-supported with implementation-defined semantics in the standard. This uses the same calling convention as a normal value parameter. * G++ now defaults to -fabi-version=9 and -fabi-compat-version=2. So various mangling bugs are fixed, but G++ will still emit aliases with the old, wrong mangling where feasible. -Wabi=2 will warn about differences between ABI version 2 and the current setting. * G++ 5.2 fixes the alignment of std::nullptr_t. Most code is likely to be unaffected, but -Wabi=8 will warn about a non-static data member with type std::nullptr_t which changes position due to this change. Runtime Library (libstdc++) * A [16]Dual ABI is provided by the library. A new ABI is enabled by default. The old ABI is still supported and can be used by defining the macro _GLIBCXX_USE_CXX11_ABI to 0 before including any C++ standard library headers. * A new implementation of std::string is enabled by default, using the small string optimization instead of copy-on-write reference counting. * A new implementation of std::list is enabled by default, with an O(1) size() function; * [17]Full support for C++11, including the following new features: + std::deque and std::vector meet the allocator-aware container requirements; + movable and swappable iostream classes; + support for std::align and std::aligned_union; + type traits std::is_trivially_copyable, std::is_trivially_constructible, std::is_trivially_assignable etc.; + I/O manipulators std::put_time, std::get_time, std::hexfloat and std::defaultfloat; + generic locale-aware std::isblank; + locale facets for Unicode conversion; + atomic operations for std::shared_ptr; + std::notify_all_at_thread_exit() and functions for making futures ready at thread exit. * Support for the C++11 hexfloat manipulator changes how the num_put facet formats floating point types when ios_base::fixed|ios_base::scientific is set in a stream's fmtflags. This change affects all language modes, even though the C++98 standard gave no special meaning to that combination of flags. To prevent the use of hexadecimal notation for floating point types use str.unsetf(std::ios_base::floatfield) to clear the relevant bits in str.flags(). * [18]Full experimental support for C++14, including the following new features: + std::is_final type trait; + heterogeneous comparison lookup in associative containers. + global functions cbegin, cend, rbegin, rend, crbegin, and crend for range access to containers, arrays and initializer lists. * [19]Improved experimental support for the Library Fundamentals TS, including: + class std::experimental::any; + function template std::experimental::apply; + function template std::experimental::sample; + function template std::experimental::search and related searcher types; + variable templates for type traits; + function template std::experimental::not_fn. * New random number distributions logistic_distribution and uniform_on_sphere_distribution as extensions. * [20]GDB Xmethods for containers and std::unique_ptr. Fortran * Compatibility notice: + The version of the module files (.mod) has been incremented. + For free-form source files [21]-Werror=line-truncation is now enabled by default. Note that comments exceeding the line length are not diagnosed. (For fixed-form source code, the same warning is available but turned off by default, such that excess characters are ignored. -ffree-line-length-n and -ffixed-line-length-n can be used to modify the default line lengths of 132 and 72 columns, respectively.) + The -Wtabs option is now more sensible: with -Wtabs the compiler warns if it encounters tabs and with -Wno-tabs this warning is turned off. Before, -Wno-tabs warned and -Wtabs disabled the warning. As before, this warning is also enabled by -Wall, -pedantic and the f95, f2003, f2008 and f2008ts options of -std=. * Incomplete support for colorizing diagnostics emitted by gfortran has been added. The option [22]-fdiagnostics-color controls when color is used in diagnostics. The default value of this option can be [23]configured when building GCC. The GCC_COLORS environment variable can be used to customize the colors or disable coloring completely. Sample diagnostics output: $ gfortran -fdiagnostics-color=always -Wuse-without-only test.f90 test.f90:6:1: 0 continue 1 Error: Zero is not a valid statement label at (1) test.f90:9:6: USE foo 1 Warning: USE statement at (1) has no ONLY qualifier [-Wuse-without-only] * The -Wuse-without-only option has been added to warn when a USE statement has no ONLY qualifier and thus implicitly imports all public entities of the used module. * Formatted READ and WRITE statements now work correctly in locale-aware programs. For more information and potential caveats, see [24]Section 5.3 Thread-safety of the runtime library in the manual. * [25]Fortran 2003: + The intrinsic IEEE modules (IEEE_FEATURES, IEEE_EXCEPTIONS and IEEE_ARITHMETIC) are now supported. * [26]Fortran 2008: + [27]Coarrays: Full experimental support of Fortran 2008's coarrays with -fcoarray=lib except for allocatable/pointer components of derived-type coarrays. GCC currently only ships with a single-image library (libcaf_single), but multi-image support based on MPI and GASNet is provided by the libraries of the [28]OpenCoarrays project. * TS18508 Additional Parallel Features in Fortran: + Support for the collective intrinsic subroutines CO_MAX, CO_MIN, CO_SUM, CO_BROADCAST and CO_REDUCE has been added, including -fcoarray=lib support. + Support for the new atomic intrinsics has been added, including -fcoarray=lib support. * Fortran 2015: + Support for IMPLICIT NONE (external, type). + ERROR STOP is now permitted in pure procedures. Go * GCC 5 provides a complete implementation of the Go 1.4.2 release. * Building GCC 5 with Go enabled will install two new programs: [29]go and [30]gofmt. libgccjit New in GCC 5 is the ability to build GCC as a shared library for embedding in other processes (such as interpreters), suitable for Just-In-Time compilation to machine code. The shared library has a [31]C API and a [32]C++ wrapper API providing some "syntactic sugar". There are also bindings available from 3rd parties for [33]Python and for [34]D. For example, this library can be used by interpreters for [35]compiling functions from bytecode to machine code. The library can also be used for ahead-of-time compilation, enabling GCC to be plugged into a pre-existing front end. An example of using this to build a compiler for an esoteric language we'll refer to as "brainf" can be seen [36]here. libgccjit is licensed under the GPLv3 (or at your option, any later version) It should be regarded as experimental at this time. New Targets and Target Specific Improvements Reporting stack usage * The BFIN, FT32, H8300, IQ2000 and M32C targets now support the -fstack-usage option. AArch64 * Code generation for the ARM Cortex-A57 processor has been improved. A more accurate instruction scheduling model for the processor is now used, and a number of compiler tuning parameters have been set to offer increased performance when compiling with -mcpu=cortex-a57 or -mtune=cortex-a57. * A workaround for the ARM Cortex-A53 erratum 835769 has been added and can be enabled by giving the -mfix-cortex-a53-835769 option. Alternatively it can be enabled by default by configuring GCC with the --enable-fix-cortex-a53-835769 option. * The optional cryptographic extensions to the ARMv8-A architecture are no longer enabled by default when specifying the -mcpu=cortex-a53, -mcpu=cortex-a57 or -mcpu=cortex-a57.cortex-a53 options. To enable these extensions add +crypto to the value of -mcpu or -march e.g. -mcpu=cortex-a53+crypto. * Support has been added for the following processors (GCC identifiers in parentheses): ARM Cortex-A72 (cortex-a72) and initial support for its big.LITTLE combination with the ARM Cortex-A53 (cortex-a72.cortex-a53), Cavium ThunderX (thunderx), Applied Micro X-Gene 1 (xgene1), and Samsung Exynos M1 (exynos-m1). The GCC identifiers can be used as arguments to the -mcpu or -mtune options, for example: -mcpu=xgene1 or -mtune=cortex-a72.cortex-a53. Using -mcpu=cortex-a72 requires a version of GNU binutils that has support for the Cortex-A72. * The transitional options -mlra and -mno-lra have been removed. The AArch64 back end now uses the local register allocator (LRA) only. ARM * Thumb-1 assembly code is now generated in unified syntax. The new option -masm-syntax-unified specifies whether inline assembly code is using unified syntax. By default the option is off which means non-unified syntax is used. However this is subject to change in future releases. Eventually the non-unified syntax will be deprecated. * It is now a configure-time error to use the --with-cpu configure option with either of --with-tune or --with-arch. * Code generation for the ARM Cortex-A57 processor has been improved. A more accurate instruction scheduling model for the processor is now used, and a number of compiler tuning parameters have been set to offer increased performance when compiling with -mcpu=cortex-a57 or -mtune=cortex-a57. * Support has been added for the following processors (GCC identifiers in parentheses): ARM Cortex-A17 (cortex-a17) and initial support for its big.LITTLE combination with the ARM Cortex-A7 (cortex-a17.cortex-a7), ARM Cortex-A72 (cortex-a72) and initial support for its big.LITTLE combination with the ARM Cortex-A53 (cortex-a72.cortex-a53), ARM Cortex-M7 (cortex-m7), Applied Micro X-Gene 1 (xgene1), and Samsung Exynos M1 (exynos-m1). The GCC identifiers can be used as arguments to the -mcpu or -mtune options, for example: -mcpu=xgene1 or -mtune=cortex-a72.cortex-a53. Using -mcpu=cortex-a72 requires a version of GNU binutils that has support for the Cortex-A72. * The deprecated option -mwords-little-endian has been removed. * The options -mapcs, -mapcs-frame, -mtpcs-frame and -mtpcs-leaf-frame which are only applicable to the old ABI have been deprecated. * The transitional options -mlra and -mno-lra have been removed. The ARM back end now uses the local register allocator (LRA) only. AVR * The compiler no more supports individual devices like ATmega8. Specifying, say, -mmcu=atmega8 triggers the usage of the device-specific [37]spec file specs-atmega8 which is part of the installation and describes options for the sub-processes like compiler proper, assembler and linker. You can add support for a new device -mmcu=mydevice as follows: 1. In an empty directory /someplace, create a new directory device-specs. 2. Copy a device spec file from the installed device-specs folder, follow the comments in that file and then save it as /someplace/device-specs/specs-mydevice. 3. Add -B /someplace -mmcu=mydevice to the compiler's command-line options. Notice that /someplace must specify an absolute path and that mydevice must not start with "avr". 4. Provided you have a device-specific library libmydevice.a available, you can put it at /someplace, dito for a device-specific startup file crtmydevice.o. The contents of the device spec files depend on the compiler's configuration, in particular on --with-avrlibc=no and whether or not it is configured for RTEMS. * A new command-line option -nodevicelib has been added. It prevents the compiler from linking against AVR-LibC's device-specific library libdevice.a. * The following three command-line options have been added: -mrmw Set if the device supports the read-modify-write instructions LAC, LAS, LAT and XCH. -mn-flash=size Specify the flash size of the device in units of 64 KiB, rounded up to the next integer as needed. This option affects the availability of the [38]AVR address-spaces. -mskip-bug Set if the device is affected by the respective silicon bug. In general, you don't need to set these options by hand. The new device-specific spec file will set them as needed. IA-32/x86-64 * New ISA extensions support AVX-512{BW,DQ,VL,IFMA,VBMI} of Intel's CPU codenamed Skylake Server was added to GCC. That includes inline assembly support, new intrinsics, and basic autovectorization. These new AVX-512 extensions are available via the following GCC switches: AVX-512 Vector Length EVEX feature: -mavx512vl, AVX-512 Byte and Word instructions: -mavx512bw, AVX-512 Dword and Qword instructions: -mavx512dq, AVX-512 FMA-52 instructions: -mavx512ifma and for AVX-512 Vector Bit Manipulation Instructions: -mavx512vbmi. * New ISA extensions support Intel MPX was added to GCC. This new extension is available via the -mmpx compiler switch. Intel MPX is a set of processor features which, with compiler, run-time library and OS support, brings increased robustness to software by run-time checking pointer references against their bounds. In GCC Intel MPX is supported by Pointer Bounds Checker and libmpx run-time libraries. * The new -mrecord-mcount option for -pg generates a Linux kernel style table of pointers to mcount or __fentry__ calls at the beginning of functions. The new -mnop-mcount option in addition also generates nops in place of the __fentry__ or mcount call, so that a call per function can be later patched in. This can be used for low overhead tracing or hot code patching. * The new -malign-data option controls how GCC aligns variables. -malign-data=compat uses increased alignment compatible with GCC 4.8 and earlier, -malign-data=abi uses alignment as specified by the psABI, and -malign-data=cacheline uses increased alignment to match the cache line size. -malign-data=compat is the default. * The new -mskip-rax-setup option skips setting up the RAX register when SSE is disabled and there are no variable arguments passed in vector registers. This can be used to optimize the Linux kernel. MIPS * MIPS Releases 3 and 5 are now directly supported. Use the command-line options -mips32r3, -mips64r3, -mips32r5 and -mips64r5 to enable code-generation for these processors. * The Imagination P5600 processor is now supported using the -march=p5600 command-line option. * The Cavium Octeon3 processor is now supported using the -march=octeon3 command-line option. * MIPS Release 6 is now supported using the -mips32r6 and -mips64r6 command-line options. * The o32 ABI has been modified and extended. The o32 64-bit floating-point register support is now obsolete and has been removed. It has been replaced by three ABI extensions FPXX, FP64A, and FP64. The meaning of the -mfp64 command-line option has changed. It is now used to enable the FP64A and FP64 ABI extensions. + The FPXX extension requires that code generated to access double-precision values use even-numbered registers. Code that adheres to this extension is link-compatible with all other o32 double-precision ABI variants and will execute correctly in all hardware FPU modes. The command-line options -mabi=32 -mfpxx can be used to enable this extension. MIPS II is the minimum processor required. + The o32 FP64A extension requires that floating-point registers be 64-bit and odd-numbered single-precision registers are not allowed. Code that adheres to the o32 FP64A variant is link-compatible with all other o32 double-precision ABI variants. The command-line options -mabi=32 -mfp64 -mno-odd-spreg can be used to enable this extension. MIPS32R2 is the minimum processor required. + The o32 FP64 extension also requires that floating-point registers be 64-bit, but permits the use of single-precision registers. Code that adheres to the o32 FP64 variant is link-compatible with o32 FPXX and o32 FP64A variants only, i.e. it is not compatible with the original o32 double-precision ABI. The command-line options -mabi=32 -mfp64 -modd-spreg can be used to enable this extension. MIPS32R2 is the minimum processor required. The new ABI variants can be enabled by default using the configure time options --with-fp-32=[32|xx|64] and --with(out)-odd-sp-reg-32. It is strongly recommended that all vendors begin to set o32 FPXX as the default ABI. This will be required to run the generated code on MIPSR5 cores in conjunction with future MIPS SIMD (MSA) code and MIPSR6 cores. * GCC will now pass all floating-point options to the assembler if GNU binutils 2.25 is used. As a result, any inline assembly code that uses hard-float instructions should be amended to include a .set directive to override the global assembler options when compiling for soft-float targets. NDS32 * The variadic function ABI implementation is now compatible with past Andes toolchains where the caller uses registers to pass arguments and the callee is in charge of pushing them on stack. * The options -mforce-fp-as-gp, -mforbid-fp-as-gp, and -mex9 have been removed since they are not yet available in the nds32 port of GNU binutils. * A new option -mcmodel=[small|medium|large] supports varied code models on code generation. The -mgp-direct option became meaningless and can be discarded. RX * A new command line option -mno-allow-string-insns can be used to disable the generation of the SCMPU, SMOVU, SMOVB, SMOVF, SUNTIL, SWHILE and RMPA instructions. An erratum released by Renesas shows that it is unsafe to use these instructions on addresses within the I/O space of the processor. The new option can be used when the programmer is concerned that the I/O space might be accessed. The default is still to enable these instructions. SH * The compiler will now pass the appropriate --isa= option to the assembler. * The default handling for the GBR has been changed from call clobbered to call preserved. The old behavior can be reinstated by specifying the option -fcall-used-gbr. * Support for the SH4A fpchg instruction has been added which will be utilized when switching between single and double precision FPU modes. * The compiler no longer uses the __fpscr_values array for switching between single and double FPU precision modes on non-SH4A targets. Instead mode switching will now be performed by storing, modifying and reloading the FPSCR, so that other FPSCR bits are preserved across mode switches. The __fpscr_values array that is defined in libgcc is still present for backwards compatibility, but it will not be referenced by compiler generated code anymore. * New builtin functions __builtin_sh_get_fpscr and __builtin_sh_set_fpscr have been added. The __builtin_sh_set_fpscr function will mask the specified bits in such a way that the SZ, PR and FR mode bits will be preserved, while changing the other bits. These new functions do not reference the __fpscr_values array. The old functions __set_fpscr and __get_fpscr in libgcc which access the __fpscr_values array are still present for backwards compatibility, but their usage is highly discouraged. * Some improvements to code generated for __atomic built-in functions. * When compiling for SH2E the compiler will no longer force the usage of delay slots for conditional branch instructions bt and bf. The old behavior can be reinstated (e.g. to work around a hardware bug in the original SH7055) by specifying the new option -mcbranch-force-delay-slot. Operating Systems AIX * GCC now supports stabs debugging continuation lines to allow long stabs debug information without overflow that generates AIX linker errors. DragonFly BSD * GCC now supports the DragonFly BSD operating system. FreeBSD * GCC now supports the FreeBSD operating system for the arm port through the arm*-*-freebsd* target triplets. VxWorks MILS * GCC now supports the MILS (Multiple Independent Levels of Security) variant of WindRiver's VxWorks operating system for PowerPC targets. Other significant improvements * The gcc-ar, gcc-nm, gcc-ranlib wrappers now understand a -B option to set the compiler to use. * When the new command-line option -freport-bug is used, GCC automatically generates a developer-friendly reproducer whenever an internal compiler error is encountered. GCC 5.2 This is the [39]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 5.2 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Target Specific Changes IA-32/x86-64 * Support for new AMD instructions monitorx and mwaitx has been added. This includes new intrinsic and built-in support. It is enabled through option -mmwaitx. The instructions monitorx and mwaitx implement the same functionality as the old monitor and mwait instructions. In addition, mwaitx adds a configurable timer. The timer value is received as third argument and stored in register %ebx. S/390, System z, IBM z Systems * Support for the IBM z13 processor has been added. When using the -march=z13 option, the compiler will generate code making use of the new instructions and registers introduced with the vector extension facility. The -mtune=z13 option enables z13 specific instruction scheduling without making use of new instructions. Compiling code with -march=z13 reduces the default alignment of vector types bigger than 8 bytes to 8. This is an ABI change and care must be taken when linking modules compiled with different arch levels which interchange variables containing vector type values. For newly compiled code the GNU linker will emit a warning. * The -mzvector option enables a C/C++ language extension. This extension provides a new keyword vector which can be used to define vector type variables. (Note: This is not available when enforcing strict standard compliance e.g. with -std=c99. Either enable GNU extensions with e.g. -std=gnu99 or use __vector instead of vector.) Additionally a set of overloaded builtins is provided which is partially compatible to the PowerPC Altivec builtins. In order to make use of these builtins the vecintrin.h header file needs to be included. GCC 5.3 This is the [40]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 5.3 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Target Specific Changes IA-32/x86-64 * GCC now supports the Intel CPU named Skylake with AVX-512 extensions through -march=skylake-avx512. The switch enables the following ISA extensions: AVX-512F, AVX512VL, AVX-512CD, AVX-512BW, AVX-512DQ. S/390, System z, IBM z Systems * With this version of GCC IBM z Systems support has been added to the GO runtime environment. GCC 5.3 has proven to be able to compile larger GO applications on IBM z Systems. GCC 5.4 This is the [41]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 5.4 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 5.5 This is the [42]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 5.5 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Target Specific Changes IA-32/x86-64 * Support for the [43]deprecated pcommit instruction has been removed. For questions related to the use of GCC, please consult these web pages and the [44]GCC manuals. If that fails, the [45]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [46]gcc@gcc.gnu.org. All of [47]our lists have public archives. Copyright (C) [48]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [49]maintained by the GCC team. Last modified 2024-06-08. References 1. https://gcc.gnu.org/gcc-5/changes.html#libstdcxx 2. https://gcc.gnu.org/onlinedocs/gcc/Spec-Files.html 3. https://savannah.nongnu.org/bugs/?44574 4. https://gcc.gnu.org/wiki/Intel MPX support in the GCC compiler 5. https://www.openmp.org/wp-content/uploads/OpenMP4.0.0.pdf 6. https://www.openmp.org/wp-content/uploads/OpenMP4.0.0.Examples.pdf 7. https://gcc.gnu.org/wiki/OpenACC 8. https://gcc.gnu.org/install/configure.html 9. https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations 10. https://gcc.gnu.org/projects/cxx1y.html 11. https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations 12. https://gcc.gnu.org/projects/cxx1y.html 13. https://gcc.gnu.org/projects/cxx1y.html 14. https://gcc.gnu.org/projects/cxx1y.html 15. https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3639.html 16. https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dual_abi.html 17. https://gcc.gnu.org/onlinedocs/gcc-5.1.0/libstdc++/manual/manual/status.html#status.iso.2011 18. https://gcc.gnu.org/onlinedocs/gcc-5.1.0/libstdc++/manual/manual/status.html#status.iso.2014 19. https://gcc.gnu.org/onlinedocs/gcc-5.1.0/libstdc++/manual/manual/status.html#status.iso.2014 20. https://sourceware.org/gdb/current/onlinedocs/gdb#Xmethods-In-Python 21. https://gcc.gnu.org/onlinedocs/gcc-5.1.0/gfortran/Error-and-Warning-Options.html 22. https://gcc.gnu.org/onlinedocs/gcc-5.1.0/gcc/Language-Independent-Options.html 23. https://gcc.gnu.org/install/configure.html 24. https://gcc.gnu.org/onlinedocs/gcc-5.1.0/gfortran/Thread-safety-of-the-runtime-library.html 25. https://gcc.gnu.org/wiki/Fortran2003Status 26. https://gcc.gnu.org/wiki/Fortran2008Status 27. https://gcc.gnu.org/wiki/Coarray 28. http://www.opencoarrays.org/ 29. https://pkg.go.dev/cmd/go 30. https://pkg.go.dev/cmd/gofmt 31. https://gcc.gnu.org/onlinedocs/gcc-5.1.0/jit/intro/index.html 32. https://gcc.gnu.org/onlinedocs/gcc-5.1.0/jit/cp/index.html 33. https://github.com/davidmalcolm/pygccjit 34. https://github.com/ibuclaw/gccjitd 35. https://gcc.gnu.org/onlinedocs/gcc-5.1.0/jit/intro/tutorial04.html 36. https://gcc.gnu.org/onlinedocs/gcc-5.1.0/jit/intro/tutorial05.html 37. https://gcc.gnu.org/onlinedocs/gcc/Spec-Files.html 38. https://gcc.gnu.org/onlinedocs/gcc/Named-Address-Spaces.html 39. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=5.2 40. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=5.3 41. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=5.4 42. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=5.5 43. https://www.intel.com/content/www/us/en/developer/articles/technical/deprecate-pcommit-instruction.html 44. https://gcc.gnu.org/onlinedocs/ 45. mailto:gcc-help@gcc.gnu.org 46. mailto:gcc@gcc.gnu.org 47. https://gcc.gnu.org/lists.html 48. https://www.fsf.org/ 49. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.9/index.html GCC 4.9 Release Series (This release series is no longer supported.) Aug 3, 2016 The [1]GNU project and the GCC developers are pleased to announce the release of GCC 4.9.4. This release is a bug-fix release, containing fixes for regressions in GCC 4.9.3 relative to previous releases of GCC. Release History GCC 4.9.4 Aug 3, 2016 ([2]changes, [3]documentation) GCC 4.9.3 June 26, 2015 ([4]changes, [5]documentation) GCC 4.9.2 October 30, 2014 ([6]changes, [7]documentation) GCC 4.9.1 July 16, 2014 ([8]changes, [9]documentation) GCC 4.9.0 April 22, 2014 ([10]changes, [11]documentation) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. A list of [12]successful builds is updated as new information becomes available. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [13]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [14]GCC project web site or contact the [15]GCC development mailing list. To obtain GCC please use [16]our mirror sites or [17]our version control system. For questions related to the use of GCC, please consult these web pages and the [18]GCC manuals. If that fails, the [19]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [20]gcc@gcc.gnu.org. All of [21]our lists have public archives. Copyright (C) [22]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [23]maintained by the GCC team. Last modified 2024-05-30. References 1. http://www.gnu.org/ 2. https://gcc.gnu.org/gcc-4.9/changes.html 3. https://gcc.gnu.org/onlinedocs/4.9.4/ 4. https://gcc.gnu.org/gcc-4.9/changes.html 5. https://gcc.gnu.org/onlinedocs/4.9.3/ 6. https://gcc.gnu.org/gcc-4.9/changes.html 7. https://gcc.gnu.org/onlinedocs/4.9.2/ 8. https://gcc.gnu.org/gcc-4.9/changes.html 9. https://gcc.gnu.org/onlinedocs/4.9.1/ 10. https://gcc.gnu.org/gcc-4.9/changes.html 11. https://gcc.gnu.org/onlinedocs/4.9.0/ 12. https://gcc.gnu.org/gcc-4.9/buildstat.html 13. https://gcc.gnu.org/onlinedocs/gcc/Contributors.html 14. https://gcc.gnu.org/index.html 15. mailto:gcc@gcc.gnu.org 16. https://gcc.gnu.org/mirrors.html 17. https://gcc.gnu.org/git.html 18. https://gcc.gnu.org/onlinedocs/ 19. mailto:gcc-help@gcc.gnu.org 20. mailto:gcc@gcc.gnu.org 21. https://gcc.gnu.org/lists.html 22. https://www.fsf.org/ 23. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.9/changes.html GCC 4.9 Release Series Changes, New Features, and Fixes Caveats * The mudflap run time checker has been removed. The mudflap options remain, but do nothing. * Support for a number of older systems and recently unmaintained or untested target ports of GCC has been declared obsolete in GCC 4.9. Unless there is activity to revive them, the next release of GCC will have their sources permanently removed. The following ports for individual systems on particular architectures have been obsoleted: + Solaris 9 (*-*-solaris2.9). Details can be found in the [1]announcement. * On AArch64, the singleton vector types int64x1_t, uint64x1_t and float64x1_t exported by arm_neon.h are defined to be the same as their base types. This results in incorrect application of parameter passing rules to arguments of types int64x1_t and uint64x1_t, with respect to the AAPCS64 ABI specification. In addition, names of C++ functions with parameters of these types (including float64x1_t) are not mangled correctly. The current typedef declarations also unintentionally allow implicit casting between singleton vector types and their base types. These issues will be resolved in a near future release. See [2]PR60825 for more information. More information on porting to GCC 4.9 from previous versions of GCC can be found in the [3]porting guide for this release. General Optimizer Improvements * AddressSanitizer, a fast memory error detector, is now available on ARM. * UndefinedBehaviorSanitizer (ubsan), a fast undefined behavior detector, has been added and can be enabled via -fsanitize=undefined. Various computations will be instrumented to detect undefined behavior at runtime. UndefinedBehaviorSanitizer is currently available for the C and C++ languages. * Link-time optimization (LTO) improvements: + Type merging was rewritten. The new implementation is significantly faster and uses less memory. + Better partitioning algorithm resulting in less streaming during link time. + Early removal of virtual methods reduces the size of object files and improves link-time memory usage and compile time. + Function bodies are now loaded on-demand and released early improving overall memory usage at link time. + C++ hidden keyed methods can now be optimized out. + When using a linker plugin, compiling with the -flto option now generates slim object files (.o) which only contain intermediate language representation for LTO. Use -ffat-lto-objects to create files which contain additionally the object code. To generate static libraries suitable for LTO processing, use gcc-ar and gcc-ranlib; to list symbols from a slim object file use gcc-nm. (This requires that ar, ranlib and nm have been compiled with plugin support.) Memory usage building Firefox with debug enabled was reduced from 15GB to 3.5GB; link time from 1700 seconds to 350 seconds. * Inter-procedural optimization improvements: + New type inheritance analysis module improving devirtualization. Devirtualization now takes into account anonymous name-spaces and the C++11 final keyword. + New speculative devirtualization pass (controlled by -fdevirtualize-speculatively. + Calls that were speculatively made direct are turned back to indirect where direct call is not cheaper. + Local aliases are introduced for symbols that are known to be semantically equivalent across shared libraries improving dynamic linking times. * Feedback directed optimization improvements: + Profiling of programs using C++ inline functions is now more reliable. + New time profiling determines typical order in which functions are executed. + A new function reordering pass (controlled by -freorder-functions) significantly reduces startup time of large applications. Until binutils support is completed, it is effective only with link-time optimization. + Feedback driven indirect call removal and devirtualization now handle cross-module calls when link-time optimization is enabled. New Languages and Language specific improvements * Version 4.0 of the [4]OpenMP specification is now supported in the C and C++ compilers and starting with the 4.9.1 release also in the Fortran compiler. The new -fopenmp-simd option can be used to enable OpenMP's SIMD directives while ignoring other OpenMP directives. The new [5]-fsimd-cost-model= option permits to tune the vectorization cost model for loops annotated with OpenMP and Cilk Plus simd directives. -Wopenmp-simd warns when the current cost model overrides simd directives set by the user. * The -Wdate-time option has been added for the C, C++ and Fortran compilers, which warns when the __DATE__, __TIME__ or __TIMESTAMP__ macros are used. Those macros might prevent bit-wise-identical reproducible compilations. Ada * GNAT switched to Ada 2012 instead of Ada 2005 by default. C family * Support for colorizing diagnostics emitted by GCC has been added. The [6]-fdiagnostics-color=auto will enable it when outputting to terminals, -fdiagnostics-color=always unconditionally. The GCC_COLORS environment variable can be used to customize the colors or disable coloring. If GCC_COLORS variable is present in the environment, the default is -fdiagnostics-color=auto, otherwise -fdiagnostics-color=never. Sample diagnostics output: $ g++ -fdiagnostics-color=always -S -Wall test.C test.C: In function ‘int foo()’: test.C:1:14: warning: no return statement in function returning non-void [-W return-type] int foo () { } ^ test.C:2:46: error: template instantiation depth exceeds maximum of 900 (use -ftemplate-depth= to increase the maximum) instantiating ‘struct X<100>’ template struct X { static const int value = X::value; }; temp late struct X<1000>; ^ test.C:2:46: recursively required from ‘const int X<999>::value’ test.C:2:46: required from ‘const int X<1000>::value’ test.C:2:88: required from here test.C:2:46: error: incomplete type ‘X<100>’ used in nested name specifier * With the new [7]#pragma GCC ivdep, the user can assert that there are no loop-carried dependencies which would prevent concurrent execution of consecutive iterations using SIMD (single instruction multiple data) instructions. * Support for Cilk Plus has been added and can be enabled with the -fcilkplus option. Cilk Plus is an extension to the C and C++ languages to support data and task parallelism. The present implementation follows ABI version 1.2; all features but _Cilk_for have been implemented. C * ISO C11 atomics (the _Atomic type specifier and qualifier and the header) are now supported. * ISO C11 generic selections (_Generic keyword) are now supported. * ISO C11 thread-local storage (_Thread_local, similar to GNU C __thread) is now supported. * ISO C11 support is now at a similar level of completeness to ISO C99 support: substantially complete modulo bugs, extended identifiers (supported except for corner cases when -fextended-identifiers is used), floating-point issues (mainly but not entirely relating to optional C99 features from Annexes F and G) and the optional Annexes K (Bounds-checking interfaces) and L (Analyzability). * A new C extension __auto_type provides a subset of the functionality of C++11 auto in GNU C. C++ * The G++ implementation of [8]C++1y return type deduction for normal functions has been updated to conform to [9]N3638, the proposal accepted into the working paper. Most notably, it adds decltype(auto) for getting decltype semantics rather than the template argument deduction semantics of plain auto: int& f(); auto i1 = f(); // int decltype(auto) i2 = f(); // int& * G++ supports [10]C++1y lambda capture initializers: [x = 42]{ ... }; Actually, they have been accepted since GCC 4.5, but now the compiler doesn't warn about them with -std=c++1y, and supports parenthesized and brace-enclosed initializers as well. * G++ supports [11]C++1y variable length arrays. G++ has supported GNU/C99-style VLAs for a long time, but now additionally supports initializers and lambda capture by reference. In C++1y mode G++ will complain about VLA uses that are not permitted by the draft standard, such as forming a pointer to VLA type or applying sizeof to a VLA variable. Note that it now appears that VLAs will not be part of C++14, but will be part of a separate document and then perhaps C++17. void f(int n) { int a[n] = { 1, 2, 3 }; // throws std::bad_array_length if n < 3 [&a]{ for (int i : a) { cout << i << endl; } }(); &a; // error, taking address of VLA } * G++ supports the [12]C++1y [[deprecated]] attribute modulo bugs in the underlying [[gnu::deprecated]] attribute. Classes and functions can be marked deprecated and a diagnostic message added: class A; int bar(int n); #if __cplusplus > 201103 class [[deprecated("A is deprecated in C++14; Use B instead")]] A; [[deprecated("bar is unsafe; use foo() instead")]] int bar(int n); int foo(int n); class B; #endif A aa; // warning: 'A' is deprecated : A is deprecated in C++14; Use B instead int j = bar(2); // warning: 'int bar(int)' is deprecated : bar is unsafe; use fo o() instead * G++ supports [13]C++1y digit separators. Long numeric literals can be subdivided with a single quote ' to enhance readability: int i = 1048576; int j = 1'048'576; int k = 0x10'0000; int m = 0'004'000'000; int n = 0b0001'0000'0000'0000'0000'0000; double x = 1.602'176'565e-19; double y = 1.602'176'565e-1'9; * G++ supports [14]C++1y generic (polymorphic) lambdas. // a functional object that will increment any type auto incr = [](auto x) { return x++; }; * As a GNU extension, G++ supports explicit template parameter syntax for generic lambdas. This can be combined in the expected way with the standard auto syntax. // a functional object that will add two like-type objects auto add = [] (T a, T b) { return a + b; }; * G++ supports unconstrained generic functions as specified by §4.1.2 and §5.1.1 of [15]N3889: Concepts Lite Specification. Briefly, auto may be used as a type-specifier in a parameter declaration of any function declarator in order to introduce an implicit function template parameter, akin to generic lambdas. // the following two function declarations are equivalent auto incr(auto x) { return x++; } template auto incr(T x) { return x++; } Runtime Library (libstdc++) * [16]Improved support for C++11, including: + support for ; + The associative containers in and and the unordered associative containers in and meet the allocator-aware container requirements; * [17]Improved experimental support for the upcoming ISO C++ standard, C++14, including: + fixing constexpr member functions without const; + implementation of the std::exchange() utility function; + addressing tuples by type; + implemention of std::make_unique; + implemention of std::shared_lock; + making std::result_of SFINAE-friendly; + adding operator() to std::integral_constant; + adding user-defined literals for standard library types std::basic_string, std::chrono::duration, and std::complex; + adding two range overloads to non-modifying sequence oprations std::equal and std::mismatch; + adding IO manipulators for quoted strings; + adding constexpr members to , , , and some containers; + adding compile-time std::integer_sequence; + adding cleaner transformation traits; + making s operator functors easier to use and more generic; * An implementation of std::experimental::optional. * An implementation of std::experimental::string_view. * The non-standard function std::copy_exception has been deprecated and will be removed in a future version. std::make_exception_ptr should be used instead. Fortran * Compatibility notice: + Module files: The version of the module files (.mod) has been incremented; additionally, module files are now compressed. Fortran MODULEs compiled by earlier GCC versions have to be recompiled, when they are USEd by files compiled with GCC 4.9. GCC 4.9 is not able to read .mod files of earlier GCC versions; attempting to do so gives an error message. Note: The ABI of the produced assembler data itself has not changed: object files and libraries are fully compatible with older versions (except as stated below). + ABI changes: o The [18]argument passing ABI has changed for scalar dummy arguments of type INTEGER, REAL, COMPLEX and LOGICAL, which have both the VALUE and the OPTIONAL attributes. o To support finalization the virtual table associated with polymorphic variables has changed. Code containing CLASS should be recompiled, including all files which define derived types involved in the type definition used by polymorphic variables. (Note: Due to the incremented module version, trying to mix old code with new code will usually give an error message.) + GNU Fortran no longer deallocates allocatable variables or allocatable components of variables declared in the main program. Since Fortran 2008, the standard explicitly states that variables declared in the Fortran main program automatically have the SAVE attribute. + When opening files, the close-on-exec flag is set if the system supports such a feature. This is generally considered good practice these days, but if there is a need to pass file descriptors to child processes the parent process must now remember to clear the close-on-exec flag by calling fcntl(), e.g. via ISO_C_BINDING, before executing the child process. * The deprecated command-line option -fno-whole-file has been removed. (-fwhole-file is the default since GCC 4.6.) -fwhole-file/-fno-whole-file continue to be accepted but do not influence the code generation. * The compiler no longer unconditionally warns about DO loops with zero iterations. This warning is now controlled by the -Wzerotrip option, which is implied by -Wall. * The new NO_ARG_CHECK attribute of the [19]!GCC$ directive can be used to disable the type-kind-rank (TKR) argument check for a dummy argument. The feature is similar to ISO/IEC TS 29133:2012's TYPE(*), except that it additionally also disables the rank check. Variables with NO_ARG_CHECK have to be dummy arguments and may only be used as argument to ISO_C_BINDING's C_LOC and as actual argument to another NO_ARG_CHECK dummy argument; also the other constraints of TYPE(*) apply. The dummy arguments should be declared as scalar or assumed-size variable of type type(*) (recommended) – or of type integer, real, complex or logical. With NO_ARG_CHECK, a pointer to the data without further type or shape information is passed, similar to C's void*. Note that also TS 29113's type(*),dimension(..) accepts arguments of any type and rank; contrary to NO_ARG_CHECK assumed-rank arguments pass an array descriptor which contains the array shape and stride of the argument. * [20]Fortran 2003: + Finalization is now supported. It is currently only done for a subset of those situations in which it should occur. + Experimental support for scalar character components with deferred length (i.e. allocatable string length) in derived types has been added. (Deferred-length character variables are supported since GCC 4.6.) * [21]Fortran 2008: + When STOP or ERROR STOP are used to terminate the execution and any exception (but inexact) is signaling, a warning is printed to ERROR_UNIT, indicating which exceptions are signaling. The [22]-ffpe-summary= command-line option can be used to fine-tune for which exceptions the warning should be shown. + Rounding on input (READ) is now handled on systems where strtod honours the rounding mode. (For output, rounding is supported since GCC 4.5.) Note that for input, the compatible rounding mode is handled as nearest (i.e., rounding to an even least significant [cf. IEC 60559:1989] for a tie, while compatible rounds away from zero in that case). Go * GCC 4.9 provides a complete implementation of the Go 1.2.1 release. New Targets and Target Specific Improvements AArch64 * The ARMv8-A crypto and CRC instructions are now supported through intrinsics. These are enabled when the architecture supports these and are available through the -march=armv8-a+crc and -march=armv8-a+crypto options. * Initial support for ILP32 has now been added to the compiler. This is now available through the command-line option -mabi=ilp32. Support for ILP32 is considered experimental as the ABI specification is still beta. * Coverage of more of the ISA including the SIMD extensions has been added. The Advanced SIMD intrinsics have also been improved. * The new local register allocator (LRA) is now on by default for the AArch64 back end. * The REE (Redundant extension elimination) pass has now been enabled by default for the AArch64 back end. * Tuning for the Cortex-A53 and Cortex-A57 has been improved. * Initial big.LITTLE tuning support for the combination of Cortex-A57 and Cortex-A53 was added through the -mcpu=cortex-a57.cortex-a53 option. * A number of structural changes have been made to both the ARM and AArch64 back ends to facilitate improved code-generation. * As of GCC 4.9.2 a workaround for the ARM Cortex-A53 erratum 835769 has been added and can be enabled by giving the -mfix-cortex-a53-835769 option. Alternatively it can be enabled by default by configuring GCC with the --enable-fix-cortex-a53-835769 option. ARC * A port for Synopsys Designware ARC has been contributed by Embecosm and Synopsys Inc. ARM * Use of Advanced SIMD (Neon) for 64-bit scalar computations has been disabled by default. This was found to generate better code in only a small number of cases. It can be turned back on with the -mneon-for-64bits option. * Further support for the ARMv8-A architecture, notably implementing the restriction around IT blocks in the Thumb32 instruction set has been added. The -mrestrict-it option can be used with -march=armv7-a or the -march=armv7ve options to make code generation fully compatible with the deprecated instructions in ARMv8-A. * Support has now been added for the ARMv7ve variant of the architecture. This can be used by the -march=armv7ve option. * The ARMv8-A crypto and CRC instructions are now supported through intrinsics and are available through the -march=armv8-a+crc and mfpu=crypto-neon-fp-armv8 options. * LRA is now on by default for the ARM target. This can be turned off using the -mno-lra option. This option is a purely transitionary command-line option and will be removed in a future release. We are interested in any bug reports regarding functional and performance regressions with LRA. * A new option -mslow-flash-data to improve performance of programs fetching data on slow flash memory has now been introduced for the ARMv7-M profile cores. * A new option -mpic-data-is-text-relative for targets that allows data segments to be relative to text segments has been added. This is on by default for all targets except VxWorks RTP. * A number of infrastructural changes have been made to both the ARM and AArch64 back ends to facilitate improved code-generation. * GCC now supports Cortex-A12 and the Cortex-R7 through the -mcpu=cortex-a12 and -mcpu=cortex-r7 options. * GCC now has tuning for the Cortex-A57 and Cortex-A53 through the -mcpu=cortex-a57 and -mcpu=cortex-a53 options. * Initial big.LITTLE tuning support for the combination of Cortex-A57 and Cortex-A53 was added through the -mcpu=cortex-a57.cortex-a53 option. Similar support was added for the combination of Cortex-A15 and Cortex-A7 through the -mcpu=cortex-a15.cortex-a7 option. * Further performance optimizations for the Cortex-A15 and the Cortex-M4 have been added. * A number of code generation improvements for Thumb2 to reduce code size when compiling for the M-profile processors. AVR * A new command-line option -mfract-convert-truncate has been added. It allows compiler to use truncation instead of rounding towards zero for fractional fixed-point types. IA-32/x86-64 * -mfpmath=sse is now implied by -ffast-math on all targets where SSE2 is supported. * Intel AVX-512 support was added to GCC. That includes inline assembly support, new registers and extending existing ones, new intrinsics (covered by corresponding testsuite), and basic autovectorization. AVX-512 instructions are available via the following GCC switches: AVX-512 foundation instructions: -mavx512f, AVX-512 prefetch instructions: -mavx512pf, AVX-512 exponential and reciprocal instructions: -mavx512er, AVX-512 conflict detection instructions: -mavx512cd. * It is now possible to call x86 intrinsics from select functions in a file that are tagged with the corresponding target attribute without having to compile the entire file with the -mxxx option. This improves the usability of x86 intrinsics and is particularly useful when doing [23]Function Multiversioning. * GCC now supports the new Intel microarchitecture named Silvermont through -march=silvermont. * GCC now supports the new Intel microarchitecture named Broadwell through -march=broadwell. * Optimizing for other Intel microarchitectures have been renamed to -march=nehalem, westmere, sandybridge, ivybridge, haswell, bonnell. * -march=generic has been retuned for better support of Intel core and AMD Bulldozer architectures. Performance of AMD K7, K8, Intel Pentium-M, and Pentium4 based CPUs is no longer considered important for generic. * -mtune=intel can now be used to generate code running well on the most current Intel processors, which are Haswell and Silvermont for GCC 4.9. * Support to encode 32-bit assembly instructions in 16-bit format is now available through the -m16 command-line option. * Better inlining of memcpy and memset that is aware of value ranges and produces shorter alignment prologues. * -mno-accumulate-outgoing-args is now honored when unwind information is output. Argument accumulation is also now turned off for portions of programs optimized for size. * Support for new AMD family 15h processors (Excavator core) is now available through the -march=bdver4 and -mtune=bdver4 options. MSP430 * A new command-line option -mcpu= has been added to the MSP430 back end. This option is used to specify the ISA to be used. Accepted values are msp430 (the default), msp430x and msp430xv2. The ISA is no longer deduced from the -mmcu= option as there are far too many different MCU names. The -mmcu= option is still supported, and this is still used to select linker scripts and generate a C preprocessor symbol that will be recognised by the msp430.h header file. NDS32 * A new nds32 port supports the 32-bit architecture from Andes Technology Corporation. * The port provides initial support for the V2, V3, V3m instruction set architectures. Nios II * A port for the Altera Nios II has been contributed by Mentor Graphics. PowerPC / PowerPC64 / RS6000 * GCC now supports Power ISA 2.07, which includes support for Hardware Transactional Memory (HTM), Quadword atomics and several VMX and VSX additions, including Crypto, 64-bit integer, 128-bit integer and decimal integer operations. * Support for the POWER8 processor is now available through the -mcpu=power8 and -mtune=power8 options. * The libitm library has been modified to add a HTM fastpath that automatically uses POWER's HTM hardware instructions when it is executing on a HTM enabled processor. * Support for the new powerpc64le-linux platform has been added. It defaults to generating code that conforms to the ELFV2 ABI. S/390, System z * Support for the Transactional Execution Facility included with the IBM zEnterprise zEC12 processor has been added. A set of GCC style builtins as well as XLC style builtins are provided. The builtins are enabled by default when using the -march=zEC12 option but can explicitly be disabled with -mno-htm. Using the GCC builtins also libitm supports hardware transactions on S/390. * The hotpatch features allows to prepare functions for hotpatching. A certain amount of bytes is reserved before the function entry label plus a NOP is inserted at its very beginning to implement a backward jump when applying a patch. The feature can either be enabled per compilation unit via the command-line option -mhotpatch or per function using the hotpatch attribute. * The shrink wrap optimization is now supported on S/390 and enabled by default. * A major rework of the routines to determine which registers need to be saved and restored in function prologue/epilogue now allow to use floating point registers as save slots. This will happen for certain leaf function with -march=z10 or higher. * The LRA rtl pass replaces reload by default on S/390. RX * The port now allows to specify the RX100, RX200, and RX600 processors with the command-line options -mcpu=rx100, -mcpu=rx200 and -mcpu=rx600. SH * Minor improvements to code generated for integer arithmetic and code that involves the T bit. * Added support for the SH2A clips and clipu instructions. The compiler will now try to utilize them for min/max expressions such as max (-128, min (127, x)). * Added support for the cmp/str instruction through built-in functions such as __builtin_strlen. When not optimizing for size, the compiler will now expand calls to e.g. strlen as an inlined sequences which utilize the cmp/str instruction. * Improved code generated around volatile memory loads and stores. * The option -mcbranchdi has been deprecated. Specifying it will result in a warning and will not influence code generation. * The option -mcmpeqdi has been deprecated. Specifying it will result in a warning and will not influence code generation. GCC 4.9.1 This is the [24]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.9.1 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Version 4.0 of the OpenMP specification is supported even in Fortran, not just C and C++. GCC 4.9.2 This is the [25]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.9.2 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.9.3 This is the [26]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.9.3 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.9.4 This is the [27]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.9.4 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). For questions related to the use of GCC, please consult these web pages and the [28]GCC manuals. If that fails, the [29]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [30]gcc@gcc.gnu.org. All of [31]our lists have public archives. Copyright (C) [32]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [33]maintained by the GCC team. Last modified 2023-09-02. References 1. https://gcc.gnu.org/ml/gcc-patches/2013-05/msg00728.html 2. https://gcc.gnu.org/PR60825 3. https://gcc.gnu.org/gcc-4.9/porting_to.html 4. https://www.openmp.org/specifications/ 5. https://gcc.gnu.org/onlinedocs/gcc-4.9.2/gcc/Optimize-Options.html#index-fsimd-cost-model-908 6. https://gcc.gnu.org/onlinedocs/gcc-4.9.2/gcc/Language-Independent-Options.html#index-fdiagnostics-color-252 7. https://gcc.gnu.org/onlinedocs/gcc-4.9.2/gcc/Loop-Specific-Pragmas.html 8. https://gcc.gnu.org/projects/cxx1y.html 9. https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3638.html 10. https://gcc.gnu.org/projects/cxx1y.html 11. https://gcc.gnu.org/projects/cxx1y.html 12. https://gcc.gnu.org/projects/cxx1y.html 13. https://gcc.gnu.org/projects/cxx1y.html 14. https://gcc.gnu.org/projects/cxx1y.html 15. https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3889.pdf 16. https://gcc.gnu.org/onlinedocs/gcc-4.9.2/libstdc++/manual/manual/status.html#status.iso.2011 17. https://gcc.gnu.org/onlinedocs/libstdc++/manual/status.html#status.iso.2014 18. https://gcc.gnu.org/onlinedocs/gcc-4.9.2/gfortran/Argument-passing-conventions.html 19. https://gcc.gnu.org/onlinedocs/gcc-4.9.2/gfortran/GNU-Fortran-Compiler-Directives.html 20. https://gcc.gnu.org/wiki/Fortran2003Status 21. https://gcc.gnu.org/wiki/Fortran2008Status 22. https://gcc.gnu.org/onlinedocs/gcc-4.9.2/gfortran/Debugging-Options.html 23. https://gcc.gnu.org/onlinedocs/gcc-4.9.2/gcc/Function-Multiversioning.html 24. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.9.1 25. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.9.2 26. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.9.3 27. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.9.4 28. https://gcc.gnu.org/onlinedocs/ 29. mailto:gcc-help@gcc.gnu.org 30. mailto:gcc@gcc.gnu.org 31. https://gcc.gnu.org/lists.html 32. https://www.fsf.org/ 33. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.8/index.html GCC 4.8 Release Series (This release series is no longer supported.) June 23, 2015 The [1]GNU project and the GCC developers are pleased to announce the release of GCC 4.8.5. This release is a bug-fix release, containing fixes for regressions in GCC 4.8.4 relative to previous releases of GCC. Release History GCC 4.8.5 June 23, 2015 ([2]changes, [3]documentation) GCC 4.8.4 December 19, 2014 ([4]changes, [5]documentation) GCC 4.8.3 May 22, 2014 ([6]changes, [7]documentation) GCC 4.8.2 October 16, 2013 ([8]changes, [9]documentation) GCC 4.8.1 May 31, 2013 ([10]changes, [11]documentation) GCC 4.8.0 March 22, 2013 ([12]changes, [13]documentation) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. A list of [14]successful builds is updated as new information becomes available. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [15]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [16]GCC project web site or contact the [17]GCC development mailing list. To obtain GCC please use [18]our mirror sites or [19]our version control system. For questions related to the use of GCC, please consult these web pages and the [20]GCC manuals. If that fails, the [21]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [22]gcc@gcc.gnu.org. All of [23]our lists have public archives. Copyright (C) [24]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [25]maintained by the GCC team. Last modified 2022-10-26. References 1. http://www.gnu.org/ 2. https://gcc.gnu.org/gcc-4.8/changes.html 3. https://gcc.gnu.org/onlinedocs/4.8.5/ 4. https://gcc.gnu.org/gcc-4.8/changes.html 5. https://gcc.gnu.org/onlinedocs/4.8.4/ 6. https://gcc.gnu.org/gcc-4.8/changes.html 7. https://gcc.gnu.org/onlinedocs/4.8.3/ 8. https://gcc.gnu.org/gcc-4.8/changes.html 9. https://gcc.gnu.org/onlinedocs/4.8.2/ 10. https://gcc.gnu.org/gcc-4.8/changes.html 11. https://gcc.gnu.org/onlinedocs/4.8.1/ 12. https://gcc.gnu.org/gcc-4.8/changes.html 13. https://gcc.gnu.org/onlinedocs/4.8.0/ 14. https://gcc.gnu.org/gcc-4.8/buildstat.html 15. https://gcc.gnu.org/onlinedocs/gcc/Contributors.html 16. https://gcc.gnu.org/index.html 17. mailto:gcc@gcc.gnu.org 18. https://gcc.gnu.org/mirrors.html 19. https://gcc.gnu.org/git.html 20. https://gcc.gnu.org/onlinedocs/ 21. mailto:gcc-help@gcc.gnu.org 22. mailto:gcc@gcc.gnu.org 23. https://gcc.gnu.org/lists.html 24. https://www.fsf.org/ 25. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.8/changes.html GCC 4.8 Release Series Changes, New Features, and Fixes Caveats GCC now uses C++ as its implementation language. This means that to build GCC from sources, you will need a C++ compiler that understands C++ 2003. For more details on the rationale and specific changes, please refer to the [1]C++ conversion page. To enable the Graphite framework for loop optimizations you now need CLooG version 0.18.0 and ISL version 0.11.1. Both can be obtained from the [2]GCC infrastructure directory. The installation manual contains more information about requirements to build GCC. GCC now uses a more aggressive analysis to derive an upper bound for the number of iterations of loops using constraints imposed by language standards. This may cause non-conforming programs to no longer work as expected, such as SPEC CPU 2006 464.h264ref and 416.gamess. A new option, -fno-aggressive-loop-optimizations, was added to disable this aggressive analysis. In some loops that have known constant number of iterations, but undefined behavior is known to occur in the loop before reaching or during the last iteration, GCC will warn about the undefined behavior in the loop instead of deriving lower upper bound of the number of iterations for the loop. The warning can be disabled with -Wno-aggressive-loop-optimizations. On ARM, a bug has been fixed in GCC's implementation of the AAPCS rules for the layout of vectors that could lead to wrong code being generated. Vectors larger than 8 bytes in size are now by default aligned to an 8-byte boundary. This is an ABI change: code that makes explicit use of vector types may be incompatible with binary objects built with older versions of GCC. Auto-vectorized code is not affected by this change. On AVR, support has been removed for the command-line option -mshort-calls deprecated in GCC 4.7. On AVR, the configure option --with-avrlibc supported since GCC 4.7.2 is turned on per default for all non-RTEMS configurations. This option arranges for a better integration of [3]AVR Libc with avr-gcc. For technical details, see [4]PR54461. To turn off the option in non-RTEMS configurations, use --with-avrlibc=no. If the compiler is configured for RTEMS, the option is always turned off. More information on porting to GCC 4.8 from previous versions of GCC can be found in the [5]porting guide for this release. General Optimizer Improvements (and Changes) * DWARF4 is now the default when generating DWARF debug information. When -g is used on a platform that uses DWARF debugging information, GCC will now default to -gdwarf-4 -fno-debug-types-section. GDB 7.5, Valgrind 3.8.0 and elfutils 0.154 debug information consumers support DWARF4 by default. Before GCC 4.8 the default version used was DWARF2. To make GCC 4.8 generate an older DWARF version use -g together with -gdwarf-2 or -gdwarf-3. The default for Darwin and VxWorks is still -gdwarf-2 -gstrict-dwarf. * A new general optimization level, -Og, has been introduced. It addresses the need for fast compilation and a superior debugging experience while providing a reasonable level of run-time performance. Overall experience for development should be better than the default optimization level -O0. * A new option -ftree-partial-pre was added to control the partial redundancy elimination (PRE) optimization. This option is enabled by default at the -O3 optimization level, and it makes PRE more aggressive. * The option -fconserve-space has been removed; it was no longer useful on most targets since GCC supports putting variables into BSS without making them common. * The struct reorg and matrix reorg optimizations (command-line options -fipa-struct-reorg and -fipa-matrix-reorg) have been removed. They did not always work correctly, nor did they work with link-time optimization (LTO), hence were only applicable to programs consisting of a single translation unit. * Several scalability bottle-necks have been removed from GCC's optimization passes. Compilation of extremely large functions, e.g. due to the use of the flatten attribute in the "Eigen" C++ linear algebra templates library, is significantly faster than previous releases of GCC. * Link-time optimization (LTO) improvements: + LTO partitioning has been rewritten for better reliability and maintanibility. Several important bugs leading to link failures have been fixed. * Interprocedural optimization improvements: + A new symbol table has been implemented. It builds on existing callgraph and varpool modules and provide a new API. Unusual symbol visibilities and aliases are handled more consistently leading to, for example, more aggressive unreachable code removal with LTO. + The inline heuristic can now bypass limits on the size of of inlined functions when the inlining is particularly profitable. This happens, for example, when loop bounds or array strides get propagated. + Values passed through aggregates (either by value or reference) are now propagated at the inter-procedural level leading to better inlining decisions (for example in the case of Fortran array descriptors) and devirtualization. * [6]AddressSanitizer , a fast memory error detector, has been added and can be enabled via -fsanitize=address. Memory access instructions will be instrumented to detect heap-, stack-, and global-buffer overflow as well as use-after-free bugs. To get nicer stacktraces, use -fno-omit-frame-pointer. The AddressSanitizer is available on IA-32/x86-64/x32/PowerPC/PowerPC64 GNU/Linux and on x86-64 Darwin. * [7]ThreadSanitizer has been added and can be enabled via -fsanitize=thread. Instructions will be instrumented to detect data races. The ThreadSanitizer is available on x86-64 GNU/Linux. * A new local register allocator (LRA) has been implemented, which replaces the 26 year old reload pass and improves generated code quality. For now it is active on the IA-32 and x86-64 targets. * Support for transactional memory has been implemented on the following architectures: IA-32/x86-64, ARM, PowerPC, SH, SPARC, and Alpha. New Languages and Language specific improvements C family * Each diagnostic emitted now includes the original source line and a caret '^' indicating the column. The option -fno-diagnostics-show-caret suppresses this information. * The option -ftrack-macro-expansion=2 is now enabled by default. This allows the compiler to display the macro expansion stack in diagnostics. Combined with the caret information, an example diagnostic showing these two features is: t.c:1:94: error: invalid operands to binary < (have ‘struct mystruct’ and ‘float ’) #define MYMAX(A,B) __extension__ ({ __typeof__(A) __a = (A); __typeof__(B) _ _b = (B); __a < __b ? __b : __a; }) ^ t.c:7:7: note: in expansion of macro 'MYMAX' X = MYMAX(P, F); ^ * A new -Wsizeof-pointer-memaccess warning has been added (also enabled by -Wall) to warn about suspicious length parameters to certain string and memory built-in functions if the argument uses sizeof. This warning warns e.g. about memset (ptr, 0, sizeof (ptr)); if ptr is not an array, but a pointer, and suggests a possible fix, or about memcpy (&foo, ptr, sizeof (&foo));. * The new option -Wpedantic is an alias for -pedantic, which is now deprecated. The forms -Wno-pedantic, -Werror=pedantic, and -Wno-error=pedantic work in the same way as for any other -W option. One caveat is that -Werror=pedantic is not equivalent to -pedantic-errors, since the latter makes into errors some warnings that are not controlled by -Wpedantic, and the former only affects diagnostics that are disabled when using -Wno-pedantic. * The option -Wshadow no longer warns if a declaration shadows a function declaration, unless the former declares a function or pointer to function, because this is [8]a common and valid case in real-world code. C++ * G++ now implements the [9]C++11 thread_local keyword; this differs from the GNU __thread keyword primarily in that it allows dynamic initialization and destruction semantics. Unfortunately, this support requires a run-time penalty for references to non-function-local thread_local variables defined in a different translation unit even if they don't need dynamic initialization, so users may want to continue to use __thread for TLS variables with static initialization semantics. If the programmer can be sure that no use of the variable in a non-defining TU needs to trigger dynamic initialization (either because the variable is statically initialized, or a use of the variable in the defining TU will be executed before any uses in another TU), they can avoid this overhead with the -fno-extern-tls-init option. OpenMP threadprivate variables now also support dynamic initialization and destruction by the same mechanism. * G++ now implements the [10]C++11 attribute syntax, e.g. [[noreturn]] void f(); and also the alignment specifier, e.g. alignas(double) int i; * G++ now implements [11]C++11 inheriting constructors, e.g. struct A { A(int); }; struct B: A { using A::A; }; // defines B::B(int) B b(42); // OK * As of GCC 4.8.1, G++ implements the change to decltype semantics from [12]N3276. struct A f(); decltype(f()) g(); // OK, return type of f() is not required to be complete. * As of GCC 4.8.1, G++ implements [13]C++11 ref-qualifiers, e.g. struct A { int f() &; }; int i = A().f(); // error, f() requires an lvalue object * G++ now supports a -std=c++1y option for experimentation with features proposed for the next revision of the standard, expected around 2014. Currently the only difference from -std=c++11 is support for return type deduction in normal functions, as proposed in [14]N3386. Status of C++1y features in GCC 4.8 can be found [15]here. * The G++ namespace association extension, __attribute ((strong)), has been deprecated. Inline namespaces should be used instead. * G++ now supports a -fext-numeric-literal option to control whether GNU numeric literal suffixes are accepted as extensions or processed as C++11 user-defined numeric literal suffixes. The flag is on (use suffixes for GNU literals) by default for -std=gnu++*, and -std=c++98. The flag is off (use suffixes for user-defined literals) by default for -std=c++11 and later. Runtime Library (libstdc++) * [16]Improved experimental support for the new ISO C++ standard, C++11, including: + forward_list meets the allocator-aware container requirements; + this_thread::sleep_for(), this_thread::sleep_until() and this_thread::yield() are defined without requiring the configure option --enable-libstdcxx-time; * Improvements to : + SSE optimized normal_distribution. + Use of hardware RNG instruction for random_device on new x86 processors (requires the assembler to support the instruction.) and : + New random number engine simd_fast_mersenne_twister_engine with an optimized SSE implementation. + New random number distributions beta_distribution, normal_mv_distribution, rice_distribution, nakagami_distribution, pareto_distribution, k_distribution, arcsine_distribution, hoyt_distribution. * Added --disable-libstdcxx-verbose configure option to disable diagnostic messages issued when a process terminates abnormally. This may be useful for embedded systems to reduce the size of executables that link statically to the library. Fortran * Compatibility notice: + Module files: The version of module files (.mod) has been incremented. Fortran MODULEs compiled by earlier GCC versions have to be recompiled, when they are USEd by files compiled with GCC 4.8. GCC 4.8 is not able to read .mod files created by earlier versions; attempting to do so gives an error message. Note: The ABI of the produced assembler data itself has not changed; object files and libraries are fully compatible with older versions except as noted below. + ABI: Some internal names (used in the assembler/object file) have changed for symbols declared in the specification part of a module. If an affected module – or a file using it via use association – is recompiled, the module and all files which directly use such symbols have to be recompiled as well. This change only affects the following kind of module symbols: o Procedure pointers. Note: C-interoperable function pointers (type(c_funptr)) are not affected nor are procedure-pointer components. o Deferred-length character strings. * The [17]BACKTRACE intrinsic subroutine has been added. It shows a backtrace at an arbitrary place in user code; program execution continues normally afterwards. * The [18]-Wc-binding-type warning option has been added (disabled by default). It warns if the a variable might not be C interoperable; in particular, if the variable has been declared using an intrinsic type with default kind instead of using a kind parameter defined for C interoperability in the intrinsic ISO_C_Binding module. Before, this warning was always printed. The -Wc-binding-type option is enabled by -Wall. * The [19]-Wrealloc-lhs and -Wrealloc-lhs-all warning command-line options have been added, which diagnose when code is inserted for automatic (re)allocation of a variable during assignment. This option can be used to decide whether it is safe to use [20]-fno-realloc-lhs. Additionally, it can be used to find automatic (re)allocation in hot loops. (For arrays, replacing "var=" by "var(:)=" disables the automatic reallocation.) * The [21]-Wcompare-reals command-line option has been added. When this is set, warnings are issued when comparing REAL or COMPLEX types for equality and inequality; consider replacing a == b by abs(a−b) < eps with a suitable eps. -Wcompare-reals is enabled by -Wextra. * The [22]-Wtarget-lifetime command-line option has been added (enabled with -Wall), which warns if the pointer in a pointer assignment might outlive its target. * Reading floating point numbers which use "q" for the exponential (such as 4.0q0) is now supported as vendor extension for better compatibility with old data files. It is strongly recommended to use for I/O the equivalent but standard conforming "e" (such as 4.0e0). (For Fortran source code, consider replacing the "q" in floating-point literals by a kind parameter (e.g. 4.0e0_qp with a suitable qp). Note that – in Fortran source code – replacing "q" by a simple "e" is not equivalent.) * The GFORTRAN_TMPDIR environment variable for specifying a non-default directory for files opened with STATUS="SCRATCH", is not used anymore. Instead gfortran checks the POSIX/GNU standard TMPDIR environment variable. If TMPDIR is not defined, gfortran falls back to other methods to determine the directory for temporary files as documented in the [23]user manual. * [24]Fortran 2003: + Support for unlimited polymorphic variables (CLASS(*)) has been added. Nonconstant character lengths are not yet supported. * [25]TS 29113: + Assumed types (TYPE(*)) are now supported. + Experimental support for assumed-rank arrays (dimension(..)) has been added. Note that currently gfortran's own array descriptor is used, which is different from the one defined in TS29113, see [26]gfortran's header file or use the [27]Chasm Language Interoperability Tools. Go * GCC 4.8.2 provides a complete implementation of the Go 1.1.2 release. * GCC 4.8.0 and 4.8.1 implement a preliminary version of the Go 1.1 release. The library support is not quite complete. * Go has been tested on GNU/Linux and Solaris platforms for various processors including x86, x86_64, PowerPC, SPARC, and Alpha. It may work on other platforms as well. New Targets and Target Specific Improvements AArch64 * A new port has been added to support AArch64, the new 64-bit architecture from ARM. Note that this is a separate port from the existing 32-bit ARM port. * The port provides initial support for the Cortex-A53 and the Cortex-A57 processors with the command line options -mcpu=cortex-a53 and -mcpu=cortex-a57. * As of GCC 4.8.4 a workaround for the ARM Cortex-A53 erratum 835769 has been added and can be enabled by giving the -mfix-cortex-a53-835769 option. Alternatively it can be enabled by default by configuring GCC with the --enable-fix-cortex-a53-835769 option. ARM * Initial support has been added for the AArch32 extensions defined in the ARMv8 architecture. * Code generation improvements for the Cortex-A7 and Cortex-A15 CPUs. * A new option, -mcpu=marvell-pj4, has been added to generate code for the Marvell PJ4 processor. * The compiler can now automatically generate the VFMA, VFMS, REVSH and REV16 instructions. * A new vectorizer cost model for Advanced SIMD configurations to improve the auto-vectorization strategies used. * The scheduler now takes into account the number of live registers to reduce the amount of spilling that can occur. This should improve code performance in large functions. The limit can be removed by using the option -fno-sched-pressure. * Improvements have been made to the Marvell iWMMX code generation and support for the iWMMX2 SIMD unit has been added. The option -mcpu=iwmmxt2 can be used to enable code generation for the latter. * A number of code generation improvements for Thumb2 to reduce code size when compiling for the M-profile processors. * The RTEMS (arm-rtems) port has been updated to use the EABI. * Code generation support for the old FPA and Maverick floating-point architectures has been removed. Ports that previously relied on these features have also been removed. This includes the targets: + arm*-*-linux-gnu (use arm*-*-linux-gnueabi) + arm*-*-elf (use arm*-*-eabi) + arm*-*-uclinux* (use arm*-*-uclinux*eabi) + arm*-*-ecos-elf (no alternative) + arm*-*-freebsd (no alternative) + arm*-wince-pe* (no alternative). AVR * Support for the "Embedded C" fixed-point has been added. For details, see the [28]GCC wiki and the [29]user manual. The support is not complete. * A new print modifier %r for register operands in inline assembler is supported. It will print the raw register number without the register prefix 'r': /* Return the most significant byte of 'val', a 64-bit value. */ unsigned char msb (long long val) { unsigned char c; __asm__ ("mov %0, %r1+7" : "=r" (c) : "r" (val)); return c; } The inline assembler in this example will generate code like mov r24, 8+7 provided c is allocated to R24 and val is allocated to R8…R15. This works because the GNU assembler accepts plain register numbers without register prefix. * Static initializers with 3-byte symbols are supported now: extern const __memx char foo; const __memx void *pfoo = &foo; This requires at least Binutils 2.23. IA-32/x86-64 * Allow -mpreferred-stack-boundary=3 for the x86-64 architecture with SSE extensions disabled. Since the x86-64 ABI requires 16 byte stack alignment, this is ABI incompatible and intended to be used in controlled environments where stack space is an important limitation. This option will lead to wrong code when functions compiled with 16 byte stack alignment (such as functions from a standard library) are called with misaligned stack. In this case, SSE instructions may lead to misaligned memory access traps. In addition, variable arguments will be handled incorrectly for 16 byte aligned objects (including x87 long double and __int128), leading to wrong results. You must build all modules with -mpreferred-stack-boundary=3, including any libraries. This includes the system libraries and startup modules. * Support for the new Intel processor codename Broadwell with RDSEED, ADCX, ADOX, PREFETCHW is available through -madx, -mprfchw, -mrdseed command-line options. * Support for the Intel RTM and HLE intrinsics, built-in functions and code generation is available via -mrtm and -mhle. * Support for the Intel FXSR, XSAVE and XSAVEOPT instruction sets. Intrinsics and built-in functions are available via -mfxsr, -mxsave and -mxsaveopt respectively. * New -maddress-mode=[short|long] options for x32. -maddress-mode=short overrides default 64-bit addresses to 32-bit by emitting the 0x67 address-size override prefix. This is the default address mode for x32. * New built-in functions to detect run-time CPU type and ISA: + A built-in function __builtin_cpu_is has been added to detect if the run-time CPU is of a particular type. It returns a positive integer on a match and zero otherwise. It accepts one string literal argument, the CPU name. For example, __builtin_cpu_is("westmere") returns a positive integer if the run-time CPU is an Intel Core i7 Westmere processor. Please refer to the [30]user manual for the list of valid CPU names recognized. + A built-in function __builtin_cpu_supports has been added to detect if the run-time CPU supports a particular ISA feature. It returns a positive integer on a match and zero otherwise. It accepts one string literal argument, the ISA feature. For example, __builtin_cpu_supports("ssse3") returns a positive integer if the run-time CPU supports SSSE3 instructions. Please refer to the [31]user manual for the list of valid ISA names recognized. Caveat: If these built-in functions are called before any static constructors are invoked, like during IFUNC initialization, then the CPU detection initialization must be explicitly run using this newly provided built-in function, __builtin_cpu_init. The initialization needs to be done only once. For example, this is how the invocation would look like inside an IFUNC initializer: static void (*some_ifunc_resolver(void))(void) { __builtin_cpu_init(); if (__builtin_cpu_is("amdfam10h") ... if (__builtin_cpu_supports("popcnt") ... } * Function Multiversioning Support with G++: It is now possible to create multiple function versions each targeting a specific processor and/or ISA. Function versions have the same signature but different target attributes. For example, here is a program with function versions: __attribute__ ((target ("default"))) int foo(void) { return 1; } __attribute__ ((target ("sse4.2"))) int foo(void) { return 2; } int main (void) { int (*p) = &foo; assert ((*p)() == foo()); return 0; } Please refer to this [32]wiki for more information. * The x86 back end has been improved to allow option -fschedule-insns to work reliably. This option can be used to schedule instructions better and leads to improved performace in certain cases. * Windows MinGW-w64 targets (*-w64-mingw*) require at least r5437 from the Mingw-w64 trunk. * Support for new AMD family 15h processors (Steamroller core) is now available through the -march=bdver3 and -mtune=bdver3 options. * Support for new AMD family 16h processors (Jaguar core) is now available through the -march=btver2 and -mtune=btver2 options. FRV * This target now supports the -fstack-usage command-line option. MIPS * GCC can now generate code specifically for the R4700, Broadcom XLP and MIPS 34kn processors. The associated -march options are -march=r4700, -march=xlp and -march=34kn respectively. * GCC now generates better DSP code for MIPS 74k cores thanks to further scheduling optimizations. * The MIPS port now supports the -fstack-check option. * GCC now passes the -mmcu and -mno-mcu options to the assembler. * Previous versions of GCC would silently accept -fpic and -fPIC for -mno-abicalls targets like mips*-elf. This combination was not intended or supported, and did not generate position-independent code. GCC 4.8 now reports an error when this combination is used. PowerPC / PowerPC64 / RS6000 * SVR4 configurations (GNU/Linux, FreeBSD, NetBSD) no longer save, restore or update the VRSAVE register by default. The respective operating systems manage the VRSAVE register directly. * Large TOC support has been added for AIX through the command line option -mcmodel=large. * Native Thread-Local Storage support has been added for AIX. * VMX (Altivec) and VSX instruction sets now are enabled implicitly when targetting processors that support those hardware features on AIX 6.1 and above. RX * This target will now issue a warning message whenever multiple fast interrupt handlers are found in the same compilation unit. This feature can be turned off by the new -mno-warn-multiple-fast-interrupts command-line option. S/390, System z * Support for the IBM zEnterprise zEC12 processor has been added. When using the -march=zEC12 option, the compiler will generate code making use of the following new instructions: + load and trap instructions + 2 new compare and trap instructions + rotate and insert selected bits - without CC clobber The -mtune=zEC12 option enables zEC12 specific instruction scheduling without making use of new instructions. * Register pressure sensitive instruction scheduling is enabled by default. * The ifunc function attribute is enabled by default. * memcpy and memcmp invokations on big memory chunks or with run time lengths are not generated inline anymore when tuning for z10 or higher. The purpose is to make use of the IFUNC optimized versions in Glibc. SH * The default alignment settings have been reduced to be less aggressive. This results in more compact code for optimization levels other than -Os. * Improved support for the __atomic built-in functions: + A new option -matomic-model=model selects the model for the generated atomic sequences. The following models are supported: soft-gusa Software gUSA sequences (SH3* and SH4* only). On SH4A targets this will now also partially utilize the movco.l and movli.l instructions. This is the default when the target is sh3*-*-linux* or sh4*-*-linux*. hard-llcs Hardware movco.l / movli.l sequences (SH4A only). soft-tcb Software thread control block sequences. soft-imask Software interrupt flipping sequences (privileged mode only). This is the default when the target is sh1*-*-linux* or sh2*-*-linux*. none Generates function calls to the respective __atomic built-in functions. This is the default for SH64 targets or when the target is not sh*-*-linux*. + The option -msoft-atomic has been deprecated. It is now an alias for -matomic-model=soft-gusa. + A new option -mtas makes the compiler generate the tas.b instruction for the __atomic_test_and_set built-in function regardless of the selected atomic model. + The __sync functions in libgcc now reflect the selected atomic model when building the toolchain. * Added support for the mov.b and mov.w instructions with displacement addressing. * Added support for the SH2A instructions movu.b and movu.w. * Various improvements to code generated for integer arithmetic. * Improvements to conditional branches and code that involves the T bit. A new option -mzdcbranch tells the compiler to favor zero-displacement branches. This is enabled by default for SH4* targets. * The pref instruction will now be emitted by the __builtin_prefetch built-in function for SH3* targets. * The fmac instruction will now be emitted by the fmaf standard function and the __builtin_fmaf built-in function. * The -mfused-madd option has been deprecated in favor of the machine-independent -ffp-contract option. Notice that the fmac instruction will now be generated by default for expressions like a * b + c. This is due to the compiler default setting -ffp-contract=fast. * Added new options -mfsrra and -mfsca to allow the compiler using the fsrra and fsca instructions on targets other than SH4A (where they are already enabled by default). * Added support for the __builtin_bswap32 built-in function. It is now expanded as a sequence of swap.b and swap.w instructions instead of a library function call. * The behavior of the -mieee option has been fixed and the negative form -mno-ieee has been added to control the IEEE conformance of floating point comparisons. By default -mieee is now enabled and the option -ffinite-math-only implicitly sets -mno-ieee. * Added support for the built-in functions __builtin_thread_pointer and __builtin_set_thread_pointer. This assumes that GBR is used to hold the thread pointer of the current thread. Memory loads and stores relative to the address returned by __builtin_thread_pointer will now also utilize GBR based displacement address modes. * The -mdiv= option for targets other than SHmedia has been fixed and documented. SPARC * Added optimized instruction scheduling for Niagara4. TILE-Gx * Added support for the -mcmodel=MODEL command-line option. The models supported are small and large. V850 * This target now supports the E3V5 architecture via the use of the new -mv850e3v5 command-line option. It also has experimental support for the e3v5 LOOP instruction which can be enabled via the new -mloop command-line option. XStormy16 * This target now supports the -fstack-usage command-line option. Operating Systems OpenBSD * Support for OpenBSD/amd64 (x86_64-*-openbsd*) has been added and support for OpenBSD/i386 (i386-*-openbsd*) has been rejuvenated. Windows (Cygwin) * Executables are now linked against shared libgcc by default. The previous default was to link statically, which can still be done by explicitly specifying -static or static-libgcc on the command line. However it is strongly advised against, as it will cause problems for any application that makes use of DLLs compiled by GCC. It should be alright for a monolithic stand-alone application that only links against the Windows DLLs, but offers little or no benefit. GCC 4.8.1 This is the [33]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.8.1 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). The C++11 std::chrono::system_clock and std::chrono::steady_clock classes have changed ABI in GCC 4.8.1, they both are now separate (never typedefs of each other), both use std::chrono::nanoseconds resolution, on most GNU/Linux configurations std::chrono::steady_clock is now finally monotonic, and both classes are mangled differently than in the previous GCC releases. std::chrono::system_clock::now() with std::chrono::microseconds resp. std::chrono::seconds resolution is still exported for backwards compatibility with default configured libstdc++. Note that libstdc++ configured with --enable-libstdcxx-time= used to be ABI incompatible with default configured libstdc++ for those two classes and no ABI compatibility can be offered for those configurations, so any C++11 code that uses those classes and has been compiled and linked against libstdc++ configured with the non-default --enable-libstdcxx-time= configuration option needs to be recompiled. GCC 4.8.2 This is the [34]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.8.2 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.8.3 This is the [35]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.8.3 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Support for the new powerpc64le-linux platform has been added. It defaults to generating code that conforms to the ELFV2 ABI. GCC 4.8.4 This is the [36]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.8.4 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.8.5 This is the [37]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.8.5 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). For questions related to the use of GCC, please consult these web pages and the [38]GCC manuals. If that fails, the [39]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [40]gcc@gcc.gnu.org. All of [41]our lists have public archives. Copyright (C) [42]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [43]maintained by the GCC team. Last modified 2022-11-05. References 1. https://gcc.gnu.org/wiki/cxx-conversion 2. ftp://gcc.gnu.org/pub/gcc/infrastructure/ 3. http://www.nongnu.org/avr-libc/ 4. https://gcc.gnu.org/PR54461 5. https://gcc.gnu.org/gcc-4.8/porting_to.html 6. https://github.com/google/sanitizers 7. https://code.google.com/archive/p/data-race-test/wikis/ThreadSanitizer.wiki 8. https://lkml.org/lkml/2006/11/28/239 9. https://gcc.gnu.org/gcc-4.8/cxx0x_status.html 10. https://gcc.gnu.org/gcc-4.8/cxx0x_status.html 11. https://gcc.gnu.org/gcc-4.8/cxx0x_status.html 12. https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3276.pdf 13. https://gcc.gnu.org/gcc-4.8/cxx0x_status.html 14. https://www.open-std.org/JTC1/SC22/WG21/docs/papers/2012/n3386.html 15. https://gcc.gnu.org/projects/cxx1y.html 16. https://gcc.gnu.org/onlinedocs/gcc-4.8.4/libstdc++/manual/manual/status.html#status.iso.2011 17. https://gcc.gnu.org/onlinedocs/gfortran/BACKTRACE.html 18. https://gcc.gnu.org/onlinedocs/gfortran/Error-and-Warning-Options.html 19. https://gcc.gnu.org/onlinedocs/gfortran/Error-and-Warning-Options.html 20. https://gcc.gnu.org/onlinedocs/gfortran/Code-Gen-Options.html 21. https://gcc.gnu.org/onlinedocs/gfortran/Error-and-Warning-Options.html 22. https://gcc.gnu.org/onlinedocs/gfortran/Error-and-Warning-Options.html 23. https://gcc.gnu.org/onlinedocs/gfortran/TMPDIR.html 24. https://gcc.gnu.org/wiki/Fortran2003Status 25. https://gcc.gnu.org/wiki/TS29113Status 26. https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=libgfortran/libgfortran.h 27. https://chasm-interop.sourceforge.net/ 28. https://gcc.gnu.org/wiki/avr-gcc#Fixed-Point_Support 29. https://gcc.gnu.org/onlinedocs/gcc/Fixed-Point.html 30. https://gcc.gnu.org/onlinedocs/gcc/x86-Built-in-Functions.html 31. https://gcc.gnu.org/onlinedocs/gcc/x86-Built-in-Functions.html 32. https://gcc.gnu.org/wiki/FunctionMultiVersioning 33. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.8.1 34. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.8.2 35. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.8.3 36. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.8.4 37. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.8.5 38. https://gcc.gnu.org/onlinedocs/ 39. mailto:gcc-help@gcc.gnu.org 40. mailto:gcc@gcc.gnu.org 41. https://gcc.gnu.org/lists.html 42. https://www.fsf.org/ 43. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.7/index.html GCC 4.7 Release Series (This release series is no longer supported.) June 12, 2014 The [1]GNU project and the GCC developers are pleased to announce the release of GCC 4.7.4. This release is a bug-fix release, containing fixes for regressions in GCC 4.7.3 relative to previous releases of GCC. Release History GCC 4.7.4 June 12, 2014 ([2]changes, [3]documentation) GCC 4.7.3 April 11, 2013 ([4]changes, [5]documentation) GCC 4.7.2 September 20, 2012 ([6]changes, [7]documentation) GCC 4.7.1 June 14, 2012 ([8]changes, [9]documentation) GCC 4.7.0 March 22, 2012 ([10]changes, [11]documentation) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. A list of [12]successful builds is updated as new information becomes available. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [13]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [14]GCC project web site or contact the [15]GCC development mailing list. To obtain GCC please use [16]our mirror sites or [17]our version control system. For questions related to the use of GCC, please consult these web pages and the [18]GCC manuals. If that fails, the [19]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [20]gcc@gcc.gnu.org. All of [21]our lists have public archives. Copyright (C) [22]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [23]maintained by the GCC team. Last modified 2022-10-26. References 1. http://www.gnu.org/ 2. https://gcc.gnu.org/gcc-4.7/changes.html 3. https://gcc.gnu.org/onlinedocs/4.7.4/ 4. https://gcc.gnu.org/gcc-4.7/changes.html 5. https://gcc.gnu.org/onlinedocs/4.7.3/ 6. https://gcc.gnu.org/gcc-4.7/changes.html 7. https://gcc.gnu.org/onlinedocs/4.7.2/ 8. https://gcc.gnu.org/gcc-4.7/changes.html 9. https://gcc.gnu.org/onlinedocs/4.7.1/ 10. https://gcc.gnu.org/gcc-4.7/changes.html 11. https://gcc.gnu.org/onlinedocs/4.7.0/ 12. https://gcc.gnu.org/gcc-4.7/buildstat.html 13. https://gcc.gnu.org/onlinedocs/gcc/Contributors.html 14. https://gcc.gnu.org/index.html 15. mailto:gcc@gcc.gnu.org 16. https://gcc.gnu.org/mirrors.html 17. https://gcc.gnu.org/git.html 18. https://gcc.gnu.org/onlinedocs/ 19. mailto:gcc-help@gcc.gnu.org 20. mailto:gcc@gcc.gnu.org 21. https://gcc.gnu.org/lists.html 22. https://www.fsf.org/ 23. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.7/changes.html GCC 4.7 Release Series Changes, New Features, and Fixes Caveats * The -fconserve-space flag has been deprecated. The flag had no effect for most targets: only targets without a global .bss section and without support for switchable sections. Furthermore, the flag only had an effect for G++, where it could result in wrong semantics (please refer to the GCC manual for further details). The flag will be removed in GCC 4.8 * Support for a number of older systems and recently unmaintained or untested target ports of GCC has been declared obsolete in GCC 4.7. Unless there is activity to revive them, the next release of GCC will have their sources permanently removed. All GCC ports for the following processor architectures have been declared obsolete: + picoChip (picochip-*) The following ports for individual systems on particular architectures have been obsoleted: + IRIX 6.5 (mips-sgi-irix6.5) + MIPS OpenBSD (mips*-*-openbsd*) + Solaris 8 (*-*-solaris2.8). Details can be found in the [1]announcement. + Tru64 UNIX V5.1 (alpha*-dec-osf5.1*) * On ARM, when compiling for ARMv6 (but not ARMv6-M), ARMv7-A, ARMv7-R, or ARMv7-M, the new option -munaligned-access is active by default, which for some sources generates code that accesses memory on unaligned addresses. This requires the kernel of those systems to enable such accesses (controlled by CP15 register c1, refer to ARM documentation). Alternatively, or for compatibility with kernels where unaligned accesses are not supported, all code has to be compiled with -mno-unaligned-access. Upstream Linux kernel releases have automatically and unconditionally supported unaligned accesses as emitted by GCC due to this option being active since version 2.6.28. * Support on ARM for the legacy floating-point accelerator (FPA) and the mixed-endian floating-point format that it used has been obsoleted. The ports that still use this format have been obsoleted as well. Many legacy ARM ports already provide an alternative that uses the VFP floating-point format. The obsolete ports will be deleted in the next release. The obsolete ports with alternatives are: + arm*-*-rtems (use arm*-*-rtemseabi) + arm*-*-linux-gnu (use arm*-*-linux-gnueabi) + arm*-*-elf (use arm*-*-eabi) + arm*-*-uclinux* (use arm*-*-uclinux*eabi) Note, however, that these alternatives are not binary compatible with their legacy counterparts (although some can support running legacy applications). The obsolete ports that currently lack a modern alternative are: + arm*-*-ecos-elf + arm*-*-freebsd + arm*-wince-pe* New ports that support more recent versions of the architecture are welcome. * Support for the Maverick co-processor on ARM has been obsoleted. Code to support it will be deleted in the next release. * Support has been removed for Unix International threads on Solaris 2, so the --enable-threads=solaris configure option and the -threads compiler option don't work any longer. * Support has been removed for the Solaris BSD Compatibility Package, which lives in /usr/ucbinclude and /usr/ucblib. It has been removed from Solaris 11, and was only intended as a migration aid from SunOS 4 to SunOS 5. The -compat-bsd compiler option is not recognized any longer. * The AVR port's libgcc has been improved and its multilib structure has been enhanced. As a result, all objects contributing to an application must either be compiled with GCC versions up to 4.6.x or with GCC versions 4.7.1 or later. If the compiler is used with AVR Libc, you need a version that supports the new layout, i.e. implements [2]#35407. * The AVR port's -mshort-calls command-line option has been deprecated. It will be removed in the GCC 4.8 release. See -mrelax for a replacement. * The AVR port only references startup code that clears .bss and the common section resp. initializes the .data and .rodata section provided respective sections (or subsections thereof) are not empty, see [3]PR18145. Applications that put all static storage objects into non-standard sections and / or define all static storage objects in assembler modules, must reference __do_clear_bss resp. __do_copy_data by hand or undefine the symbol(s) by means of -Wl,-u,__do_clear_bss resp. -Wl,-u,__do_copy_data. * The ARM port's -mwords-little-endian option has been deprecated. It will be removed in a future release. * Support has been removed for the NetWare x86 configuration obsoleted in GCC 4.6. * It is no longer possible to use the "l" constraint in MIPS16 asm statements. * GCC versions 4.7.0 and 4.7.1 had changes to the C++ standard library which affected the ABI in C++11 mode: a data member was added to std::list changing its size and altering the definitions of some member functions, and std::pair's move constructor was non-trivial which altered the calling convention for functions with std::pair arguments or return types. The ABI incompatibilities have been fixed for GCC version 4.7.2 but as a result C++11 code compiled with GCC 4.7.0 or 4.7.1 may be incompatible with C++11 code compiled with different GCC versions and with C++98/C++03 code compiled with any version. * On ARM, a bug has been fixed in GCC's implementation of the AAPCS rules for the layout of vectors that could lead to wrong code being generated. Vectors larger than 8 bytes in size are now by default aligned to an 8-byte boundary. This is an ABI change: code that makes explicit use of vector types may be incompatible with binary objects built with older versions of GCC. Auto-vectorized code is not affected by this change. (This change affects GCC versions 4.7.2 and later.) * More information on porting to GCC 4.7 from previous versions of GCC can be found in the [4]porting guide for this release. General Optimizer Improvements * Support for a new parameter --param case-values-threshold=n was added to allow users to control the cutoff between doing switch statements as a series of if statements and using a jump table. * Link-time optimization (LTO) improvements: + Improved scalability and reduced memory usage. Link time optimization of Firefox now requires 3GB of RAM on a 64-bit system, while over 8GB was needed previously. Linking time has been improved, too. The serial stage of linking Firefox has been sped up by about a factor of 10. + Reduced size of object files and temporary storage used during linking. + Streaming performance (both outbound and inbound) has been improved. + ld -r is now supported with LTO. + Several bug fixes, especially in symbol table handling and merging. * Interprocedural optimization improvements: + Heuristics now take into account that after inlining code will be optimized out because of known values (or properties) of function parameters. For example: void foo(int a) { if (a > 10) ... huge code ... } void bar (void) { foo (0); } The call of foo will be inlined into bar even when optimizing for code size. Constructs based on __builtin_constant_p are now understood by the inliner and code size estimates are evaluated a lot more realistically. + The representation of C++ virtual thunks and aliases (both implicit and defined via the alias attribute) has been re-engineered. Aliases no longer pose optimization barriers and calls to an alias can be inlined and otherwise optimized. + The inter-procedural constant propagation pass has been rewritten. It now performs generic function specialization. For example when compiling the following: void foo(bool flag) { if (flag) ... do something ... else ... do something else ... } void bar (void) { foo (false); foo (true); foo (false); foo (true); foo (false); foo (true); } GCC will now produce two copies of foo. One with flag being true, while other with flag being false. This leads to performance improvements previously possible only by inlining all calls. Cloning causes a lot less code size growth. * A string length optimization pass has been added. It attempts to track string lengths and optimize various standard C string functions like strlen, strchr, strcpy, strcat, stpcpy and their _FORTIFY_SOURCE counterparts into faster alternatives. This pass is enabled by default at -O2 or above, unless optimizing for size, and can be disabled by the -fno-optimize-strlen option. The pass can e.g. optimize char *bar (const char *a) { size_t l = strlen (a) + 2; char *p = malloc (l); if (p == NULL) return p; strcpy (p, a); strcat (p, "/"); return p; } into: char *bar (const char *a) { size_t tmp = strlen (a); char *p = malloc (tmp + 2); if (p == NULL) return p; memcpy (p, a, tmp); memcpy (p + tmp, "/", 2); return p; } or for hosted compilations where stpcpy is available in the runtime and headers provide its prototype, e.g. void foo (char *a, const char *b, const char *c, const char *d) { strcpy (a, b); strcat (a, c); strcat (a, d); } can be optimized into: void foo (char *a, const char *b, const char *c, const char *d) { strcpy (stpcpy (stpcpy (a, b), c), d); } New Languages and Language specific improvements * Version 3.1 of the OpenMP specification is now supported for the C, C++, and Fortran compilers. Ada * The command-line option -feliminate-unused-debug-types has been re-enabled by default, as it is for the other languages, leading to a reduction in debug info size of 12.5% and more for relevant cases, as well as to a small compilation speedup. C family * A new built-in, __builtin_assume_aligned, has been added, through which the compiler can be hinted about pointer alignment and can use it to improve generated code. * A new warning option -Wunused-local-typedefs was added for C, C++, Objective-C and Objective-C++. This warning diagnoses typedefs locally defined in a function, and otherwise not used. * A new experimental command-line option -ftrack-macro-expansion was added for C, C++, Objective-C, Objective-C++ and Fortran. It allows the compiler to emit diagnostic about the current macro expansion stack when a compilation error occurs in a macro expansion. * Experimental support for transactional memory has been added. It includes support in the compiler, as well as a supporting runtime library called libitm. To compile code with transactional memory constructs, use the -fgnu-tm option. Support is currently available for Alpha, ARM, PowerPC, SH, SPARC, and 32-bit/64-bit x86 platforms. For more details on transactional memory see [5]the GCC WiKi. * Support for atomic operations specifying the C++11/C11 memory model has been added. These new __atomic routines replace the existing __sync built-in routines. Atomic support is also available for memory blocks. Lock-free instructions will be used if a memory block is the same size and alignment as a supported integer type. Atomic operations which do not have lock-free support are left as function calls. A set of library functions is available on the GCC atomic wiki in the "External Atomics Library" section. For more details on the memory models and features, see the [6]atomic wiki. * When a binary operation is performed on vector types and one of the operands is a uniform vector, it is possible to replace the vector with the generating element. For example: typedef int v4si __attribute__ ((vector_size (16))); v4si res, a = {1,2,3,4}; int x; res = 2 + a; /* means {2,2,2,2} + a */ res = a - x; /* means a - {x,x,x,x} */ C * There is support for some more features from the C11 revision of the ISO C standard. GCC now accepts the options -std=c11 and -std=gnu11, in addition to the previous -std=c1x and -std=gnu1x. + Unicode strings (previously supported only with options such as -std=gnu11, now supported with -std=c11), and the predefined macros __STDC_UTF_16__ and __STDC_UTF_32__. + Nonreturning functions (_Noreturn and ). + Alignment support (_Alignas, _Alignof, max_align_t, ). + A built-in function __builtin_complex is provided to support C library implementation of the CMPLX family of macros. C++ * G++ now accepts the -std=c++11, -std=gnu++11, and -Wc++11-compat options, which are equivalent to -std=c++0x, -std=gnu++0x, and -Wc++0x-compat, respectively. * G++ now implements [7]C++11 extended friend syntax: template class Q { static const int I = 2; public: friend W; }; struct B { int ar[Q::I]; }; * Thanks to Ville Voutilainen, G++ now implements [8]C++11 explicit override control. struct B { virtual void f() const final; virtual void f(int); }; struct D : B { void f() const; // error: D::f attempts to override final B::f void f(long) override; // error: doesn't override anything void f(int) override; // ok }; struct E final { }; struct F: E { }; // error: deriving from final class * G++ now implements [9]C++11 non-static data member initializers. struct A { int i = 42; } a; // initializes a.i to 42 * Thanks to Ed Smith-Rowland, G++ now implements [10]C++11 user-defined literals. // Not actually a good approximation. :) constexpr long double operator"" _degrees (long double d) { return d * 0.0175; } long double pi = 180.0_degrees; * G++ now implements [11]C++11 alias-declarations. template using Ptr = T*; Ptr ip; // decltype(ip) is int* * Thanks to Ville Voutilainen and Pedro Lamarão, G++ now implements [12]C++11 delegating constructors. struct A { A(int); A(): A(42) { } // delegate to the A(int) constructor }; * G++ now fully implements C++11 atomic classes rather than just integer derived classes. class POD { int a; int b; }; std::atomic my_atomic_POD; * G++ now sets the predefined macro __cplusplus to the correct value, 199711L for C++98/03, and 201103L for C++11. * G++ now correctly implements the two-phase lookup rules such that an unqualified name used in a template must have an appropriate declaration found either in scope at the point of definition of the template or by argument-dependent lookup at the point of instantiation. As a result, code that relies on a second unqualified lookup at the point of instantiation to find functions declared after the template or in dependent bases will be rejected. The compiler will suggest ways to fix affected code, and using the -fpermissive compiler flag will allow the code to compile with a warning. template void f() { g(T()); } // error, g(int) not found by argument-dependent lookup void g(int) { } // fix by moving this declaration before the declaration of f template struct A: T { // error, B::g(B) not found by argument-dependent lookup void f() { g(T()); } // fix by using this->g or A::g }; struct B { void g(B); }; int main() { f(); A().f(); } * G++ now properly re-uses stack space allocated for temporary objects when their lifetime ends, which can significantly lower stack consumption for some C++ functions. As a result of this, some code with undefined behavior will now break: const int &f(const int &i) { return i; } .... const int &x = f(1); const int &y = f(2); Here, x refers to the temporary allocated to hold the 1 argument, which only lives until the end of the initialization; it immediately becomes a dangling reference. So the next statement re-uses the stack slot to hold the 2 argument, and users of x get that value instead. Note that this should not cause any change of behavior for temporaries of types with non-trivial destructors, as they are already destroyed at end of full-expression; the change is that now the storage is released as well. * A new command-line option -Wdelete-non-virtual-dtor has been added to warn when delete is used to destroy an instance of a class which has virtual functions and non-virtual destructor. It is unsafe to delete an instance of a derived class through a pointer to a base class if the base class does not have a virtual destructor. This warning is enabled by -Wall. * A new command-line option -Wzero-as-null-pointer-constant has been added to warn when a literal '0' is used as null pointer constant. It can be useful to facilitate the conversion to nullptr in C++11. * As per C++98, access-declarations are now deprecated by G++. Using-declarations are to be used instead. Furthermore, some efforts have been made to improve the support of class scope using-declarations. In particular, using-declarations referring to a dependent type now work as expected ([13]bug c++/14258). * The ELF symbol visibility of a template instantiation is now properly constrained by the visibility of its template arguments ([14]bug c++/35688). Runtime Library (libstdc++) * [15]Improved experimental support for the new ISO C++ standard, C++11, including: + using noexcept in most of the library; + implementations of pointer_traits, allocator_traits and scoped_allocator_adaptor; + uses-allocator construction for tuple; + vector meets the allocator-aware container requirements; + replacing monotonic_clock with steady_clock; + enabling the thread support library on most POSIX targets; + many small improvements to conform to the FDIS. * Added --enable-clocale=newlib configure option. * Debug Mode iterators for unordered associative containers. * Avoid polluting the global namespace and do not include . Fortran * The compile flag [16]-fstack-arrays has been added, which causes all local arrays to be put on stack memory. For some programs this will improve the performance significantly. If your program uses very large local arrays, it is possible that you will have to extend your runtime limits for stack memory. * The [17]-Ofast flag now also implies [18]-fno-protect-parens and [19]-fstack-arrays. * Front-end optimizations can now be selected by the [20]-ffrontend-optimize option and deselected by the -fno-frontend-optimize option. * When front-end optimization removes a function call, [21]-Wfunction-elimination warns about that. * When performing front-end-optimization, the [22]-faggressive-function-elimination option allows the removal of duplicate function calls even for impure functions. * The flag [23]-Wreal-q-constant has been added, which warns if floating-point literals have been specified using q (such as 1.0q0); the q marker is now supported as a vendor extension to denote quad precision (REAL(16) or, if not available, REAL(10)). Consider using a kind parameter (such as in 1.0_qp) instead, which can be obtained via [24]SELECTED_REAL_KIND. * The GFORTRAN_USE_STDERR environment variable has been removed. GNU Fortran now always prints error messages to standard error. If you wish to redirect standard error, please consult the manual for your OS, shell, batch environment etc. as appropriate. * The -fdump-core option and GFORTRAN_ERROR_DUMPCORE environment variable have been removed. When encountering a serious error, gfortran will now always abort the program. Whether a core dump is generated depends on the user environment settings; see the ulimit -c setting for POSIX shells, limit coredumpsize for C shells, and the [25]WER user-mode dumps settings on Windows. * The [26]-fbacktrace option is now enabled by default. When encountering a fatal error, gfortran will attempt to print a backtrace to standard error before aborting. It can be disabled with -fno-backtrace. Note: On POSIX targets with the addr2line utility from GNU binutils, GNU Fortran can print a backtrace with function name, file name, line number information in addition to the addresses; otherwise only the addresses are printed. * [27]Fortran 2003: + Generic interface names which have the same name as derived types are now supported, which allows to write constructor functions. Note that Fortran does not support static constructor functions; only default initialization or an explicit structure-constructor initialization are available. + [28]Polymorphic (class) arrays are now supported. * [29]Fortran 2008: + Support for the DO CONCURRENT construct has been added, which allows the user to specify that individual loop iterations have no interdependencies. + [30]Coarrays: Full single-image support except for polymorphic coarrays. Additionally, preliminary support for multiple images via an MPI-based [31]coarray communication library has been added. Note: The library version is not yet usable as remote coarray access is not yet possible. * [32]TS 29113: + New flag [33]-std=f2008ts permits programs that are expected to conform to the Fortran 2008 standard and the draft Technical Specification (TS) 29113 on Further Interoperability of Fortran with C. + The OPTIONAL attribute is now allowed for dummy arguments of BIND(C) procedures. + The RANK intrinsic has been added. + The implementation of the ASYNCHRONOUS attribute in GCC is compatible with the candidate draft of TS 29113 (since GCC 4.6). Go * GCC 4.7 implements the [34]Go 1 language standard. The library support in 4.7.0 is not quite complete, due to release timing. Release 4.7.1 includes complete support for Go 1. The Go library is from the Go 1.0.1 release. * Go has been tested on GNU/Linux and Solaris platforms. It may work on other platforms as well. New Targets and Target Specific Improvements ARM * GCC now supports the Cortex-A7 processor implementing the v7-a version of the architecture using the option -mcpu=cortex-a7. * The default vector size in auto-vectorization for NEON is now 128 bits. If vectorization fails thusly, the vectorizer tries again with 64-bit vectors. * A new option -mvectorize-with-neon-double was added to allow users to change the vector size to 64 bits. AVR * GCC now supports the XMEGA architecture. This requires GNU binutils 2.22 or later. * Support for the [35]named address spaces __flash, __flash1, …, __flash5 and __memx has been added. These address spaces locate read-only data in flash memory and allow reading from flash memory by means of ordinary C code, i.e. without the need of (inline) assembler code: const __flash int values[] = { 42, 31 }; int add_values (const __flash int *p, int i) { return values[i] + *p; } * Support has been added for the AVR-specific configure option --with-avrlibc=yes in order to arrange for better integration of [36]AVR-Libc. This configure option is supported in avr-gcc 4.7.2 and newer and will only take effect in non-RTEMS configurations. If avr-gcc is configured for RTEMS, the option will be ignored which is the same as specifying --with-avrlibc=no. See [37]PR54461 for more technical details. * Support for AVR-specific [38]built-in functions has been added. * Support has been added for the signed and unsigned 24-bit scalar integer types __int24 and __uint24. * New command-line options -maccumulate-args, -mbranch-cost=cost and -mstrict-X were added to allow better fine-tuning of code optimization. * The command-line option -fdata-sections now also takes affect on the section names of variables with the progmem attribute. * A new inline assembler print modifier %i to print a RAM address as I/O address has been added: #include /* Port Definitions from AVR-LibC */ void set_portb (uint8_t value) { asm volatile ("out %i0, %1" :: "n" (&PORTB), "r" (value) : "memory"); } The offset between an I/O address and the RAM address for that I/O location is device-specific. This offset is taken into account when printing a RAM address with the %i modifier so that the address is suitable to be used as operand in an I/O command. The address must be a constant integer known at compile time. * The inline assembler constraint "R" to represent integers in the range −6 … 5 has been removed without replacement. * Many optimizations to: + 64-bit integer arithmetic + Widening multiplication + Integer division by a constant + Avoid constant reloading in multi-byte instructions. + Micro-optimizations for special instruction sequences. + Generic built-in functions like __builtin_ffs*, __builtin_clz*, etc. + If-else decision trees generated by switch instructions + Merging of data located in flash memory + New libgcc variants for devices with 8-bit wide stack pointer + … * Better documentation: + Handling of EIND and indirect jumps on devices with more than 128 KiB of program memory. + Handling of the RAMPD, RAMPX, RAMPY and RAMPZ special function registers. + Function attributes OS_main and OS_task. + AVR-specific built-in macros. C6X * Support has been added for the Texas Instruments C6X family of processors. CR16 * Support has been added for National Semiconductor's CR16 architecture. Epiphany * Support has been added for Adapteva's Epiphany architecture. IA-32/x86-64 * Support for Intel AVX2 intrinsics, built-in functions and code generation is available via -mavx2. * Support for Intel BMI2 intrinsics, built-in functions and code generation is available via -mbmi2. * Implementation and automatic generation of __builtin_clz* using the lzcnt instruction is available via -mlzcnt. * Support for Intel FMA3 intrinsics and code generation is available via -mfma. * A new -mfsgsbase command-line option is available that makes GCC generate new segment register read/write instructions through dedicated built-ins. * Support for the new Intel rdrnd instruction is available via -mrdrnd. * Two additional AVX vector conversion instructions are available via -mf16c. * Support for new Intel processor codename IvyBridge with RDRND, FSGSBASE and F16C is available through -march=core-avx-i. * Support for the new Intel processor codename Haswell with AVX2, FMA, BMI, BMI2, LZCNT is available through -march=core-avx2. * Support for new AMD family 15h processors (Piledriver core) is now available through -march=bdver2 and -mtune=bdver2 options. * Support for [39]the x32 psABI is now available through the -mx32 option. * Windows mingw targets are using the -mms-bitfields option by default. * Windows x86 targets are using the __thiscall calling convention for C++ class-member functions. * Support for the configure option --with-threads=posix for Windows mingw targets. MIPS * GCC now supports thread-local storage (TLS) for MIPS16. This requires GNU binutils 2.22 or later. * GCC can now generate code specifically for the Cavium Octeon+ and Octeon2 processors. The associated command-line options are -march=octeon+ and -march=octeon2 respectively. Both options require GNU binutils 2.22 or later. * GCC can now work around certain 24k errata, under the control of the command-line option -mfix-24k. These workarounds require GNU binutils 2.20 or later. * 32-bit MIPS GNU/Linux targets such as mips-linux-gnu can now build n32 and n64 multilibs. The result is effectively a 64-bit GNU/Linux toolchain that generates 32-bit code by default. Use the configure-time option --enable-targets=all to select these extra multilibs. * Passing -fno-delayed-branch now also stops the assembler from automatically filling delay slots. PowerPC/PowerPC64 * Vectors of type vector long long or vector long are passed and returned using the same method as other vectors with the VSX instruction set. Previously GCC did not adhere to the ABI for 128-bit vectors with 64-bit integer base types (PR 48857). This will also be fixed in the GCC 4.6.1 and 4.5.4 releases. * A new option -mno-pointers-to-nested-functions was added to allow AIX 32-bit/64-bit and GNU/Linux 64-bit PowerPC users to specify that the compiler should not load up the chain register (r11) before calling a function through a pointer. If you use this option, you cannot call nested functions through a pointer, or call other languages that might use the static chain. * A new option msave-toc-indirect was added to allow AIX 32-bit/64-bit and GNU/Linux 64-bit PowerPC users control whether we save the TOC in the prologue for indirect calls or generate the save inline. This can speed up some programs that call through a function pointer a lot, but it can slow down other functions that only call through a function pointer in exceptional cases. * The PowerPC port will now enable machine-specific built-in functions when the user switches the target machine using the #pragma GCC target or __attribute__ ((__target__ ("target"))) code sequences. In addition, the target macros are updated. However, due to the way the -save-temps switch is implemented, you won't see the effect of these additional macros being defined in preprocessor output. SH * A new option -msoft-atomic has been added. When it is specified, GCC will generate GNU/Linux-compatible gUSA atomic sequences for the new __atomic routines. * Since it is neither supported by GAS nor officially documented, code generation for little endian SH2A has been disabled. Specifying -ml with -m2a* will now result in a compiler error. * The defunct -mbranch-cost option has been fixed. * Some improvements to the generated code of: + Utilization of the tst #imm,R0 instruction. + Dynamic shift instructions on SH2A. + Integer absolute value calculations. * The -mdiv= option for targets other than SHmedia has been fixed and documented. SPARC * The option -mflat has been reinstated. When it is specified, the compiler will generate code for a single register window model. This is essentially a new implementation and the corresponding debugger support has been added to GDB 7.4. * Support for the options -mtune=native and -mcpu=native has been added on selected native platforms (GNU/Linux and Solaris). * Support for the SPARC T3 (Niagara 3) processor has been added. * VIS: + An intrinsics header visintrin.h has been added. + Builtin intrinsics for the VIS 1.0 edge handling and pixel compare instructions have been added. + The little-endian version of alignaddr is now supported. + When possible, VIS builtins are marked const, which should increase the compiler's ability to optimize VIS operations. + The compiler now properly tracks the %gsr register and how it behaves as an input for various VIS instructions. + Akin to fzero, the compiler can now generate fone instructions in order to set all of the bits of a floating-point register to 1. + The documentation for the VIS intrinsics in the GCC manual has been brought up to date and many inaccuracies were fixed. + Intrinsics for the VIS 2.0 bmask, bshuffle, and non-condition-code setting edge instructions have been added. Their availability is controlled by the new -mvis2 and -mno-vis2 options. They are enabled by default on UltraSPARC-III and later CPUs. * Support for UltraSPARC Fused Multiply-Add floating-point extensions has been added. These instructions are enabled by default on SPARC T3 (Niagara 3) and later CPUs. TILE-Gx/TILEPro * Support has been added for the Tilera TILE-Gx and TILEPro families of processors. Other significant improvements * A new option (-grecord-gcc-switches) was added that appends compiler command-line options that might affect code generation to the DW_AT_producer attribute string in the DWARF debugging information. * GCC now supports various new GNU extensions to the DWARF debugging information format, like [40]entry value and [41]call site information, [42]typed DWARF stack or [43]a more compact macro representation. Support for these extensions has been added to GDB 7.4. They can be disabled through the -gstrict-dwarf command-line option. GCC 4.7.1 This is the [44]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.7.1 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). The Go front end in the 4.7.1 release fully supports the [45]Go 1 language standard. GCC 4.7.2 This is the [46]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.7.2 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.7.3 This is the [47]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.7.3 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.7.4 This is the [48]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.7.4 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). For questions related to the use of GCC, please consult these web pages and the [49]GCC manuals. If that fails, the [50]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [51]gcc@gcc.gnu.org. All of [52]our lists have public archives. Copyright (C) [53]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [54]maintained by the GCC team. Last modified 2023-03-29. References 1. https://gcc.gnu.org/ml/gcc-patches/2011-03/msg01263.html 2. http://savannah.nongnu.org/bugs/?35407 3. https://gcc.gnu.org/PR18145 4. https://gcc.gnu.org/gcc-4.7/porting_to.html 5. https://gcc.gnu.org/wiki/TransactionalMemory 6. https://gcc.gnu.org/wiki/Atomic/GCCMM 7. https://gcc.gnu.org/gcc-4.7/cxx0x_status.html 8. https://gcc.gnu.org/gcc-4.7/cxx0x_status.html 9. https://gcc.gnu.org/gcc-4.7/cxx0x_status.html 10. https://gcc.gnu.org/gcc-4.7/cxx0x_status.html 11. https://gcc.gnu.org/gcc-4.7/cxx0x_status.html 12. https://gcc.gnu.org/gcc-4.7/cxx0x_status.html 13. https://gcc.gnu.org/PR14258 14. https://gcc.gnu.org/PR35688 15. https://gcc.gnu.org/onlinedocs/gcc-4.7.4/libstdc++/manual/manual/status.html#status.iso.2011 16. https://gcc.gnu.org/onlinedocs/gcc-4.7.1/gfortran/Code-Gen-Options.html#index-g_t_0040code_007bfstack-arrays_007d-254 17. https://gcc.gnu.org/onlinedocs/gcc-4.7.1/gcc/Optimize-Options.html#index-Ofast-689 18. https://gcc.gnu.org/onlinedocs/gcc-4.7.1/gfortran/Code-Gen-Options.html#index-g_t_0040code_007bfno-protect-parens_007d-270 19. https://gcc.gnu.org/onlinedocs/gcc-4.7.1/gfortran/Code-Gen-Options.html#index-g_t_0040code_007bfstack-arrays_007d-254 20. https://gcc.gnu.org/onlinedocs/gcc-4.7.1/gfortran/Code-Gen-Options.html#index-g_t_0040code_007bfrontend-optimize_007d-275 21. https://gcc.gnu.org/onlinedocs/gcc-4.7.1/gfortran/Error-and-Warning-Options.html#index-g_t_0040code_007bWfunction-elimination_007d-170 22. https://gcc.gnu.org/onlinedocs/gcc-4.7.1/gfortran/Code-Gen-Options.html#index-g_t_0040code_007bfaggressive-function-elimination_007d-270 23. https://gcc.gnu.org/onlinedocs/gcc-4.7.1/gfortran/Error-and-Warning-Options.html#index-g_t_0040code_007bWreal-q-constant_007d-149 24. https://gcc.gnu.org/onlinedocs/gcc-4.7.1/gfortran/SELECTED_005fREAL_005fKIND.html 25. https://learn.microsoft.com/en-us/windows/win32/wer/collecting-user-mode-dumps 26. https://gcc.gnu.org/onlinedocs/gcc-4.7.1/gfortran/Debugging-Options.html#index-g_t_0040code_007bfno-backtrace_007d-183 27. https://gcc.gnu.org/wiki/Fortran2003Status 28. https://gcc.gnu.org/wiki/OOP 29. https://gcc.gnu.org/wiki/Fortran2008Status 30. https://gcc.gnu.org/wiki/Coarray 31. https://gcc.gnu.org/wiki/CoarrayLib 32. https://gcc.gnu.org/wiki/TS29113Status 33. https://gcc.gnu.org/onlinedocs/gcc-4.7.1/gfortran/Fortran-Dialect-Options.html#index-g_t_0040code_007bstd_003d_007d_0040var_007bstd_007d-option-53 34. https://go.dev/doc/go1 35. https://gcc.gnu.org/onlinedocs/gcc-4.7.1/gcc/Named-Address-Spaces.html 36. http://www.nongnu.org/avr-libc/ 37. https://gcc.gnu.org/PR54461 38. https://gcc.gnu.org/onlinedocs/gcc-4.7.1/gcc/AVR-Built_002din-Functions.html 39. https://sites.google.com/site/x32abi/ 40. https://dwarfstd.org/issues/100909.1.html 41. https://dwarfstd.org/issues/100909.2.html 42. https://dwarfstd.org/issues/140425.1.html 43. https://dwarfstd.org/issues/110722.1.html 44. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.7.1 45. https://go.dev/doc/go1 46. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.7.2 47. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.7.3 48. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.7.4 49. https://gcc.gnu.org/onlinedocs/ 50. mailto:gcc-help@gcc.gnu.org 51. mailto:gcc@gcc.gnu.org 52. https://gcc.gnu.org/lists.html 53. https://www.fsf.org/ 54. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.6/index.html GCC 4.6 Release Series (This release series is no longer supported.) April 12, 2013 The [1]GNU project and the GCC developers are pleased to announce the release of GCC 4.6.4. This release is a bug-fix release, containing fixes for regressions in GCC 4.6.3 relative to previous releases of GCC. Release History GCC 4.6.4 April 12, 2013 ([2]changes, [3]documentation) GCC 4.6.3 March 1, 2012 ([4]changes, [5]documentation) GCC 4.6.2 October 26, 2011 ([6]changes, [7]documentation) GCC 4.6.1 June 27, 2011 ([8]changes, [9]documentation) GCC 4.6.0 March 25, 2011 ([10]changes, [11]documentation) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. A list of [12]successful builds is updated as new information becomes available. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [13]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [14]GCC project web site or contact the [15]GCC development mailing list. To obtain GCC please use [16]our mirror sites or [17]our version control system. For questions related to the use of GCC, please consult these web pages and the [18]GCC manuals. If that fails, the [19]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [20]gcc@gcc.gnu.org. All of [21]our lists have public archives. Copyright (C) [22]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [23]maintained by the GCC team. Last modified 2022-10-26. References 1. http://www.gnu.org/ 2. https://gcc.gnu.org/gcc-4.6/changes.html 3. https://gcc.gnu.org/onlinedocs/4.6.4/ 4. https://gcc.gnu.org/gcc-4.6/changes.html 5. https://gcc.gnu.org/onlinedocs/4.6.3/ 6. https://gcc.gnu.org/gcc-4.6/changes.html 7. https://gcc.gnu.org/onlinedocs/4.6.2/ 8. https://gcc.gnu.org/gcc-4.6/changes.html 9. https://gcc.gnu.org/onlinedocs/4.6.1/ 10. https://gcc.gnu.org/gcc-4.6/changes.html 11. https://gcc.gnu.org/onlinedocs/4.6.0/ 12. https://gcc.gnu.org/gcc-4.6/buildstat.html 13. https://gcc.gnu.org/onlinedocs/gcc/Contributors.html 14. https://gcc.gnu.org/index.html 15. mailto:gcc@gcc.gnu.org 16. https://gcc.gnu.org/mirrors.html 17. https://gcc.gnu.org/git.html 18. https://gcc.gnu.org/onlinedocs/ 19. mailto:gcc-help@gcc.gnu.org 20. mailto:gcc@gcc.gnu.org 21. https://gcc.gnu.org/lists.html 22. https://www.fsf.org/ 23. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.6/changes.html GCC 4.6 Release Series Changes, New Features, and Fixes Caveats * The options -b and -V have been removed because they were unreliable. Instead, users should directly run -gcc when cross-compiling, or -gcc- to run a different version of gcc. * GCC now has stricter checks for invalid command-line options. In particular, when gcc was called to link object files rather than compile source code, it would previously accept and ignore all options starting with --, including linker options such as --as-needed and --export-dynamic, although such options would result in errors if any source code was compiled. Such options, if unknown to the compiler, are now rejected in all cases; if the intent was to pass them to the linker, options such as -Wl,--as-needed should be used. * Versions of the GNU C library up to and including 2.11.1 included an [1]incorrect implementation of the cproj function. GCC optimizes its builtin cproj according to the behavior specified and allowed by the ISO C99 standard. If you want to avoid discrepancies between the C library and GCC's builtin transformations when using cproj in your code, use GLIBC 2.12 or later. If you are using an older GLIBC and actually rely on the incorrect behavior of cproj, then you can disable GCC's transformations using -fno-builtin-cproj. * The C-only intermodule optimization framework (IMA, enabled by -combine) has been removed in favor of the new generic link-time optimization framework (LTO) introduced in [2]GCC 4.5.0. * GCC now ships with the LGPL-licensed libquadmath library, which provides quad-precision mathematical functions for targets with a __float128 datatype. __float128 is available for targets on 32-bit x86, x86-64 and Itanium architectures. The libquadmath library is automatically built on such targets when building the Fortran compiler. * New -Wunused-but-set-variable and -Wunused-but-set-parameter warnings were added for C, C++, Objective-C and Objective-C++. These warnings diagnose variables respective parameters which are only set in the code and never otherwise used. Usually such variables are useless and often even the value assigned to them is computed needlessly, sometimes expensively. The -Wunused-but-set-variable warning is enabled by default by -Wall flag and -Wunused-but-set-parameter by -Wall -Wextra flags. * On ARM, a bug has been fixed in GCC's implementation of the AAPCS rules for the layout of vectors that could lead to wrong code being generated. Vectors larger than 8 bytes in size are now by default aligned to an 8-byte boundary. This is an ABI change: code that makes explicit use of vector types may be incompatible with binary objects built with older versions of GCC. Auto-vectorized code is not affected by this change. (This change affects GCC versions 4.6.4 and later, with the exception of versions 4.7.0 and 4.7.1.) * On AVR, variables with the progmem attribute to locate data in flash memory must be qualified as const. * Support for a number of older systems and recently unmaintained or untested target ports of GCC has been declared obsolete in GCC 4.6. Unless there is activity to revive them, the next release of GCC will have their sources permanently removed. All GCC ports for the following processor architectures have been declared obsolete: + Argonaut ARC (arc-*) + National Semiconductor CRX (crx-*) + Motorola 68HC11 and 68HC12 (m68hc11-*-*, m6811-*-*, m68hc12-*-*, m6812-*-*) + Sunplus S+core (score-*) The following ports for individual systems on particular architectures have been obsoleted: + Interix (i[34567]86-*-interix3*) + NetWare x86 (i[3456x]86-*-netware*) + Generic ARM PE (arm-*-pe* other than arm*-wince-pe*) + MCore PE (mcore-*-pe*) + SH SymbianOS (sh*-*-symbianelf*) + GNU Hurd on Alpha and PowerPC (alpha*-*-gnu*, powerpc*-*-gnu*) + M68K uClinux old ABI (m68k-*-uclinuxoldabi*) + a.out NetBSD (arm*-*-netbsd*, i[34567]86-*-netbsd*, vax-*-netbsd*, but not *-*-netbsdelf*) The i[34567]86-*-pe alias for Cygwin targets has also been obsoleted; users should configure for i[34567]86-*-cygwin* instead. Certain configure options to control the set of libraries built with GCC on some targets have been obsoleted. On ARM targets, the options --disable-fpu, --disable-26bit, --disable-underscore, --disable-interwork, --disable-biendian and --disable-nofmult have been obsoleted. On MIPS targets, the options --disable-single-float, --disable-biendian and --disable-softfloat have been obsoleted. * Support has been removed for all the [3]configurations obsoleted in GCC 4.5. * More information on porting to GCC 4.6 from previous versions of GCC can be found in the [4]porting guide for this release. General Optimizer Improvements * A new general optimization level, -Ofast, has been introduced. It combines the existing optimization level -O3 with options that can affect standards compliance but result in better optimized code. For example, -Ofast enables -ffast-math. * Link-time optimization improvements: + The [5]Scalable Whole Program Optimizer (WHOPR) project has stabilized to the point of being usable. It has become the default mode when using the LTO optimization model. Link time optimization can now split itself into multiple parallel compilations. Parallelism is controlled with -flto=n (where n specifies the number of compilations to execute in parallel). GCC can also cooperate with a GNU make job server by specifying the -flto=jobserver option and adding + to the beginning of the Makefile rule executing the linker. Classical LTO mode can be enforced by -flto-partition=none. This may result in small code quality improvements. + A large number of bugs were fixed. GCC itself, Mozilla Firefox and other large applications can be built with LTO enabled. + The linker plugin support improvements o Linker plugin is now enabled by default when the linker is detected to have plugin support. This is the case for GNU ld 2.21.51 or newer (on ELF and Cygwin targets) and the Gold linker on ELF targets. Plugin support of the Apple linker on Darwin is not compatible with GCC. The linker plugin can also be controlled by the -fuse-linker-plugin command-line option. o Resolution information from the linker plugin is used to drive whole program assumptions. Use of the linker plugin results in more aggressive optimization on binaries and on shared libraries that use the hidden visibility attribute. Consequently the use of -fwhole-program is not necessary in addition to LTO. + Hidden symbols used from non-LTO objects now have to be explicitly annotated with externally_visible when the linker plugin is not used. + C++ inline functions and virtual tables are now privatized more aggressively, leading to better inter-procedural optimization and faster dynamic linking. + Memory usage and intermediate language streaming performance have been improved. + Static constructors and destructors from individual units are inlined into a single function. This can significantly improve startup times of large C++ applications where static constructors are very common. For example, static constructors are used when including the iostream header. + Support for the Ada language has been added. * Interprocedural optimization improvements + The interprocedural framework was re-tuned for link time optimization. Several scalability issues were resolved. + Improved auto-detection of const and pure functions. Newly, noreturn functions are auto-detected. The [6]-Wsuggest-attribute=[const|pure|noreturn] flag is available that informs users when adding attributes to headers might improve code generation. + A number of inlining heuristic improvements. In particular: o Partial inlining is now supported and enabled by default at -O2 and greater. The feature can be controlled via -fpartial-inlining. Partial inlining splits functions with short hot path to return. This allows more aggressive inlining of the hot path leading to better performance and often to code size reductions (because cold parts of functions are not duplicated). o Scalability for large compilation units was improved significantly. o Inlining of callbacks is now more aggressive. o Virtual methods are considered for inlining when the caller is inlined and devirtualization is then possible. o Inlining when optimizing for size (either in cold regions of a program or when compiling with -Os) was improved to better handle C++ programs with larger abstraction penalty, leading to smaller and faster code. + The IPA reference optimization pass detecting global variables used or modified by functions was strengthened and sped up. + Functions whose address was taken are now optimized out when all references to them are dead. + A new inter-procedural static profile estimation pass detects functions that are executed once or unlikely to be executed. Unlikely executed functions are optimized for size. Functions executed once are optimized for size except for the inner loops. + On most targets with named section support, functions used only at startup (static constructors and main), functions used only at exit and functions detected to be cold are placed into separate text segment subsections. This extends the -freorder-functions feature and is controlled by the same switch. The goal is to improve the startup time of large C++ programs. Proper function placement requires linker support. GNU ld 2.21.51 on ELF targets was updated to place those functions together within the text section leading to better code locality and faster startup times of large C++ programs. The feature is also supported in the Apple linker. Support in the gold linker is planned. * A new switch -fstack-usage has been added. It makes the compiler output stack usage information for the program, on a per-function basis, in an auxiliary file. * A new switch -fcombine-stack-adjustments has been added. It can be used to enable or disable the compiler's stack-slot combining pass which before was enabled automatically at -O1 and above, but could not be controlled on its own. * A new switch -fstrict-volatile-bitfields has been added. Using it indicates that accesses to volatile bitfields should use a single access of the width of the field's type. This option can be useful for precisely defining and accessing memory-mapped peripheral registers from C or C++. Compile time and memory usage improvements * Datastructures used by the dataflow framework in GCC were reorganized for better memory usage and more cache locality. Compile time is improved especially on units with large functions (possibly resulting from a lot of inlining) not fitting into the processor cache. The compile time of the GCC C compiler binary with link-time optimization went down by over 10% (benchmarked on x86-64 target). New Languages and Language specific improvements Ada * Stack checking has been improved on selected architectures (Alpha, IA-32/x86-64, RS/6000 and SPARC): it now will detect stack overflows in all cases on these architectures. * Initial support for Ada 2012 has been added. C family * A new warning, enabled by -Wdouble-promotion, has been added that warns about cases where a value of type float is implicitly promoted to double. This is especially helpful for CPUs that handle the former in hardware, but emulate the latter in software. * A new function attribute leaf was introduced. This attribute allows better inter-procedural optimization across calls to functions that return to the current unit only via returning or exception handling. This is the case for most library functions that have no callbacks. * Support for a new data type __int128 for targets having wide enough machine-mode support. * The new function attribute callee_pop_aggregate allows to specify if the caller or callee is responsible for popping the aggregate return pointer value from the stack. * Support for selectively enabling and disabling warnings via #pragma GCC diagnostic has been added. For instance: #pragma GCC diagnostic error "-Wuninitialized" foo(a); /* error is given for this one */ #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Wuninitialized" foo(b); /* no diagnostic for this one */ #pragma GCC diagnostic pop foo(c); /* error is given for this one */ #pragma GCC diagnostic pop foo(d); /* depends on command-line options */ * The -fmax-errors=N option is now supported. Using this option causes the compiler to exit after N errors have been issued. C * There is now experimental support for some features from the upcoming C1X revision of the ISO C standard. This support may be selected with -std=c1x, or -std=gnu1x for C1X with GNU extensions. Note that this support is experimental and may change incompatibly in future releases for consistency with changes to the C1X standard draft. The following features are newly supported as described in the N1539 draft of C1X (with changes agreed at the March 2011 WG14 meeting); some other features were already supported with no compiler changes being needed, or have some support but not in full accord with N1539 (as amended). + Static assertions (_Static_assert keyword) + Typedef redefinition + New macros in + Anonymous structures and unions * The new -fplan9-extensions option directs the compiler to support some extensions for anonymous struct fields which are implemented by the Plan 9 compiler. A pointer to a struct may be automatically converted to a pointer to an anonymous field when calling a function, in order to make the types match. An anonymous struct field whose type is a typedef name may be referred to using the typedef name. C++ * Improved [7]experimental support for the upcoming C++0x ISO C++ standard, including support for constexpr (thanks to Gabriel Dos Reis and Jason Merrill), nullptr (thanks to Magnus Fromreide), noexcept, unrestricted unions, range-based for loops (thanks to Rodrigo Rivas Costa), opaque enum declarations (thanks also to Rodrigo), implicitly deleted functions and implicit move constructors. * When an extern declaration within a function does not match a declaration in the enclosing context, G++ now properly declares the name within the namespace of the function rather than the namespace which was open just before the function definition ([8]c++/43145). * GCC now warns by default when casting integers to larger pointer types. These warnings can be disabled with the option -Wno-int-to-pointer-cast, which is now also available in C++. * G++ no longer optimizes using the assumption that a value of enumeration type will fall within the range specified by the standard, since that assumption is easily violated with a conversion from integer type ([9]c++/43680). The old behavior can be restored with -fstrict-enums. * The new -fnothrow-opt flag changes the semantics of a throw() exception specification to match the proposed semantics of the noexcept specification: just call terminate if an exception tries to propagate out of a function with such an exception specification. This dramatically reduces or eliminates the code size overhead from adding the exception specification. * The new -Wnoexcept flag will suggest adding a noexcept qualifier to a function that the compiler can tell doesn't throw if it would change the value of a noexcept expression. * The -Wshadow option now warns if a local variable or type declaration shadows another type in C++. Note that the compiler will not warn if a local variable shadows a struct/class/enum, but will warn if it shadows an explicit typedef. * When an identifier is not found in the current scope, G++ now offers suggestions about which identifier might have been intended. * G++ now issues clearer diagnostics for missing semicolons after class, struct, and union definitions. * G++ now issues clearer diagnostics for missing semicolons after class member declarations. * G++ now issues clearer diagnostics when a colon is used in a place where a double-colon was intended. * G++ no longer accepts mutable on reference members ([10]c++/33558). Use -fpermissive to allow the old, non-conforming behaviour. * A few mangling fixes have been made, to attribute const/volatile on function pointer types, decltype of a plain decl, and use of a function parameter in the declaration of another parameter. By default the compiler still uses the old mangling, but emits aliases with the new mangling on targets that support strong aliases. Users can switch over entirely to the new mangling with -fabi-version=5 or -fabi-version=0. -Wabi will now warn about code that uses the old mangling. * In 4.6.0 and 4.6.1 G++ no longer allows objects of const-qualified type to be default initialized unless the type has a user-declared default constructor. In 4.6.2 G++ implements the proposed resolution of [11]DR 253, so default initialization is allowed if it initializes all subobjects. Code that fails to compile can be fixed by providing an initializer e.g. struct A { A(); }; struct B : A { int i; }; const B b = B(); Use -fpermissive to allow the old, non-conforming behaviour. Runtime Library (libstdc++) * [12]Improved experimental support for the upcoming ISO C++ standard, C++0x, including using constexpr and nullptr. * Performance improvements to the [13]Debug Mode, thanks to François Dumont. * Atomic operations used for reference-counting are annotated so that they can be understood by race detectors such as Helgrind, see [14]Data Race Hunting. * Most libstdc++ standard headers have been changed to no longer include the cstddef header as an implementation detail. Code that relied on that header being included as side-effect of including other standard headers will need to include cstddef explicitly. Fortran * On systems supporting the libquadmath library, GNU Fortran now also supports a quad-precision, kind=16 floating-point data type (REAL(16), COMPLEX(16)). As the data type is not fully supported in hardware, calculations might be one to two orders of magnitude slower than with the 4, 8 or 10 bytes floating-point data types. This change does not affect systems which support REAL(16) in hardware nor those which do not support libquadmath. * Much improved compile time for large array constructors. * In order to reduce execution time and memory consumption, use of temporary arrays in assignment expressions is avoided for many cases. The compiler now reverses loops in order to avoid generating a temporary array where possible. * Improved diagnostics, especially with -fwhole-file. * The -fwhole-file flag is now enabled by default. This improves code generation and diagnostics. It can be disabled using the deprecated -fno-whole-file flag. * Support the generation of Makefile dependencies via the [15]-M... flags of GCC; you may need to specify the -cpp option in addition. The dependencies take modules, Fortran's include, and CPP's #include into account. Note: Using -M for the module path is no longer supported, use -J instead. * The flag -Wconversion has been modified to only issue warnings where a conversion leads to information loss. This drastically reduces the number of warnings; -Wconversion is thus now enabled with -Wall. The flag -Wconversion-extra has been added and also warns about other conversions; -Wconversion-extra typically issues a huge number of warnings, most of which can be ignored. * A new command-line option -Wunused-dummy-argument warns about unused dummy arguments and is included in -Wall. Before, -Wunused-variable also warned about unused dummy arguments. * Fortran 2003 support has been extended: + Improved support for polymorphism between libraries and programs and for complicated inheritance patterns (cf. [16]object-oriented programming). + Experimental support of the ASSOCIATE construct. + In pointer assignments it is now possible to specify the lower bounds of the pointer and, for a rank-1 or a simply contiguous data-target, to remap the bounds. + Automatic (re)allocation: In intrinsic assignments to allocatable variables the left-hand side will be automatically allocated (if unallocated) or reallocated (if the shape or type parameter is different). To avoid the small performance penalty, you can use a(:) = ... instead of a = ... for arrays and character strings – or disable the feature using -std=f95 or -fno-realloc-lhs. + Deferred type parameter: For scalar allocatable and pointer variables the character length can be deferred. + Namelist variables with allocatable and pointer attribute and nonconstant length type parameter are supported. * Fortran 2008 support has been extended: + Experimental [17]coarray support (for one image only, i.e. num_images() == 1); use the [18]-fcoarray=single flag to enable it. + The STOP and the new ERROR STOP statements now support all constant expressions. + Support for the CONTIGUOUS attribute. + Support for ALLOCATE with MOLD. + Support for the STORAGE_SIZE intrinsic inquiry function. + Support of the NORM2 and PARITY intrinsic functions. + The following bit intrinsics were added: POPCNT and POPPAR for counting the number of 1 bits and returning the parity; BGE, BGT, BLE, and BLT for bitwise comparisons; DSHIFTL and DSHIFTR for combined left and right shifts, MASKL and MASKR for simple left and right justified masks, MERGE_BITS for a bitwise merge using a mask, SHIFTA, SHIFTL and SHIFTR for shift operations, and the transformational bit intrinsics IALL, IANY and IPARITY. + Support of the EXECUTE_COMMAND_LINE intrinsic subroutine. + Support for the IMPURE attribute for procedures, which allows for ELEMENTAL procedures without the restrictions of PURE. + Null pointers (including NULL()) and not allocated variables can be used as actual argument to optional non-pointer, non-allocatable dummy arguments, denoting an absent argument. + Non-pointer variables with TARGET attribute can be used as actual argument to POINTER dummies with INTENT(IN) + Pointers including procedure pointers and those in a derived type (pointer components) can now be initialized by a target instead of only by NULL. + The EXIT statement (with construct-name) can now be used to leave not only the DO but also the ASSOCIATE, BLOCK, IF, SELECT CASE and SELECT TYPE constructs. + Internal procedures can now be used as actual argument. + The named constants INTEGER_KINDS, LOGICAL_KINDS, REAL_KINDS and CHARACTER_KINDS of the intrinsic module ISO_FORTRAN_ENV have been added; these arrays contain the supported kind values for the respective types. + The module procedures C_SIZEOF of the intrinsic module ISO_C_BINDINGS and COMPILER_VERSION and COMPILER_OPTIONS of ISO_FORTRAN_ENV have been implemented. + Minor changes: obsolescence diagnostics for ENTRY was added for -std=f2008; a line may start with a semicolon; for internal and module procedures END can be used instead of END SUBROUTINE and END FUNCTION; SELECTED_REAL_KIND now also takes a RADIX argument; intrinsic types are supported for TYPE(intrinsic-type-spec); multiple type-bound procedures can be declared in a single PROCEDURE statement; implied-shape arrays are supported for named constants (PARAMETER). The transformational, three argument versions of BESSEL_JN and BESSEL_YN were added – the elemental, two-argument version had been added in GCC 4.4; note that the transformational functions use a recurrence algorithm. Go Support for the Go programming language has been added to GCC. It is not enabled by default when you build GCC; use the --enable-languages configure option to build it. The driver program for compiling Go code is gccgo. Go is currently known to work on GNU/Linux and RTEMS. Solaris support is in progress. It may or may not work on other platforms. Objective-C and Objective-C++ * The -fobjc-exceptions flag is now required to enable Objective-C exception and synchronization syntax (introduced by the keywords @try, @catch, @finally and @synchronized). * A number of Objective-C 2.0 features and extensions are now supported by GCC. These features are enabled by default; you can disable them by using the new -fobjc-std=objc1 command-line option. * The Objective-C 2.0 dot-syntax is now supported. It is an alternative syntax for using getters and setters; object.count is automatically converted into [object count] or [object setCount: ...] depending on context; for example if (object.count > 0) is automatically compiled into the equivalent of if ([object count] > 0) while object.count = 0; is automatically compiled into the equivalent ot [object setCount: 0];. The dot-syntax can be used with instance and class objects and with any setters or getters, no matter if they are part of a declared property or not. * Objective-C 2.0 declared properties are now supported. They are declared using the new @property keyword, and are most commonly used in conjunction with the new Objective-C 2.0 dot-syntax. The nonatomic, readonly, readwrite, assign, retain, copy, setter and getter attributes are all supported. Marking declared properties with __attribute__ ((deprecated)) is supported too. * The Objective-C 2.0 @synthesize and @dynamic keywords are supported. @synthesize causes the compiler to automatically synthesize a declared property, while @dynamic is used to disable all warnings for a declared property for which no implementation is provided at compile time. Synthesizing declared properties requires runtime support in most useful cases; to be able to use it with the GNU runtime, appropriate helper functions have been added to the GNU Objective-C runtime ABI, and are implemented by the GNU Objective-C runtime library shipped with GCC. * The Objective-C 2.0 fast enumeration syntax is supported in Objective-C. This is currently not yet available in Objective-C++. Fast enumeration requires support in the runtime, and such support has been added to the GNU Objective-C runtime library (shipped with GCC). * The Objective-C 2.0 @optional keyword is supported. It allows you to mark methods or properties in a protocol as optional as opposed to required. * The Objective-C 2.0 @package keyword is supported. It has currently the same effect as the @public keyword. * Objective-C 2.0 method attributes are supported. Currently the supported attributes are deprecated, sentinel, noreturn and format. * Objective-C 2.0 method argument attributes are supported. The most widely used attribute is unused, to mark an argument as unused in the implementation. * Objective-C 2.0 class and protocol attributes are supported. Currently the only supported attribute is deprecated. * Objective-C 2.0 class extensions are supported. A class extension has the same syntax as a category declaration with no category name, and the methods and properties declared in it are added directly to the main class. It is mostly used as an alternative to a category to add methods to a class without advertising them in the public headers, with the advantage that for class extensions the compiler checks that all the privately declared methods are actually implemented. * As a result of these enhancements, GCC can now be used to build Objective-C and Objective-C++ software that uses Foundation and other important system frameworks with the NeXT runtime on Darwin 9 and Darwin 10 (OSX 10.5 and 10.6). * Many bugs in the compiler have been fixed in this release; in particular, LTO can now be used when compiling Objective-C and Objective-C++ and the parser is much more robust in dealing with invalid code. Runtime Library (libobjc) * The GNU Objective-C runtime library now defines the macro __GNU_LIBOBJC__ (with a value that is increased at every release where there is any change to the API) in objc/objc.h, making it easy to determine if the GNU Objective-C runtime library is being used, and if so, which version. Previous versions of the GNU Objective-C runtime library (and other Objective-C runtime libraries such as the Apple one) do not define this macro. * A new Objective-C 2.0 API, almost identical to the one implemented by the Apple Objective-C runtime, has been implemented in the GNU Objective-C runtime library. The new API hides the internals of most runtime structures but provides a more extensive set of functions to operate on them. It is much easier, for example, to create or modify classes at runtime. The new API also makes it easier to port software from Apple to GNU as almost no changes should be required. The old API is still supported for backwards compatibility; including the old objc/objc-api.h header file automatically selects the old API, while including the new objc/runtime.h header file automatically selects the new API. Support for the old API is being phased out and upgrading the software to use the new API is strongly recommended. To check for the availability of the new API, the __GNU_LIBOBJC__ macro can be used as older versions of the GNU Objective-C runtime library, which do not support the new API, do not define such a macro. * Runtime support for @synchronized has been added. * Runtime support for Objective-C 2.0 synthesized property accessors has been added. * Runtime support for Objective-C 2.0 fast enumeration has been added. New Targets and Target Specific Improvements ARM * GCC now supports the Cortex-M4 processor implementing the v7-em version of the architecture using the option -mcpu=cortex-m4. * Scheduling descriptions for the Cortex-M4, the Neon and the floating point units of the Cortex-A9 and a pipeline description for the Cortex-A5 have been added. * Synchronization primitives such as __sync_fetch_and_add and friends are now inlined for supported architectures rather than calling into a kernel helper function. * SSA loop prefetching is enabled by default for the Cortex-A9 at -O3. * Several improvements were committed to improve code generation for the ARM architecture including a rewritten implementation for load and store multiples. * Several enhancements were committed to improve SIMD code generation for NEON by adding support for widening instructions, misaligned loads and stores, vector conditionals and support for 64-bit arithmetic. * Support was added for the Faraday cores fa526, fa606te, fa626te, fmp626te, fmp626 and fa726te and can be used with the respective names as parameters to the -mcpu= option. * Basic support was added for Cortex-A15 and is available through -mcpu=cortex-a15. * GCC for AAPCS configurations now more closely adheres to the AAPCS specification by enabling -fstrict-volatile-bitfields by default. IA-32/x86-64 * The new -fsplit-stack option permits programs to use a discontiguous stack. This is useful for threaded programs, in that it is no longer necessary to specify the maximum stack size when creating a thread. This feature is currently only implemented for 32-bit and 64-bit x86 GNU/Linux targets. * Support for emitting profiler counter calls before function prologues. This is enabled via a new command-line option -mfentry. * Optimization for the Intel Core 2 processors is now available through the -march=core2 and -mtune=core2 options. * Support for Intel Core i3/i5/i7 processors is now available through the -march=corei7 and -mtune=corei7 options. * Support for Intel Core i3/i5/i7 processors with AVX is now available through the -march=corei7-avx and -mtune=corei7-avx options. * Support for AMD Bobcat (family 14) processors is now available through the -march=btver1 and -mtune=btver1 options. * Support for AMD Bulldozer (family 15) processors is now available through the -march=bdver1 and -mtune=bdver1 options. * The default setting (when not optimizing for size) for 32-bit GNU/Linux and Darwin x86 targets has been changed to -fomit-frame-pointer. The default can be reverted to -fno-omit-frame-pointer by configuring GCC with the --enable-frame-pointer configure option. * Darwin, FreeBSD, Solaris 2, MinGW and Cygwin now all support __float128 on 32-bit and 64-bit x86 targets. * AVX floating-point arithmetic can now be enabled by default at configure time with the new --with-fpmath=avx option. * The SSA loop prefetching pass is enabled when using -O3 when optimizing for CPUs where prefetching is beneficial (AMD CPUs newer than K6). * Support for TBM (Trailing Bit Manipulation) built-in functions and code generation is available via -mtbm. * Support for AMD's BMI (Bit Manipulation) built-in functions and code generation is available via -mbmi. MicroBlaze * Support has been added for the Xilinx MicroBlaze softcore processor (microblaze-elf) embedded target. This configurable processor is supported on several Xilinx Spartan and Virtex FPGAs. MIPS * GCC now supports the Loongson 3A processor. Its canonical -march= and -mtune= name is loongson3a. MN10300 / AM33 * The inline assembly register constraint "A" has been renamed "c". This constraint is used to select a floating-point register that can be used as the destination of a multiply-accumulate instruction. * New inline assembly register constraints "A" and "D" have been added. These constraint letters resolve to all general registers when compiling for AM33, and resolve to address registers only or data registers only when compiling for MN10300. * The MDR register is represented in the compiler. One can access the register via the "z" constraint in inline assembly. It can be marked as clobbered or used as a local register variable via the "mdr" name. The compiler uses the RETF instruction if the function does not modify the MDR register, so it is important that inline assembly properly annotate any usage of the register. PowerPC/PowerPC64 * GCC now supports the Applied Micro Titan processor with -mcpu=titan. * The -mrecip option has been added, which indicates whether the reciprocal and reciprocal square root instructions should be used. * The -mveclibabi=mass option can be used to enable the compiler to autovectorize mathematical functions using the Mathematical Acceleration Subsystem library. * The -msingle-pic-base option has been added, which instructs the compiler to avoid loading the PIC base register in function prologues. The PIC base register must be initialized by the runtime system. * The -mblock-move-inline-limit option has been added, which enables the user to control the maximum size of inlined memcpy calls and similar. * PowerPC64 GNU/Linux support for applications requiring a large TOC section has been improved. A new command-line option, -mcmodel=MODEL, controls this feature; valid values for MODEL are small, medium, or large. * The Altivec builtin functions vec_ld and vec_st have been modified to generate the Altivec memory instructions LVX and STVX, even if the -mvsx option is used. In the initial GCC 4.5 release, these builtin functions were changed to generate VSX memory reference instructions instead of Altivec memory instructions, but there are differences between the two instructions. If the VSX instruction set is available, you can now use the new builtin functions vec_vsx_ld and vec_vsx_st which always generates the VSX memory instructions. * The GCC compiler on AIX now defaults to a process layout with a larger data space allowing larger programs to be compiled. * The GCC long double type on AIX 6.1 and above has reverted to 64-bit double precision, matching the AIX XL compiler default, because of missing C99 symbols required by the GCC runtime. * The default processor scheduling model and tuning for PowerPC64 GNU/Linux and for AIX 6.1 and above now is POWER7. * Starting with GCC 4.6.1, vectors of type vector long long or vector long are passed and returned in the same method as other vectors with the VSX instruction set. Previously the GCC compiler did not adhere to the ABI for 128-bit vectors with 64-bit integer base types (PR 48857). This is also fixed in the GCC 4.5.4 release. S/390, zSeries and System z9/z10, IBM zEnterprise z196 * Support for the zEnterprise z196 processor has been added. When using the -march=z196 option, the compiler will generate code making use of the following instruction facilities: + Conditional load/store + Distinct-operands + Floating-point-extension + Interlocked-access + Population-count The -mtune=z196 option avoids the compare and branch instructions as well as the load address instruction with an index register as much as possible and performs instruction scheduling appropriate for the new out-of-order pipeline architecture. * When using the -m31 -mzarch options the generated code still conforms to the 32-bit ABI but uses the general purpose registers as 64-bit registers internally. This requires a Linux kernel saving the whole 64-bit registers when doing a context switch. Kernels providing that feature indicate that by the 'highgprs' string in /proc/cpuinfo. * The SSA loop prefetching pass is enabled when using -O3. SPARC * GCC now supports the LEON series of SPARC V8 processors. The code generated by the compiler can either be tuned to it by means of the --with-tune=leon configure option and -mtune=leon compilation option, or the compiler can be built for the sparc-leon-{elf,linux} and sparc-leon3-{elf,linux} targets directly. * GCC has stopped sign/zero-extending parameter registers in the callee for functions taking parameters with sub-word size in 32-bit mode, since this is redundant with the specification of the ABI. GCC has never done so in 64-bit mode since this is also redundant. * The command-line option -mfix-at697f has been added to enable the documented workaround for the single erratum of the Atmel AT697F processor. Operating Systems Android * GCC now supports the Bionic C library and provides a convenient way of building native libraries and applications for the Android platform. Refer to the documentation of the -mandroid and -mbionic options for details on building native code. At the moment, Android support is enabled only for ARM. Darwin/Mac OS X * General + Initial support for CFString types has been added. This allows GCC to build projects including the system Core Foundation frameworks. The GCC Objective-C family supports CFString "toll-free bridged" as per the Mac OS X system tools. CFString is also recognized in the context of format attributes and arguments (see the documentation for format attributes for limitations). At present, 8-bit character types are supported. + Object file size reduction. The Darwin zeroed memory allocators have been re-written to make more use of .zerofill sections. For non-debug code, this can reduce object file size significantly. + Objective-C family 64-bit support (NeXT ABI 2). Initial support has been added to support 64-bit Objective-C code using the Darwin/OS X native (NeXT) runtime. ABI version 2 will be selected automatically when 64-bit code is built. + Objective-C family 32-bit ABI 1. For 32-bit code ABI 1 is also now also allowed. At present it must be selected manually using -fobjc-abi-version=1 where applicable - i.e. on Darwin 9/10 (OS X 10.5/10.6). * x86 Architecture + The -mdynamic-no-pic option has been enabled. Code supporting -mdynamic-no-pic optimization has been added and is applicable to -m32 builds. The compiler bootstrap uses the option where appropriate. + The default value for -mtune= has been changed. Since Darwin systems are primarily Xeon, Core-2 or similar the default tuning has been changed to -mtune=core2. + Enable 128-bit long double (__float128) support on Darwin. * PPC Architecture + Darwin64 ABI. Several significant bugs have been fixed, such that GCC now produces code compatible with the Darwin64 PowerPC ABI. + libffi and boehm-gc. The Darwin ports of the libffi and boehm-gc libraries have been upgraded to include a Darwin64 implementation. This means that powerpc*-*-darwin9 platforms may now, for example, build Java applications with -m64 enabled. + Plug-in support has been enabled. + The -fsection-anchors option is now available although, presently, not heavily tested. Solaris 2 New Features * Support symbol versioning with the Sun linker. * Allow libstdc++ to leverage full ISO C99 support on Solaris 10+. * Support thread-local storage (TLS) with the Sun assembler on Solaris 2/x86. * Support TLS on Solaris 8/9 if prerequisites are met. * Support COMDAT group with the GNU assembler and recent Sun linker. * Support the Sun assembler visibility syntax. * Default Solaris 2/x86 to -march=pentium4 (Solaris 10+) resp. -march=pentiumpro (Solaris 8/9). * Don't use SSE on Solaris 8/9 x86 by default. * Enable 128-bit long double (__float128) support on Solaris 2/x86. ABI Change * Change the ABI for returning 8-byte vectors like __m64 in MMX registers on Solaris 10+/x86 to match the Sun Studio 12.1+ compilers. This is an incompatible change. If you use such types, you must either recompile all your code with the new compiler or use the new -mvect8-ret-in-mem option to remain compatible with previous versions of GCC and Sun Studio. Windows x86/x86_64 * Initial support for decimal floating point. * Support for the __thiscall calling-convention. * Support for hot-patchable function prologues via the ms_hook_prologue attribute for x86_64 in addition to 32-bit x86. * Improvements of stack-probing and stack-allocation mechanisms. * Support of push/pop-macro pragma as preprocessor command. With #pragma push_macro("macro-name") the current definition of macro-name is saved and can be restored with #pragma pop_macro("macro-name") to its saved definition. * Enable 128-bit long double (__float128) support on MinGW and Cygwin. Other significant improvements Installation changes * An install-strip make target is provided that installs stripped executables, and may install libraries with unneeded or debugging sections stripped. * On Power7 systems, there is a potential problem if you build the GCC compiler with a host compiler using options that enable the VSX instruction set generation. If the host compiler has been patched so that the vec_ld and vec_st builtin functions generate Altivec memory instructions instead of VSX memory instructions, then you should be able to build the compiler with VSX instruction generation. Changes for GCC Developers Note: these changes concern developers that develop GCC itself or software that integrates with GCC, such as plugins, and not the general GCC users. * The gengtype utility, which previously was internal to the GCC build process, has been enchanced to provide GC root information for plugins as necessary. * The old GC allocation interface of ggc_alloc and friends was replaced with a type-safe alternative. GCC 4.6.1 This is the [19]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.6.1 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.6.2 This is the [20]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.6.2 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.6.3 This is the [21]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.6.3 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.6.4 This is the [22]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.6.4 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). For questions related to the use of GCC, please consult these web pages and the [23]GCC manuals. If that fails, the [24]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [25]gcc@gcc.gnu.org. All of [26]our lists have public archives. Copyright (C) [27]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [28]maintained by the GCC team. Last modified 2024-05-17. References 1. https://sourceware.org/bugzilla/show_bug.cgi?id=10401 2. https://gcc.gnu.org/gcc-4.5/changes.html 3. https://gcc.gnu.org/gcc-4.5/changes.html#obsoleted 4. https://gcc.gnu.org/gcc-4.6/porting_to.html 5. https://gcc.gnu.org/projects/lto/whopr.pdf 6. https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#Warning-Options 7. https://gcc.gnu.org/gcc-4.6/cxx0x_status.html 8. https://gcc.gnu.org/PR43145 9. https://gcc.gnu.org/PR43680 10. https://gcc.gnu.org/PR33558 11. https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#253 12. https://gcc.gnu.org/onlinedocs/gcc-4.6.4/libstdc++/manual/manual/status.html#status.iso.200x 13. https://gcc.gnu.org/onlinedocs/libstdc++/manual/debug_mode.html 14. https://gcc.gnu.org/onlinedocs/libstdc++/manual/debug.html#debug.races 15. https://gcc.gnu.org/onlinedocs/gcc/Preprocessor-Options.html 16. https://gcc.gnu.org/wiki/OOP 17. https://gcc.gnu.org/wiki/Coarray 18. https://gcc.gnu.org/onlinedocs/gfortran/Code-Gen-Options.html#index-g_t_0040code_007bfcoarray_007d-233 19. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.6.1 20. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.6.2 21. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.6.3 22. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.6.4 23. https://gcc.gnu.org/onlinedocs/ 24. mailto:gcc-help@gcc.gnu.org 25. mailto:gcc@gcc.gnu.org 26. https://gcc.gnu.org/lists.html 27. https://www.fsf.org/ 28. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.5/index.html GCC 4.5 Release Series (This release series is no longer supported.) Jul 2, 2012 The [1]GNU project and the GCC developers are pleased to announce the release of GCC 4.5.4. This release is a bug-fix release, containing fixes for regressions in GCC 4.5.3 relative to previous releases of GCC. Release History GCC 4.5.4 Jul 2, 2012 ([2]changes) GCC 4.5.3 Apr 28, 2011 ([3]changes) GCC 4.5.2 Dec 16, 2010 ([4]changes) GCC 4.5.1 Jul 31, 2010 ([5]changes) GCC 4.5.0 April 14, 2010 ([6]changes) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. A list of [7]successful builds is updated as new information becomes available. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [8]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [9]GCC project web site or contact the [10]GCC development mailing list. To obtain GCC please use [11]our mirror sites or [12]our version control system. For questions related to the use of GCC, please consult these web pages and the [13]GCC manuals. If that fails, the [14]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [15]gcc@gcc.gnu.org. All of [16]our lists have public archives. Copyright (C) [17]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [18]maintained by the GCC team. Last modified 2022-10-26. References 1. http://www.gnu.org/ 2. https://gcc.gnu.org/gcc-4.5/changes.html 3. https://gcc.gnu.org/gcc-4.5/changes.html 4. https://gcc.gnu.org/gcc-4.5/changes.html 5. https://gcc.gnu.org/gcc-4.5/changes.html 6. https://gcc.gnu.org/gcc-4.5/changes.html 7. https://gcc.gnu.org/gcc-4.5/buildstat.html 8. https://gcc.gnu.org/onlinedocs/gcc/Contributors.html 9. https://gcc.gnu.org/index.html 10. mailto:gcc@gcc.gnu.org 11. https://gcc.gnu.org/mirrors.html 12. https://gcc.gnu.org/git.html 13. https://gcc.gnu.org/onlinedocs/ 14. mailto:gcc-help@gcc.gnu.org 15. mailto:gcc@gcc.gnu.org 16. https://gcc.gnu.org/lists.html 17. https://www.fsf.org/ 18. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.5/changes.html GCC 4.5 Release Series Changes, New Features, and Fixes Caveats * GCC now requires the [1]MPC library in order to build. See the [2]prerequisites page for version requirements. * Support for a number of older systems and recently unmaintained or untested target ports of GCC has been declared obsolete in GCC 4.5. Unless there is activity to revive them, the next release of GCC will have their sources permanently removed. The following ports for individual systems on particular architectures have been obsoleted: + IRIX releases before 6.5 (mips-sgi-irix5*, mips-sgi-irix6.[0-4]) + Solaris 7 (*-*-solaris2.7) + Tru64 UNIX releases before V5.1 (alpha*-dec-osf4*, alpha-dec-osf5.0*) + Details for the IRIX, Solaris 7, and Tru64 UNIX obsoletions can be found in the [3]announcement. Support for the classic POWER architecture implemented in the original RIOS and RIOS2 processors of the old IBM RS/6000 product line has been obsoleted in the rs6000 port. This does not affect the new generation Power and PowerPC architectures. * Support has been removed for all the [4]configurations obsoleted in GCC 4.4. * Support has been removed for the protoize and unprotoize utilities, obsoleted in GCC 4.4. * Support has been removed for tuning for Itanium1 (Merced) variants. Note that code tuned for Itanium2 should also run correctly on Itanium1. * GCC now generates unwind info also for epilogues. DWARF debuginfo generated by GCC now uses more features of DWARF3 than before, and also some DWARF4 features. GDB older than 7.0 is not able to handle either of these, so to debug GCC 4.5 generated binaries or libraries GDB 7.0 or later is needed. You can disable use of DWARF4 features with the -gdwarf-3 -gstrict-dwarf options, or use -gdwarf-2 -gstrict-dwarf to restrict GCC to just DWARF2, but epilogue unwind info is emitted unconditionally whenever unwind info is emitted. * On x86 targets, code containing floating-point calculations may run significantly more slowly when compiled with GCC 4.5 in strict C99 conformance mode than they did with earlier GCC versions. This is due to stricter standard conformance of the compiler and can be avoided by using the option -fexcess-precision=fast; also see [5]below. * The function attribute noinline no longer prevents GCC from cloning the function. A new attribute noclone has been introduced for this purpose. Cloning a function means that it is duplicated and the new copy is specialized for certain contexts (for example when a parameter is a known constant). General Optimizer Improvements * The -save-temps now takes an optional argument. The -save-temps and -save-temps=cwd switches write the temporary files in the current working directory based on the original source file. The -save-temps=obj switch will write files into the directory specified with the -o option, and the intermediate filenames are based on the output file. This will allow the user to get the compiler intermediate files when doing parallel builds without two builds of the same filename located in different directories from interfering with each other. * Debugging dumps are now created in the same directory as the object file rather than in the current working directory. This allows the user to get debugging dumps when doing parallel builds without two builds of the same filename interfering with each other. * GCC has been integrated with the MPC library. This allows GCC to evaluate complex arithmetic at compile time [6]more accurately. It also allows GCC to evaluate calls to complex built-in math functions having constant arguments and replace them at compile time with their mathematically equivalent results. In doing so, GCC can generate correct results regardless of the math library implementation or floating point precision of the host platform. This also allows GCC to generate identical results regardless of whether one compiles in native or cross-compile configurations to a particular target. The following built-in functions take advantage of this new capability: cacos, cacosh, casin, casinh, catan, catanh, ccos, ccosh, cexp, clog, cpow, csin, csinh, csqrt, ctan, and ctanh. The float and long double variants of these functions (e.g. csinf and csinl) are also handled. * A new link-time optimizer has been added ([7]-flto). When this option is used, GCC generates a bytecode representation of each input file and writes it to specially-named sections in each object file. When the object files are linked together, all the function bodies are read from these named sections and instantiated as if they had been part of the same translation unit. This enables interprocedural optimizations to work across different files (and even different languages), potentially improving the performance of the generated code. To use the link-timer optimizer, -flto needs to be specified at compile time and during the final link. If the program does not require any symbols to be exported, it is possible to combine -flto and the experimental [8]-fwhopr with [9]-fwhole-program to allow the interprocedural optimizers to use more aggressive assumptions. * The automatic parallelization pass was enhanced to support parallelization of outer loops. * Automatic parallelization can be enabled as part of Graphite. In addition to -ftree-parallelize-loops=, specify -floop-parallelize-all to enable the Graphite-based optimization. * The infrastructure for optimizing based on [10]restrict qualified pointers has been rewritten and should result in code generation improvements. Optimizations based on restrict qualified pointers are now also available when using -fno-strict-aliasing. * There is a new optimization pass that attempts to change prototype of functions to avoid unused parameters, pass only relevant parts of structures and turn arguments passed by reference to arguments passed by value when possible. It is enabled by -O2 and above as well as -Os and can be manually invoked using the new command-line switch -fipa-sra. * GCC now optimize exception handling code. In particular cleanup regions that are proved to not have any effect are optimized out. New Languages and Language specific improvements All languages * The -fshow-column option is now on by default. This means error messages now have a column associated with them. Ada * Compilation of programs heavily using discriminated record types with variant parts has been sped up and generates more compact code. * Stack checking now works reasonably well on most plaforms. In some specific cases, stack overflows may still fail to be detected, but a compile-time warning will be issued for these cases. C family * If a header named in a #include directive is not found, the compiler exits immediately. This avoids a cascade of errors arising from declarations expected to be found in that header being missing. * A new built-in function __builtin_unreachable() has been added that tells the compiler that control will never reach that point. It may be used after asm statements that terminate by transferring control elsewhere, and in other places that are known to be unreachable. * The -Wlogical-op option now warns for logical expressions such as (c == 1 && c == 2) and (c != 1 || c != 2), which are likely to be mistakes. This option is disabled by default. * An asm goto feature has been added to allow asm statements that jump to C labels. * C++0x raw strings are supported for C++ and for C with -std=gnu99. * The deprecated attribute now takes an optional string argument, for example, __attribute__((deprecated("text string"))), that will be printed together with the deprecation warning. C * The -Wenum-compare option, which warns when comparing values of different enum types, now works for C. It formerly only worked for C++. This warning is enabled by -Wall. It may be avoided by using a type cast. * The -Wcast-qual option now warns about casts which are unsafe in that they permit const-correctness to be violated without further warnings. Specifically, it warns about cases where a qualifier is added when all the lower types are not const. For example, it warns about a cast from char ** to const char **. * The -Wc++-compat option is significantly improved. It issues new warnings for: + Using C++ reserved operator names as identifiers. + Conversions to enum types without explicit casts. + Using va_arg with an enum type. + Using different enum types in the two branches of ?:. + Using ++ or -- on a variable of enum type. + Using the same name as both a struct, union or enum tag and a typedef, unless the typedef refers to the tagged type itself. + Using a struct, union, or enum which is defined within another struct or union. + A struct field defined using a typedef if there is a field in the struct, or an enclosing struct, whose name is the typedef name. + Duplicate definitions at file scope. + Uninitialized const variables. + A global variable with an anonymous struct, union, or enum type. + Using a string constant to initialize a char array whose size is the length of the string. * The new -Wjump-misses-init option warns about cases where a goto or switch skips the initialization of a variable. This sort of branch is an error in C++ but not in C. This warning is enabled by -Wc++-compat. * GCC now ensures that a C99-conforming is present on most targets, and uses information about the types in this header to implement the Fortran bindings to those types. GCC does not ensure the presence of such a header, and does not implement the Fortran bindings, on the following targets: NetBSD, VxWorks, VMS, SymbianOS, WinCE, LynxOS, Netware, QNX, Interix, TPF. * GCC now implements C90- and C99-conforming rules for constant expressions. This may cause warnings or errors for some code using expressions that can be folded to a constant but are not constant expressions as defined by ISO C. * All known target-independent C90 and C90 Amendment 1 conformance bugs, and all known target-independent C99 conformance bugs not related to floating point or extended identifiers, have been fixed. * The C decimal floating point support now includes support for the FLOAT_CONST_DECIMAL64 pragma. * The named address space feature from ISO/IEC TR 18037 is now supported. This is currently only implemented for the SPU processor. C++ * Improved [11]experimental support for the upcoming C++0x ISO C++ standard, including support for raw strings, lambda expressions and explicit type conversion operators. * When printing the name of a class template specialization, G++ will now omit any template arguments which come from default template arguments. This behavior (and the pretty-printing of function template specializations as template signature and arguments) can be disabled with the -fno-pretty-templates option. * Access control is now applied to typedef names used in a template, which may cause G++ to reject some ill-formed code that was accepted by earlier releases. The -fno-access-control option can be used as a temporary workaround until the code is corrected. * Compilation time for code that uses templates should now scale linearly with the number of instantiations rather than quadratically, as template instantiations are now looked up using hash tables. * Declarations of functions that look like builtin declarations of library functions are only considered to be redeclarations if they are declared with extern "C". This may cause problems with code that omits extern "C" on hand-written declarations of C library functions such as abort or memcpy. Such code is ill-formed, but was accepted by earlier releases. * Diagnostics that used to complain about passing non-POD types to ... or jumping past the declaration of a non-POD variable now check for triviality rather than PODness, as per C++0x. * In C++0x mode local and anonymous classes are now allowed as template arguments, and in declarations of variables and functions with linkage, so long as any such declaration that is used is also defined ([12]DR 757). * Labels may now have attributes, as has been permitted for a while in C. This is only permitted when the label definition and the attribute specifier is followed by a semicolon—i.e., the label applies to an empty statement. The only useful attribute for a label is unused. * G++ now implements [13]DR 176. Previously G++ did not support using the injected-class-name of a template base class as a type name, and lookup of the name found the declaration of the template in the enclosing scope. Now lookup of the name finds the injected-class-name, which can be used either as a type or as a template, depending on whether or not the name is followed by a template argument list. As a result of this change, some code that was previously accepted may be ill-formed because 1. The injected-class-name is not accessible because it's from a private base, or 2. The injected-class-name cannot be used as an argument for a template template parameter. In either of these cases, the code can be fixed by adding a nested-name-specifier to explicitly name the template. The first can be worked around with -fno-access-control; the second is only rejected with -pedantic. * A new standard mangling for SIMD vector types has been added, to avoid name clashes on systems with vectors of varying length. By default the compiler still uses the old mangling, but emits aliases with the new mangling on targets that support strong aliases. Users can switch over entirely to the new mangling with -fabi-version=4 or -fabi-version=0. -Wabi will now warn about code that uses the old mangling. * The command-line option -ftemplate-depth-N is now written as -ftemplate-depth=N and the old form is deprecated. * Conversions between NULL and non-pointer types are now warned by default. The new option -Wno-conversion-null disables these warnings. Previously these warnings were only available when using -Wconversion explicitly. Runtime Library (libstdc++) * Improved experimental support for the upcoming ISO C++ standard, C++0x, including: + Support for , , and . + Existing facilities now exploit explicit operators and the newly implemented core C++0x features. + The header has been renamed to . * An experimental [14]profile mode has been added. This is an implementation of many C++ standard library constructs with an additional analysis layer that gives performance improvement advice based on recognition of suboptimal usage patterns. For example, #include int main() { std::vector v; for (int k = 0; k < 1024; ++k) v.insert(v.begin(), k); } When instrumented via the profile mode, can return suggestions about the initial size and choice of the container used as follows: vector-to-list: improvement = 5: call stack = 0x804842c ... : advice = change std::vector to std::list vector-size: improvement = 3: call stack = 0x804842c ... : advice = change initial container size from 0 to 1024 These constructs can be substituted for the normal libstdc++ constructs on a piecemeal basis, or all existing components can be transformed via the -D_GLIBCXX_PROFILE macro. * [15]Support for decimal floating-point arithmetic (aka ISO C++ TR 24733) has been added. This support is in header file , uses namespace std::decimal, and includes classes decimal32, decimal64, and decimal128. * Sources have been audited for application of function attributes nothrow, const, pure, and noreturn. * Python pretty-printers have been added for many standard library components that simplify the internal representation and present a more intuitive view of components when used with appropriately-advanced versions of GDB. For more information, please consult the more [16]detailed description. * The default behavior for comparing typeinfo names has changed, so in , __GXX_MERGED_TYPEINFO_NAMES now defaults to zero. * The new -static-libstdc++ option directs g++ to link the C++ library statically, even if the default would normally be to link it dynamically. Fortran * The COMMON default padding has been changed – instead of adding the padding before a variable it is now added afterwards, which increases the compatibility with other vendors and helps to obtain the correct output in some cases. Cf. also the -falign-commons option ([17]added in 4.4). * The -finit-real= option now also supports the value snan for signaling not-a-number; to be effective, one additionally needs to enable trapping (e.g. via -ffpe-trap=). Note: Compile-time optimizations can turn a signaling NaN into a quiet one. * The new option -fcheck= has been added with the options bounds, array-temps, do, pointer, and recursive. The bounds and array-temps options are equivalent to -fbounds-check and -fcheck-array-temporaries. The do option checks for invalid modification of loop iteration variables, and the recursive option tests for recursive calls to subroutines/functions which are not marked as recursive. With pointer pointer association checks in calls are performed; however, neither undefined pointers nor pointers in expressions are handled. Using -fcheck=all enables all these run-time checks. * The run-time checking -fcheck=bounds now warns about invalid string lengths of character dummy arguments. Additionally, more compile-time checks have been added. * The new option [18]-fno-protect-parens has been added; if set, the compiler may reorder REAL and COMPLEX expressions without regard to parentheses. * GNU Fortran no longer links against libgfortranbegin. As before, MAIN__ (assembler symbol name) is the actual Fortran main program, which is invoked by the main function. However, main is now generated and put in the same object file as MAIN__. For the time being, libgfortranbegin still exists for backward compatibility. For details see the new [19]Mixed-Language Programming chapter in the manual. * The I/O library was restructured for performance and cleaner code. * Array assignments and WHERE are now run in parallel when OpenMP's WORKSHARE is used. * The experimental option -fwhole-file was added. The option allows whole-file checking of procedure arguments and allows for better optimizations. It can also be used with -fwhole-program, which is now also supported in gfortran. * More Fortran 2003 and Fortran 2008 mathematical functions can now be used as initialization expressions. * Some extended attributes such as STDCALL are now supported via the [20]GCC$ compiler directive. * For Fortran 77 compatibility: If -fno-sign-zero is used, the SIGN intrinsic behaves now as if zero were always positive. * For legacy compatibiliy: On Cygwin and MinGW, the special files CONOUT$ and CONIN$ (and CONERR$ which maps to CONOUT$) are now supported. * Fortran 2003 support has been extended: + Procedure-pointer function results and procedure-pointer components (including PASS), + allocatable scalars (experimental), + DEFERRED type-bound procedures, + the ERRMSG= argument of the ALLOCATE and DEALLOCATE statements have been implemented. + The ALLOCATE statement supports type-specs and the SOURCE= argument. + OPERATOR(*) and ASSIGNMENT(=) are now allowed as GENERIC type-bound procedure (i.e. as type-bound operators). + Rounding (ROUND=, RZ, ...) for output is now supported. + The INT_FAST{8,16,32,64,128}_T kind type parameters of the intrinsic module ISO_C_BINDING are now supported, except for the targets listed above as ones where GCC does not have type information. + Extensible derived types with type-bound procedure or procedure pointer with PASS attribute now have to use CLASS in line with the Fortran 2003 standard; the workaround to use TYPE is no longer supported. + [21]Experimental, incomplete support for polymorphism, including CLASS, SELECT TYPE and dynamic dispatch of type-bound procedure calls. Some features do not work yet such as unlimited polymorphism (CLASS(*)). * Fortran 2008 support has been extended: + The OPEN statement now supports the NEWUNIT= option, which returns a unique file unit, thus preventing inadvertent use of the same unit in different parts of the program. + Support for unlimited format items has been added. + The INT{8,16,32} and REAL{32,64,128} kind type parameters of the intrinsic module ISO_FORTRAN_ENV are now supported. + Using complex arguments with TAN, SINH, COSH, TANH, ASIN, ACOS, and ATAN is now possible; the functions ASINH, ACOSH, and ATANH have been added (for real and complex arguments) and ATAN(Y,X) is now an alias for ATAN2(Y,X). + The BLOCK construct has been implemented. New Targets and Target Specific Improvements AIX * Full cross-toolchain support now available with GNU Binutils ARM * GCC now supports the Cortex-M0 and Cortex-A5 processors. * GCC now supports the ARM v7E-M architecture. * GCC now supports VFPv4-based FPUs and FPUs with single-precision-only VFP. * GCC has many improvements to optimization for other ARM processors, including scheduling support for the integer pipeline on Cortex-A9. * GCC now supports the IEEE 754-2008 half-precision floating-point type, and a variant ARM-specific half-precision type. This type is specified using __fp16, with the layout determined by -mfp16-format. With appropriate -mfpu options, the Cortex-A9 and VFPv4 half-precision instructions will be used. * GCC now supports the variant of AAPCS that uses VFP registers for parameter passing and return values. AVR * The -mno-tablejump option has been removed because it has the same effect as the -fno-jump-tables option. * Added support for these new AVR devices: + ATmega8U2 + ATmega16U2 + ATmega32U2 IA-32/x86-64 * GCC now will set the default for -march= based on the configure target. * GCC now supports handling floating-point excess precision arising from use of the x87 floating-point unit in a way that conforms to ISO C99. This is enabled with -fexcess-precision=standard and with standards conformance options such as -std=c99, and may be disabled using -fexcess-precision=fast. * Support for the Intel Atom processor is now available through the -march=atom and -mtune=atom options. * A new -mcrc32 option is now available to enable crc32 intrinsics. * A new -mmovbe option is now available to enable GCC to use the movbe instruction to implement __builtin_bswap32 and __builtin_bswap64. * SSE math now can be enabled by default at configure time with the new --with-fpmath=sse option. * There is a new intrinsic header file, . It should be included before using any IA-32/x86-64 intrinsics. * Support for the XOP, FMA4, and LWP instruction sets for the AMD Orochi processors are now available with the -mxop, -mfma4, and -mlwp options. * The -mabm option enables GCC to use the popcnt and lzcnt instructions on AMD processors. * The -mpopcnt option enables GCC to use the popcnt instructions on both AMD and Intel processors. M68K/ColdFire * GCC now supports ColdFire 51xx, 5221x, 5225x, 52274, 52277, 5301x and 5441x devices. * GCC now supports thread-local storage (TLS) on M68K and ColdFire processors. MeP Support has been added for the Toshiba Media embedded Processor (MeP, or mep-elf) embedded target. MIPS * GCC now supports MIPS 1004K processors. * GCC can now be configured with options --with-arch-32, --with-arch-64, --with-tune-32 and --with-tune-64 to control the default optimization separately for 32-bit and 64-bit modes. * MIPS targets now support an alternative _mcount interface, in which register $12 points to the function's save slot for register $31. This interface is selected by the -mcount-ra-address option; see the documentation for more details. * GNU/Linux targets can now generate read-only .eh_frame sections. This optimization requires GNU binutils 2.20 or above, and is only available if GCC is configured with a suitable version of binutils. * GNU/Linux targets can now attach special relocations to indirect calls, so that the linker can turn them into direct jumps or branches. This optimization requires GNU binutils 2.20 or later, and is automatically selected if GCC is configured with an appropriate version of binutils. It can be explicitly enabled or disabled using the -mrelax-pic-calls command-line option. * GCC now generates more heavily-optimized atomic operations on Octeon processors. * MIPS targets now support the -fstack-protector option. * GCC now supports an -msynci option, which specifies that synci is enough to flush the instruction cache, without help from the operating system. GCC uses this information to optimize automatically-generated cache flush operations, such as those used for nested functions in C. There is also a --with-synci configure-time option, which makes -msynci the default. * GCC supports four new function attributes for interrupt handlers: interrupt, use_shadow_register_set, keep_interrupts_masked and use_debug_exception_return. See the documentation for more details about these attributes. RS/6000 (POWER/PowerPC) * GCC now supports the Power ISA 2.06, which includes the VSX instructions that add vector 64-bit floating point support, new population count instructions, and conversions between floating point and unsigned types. * Support for the power7 processor is now available through the -mcpu=power7 and -mtune=power7. * GCC will now vectorize loops that contain simple math functions like copysign when generating code for altivec or VSX targets. * Support for the A2 processor is now available through the -mcpu=a2 and -mtune=a2 options. * Support for the 476 processor is now available through the -mcpu={476,476fp} and -mtune={476,476fp} options. * Support for the e500mc64 processor is now available through the -mcpu=e500mc64 and -mtune=e500mc64 options. * GCC can now be configured with options --with-cpu-32, --with-cpu-64, --with-tune-32 and --with-tune-64 to control the default optimization separately for 32-bit and 64-bit modes. * Starting with GCC 4.5.4, vectors of type vector long long or vector long are passed and returned in the same method as other vectors with the VSX instruction set. Previously the GCC compiler did not adhere to the ABI for 128-bit vectors with 64-bit integer base types (PR 48857). This is also fixed in the GCC 4.6.1 release. RX Support has been added for the Renesas RX Processor (rx-elf) target. Operating Systems Windows (Cygwin and MinGW) * GCC now installs all the major language runtime libraries as DLLs when configured with the --enable-shared option. * GCC now makes use of the new support for aligned common variables in versions of binutils >= 2.20 to fix bugs in the support for SSE data types. * Improvements to the libffi support library increase the reliability of code generated by GCJ on all Windows platforms. Libgcj is enabled by default for the first time. * Libtool improvements simplify installation by placing the generated DLLs in the correct binaries directory. * Numerous other minor bugfixes and improvements, and substantial enhancements to the Fortran language support library. > Other significant improvements Plugins * It is now possible to extend the compiler without having to modify its source code. A new option -fplugin=file.so tells GCC to load the shared object file.so and execute it as part of the compiler. The internal documentation describes the details on how plugins can interact with the compiler. Installation changes * The move to newer autotools changed default installation directories and switches to control them: The --with-datarootdir, --with-docdir, --with-pdfdir, and --with-htmldir switches are not used any more. Instead, you can now use --datarootdir, --docdir, --htmldir, and --pdfdir. The default installation directories have changed as follows according to the GNU Coding Standards: datarootdir read-only architecture-independent data root [PREFIX/share] localedir locale-specific message catalogs [DATAROOTDIR/locale] docdir documentation root [DATAROOTDIR/doc/PACKAGE] htmldir html documentation [DOCDIR] dvidir dvi documentation [DOCDIR] pdfdir pdf documentation [DOCDIR] psdir ps documentation [DOCDIR] The following variables have new default values: datadir read-only architecture-independent data [DATAROOTDIR] infodir info documentation [DATAROOTDIR/info] mandir man documentation [DATAROOTDIR/man] GCC 4.5.1 This is the [22]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.5.1 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). All languages * GCC's new link-time optimizer ([23]-flto) now also works on a few non-ELF targets: + Cygwin (*-cygwin*) + MinGW (*-mingw*) + Darwin on x86-64 (x86_64-apple-darwin*) LTO is not enabled by default for these targets. To enable LTO, you should configure with the --enable-lto option. GCC 4.5.2 This is the [24]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.5.2 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.5.3 This is the [25]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.5.3 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). On the PowerPC compiler, the Altivec builtin functions vec_ld and vec_st have been modified to generate the Altivec memory instructions LVX and STVX, even if the -mvsx option is used. In the initial GCC 4.5 release, these builtin functions were changed to generate VSX memory reference instructions instead of Altivec memory instructions, but there are differences between the two instructions. If the VSX instruction set is available, you can now use the new builtin functions vec_vsx_ld and vec_vsx_st which always generates the VSX memory instructions. GCC 4.5.4 This is the [26]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.5.4 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). For questions related to the use of GCC, please consult these web pages and the [27]GCC manuals. If that fails, the [28]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [29]gcc@gcc.gnu.org. All of [30]our lists have public archives. Copyright (C) [31]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [32]maintained by the GCC team. Last modified 2023-07-30. References 1. https://www.multiprecision.org/ 2. https://gcc.gnu.org/install/prerequisites.html 3. https://gcc.gnu.org/ml/gcc/2010-01/msg00510.html 4. https://gcc.gnu.org/gcc-4.4/changes.html#obsoleted 5. https://gcc.gnu.org/gcc-4.5/changes.html#x86 6. https://gcc.gnu.org/PR30789 7. https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-flto-801 8. https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-fwhopr-802 9. https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-fwhole-program-800 10. https://gcc.gnu.org/onlinedocs/gcc/Restricted-Pointers.html 11. https://gcc.gnu.org/gcc-4.5/cxx0x_status.html 12. https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#757 13. https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#176 14. https://gcc.gnu.org/onlinedocs/libstdc++/manual/profile_mode.html 15. https://gcc.gnu.org/onlinedocs/libstdc++/manual/status.html#status.iso.tr24733 16. https://sourceware.org/gdb/wiki/STLSupport 17. https://gcc.gnu.org/gcc-4.4/changes.html 18. https://gcc.gnu.org/onlinedocs/gfortran/Code-Gen-Options.html 19. https://gcc.gnu.org/onlinedocs/gfortran/Mixed-Language-Programming.html 20. https://gcc.gnu.org/onlinedocs/gfortran/GNU-Fortran-Compiler-Directives.html 21. https://gcc.gnu.org/wiki/OOP 22. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.5.1 23. https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-flto-801 24. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.5.2 25. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.5.3 26. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.5.4 27. https://gcc.gnu.org/onlinedocs/ 28. mailto:gcc-help@gcc.gnu.org 29. mailto:gcc@gcc.gnu.org 30. https://gcc.gnu.org/lists.html 31. https://www.fsf.org/ 32. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.4/index.html GCC 4.4 Release Series This release series is no longer maintained. March 13, 2012 The [1]GNU project and the GCC developers are pleased to announce the release of GCC 4.4.7. This release is a bug-fix release, containing fixes for regressions in GCC 4.4.6 relative to previous releases of GCC. Release History GCC 4.4.7 March 13, 2012 ([2]changes) GCC 4.4.6 April 16, 2011 ([3]changes) GCC 4.4.5 October 1, 2010 ([4]changes) GCC 4.4.4 April 29, 2010 ([5]changes) GCC 4.4.3 January 21, 2010 ([6]changes) GCC 4.4.2 October 15, 2009 ([7]changes) GCC 4.4.1 July 22, 2009 ([8]changes) GCC 4.4.0 April 21, 2009 ([9]changes) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. A list of [10]successful builds is updated as new information becomes available. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [11]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [12]GCC project web site or contact the [13]GCC development mailing list. To obtain GCC please use [14]our mirror sites or [15]our version control system. For questions related to the use of GCC, please consult these web pages and the [16]GCC manuals. If that fails, the [17]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [18]gcc@gcc.gnu.org. All of [19]our lists have public archives. Copyright (C) [20]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [21]maintained by the GCC team. Last modified 2022-10-26. References 1. http://www.gnu.org/ 2. https://gcc.gnu.org/gcc-4.4/changes.html 3. https://gcc.gnu.org/gcc-4.4/changes.html 4. https://gcc.gnu.org/gcc-4.4/changes.html 5. https://gcc.gnu.org/gcc-4.4/changes.html 6. https://gcc.gnu.org/gcc-4.4/changes.html 7. https://gcc.gnu.org/gcc-4.4/changes.html 8. https://gcc.gnu.org/gcc-4.4/changes.html 9. https://gcc.gnu.org/gcc-4.4/changes.html 10. https://gcc.gnu.org/gcc-4.4/buildstat.html 11. https://gcc.gnu.org/onlinedocs/gcc/Contributors.html 12. https://gcc.gnu.org/index.html 13. mailto:gcc@gcc.gnu.org 14. https://gcc.gnu.org/mirrors.html 15. https://gcc.gnu.org/git.html 16. https://gcc.gnu.org/onlinedocs/ 17. mailto:gcc-help@gcc.gnu.org 18. mailto:gcc@gcc.gnu.org 19. https://gcc.gnu.org/lists.html 20. https://www.fsf.org/ 21. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.4/changes.html GCC 4.4 Release Series Changes, New Features, and Fixes The latest release in the 4.4 release series is [1]GCC 4.4.7. Caveats * __builtin_stdarg_start has been completely removed from GCC. Support for had been deprecated since GCC 4.0. Use __builtin_va_start as a replacement. * Some of the errors issued by the C++ front end that could be downgraded to warnings in previous releases by using -fpermissive are now warnings by default. They can be converted into errors by using -pedantic-errors. * Use of the cpp assertion extension will now emit a warning when -Wdeprecated or -pedantic is used. This extension has been deprecated for many years, but never warned about. * Packed bit-fields of type char were not properly bit-packed on many targets prior to GCC 4.4. On these targets, the fix in GCC 4.4 causes an ABI change. For example there is no longer a 4-bit padding between field a and b in this structure: struct foo { char a:4; char b:8; } __attribute__ ((packed)); There is a new warning to help identify fields that are affected: foo.c:5: note: Offset of packed bit-field 'b' has changed in GCC 4.4 The warning can be disabled with -Wno-packed-bitfield-compat. * On ARM EABI targets, the C++ mangling of the va_list type has been changed to conform to the current revision of the EABI. This does not affect the libstdc++ library included with GCC. * The SCOUNT and POS bits of the MIPS DSP control register are now treated as global. Previous versions of GCC treated these fields as call-clobbered instead. * The MIPS port no longer recognizes the h asm constraint. It was necessary to remove this constraint in order to avoid generating unpredictable code sequences. One of the main uses of the h constraint was to extract the high part of a multiplication on 64-bit targets. For example: asm ("dmultu\t%1,%2" : "=h" (result) : "r" (x), "r" (y)); You can now achieve the same effect using 128-bit types: typedef unsigned int uint128_t __attribute__((mode(TI))); result = ((uint128_t) x * y) >> 64; The second sequence is better in many ways. For example, if x and y are constants, the compiler can perform the multiplication at compile time. If x and y are not constants, the compiler can schedule the runtime multiplication better than it can schedule an asm statement. * Support for a number of older systems and recently unmaintained or untested target ports of GCC has been declared obsolete in GCC 4.4. Unless there is activity to revive them, the next release of GCC will have their sources permanently removed. The following ports for individual systems on particular architectures have been obsoleted: + Generic a.out on IA32 and m68k (i[34567]86-*-aout*, m68k-*-aout*) + Generic COFF on ARM, H8300, IA32, m68k and SH (arm-*-coff*, armel-*-coff*, h8300-*-*, i[34567]86-*-coff*, m68k-*-coff*, sh-*-*). This does not affect other more specific targets using the COFF object format on those architectures, or the more specific H8300 and SH targets (h8300-*-rtems*, h8300-*-elf*, sh-*-elf*, sh-*-symbianelf*, sh-*-linux*, sh-*-netbsdelf*, sh-*-rtems*, sh-wrs-vxworks). + 2BSD on PDP-11 (pdp11-*-bsd) + AIX 4.1 and 4.2 on PowerPC (rs6000-ibm-aix4.[12]*, powerpc-ibm-aix4.[12]*) + Tuning support for Itanium1 (Merced) variants. Note that code tuned for Itanium2 should also run correctly on Itanium1. * The protoize and unprotoize utilities have been obsoleted and will be removed in GCC 4.5. These utilities have not been installed by default since GCC 3.0. * Support has been removed for all the [2]configurations obsoleted in GCC 4.3. * Unknown -Wno-* options are now silently ignored by GCC if no other diagnostics are issued. If other diagnostics are issued, then GCC warns about the unknown options. * More information on porting to GCC 4.4 from previous versions of GCC can be found in the [3]porting guide for this release. General Optimizer Improvements * A new command-line switch -findirect-inlining has been added. When turned on it allows the inliner to also inline indirect calls that are discovered to have known targets at compile time thanks to previous inlining. * A new command-line switch -ftree-switch-conversion has been added. This new pass turns simple initializations of scalar variables in switch statements into initializations from a static array, given that all the values are known at compile time and the ratio between the new array size and the original switch branches does not exceed the parameter --param switch-conversion-max-branch-ratio (default is eight). * A new command-line switch -ftree-builtin-call-dce has been added. This optimization eliminates unnecessary calls to certain builtin functions when the return value is not used, in cases where the calls can not be eliminated entirely because the function may set errno. This optimization is on by default at -O2 and above. * A new command-line switch -fconserve-stack directs the compiler to minimize stack usage even if it makes the generated code slower. This affects inlining decisions. * When the assembler supports it, the compiler will now emit unwind information using assembler .cfi directives. This makes it possible to use such directives in inline assembler code. The new option -fno-dwarf2-cfi-asm directs the compiler to not use .cfi directives. * The [4]Graphite branch has been merged. This merge has brought in a new framework for loop optimizations based on a polyhedral intermediate representation. These optimizations apply to all the languages supported by GCC. The following new code transformations are available in GCC 4.4: + -floop-interchange performs loop interchange transformations on loops. Interchanging two nested loops switches the inner and outer loops. For example, given a loop like: DO J = 1, M DO I = 1, N A(J, I) = A(J, I) * C ENDDO ENDDO loop interchange will transform the loop as if the user had written: DO I = 1, N DO J = 1, M A(J, I) = A(J, I) * C ENDDO ENDDO which can be beneficial when N is larger than the caches, because in Fortran, the elements of an array are stored in memory contiguously by column, and the original loop iterates over rows, potentially creating at each access a cache miss. + -floop-strip-mine performs loop strip mining transformations on loops. Strip mining splits a loop into two nested loops. The outer loop has strides equal to the strip size and the inner loop has strides of the original loop within a strip. For example, given a loop like: DO I = 1, N A(I) = A(I) + C ENDDO loop strip mining will transform the loop as if the user had written: DO II = 1, N, 4 DO I = II, min (II + 3, N) A(I) = A(I) + C ENDDO ENDDO + -floop-block performs loop blocking transformations on loops. Blocking strip mines each loop in the loop nest such that the memory accesses of the element loops fit inside caches. For example, given a loop like: DO I = 1, N DO J = 1, M A(J, I) = B(I) + C(J) ENDDO ENDDO loop blocking will transform the loop as if the user had written: DO II = 1, N, 64 DO JJ = 1, M, 64 DO I = II, min (II + 63, N) DO J = JJ, min (JJ + 63, M) A(J, I) = B(I) + C(J) ENDDO ENDDO ENDDO ENDDO which can be beneficial when M is larger than the caches, because the innermost loop will iterate over a smaller amount of data that can be kept in the caches. * A new register allocator has replaced the old one. It is called integrated register allocator (IRA) because coalescing, register live range splitting, and hard register preferencing are done on-the-fly during coloring. It also has better integration with the reload pass. IRA is a regional register allocator which uses modern Chaitin-Briggs coloring instead of Chow's priority coloring used in the old register allocator. More info about IRA internals and options can be found in the GCC manuals. * A new instruction scheduler and software pipeliner, based on the selective scheduling approach, has been added. The new pass performs instruction unification, register renaming, substitution through register copies, and speculation during scheduling. The software pipeliner is able to pipeline non-countable loops. The new pass is targeted at scheduling-eager in-order platforms. In GCC 4.4 it is available for the Intel Itanium platform working by default as the second scheduling pass (after register allocation) at the -O3 optimization level. * When using -fprofile-generate with a multi-threaded program, the profile counts may be slightly wrong due to race conditions. The new -fprofile-correction option directs the compiler to apply heuristics to smooth out the inconsistencies. By default the compiler will give an error message when it finds an inconsistent profile. * The new -fprofile-dir=PATH option permits setting the directory where profile data files are stored when using -fprofile-generate and friends, and the directory used when reading profile data files using -fprofile-use and friends. New warning options * The new -Wframe-larger-than=NUMBER option directs GCC to emit a warning if any stack frame is larger than NUMBER bytes. This may be used to help ensure that code fits within a limited amount of stack space. * The command-line option -Wlarger-than-N is now written as -Wlarger-than=N and the old form is deprecated. * The new -Wno-mudflap option disables warnings about constructs which can not be instrumented when using -fmudflap. New Languages and Language specific improvements * Version 3.0 of the OpenMP specification is now supported for the C, C++, and Fortran compilers. * New character data types, per [5]TR 19769: New character types in C, are now supported for the C compiler in -std=gnu99 mode, as __CHAR16_TYPE__ and __CHAR32_TYPE__, and for the C++ compiler in -std=c++0x and -std=gnu++0x modes, as char16_t and char32_t too. C family * A new optimize attribute was added to allow programmers to change the optimization level and particular optimization options for an individual function. You can also change the optimization options via the GCC optimize pragma for functions defined after the pragma. The GCC push_options pragma and the GCC pop_options pragma allow you temporarily save and restore the options used. The GCC reset_options pragma restores the options to what was specified on the command line. * Uninitialized warnings do not require enabling optimization anymore, that is, -Wuninitialized can be used together with -O0. Nonetheless, the warnings given by -Wuninitialized will probably be more accurate if optimization is enabled. * -Wparentheses now warns about expressions such as (!x | y) and (!x & y). Using explicit parentheses, such as in ((!x) | y), silences this warning. * -Wsequence-point now warns within if, while,do while and for conditions, and within for begin/end expressions. * A new option -dU is available to dump definitions of preprocessor macros that are tested or expanded. C++ * [6]Improved experimental support for the upcoming ISO C++ standard, C++0x. Including support for auto, inline namespaces, generalized initializer lists, defaulted and deleted functions, new character types, and scoped enums. * Those errors that may be downgraded to warnings to build legacy code now mention -fpermissive when -fdiagnostics-show-option is enabled. * -Wconversion now warns if the result of a static_cast to enumeral type is unspecified because the value is outside the range of the enumeral type. * -Wuninitialized now warns if a non-static reference or non-static const member appears in a class without constructors. * G++ now properly implements value-initialization, so objects with an initializer of () and an implicitly defined default constructor will be zero-initialized before the default constructor is called. Runtime Library (libstdc++) * Improved experimental support for the upcoming ISO C++ standard, C++0x, including: + Support for , , , , , , , , and . + unique_ptr, additions, exception propagation, and support for the new character types in and . + Existing facilities now exploit initializer lists, defaulted and deleted functions, and the newly implemented core C++0x features. + Some standard containers are more efficient together with stateful allocators, i.e., no allocator is constructed on the fly at element construction time. * Experimental support for non-standard pointer types in containers. * The long standing libstdc++/30928 has been fixed for targets running glibc 2.10 or later. * As usual, many small and larger bug fixes, in particular quite a few corner cases in . Fortran * GNU Fortran now employs libcpp directly instead of using cc1 as an external preprocessor. The [7]-cpp option was added to allow manual invocation of the preprocessor without relying on filename extensions. * The [8]-Warray-temporaries option warns about array temporaries generated by the compiler, as an aid to optimization. * The [9]-fcheck-array-temporaries option has been added, printing a notification at run time, when an array temporary had to be created for an function argument. Contrary to -Warray-temporaries the warning is only printed if the array is noncontiguous. * Improved generation of DWARF debugging symbols * If using an intrinsic not part of the selected standard (via -std= and -fall-intrinsics) gfortran will now treat it as if this procedure were declared EXTERNAL and try to link to a user-supplied procedure. -Wintrinsics-std will warn whenever this happens. The now-useless option -Wnonstd-intrinsic was removed. * The flag -falign-commons has been added to control the alignment of variables in COMMON blocks, which is enabled by default in line with previous GCC version. Using -fno-align-commons one can force commons to be contiguous in memory as required by the Fortran standard, however, this slows down the memory access. The option -Walign-commons, which is enabled by default, warns when padding bytes were added for alignment. The proper solution is to sort the common objects by decreasing storage size, which avoids the alignment problems. * Fortran 2003 support has been extended: + Wide characters (ISO 10646, UCS-4, kind=4) and UTF-8 I/O is now supported (except internal reads from/writes to wide strings). [10]-fbackslash now supports also \unnnn and \Unnnnnnnn to enter Unicode characters. + Asynchronous I/O (implemented as synchronous I/O) and the decimal=, size=, sign=, pad=, blank=, and delim= specifiers are now supported in I/O statements. + Support for Fortran 2003 structure constructors and for array constructor with typespec has been added. + Procedure Pointers (but not yet as component in derived types and as function results) are now supported. + Abstract types, type extension, and type-bound procedures (both PROCEDURE and GENERIC but not as operators). Note: As CLASS/polymorphyic types are not implemented, type-bound procedures with PASS accept as non-standard extension TYPE arguments. * Fortran 2008 support has been added: + The -std=f2008 option and support for the file extensions .f2008 and .F2008 has been added. + The g0 format descriptor is now supported. + The Fortran 2008 mathematical intrinsics ASINH, ACOSH, ATANH, ERF, ERFC, GAMMA, LOG_GAMMA, BESSEL_*, HYPOT, and ERFC_SCALED are now available (some of them existed as GNU extension before). Note: The hyperbolic functions are not yet supporting complex arguments and the three- argument version of BESSEL_*N is not available. + The bit intrinsics LEADZ and TRAILZ have been added. Java (GCJ) Ada * The Ada runtime now supports multilibs on many platforms including x86_64, SPARC and PowerPC. Their build is enabled by default. New Targets and Target Specific Improvements ARM * GCC now supports optimizing for the Cortex-A9, Cortex-R4 and Cortex-R4F processors and has many other improvements to optimization for ARM processors. * GCC now supports the VFPv3 variant with 16 double-precision registers with -mfpu=vfpv3-d16. The option -mfpu=vfp3 has been renamed to -mfpu=vfpv3. * GCC now supports the -mfix-cortex-m3-ldrd option to work around an erratum on Cortex-M3 processors. * GCC now supports the __sync_* atomic operations for ARM EABI GNU/Linux. * The section anchors optimization is now enabled by default when optimizing for ARM. * GCC now uses a new EABI-compatible profiling interface for EABI targets. This requires a function __gnu_mcount_nc, which is provided by GNU libc versions 2.8 and later. AVR * The -mno-tablejump option has been deprecated because it has the same effect as the -fno-jump-tables option. * Added support for these new AVR devices: + ATA6289 + ATtiny13A + ATtiny87 + ATtiny167 + ATtiny327 + ATmega8C1 + ATmega16C1 + ATmega32C1 + ATmega8M1 + ATmega16M1 + ATmega32M1 + ATmega32U4 + ATmega16HVB + ATmega4HVD + ATmega8HVD + ATmega64C1 + ATmega64M1 + ATmega16U4 + ATmega32U6 + ATmega128RFA1 + AT90PWM81 + AT90SCR100 + M3000F + M3000S + M3001B IA-32/x86-64 * Support for Intel AES built-in functions and code generation is available via -maes. * Support for Intel PCLMUL built-in function and code generation is available via -mpclmul. * Support for Intel AVX built-in functions and code generation is available via -mavx. * Automatically align the stack for local variables with alignment requirement. * GCC can now utilize the SVML library for vectorizing calls to a set of C99 functions if -mveclibabi=svml is specified and you link to an SVML ABI compatible library. * On x86-64, the ABI has been changed in the following cases to conform to the x86-64 ABI: + Passing/returning structures with flexible array member: struct foo { int i; int flex[]; }; + Passing/returning structures with complex float member: struct foo { int i; __complex__ float f; }; + Passing/returning unions with long double member: union foo { int x; long double ld; }; Code built with previous versions of GCC that uses any of these is not compatible with code built with GCC 4.4.0 or later. * A new target attribute was added to allow programmers to change the target options like -msse2 or -march=k8 for an individual function. You can also change the target options via the GCC target pragma for functions defined after the pragma. * GCC can now be configured with options --with-arch-32, --with-arch-64, --with-cpu-32, --with-cpu-64, --with-tune-32 and --with-tune-64 to control the default optimization separately for 32-bit and 64-bit modes. IA-32/IA64 * Support for __float128 (TFmode) IEEE quad type and corresponding TCmode IEEE complex quad type is available via the soft-fp library on IA-32/IA64 targets. This includes basic arithmetic operations (addition, subtraction, negation, multiplication and division) on __float128 real and TCmode complex values, the full set of IEEE comparisons between __float128 values, conversions to and from float, double and long double floating point types, as well as conversions to and from signed or unsigned integer, signed or unsigned long integer and signed or unsigned quad (TImode, IA64 only) integer types. Additionally, all operations generate the full set of IEEE exceptions and support the full set of IEEE rounding modes. M68K/ColdFire * GCC now supports instruction scheduling for ColdFire V1, V3 and V4 processors. (Scheduling support for ColdFire V2 processors was added in GCC 4.3.) * GCC now supports the -mxgot option to support programs requiring many GOT entries on ColdFire. * The m68k-*-linux-gnu target now builds multilibs by default. MIPS * MIPS Technologies have extended the original MIPS SVR4 ABI to include support for procedure linkage tables (PLTs) and copy relocations. These extensions allow GNU/Linux executables to use a significantly more efficient code model than the one defined by the original ABI. GCC support for this code model is available via a new command-line option, -mplt. There is also a new configure-time option, --with-mips-plt, to make -mplt the default. The new code model requires support from the assembler, the linker, and the runtime C library. This support is available in binutils 2.19 and GLIBC 2.9. * GCC can now generate MIPS16 code for 32-bit GNU/Linux executables and 32-bit GNU/Linux shared libraries. This feature requires GNU binutils 2.19 or above. * Support for RMI's XLR processor is now available through the -march=xlr and -mtune=xlr options. * 64-bit targets can now perform 128-bit multiplications inline, instead of relying on a libgcc function. * Native GNU/Linux toolchains now support -march=native and -mtune=native, which select the host processor. * GCC now supports the R10K, R12K, R14K and R16K processors. The canonical -march= and -mtune= names for these processors are r10000, r12000, r14000 and r16000 respectively. * GCC can now work around the side effects of speculative execution on R10K processors. Please see the documentation of the -mr10k-cache-barrier option for details. * Support for the MIPS64 Release 2 instruction set has been added. The option -march=mips64r2 enables generation of these instructions. * GCC now supports Cavium Networks' Octeon processor. This support is available through the -march=octeon and -mtune=octeon options. * GCC now supports STMicroelectronics' Loongson 2E/2F processors. The canonical -march= and -mtune= names for these processors are loongson2e and loongson2f. picochip Picochip is a 16-bit processor. A typical picoChip contains over 250 small cores, each with small amounts of memory. There are three processor variants (STAN, MEM and CTRL) with different instruction sets and memory configurations and they can be chosen using the -mae option. This port is intended to be a "C" only port. Power Architecture and PowerPC * GCC now supports the e300c2, e300c3 and e500mc processors. * GCC now supports Xilinx processors with a single-precision FPU. * Decimal floating point is now supported for e500 processors. S/390, zSeries and System z9/z10 * Support for the IBM System z10 EC/BC processor has been added. When using the -march=z10 option, the compiler will generate code making use of instructions provided by the General-Instruction-Extension Facility and the Execute-Extension Facility. VxWorks * GCC now supports the thread-local storage mechanism used on VxWorks. Xtensa * GCC now supports thread-local storage (TLS) for Xtensa processor configurations that include the Thread Pointer option. TLS also requires support from the assembler and linker; this support is provided in the GNU binutils beginning with version 2.19. Documentation improvements Other significant improvements GCC 4.4.1 This is the [11]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.4.1 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.4.2 This is the [12]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.4.2 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.4.3 This is the [13]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.4.3 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.4.4 This is the [14]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.4.4 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.4.5 This is the [15]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.4.5 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.4.6 This is the [16]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.4.6 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.4.7 This is the [17]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.4.7 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). For questions related to the use of GCC, please consult these web pages and the [18]GCC manuals. If that fails, the [19]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [20]gcc@gcc.gnu.org. All of [21]our lists have public archives. Copyright (C) [22]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [23]maintained by the GCC team. Last modified 2022-11-01. References 1. https://gcc.gnu.org/gcc-4.4/changes.html#4.4.7 2. https://gcc.gnu.org/gcc-4.3/changes.html#obsoleted 3. https://gcc.gnu.org/gcc-4.4/porting_to.html 4. https://gcc.gnu.org/wiki/Graphite 5. https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1040.pdf 6. https://gcc.gnu.org/gcc-4.4/cxx0x_status.html 7. https://gcc.gnu.org/onlinedocs/gfortran/Preprocessing-Options.html 8. https://gcc.gnu.org/onlinedocs/gfortran/Error-and-Warning-Options.html#index-g_t_0040code_007bWarray-temporaries_007d-125 9. https://gcc.gnu.org/onlinedocs/gfortran/Code-Gen-Options.html#index-g_t_0040code_007bfcheck-array-temporaries_007d-221 10. https://gcc.gnu.org/onlinedocs/gfortran/Fortran-Dialect-Options.html#index-g_t_0040code_007bbackslash_007d-34 11. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.4.1 12. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.4.2 13. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.4.3 14. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.4.4 15. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.4.5 16. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.4.6 17. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.4.7 18. https://gcc.gnu.org/onlinedocs/ 19. mailto:gcc-help@gcc.gnu.org 20. mailto:gcc@gcc.gnu.org 21. https://gcc.gnu.org/lists.html 22. https://www.fsf.org/ 23. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.3/index.html GCC 4.3 Release Series (This release series is no longer supported.) Jun 27, 2011 The [1]GNU project and the GCC developers are pleased to announce the release of GCC 4.3.6. This release is a bug-fix release, containing fixes for regressions in GCC 4.3.5 relative to previous releases of GCC. Release History GCC 4.3.6 Jun 27, 2011 ([2]changes) GCC 4.3.5 May 22, 2010 ([3]changes) GCC 4.3.4 August 4, 2009 ([4]changes) GCC 4.3.3 January 24, 2009 ([5]changes) GCC 4.3.2 August 27, 2008 ([6]changes) GCC 4.3.1 June 6, 2008 ([7]changes) GCC 4.3.0 March 5, 2008 ([8]changes) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. A list of [9]successful builds is updated as new information becomes available. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [10]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [11]GCC project web site or contact the [12]GCC development mailing list. To obtain GCC please use [13]our mirror sites or [14]our version control system. For questions related to the use of GCC, please consult these web pages and the [15]GCC manuals. If that fails, the [16]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [17]gcc@gcc.gnu.org. All of [18]our lists have public archives. Copyright (C) [19]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [20]maintained by the GCC team. Last modified 2022-10-26. References 1. http://www.gnu.org/ 2. https://gcc.gnu.org/gcc-4.3/changes.html 3. https://gcc.gnu.org/gcc-4.3/changes.html 4. https://gcc.gnu.org/gcc-4.3/changes.html 5. https://gcc.gnu.org/gcc-4.3/changes.html 6. https://gcc.gnu.org/gcc-4.3/changes.html 7. https://gcc.gnu.org/gcc-4.3/changes.html 8. https://gcc.gnu.org/gcc-4.3/changes.html 9. https://gcc.gnu.org/gcc-4.3/buildstat.html 10. https://gcc.gnu.org/onlinedocs/gcc/Contributors.html 11. https://gcc.gnu.org/index.html 12. mailto:gcc@gcc.gnu.org 13. https://gcc.gnu.org/mirrors.html 14. https://gcc.gnu.org/git.html 15. https://gcc.gnu.org/onlinedocs/ 16. mailto:gcc-help@gcc.gnu.org 17. mailto:gcc@gcc.gnu.org 18. https://gcc.gnu.org/lists.html 19. https://www.fsf.org/ 20. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.3/changes.html GCC 4.3 Release Series Changes, New Features, and Fixes The latest release in the 4.3 release series is [1]GCC 4.3.5. Caveats * GCC requires the [2]GMP and [3]MPFR libraries for building all the various front-end languages it supports. See the [4]prerequisites page for version requirements. * ColdFire targets now treat long double as having the same format as double. In earlier versions of GCC, they used the 68881 long double format instead. * The m68k-uclinux target now uses the same calling conventions as m68k-linux-gnu. You can select the original calling conventions by configuring for m68k-uclinuxoldabi instead. Note that m68k-uclinuxoldabi also retains the original 80-bit long double on ColdFire targets. * The -fforce-mem option has been removed because it has had no effect in the last few GCC releases. * The i386 -msvr3-shlib option has been removed since it is no longer used. * Fastcall for i386 has been changed not to pass aggregate arguments in registers, following Microsoft compilers. * Support for the AOF assembler has been removed from the ARM back end; this affects only the targets arm-semi-aof and armel-semi-aof, which are no longer recognized. We removed these targets without a deprecation period because we discovered that they have been unusable since GCC 4.0.0. * Support for the TMS320C3x/C4x processor (targets c4x-* and tic4x-*) has been removed. This support had been deprecated since GCC 4.0.0. * Support for a number of older systems and recently unmaintained or untested target ports of GCC has been declared obsolete in GCC 4.3. Unless there is activity to revive them, the next release of GCC will have their sources permanently removed. All GCC ports for the following processor architectures have been declared obsolete: + Morpho MT (mt-*) The following aliases for processor architectures have been declared obsolete. Users should use the indicated generic target names instead, with compile-time options such as -mcpu or configure-time options such as --with-cpu to control the configuration more precisely. + strongarm*-*-*, ep9312*-*-*, xscale*-*-* (use arm*-*-* instead). + parisc*-*-* (use hppa*-*-* instead). + m680[012]0-*-* (use m68k-*-* instead). All GCC ports for the following operating systems have been declared obsolete: + BeOS (*-*-beos*) + kaOS (*-*-kaos*) + GNU/Linux using the a.out object format (*-*-linux*aout*) + GNU/Linux using version 1 of the GNU C Library (*-*-linux*libc1*) + Solaris versions before Solaris 7 (*-*-solaris2.[0-6], *-*-solaris2.[0-6].*) + Miscellaneous System V (*-*-sysv*) + WindISS (*-*-windiss*) Also, those for some individual systems on particular architectures have been obsoleted: + UNICOS/mk on DEC Alpha (alpha*-*-unicosmk*) + CRIS with a.out object format (cris-*-aout) + BSD 4.3 on PA-RISC (hppa1.1-*-bsd*) + OSF/1 on PA-RISC (hppa1.1-*-osf*) + PRO on PA-RISC (hppa1.1-*-pro*) + Sequent PTX on IA32 (i[34567]86-sequent-ptx4*, i[34567]86-sequent-sysv4*) + SCO Open Server 5 on IA32 (i[34567]86-*-sco3.2v5*) + UWIN on IA32 (i[34567]86-*-uwin*) (support for UWIN as a host was previously [5]removed in 2001, leaving only the support for UWIN as a target now being deprecated) + ChorusOS on PowerPC (powerpc-*-chorusos*) + All VAX configurations apart from NetBSD and OpenBSD (vax-*-bsd*, vax-*-sysv*, vax-*-ultrix*) * The [6]-Wconversion option has been modified. Its purpose now is to warn for implicit conversions that may alter a value. This new behavior is available for both C and C++. Warnings about conversions between signed and unsigned integers can be disabled by using -Wno-sign-conversion. In C++, they are disabled by default unless -Wsign-conversion is explicitly requested. The old behavior of -Wconversion, that is, warn for prototypes causing a type conversion that is different from what would happen to the same argument in the absence of a prototype, has been moved to a new option -Wtraditional-conversion, which is only available for C. * The -m386, -m486, -mpentium and -mpentiumpro tuning options have been removed because they were deprecated for more than 3 GCC major releases. Use -mtune=i386, -mtune=i486, -mtune=pentium or -mtune=pentiumpro as a replacement. * The -funsafe-math-optimizations option now automatically turns on -fno-trapping-math in addition to -fno-signed-zeros, as it enables reassociation and thus may introduce or remove traps. * The -ftree-vectorize option is now on by default under -O3. In order to generate code for a SIMD extension, it has to be enabled as well: use -maltivec for PowerPC platforms and -msse/-msse2 for i?86 and x86_64. * More information on porting to GCC 4.3 from previous versions of GCC can be found in the [7]porting guide for this release. General Optimizer Improvements * The GCC middle-end has been integrated with the MPFR library. This allows GCC to evaluate and replace at compile-time calls to built-in math functions having constant arguments with their mathematically equivalent results. In making use of MPFR, GCC can generate correct results regardless of the math library implementation or floating point precision of the host platform. This also allows GCC to generate identical results regardless of whether one compiles in native or cross-compile configurations to a particular target. The following built-in functions take advantage of this new capability: acos, acosh, asin, asinh, atan2, atan, atanh, cbrt, cos, cosh, drem, erf, erfc, exp10, exp2, exp, expm1, fdim, fma, fmax, fmin, gamma_r, hypot, j0, j1, jn, lgamma_r, log10, log1p, log2, log, pow10, pow, remainder, remquo, sin, sincos, sinh, tan, tanh, tgamma, y0, y1 and yn. The float and long double variants of these functions (e.g. sinf and sinl) are also handled. The sqrt and cabs functions with constant arguments were already optimized in prior GCC releases. Now they also use MPFR. * A new forward propagation pass on RTL was added. The new pass replaces several slower transformations, resulting in compile-time improvements as well as better code generation in some cases. * A new command-line switch -frecord-gcc-switches has been added to GCC, although it is only enabled for some targets. The switch causes the command line that was used to invoke the compiler to be recorded into the object file that is being created. The exact format of this recording is target and binary file format dependent, but it usually takes the form of a note section containing ASCII text. The switch is related to the -fverbose-asm switch, but that one only records the information in the assembler output file as comments, so the information never reaches the object file. * The inliner heuristic is now aware of stack frame consumption. New command-line parameters --param large-stack-frame and --param large-stack-frame-growth can be used to limit stack frame size growth caused by inlining. * During feedback directed optimizations, the expected block size the memcpy, memset and bzero functions operate on is discovered and for cases of commonly used small sizes, specialized inline code is generated. * __builtin_expect no longer requires its argument to be a compile time constant. * Interprocedural optimization was reorganized to work on functions in SSA form. This enables more precise and cheaper dataflow analysis and makes writing interprocedural optimizations easier. The following improvements have been implemented on top of this framework: + Pre-inline optimization: Selected local optimization passes are run before the inliner (and other interprocedural passes) are executed. This significantly improves the accuracy of code growth estimates used by the inliner and reduces the overall memory footprint for large compilation units. + Early inlining (a simple bottom-up inliner pass inlining only functions whose body is smaller than the expected call overhead) is now executed with the early optimization passes, thus inlining already optimized function bodies into an unoptimized function that is subsequently optimized by early optimizers. This enables the compiler to quickly eliminate abstraction penalty in C++ programs. + Interprocedural constant propagation now operate on SSA form increasing accuracy of the analysis. * A new internal representation for GIMPLE statements has been contributed, resulting in compile-time memory savings. * The vectorizer was enhanced to support vectorization of outer loops, intra-iteration parallelism (loop-aware SLP), vectorization of strided accesses and loops with multiple data-types. Run-time dependency testing using loop versioning was added. The cost model, turned on by -fvect-cost-model, was developed. New Languages and Language specific improvements * We have added new command-line options -finstrument-functions-exclude-function-list and -finstrument-functions-exclude-file-list. They provide more control over which functions are annotated by the -finstrument-functions option. C family * Implicit conversions between generic vector types are now only permitted when the two vectors in question have the same number of elements and compatible element types. (Note that the restriction involves compatible element types, not implicitly-convertible element types: thus, a vector type with element type int may not be implicitly converted to a vector type with element type unsigned int.) This restriction, which is in line with specifications for SIMD architectures such as AltiVec, may be relaxed using the flag -flax-vector-conversions. This flag is intended only as a compatibility measure and should not be used for new code. * -Warray-bounds has been added and is now enabled by default for -Wall . It produces warnings for array subscripts that can be determined at compile time to be always out of bounds. -Wno-array-bounds will disable the warning. * The constructor and destructor function attributes now accept optional priority arguments which control the order in which the constructor and destructor functions are run. * New [8]command-line options -Wtype-limits, -Wold-style-declaration, -Wmissing-parameter-type, -Wempty-body, -Wclobbered and -Wignored-qualifiers have been added for finer control of the diverse warnings enabled by -Wextra. * A new function attribute alloc_size has been added to mark up malloc style functions. For constant sized allocations this can be used to find out the size of the returned pointer using the __builtin_object_size() function for buffer overflow checking and similar. This supplements the already built-in malloc and calloc constant size handling. * Integer constants written in binary are now supported as a GCC extension. They consist of a prefix 0b or 0B, followed by a sequence of 0 and 1 digits. * A new predefined macro __COUNTER__ has been added. It expands to sequential integral values starting from 0. In conjunction with the ## operator, this provides a convenient means to generate unique identifiers. * A new command-line option -fdirectives-only has been added. It enables a special preprocessing mode which improves the performance of applications like distcc and ccache. * Fixed-point data types and operators have been added. They are based on Chapter 4 of the Embedded-C specification (n1169.pdf). Currently, only MIPS targets are supported. * Decimal floating-point arithmetic based on draft ISO/IEC TR 24732, N1241, is now supported as a GCC extension to C for targets i[34567]86-*-linux-gnu, powerpc*-*-linux-gnu, s390*-ibm-linux-gnu, and x86_64-*-linux-gnu. The feature introduces new data types _Decimal32, _Decimal64, and _Decimal128 with constant suffixes DF, DD, and DL. C++ * [9]Experimental support for the upcoming ISO C++ standard, C++0x. * -Wc++0x-compat has been added and is now enabled by default for -Wall. It produces warnings for constructs whose meaning differs between ISO C++ 1998 and C++0x. * The -Wparentheses option now works for C++ as it does for C. It warns if parentheses are omitted when operators with confusing precedence are nested. It also warns about ambiguous else statements. Since -Wparentheses is enabled by -Wall, this may cause additional warnings with existing C++ code which uses -Wall. These new warnings may be disabled by using -Wall -Wno-parentheses. * The -Wmissing-declarations now works for C++ as it does for C. * The -fvisibility-ms-compat flag was added, to make it easier to port larger projects using shared libraries from Microsoft's Visual Studio to ELF and Mach-O systems. * C++ attribute handling has been overhauled for template arguments (ie dependent types). In particular, __attribute__((aligned(T))); works for C++ types. Runtime Library (libstdc++) * [10]Experimental support for the upcoming ISO C++ standard, C++0x. * Support for TR1 mathematical special functions and regular expressions. * Default what implementations give more elaborate exception strings for bad_cast, bad_typeid, bad_exception, and bad_alloc. * Header dependencies have been streamlined, reducing unnecessary includes and pre-processed bloat. * Variadic template implementations of items in and . * An experimental [11]parallel mode has been added. This is a parallel implementation of many C++ Standard library algorithms, like std::accumulate, std::for_each, std::transform, or std::sort, to give but four examples. These algorithms can be substituted for the normal (sequential) libstdc++ algorithms on a piecemeal basis, or all existing algorithms can be transformed via the -D_GLIBCXX_PARALLEL macro. * Debug mode versions of classes in and . * Formal deprecation of and , which are now and . This code: #include __gnu_cxx::hash_set s; Can be transformed (in order of preference) to: #include std::tr1::unordered_set s; or #include __gnu_cxx::hash_set s; Similar transformations apply to __gnu_cxx::hash_map, __gnu_cxx::hash_multimap, __gnu_cxx::hash_set, __gnu_cxx::hash_multiset. Fortran * Due to the fact that the GMP and MPFR libraries are required for all languages, Fortran is no longer special in this regard and is available by default. * The [12]-fexternal-blas option has been added, which generates calls to BLAS routines for intrinsic matrix operations such as matmul rather than using the built-in algorithms. * Support to give a backtrace (compiler flag -fbacktrace or environment variable GFORTRAN_ERROR_BACKTRACE; on glibc systems only) or a core dump (-fdump-core, GFORTRAN_ERROR_DUMPCORE) when a run-time error occured. * GNU Fortran now defines __GFORTRAN__ when it runs the C preprocessor (CPP). * The [13]-finit-local-zero, -finit-real, -finit-integer, -finit-character, and -finit-logical options have been added, which can be used to initialize local variables. * The intrinsic procedures [14]GAMMA and [15]LGAMMA have been added, which calculate the Gamma function and its logarithm. Use EXTERNAL gamma if you want to use your own gamma function. * GNU Fortran now regards the backslash character as literal (as required by the Fortran 2003 standard); using [16]-fbackslash GNU Fortran interprets backslashes as C-style escape characters. * The [17]interpretation of binary, octal and hexadecimal (BOZ) literal constants has been changed. Before they were always interpreted as integer; now they are bit-wise transferred as argument of INT, REAL, DBLE and CMPLX as required by the Fortran 2003 standard, and for real and complex variables in DATA statements or when directly assigned to real and complex variables. Everywhere else and especially in expressions they are still regarded as integer constants. * Fortran 2003 support has been extended: + Intrinsic statements IMPORT, PROTECTED, VALUE and VOLATILE + Pointer intent + Intrinsic module ISO_ENV_FORTRAN + Interoperability with C (ISO C Bindings) + ABSTRACT INTERFACES and PROCEDURE statements (without POINTER attribute) + Fortran 2003 BOZ Java (GCJ) * GCJ now uses the Eclipse Java compiler for its Java parsing needs. This enables the use of all 1.5 language features, and fixes most existing front end bugs. * libgcj now supports all 1.5 language features which require runtime support: foreach, enum, annotations, generics, and auto-boxing. * We've made many changes to the tools shipped with gcj. + The old jv-scan tool has been removed. This tool never really worked properly. There is no replacement. + gcjh has been rewritten. Some of its more obscure options no longer work, but are still recognized in an attempt at compatibility. gjavah is a new program with similar functionality but different command-line options. + grmic and grmiregistry have been rewritten. grmid has been added. + gjar replaces the old fastjar. + gjarsigner (used for signing jars), gkeytool (used for key management), gorbd (for CORBA), gserialver (computes serialization UIDs), and gtnameserv (also for CORBA) are now installed. * The ability to dump the contents of the java run time heap to a file for off-line analysis has been added. The heap dumps may be analyzed with the new gc-analyze tool. They may be generated on out-of-memory conditions or on demand and are controlled by the new run time class gnu.gcj.util.GCInfo. * java.util.TimeZone can now read files from /usr/share/zoneinfo to provide correct, updated, timezone information. This means that packagers no longer have to update libgcj when a time zone change is published. New Targets and Target Specific Improvements IA-32/x86-64 * Tuning for Intel Core 2 processors is available via -mtune=core2 and -march=core2. * Tuning for AMD Geode processors is available via -mtune=geode and -march=geode. * Code generation of block move (memcpy) and block set (memset) was rewritten. GCC can now pick the best algorithm (loop, unrolled loop, instruction with rep prefix or a library call) based on the size of the block being copied and the CPU being optimized for. A new option -minline-stringops-dynamically has been added. With this option string operations of unknown size are expanded such that small blocks are copied by in-line code, while for large blocks a library call is used. This results in faster code than -minline-all-stringops when the library implementation is capable of using cache hierarchy hints. The heuristic choosing the particular algorithm can be overwritten via -mstringop-strategy. Newly also memset of values different from 0 is inlined. * GCC no longer places the cld instruction before string operations. Both i386 and x86-64 ABI documents mandate the direction flag to be clear at the entry of a function. It is now invalid to set the flag in asm statement without reseting it afterward. * Support for SSSE3 built-in functions and code generation are available via -mssse3. * Support for SSE4.1 built-in functions and code generation are available via -msse4.1. * Support for SSE4.2 built-in functions and code generation are available via -msse4.2. * Both SSE4.1 and SSE4.2 support can be enabled via -msse4. * A new set of options -mpc32, -mpc64 and -mpc80 have been added to allow explicit control of x87 floating point precision. * Support for __float128 (TFmode) IEEE quad type and corresponding TCmode IEEE complex quad type is available via the soft-fp library on x86_64 targets. This includes basic arithmetic operations (addition, subtraction, negation, multiplication and division) on __float128 real and TCmode complex values, the full set of IEEE comparisons between __float128 values, conversions to and from float, double and long double floating point types, as well as conversions to and from signed or unsigned integer, signed or unsigned long integer and signed or unsigned quad (TImode) integer types. Additionally, all operations generate the full set of IEEE exceptions and support the full set of IEEE rounding modes. * GCC can now utilize the ACML library for vectorizing calls to a set of C99 functions on x86_64 if -mveclibabi=acml is specified and you link to an ACML ABI compatible library. ARM * Compiler and Library support for Thumb-2 and the ARMv7 architecture has been added. CRIS New features * Compiler and Library support for the CRIS v32 architecture, as found in Axis Communications ETRAX FS and ARTPEC-3 chips, has been added. Configuration changes * The cris-*-elf target now includes support for CRIS v32, including libraries, through the -march=v32 option. * A new crisv32-*-elf target defaults to generate code for CRIS v32. * A new crisv32-*-linux* target defaults to generate code for CRIS v32. * The cris-*-aout target has been obsoleted. Improved support for built-in functions * GCC can now use the lz and swapwbr instructions to implement the __builtin_clz, __builtin_ctz and __builtin_ffs family of functions. * __builtin_bswap32 is now implemented using the swapwb instruction, when available. m68k and ColdFire New features * Support for several new ColdFire processors has been added. You can generate code for them using the new -mcpu option. * All targets now support ColdFire processors. * m68k-uclinux targets have improved support for C++ constructors and destructors, and for shared libraries. * It is now possible to set breakpoints on the first or last line of a function, even if there are no statements on that line. Optimizations * Support for sibling calls has been added. * More use is now made of the ColdFire mov3q instruction. * __builtin_clz is now implemented using the ff1 ColdFire instruction, when available. * GCC now honors the -m68010 option. 68010 code now uses clr rather than move to zero volatile memory. * 68020 targets and above can now use symbol(index.size*scale) addresses for indexed array accesses. Earlier compilers would always load the symbol into a base register first. Configuration changes * All m68k and ColdFire targets now allow the default processor to be set at configure time using --with-cpu. * A --with-arch configuration option has been added. This option allows you to restrict a target to ColdFire or non-ColdFire processors. Preprocessor macros * An __mcfv*__ macro is now defined for all ColdFire targets. (Earlier versions of GCC only defined __mcfv4e__.) * __mcf_cpu_*, __mcf_family_* and __mcffpu__ macros have been added. * All targets now define __mc68010 and __mc68010__ when generating 68010 code. Command-line changes * New command-line options -march, -mcpu, -mtune and -mhard-float have been added. These options apply to both m68k and ColdFire targets. * -mno-short, -mno-bitfield and -mno-rtd are now accepted as negative versions of -mshort, etc. * -fforce-addr has been removed. It is now ignored by the compiler. Other improvements * ColdFire targets now try to maintain a 4-byte-aligned stack where possible. * m68k-uclinux targets now try to avoid situations that lead to the load-time error: BINFMT_FLAT: reloc outside program. MIPS Changes to existing configurations * libffi and libjava now support all three GNU/Linux ABIs: o32, n32 and n64. Every GNU/Linux configuration now builds these libraries by default. * GNU/Linux configurations now generate -mno-shared code unless overridden by -fpic, -fPIC, -fpie or -fPIE. * mipsisa32*-linux-gnu configurations now generate hard-float code by default, just like other mipsisa32* and mips*-linux-gnu configurations. You can build a soft-float version of any mips*-linux-gnu configuration by passing --with-float=soft to configure. * mips-wrs-vxworks now supports run-time processes (RTPs). Changes to existing command-line options * The -march and -mtune options no longer accept 24k as a processor name. Please use 24kc, 24kf2_1 or 24kf1_1 instead. * The -march and -mtune options now accept 24kf2_1, 24kef2_1 and 34kf2_1 as synonyms for 24kf, 24kef and 34kf respectively. The options also accept 24kf1_1, 24kef1_1 and 34kf1_1 as synonyms for 24kx, 24kex and 34kx. New configurations GCC now supports the following configurations: * mipsisa32r2*-linux-gnu*, which generates MIPS32 revision 2 code by default. Earlier releases also recognized this configuration, but they treated it in the same way as mipsisa32*-linux-gnu*. Note that you can customize any mips*-linux-gnu* configuration to a particular ISA or processor by passing an appropriate --with-arch option to configure. * mipsisa*-sde-elf*, which provides compatibility with MIPS Technologies' SDE toolchains. The configuration uses the SDE libraries by default, but you can use it like other newlib-based ELF configurations by passing --with-newlib to configure. It is the only configuration besides mips64vr*-elf* to build MIPS16 as well as non-MIPS16 libraries. * mipsisa*-elfoabi*, which is similar to the general mipsisa*-elf* configuration, but uses the o32 and o64 ABIs instead of the 32-bit and 64-bit forms of the EABI. New processors and application-specific extensions * Support for the SmartMIPS ASE is available through the new -msmartmips option. * Support for revision 2 of the DSP ASE is available through the new -mdspr2 option. A new preprocessor macro called __mips_dsp_rev indicates the revision of the ASE in use. * Support for the 4KS and 74K families of processors is available through the -march and -mtune options. Improved support for built-in functions * GCC can now use load-linked, store-conditional and sync instructions to implement atomic built-in functions such as __sync_fetch_and_add. The memory reference must be 4 bytes wide for 32-bit targets and either 4 or 8 bytes wide for 64-bit targets. * GCC can now use the clz and dclz instructions to implement the __builtin_ctz and __builtin_ffs families of functions. * There is a new __builtin___clear_cache function for flushing the instruction cache. GCC expands this function inline on MIPS32 revision 2 targets, otherwise it calls the function specified by -mcache-flush-func. MIPS16 improvements * GCC can now compile objects that contain a mixture of MIPS16 and non-MIPS16 code. There are two new attributes, mips16 and nomips16, for specifying which mode a function should use. * A new option called -minterlink-mips16 makes non-MIPS16 code link-compatible with MIPS16 code. * After many bug fixes, the long-standing MIPS16 -mhard-float support should now work fairly reliably. * GCC can now use the MIPS16e save and restore instructions. * -fsection-anchors now works in MIPS16 mode. MIPS16 code compiled with -G0 -fsection-anchors is often smaller than code compiled with -G8. However, please note that you must usually compile all objects in your application with the same -G option; see the documentation of -G for details. * A new option called-mcode-readable specifies which instructions are allowed to load from the code segment. -mcode-readable=yes is the default and says that any instruction may load from the code segment. The other alternatives are -mcode-readable=pcrel, which says that only PC-relative MIPS16 instructions may load from the code segment, and -mcode-readable=no, which says that no instruction may do so. Please see the documentation for more details, including example uses. Small-data improvements There are three new options for controlling small data: * -mno-extern-sdata, which disables small-data accesses for externally-defined variables. Code compiled with -Gn -mno-extern-sdata will be link-compatible with any -G setting between -G0 and -Gn inclusive. * -mno-local-sdata, which disables the use of small-data sections for data that is not externally visible. This option can be a useful way of reducing small-data usage in less performance-critical parts of an application. * -mno-gpopt, which disables the use of the $gp register while still honoring the -G limit when placing externally-visible data. This option implies -mno-extern-sdata and -mno-local-sdata and it can be useful in situations where $gp does not necessarily hold the expected value. Miscellaneous improvements * There is a new option called -mbranch-cost for tweaking the perceived cost of branches. * If GCC is configured to use a version of GAS that supports the .gnu_attribute directive, it will use that directive to record certain properties of the output code. .gnu_attribute is new to GAS 2.18. * There are two new function attributes, near and far, for overriding the command-line setting of -mlong-calls on a function-by-function basis. * -mfp64, which previously required a 64-bit target, now works with MIPS32 revision 2 targets as well. The mipsisa*-elfoabi* and mipsisa*-sde-elf* configurations provide suitable library support. * GCC now recognizes the -mdmx and -mmt options and passes them down to the assembler. It does nothing else with the options at present. SPU (Synergistic Processor Unit) of the Cell Broadband Engine Architecture (BEA) * Support has been added for this new architecture. RS6000 (POWER/PowerPC) * Support for the PowerPC 750CL paired-single instructions has been added with a new powerpc-*-linux*paired* target configuration. It is enabled by an associated -mpaired option and can be accessed using new built-in functions. * Support for auto-detecting architecture and system configuration to auto-select processor optimization tuning. * Support for VMX on AIX 5.3 has been added. * Support for AIX Version 6.1 has been added. S/390, zSeries and System z9 * Support for the IBM System z9 EC/BC processor (z9 GA3) has been added. When using the -march=z9-ec option, the compiler will generate code making use of instructions provided by the decimal floating point facility and the floating point conversion facility (pfpo). Besides the instructions used to implement decimal floating point operations these facilities also contain instructions to move between general purpose and floating point registers and to modify and copy the sign-bit of floating point values. * When the -march=z9-ec option is used the new -mhard-dfp/-mno-hard-dfp options can be used to specify whether the decimal floating point hardware instructions will be used or not. If none of them is given the hardware support is enabled by default. * The -mstack-guard option can now be omitted when using stack checking via -mstack-size in order to let GCC choose a sensible stack guard value according to the frame size of each function. * Various changes to improve performance of generated code have been implemented, including: + The condition code set by an add logical with carry instruction is now available for overflow checks like: a + b + carry < b. + The test data class instruction is now used to implement sign-bit and infinity checks of binary and decimal floating point numbers. SPARC * Support for the Sun UltraSPARC T2 (Niagara 2) processor has been added. Xtensa * Stack unwinding for exception handling now uses by default a specialized version of DWARF unwinding. This is not binary-compatible with the setjmp/longjmp (sjlj) unwinding used for Xtensa with previous versions of GCC. * For Xtensa processors that include the Conditional Store option, the built-in functions for atomic memory access are now implemented using S32C1I instructions. * If the Xtensa NSA option is available, GCC will use it to implement the __builtin_ctz and __builtin_clz functions. Documentation improvements * Existing libstdc++ documentation has been edited and restructured into a single DocBook XML manual. The results can be viewed online [18]here. Other significant improvements * The compiler's --help command-line option has been extended so that it now takes an optional set of arguments. These arguments restrict the information displayed to specific classes of command-line options, and possibly only a subset of those options. It is also now possible to replace the descriptive text associated with each displayed option with an indication of its current value, or for binary options, whether it has been enabled or disabled. Here are some examples. The following will display all the options controlling warning messages: --help=warnings Whereas this will display all the undocumented, target specific options: --help=target,undocumented This sequence of commands will display the binary optimizations that are enabled by -O3: gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts diff /tmp/O2-opts /tmp/O3-opts | grep enabled * The configure options --with-pkgversion and --with-bugurl have been added. These allow distributors of GCC to include a distributor-specific string in manuals and --version output and to specify the URL for reporting bugs in their versions of GCC. GCC 4.3.1 This is the [19]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.3.1 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). Target Specific Changes IA-32/x86-64 ABI changes * Starting with GCC 4.3.1, decimal floating point variables are aligned to their natural boundaries when they are passed on the stack for i386. Command-line changes * Starting with GCC 4.3.1, the -mcld option has been added to automatically generate a cld instruction in the prologue of functions that use string instructions. This option is used for backward compatibility on some operating systems and can be enabled by default for 32-bit x86 targets by configuring GCC with the --enable-cld configure option. GCC 4.3.2 This is the [20]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.3.2 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.3.3 This is the [21]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.3.3 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.3.4 This is the [22]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.3.4 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.3.5 This is the [23]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.3.5 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). GCC 4.3.6 This is the [24]list of problem reports (PRs) from GCC's bug tracking system that are known to be fixed in the 4.3.6 release. This list might not be complete (that is, it is possible that some PRs that have been fixed are not listed here). For questions related to the use of GCC, please consult these web pages and the [25]GCC manuals. If that fails, the [26]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [27]gcc@gcc.gnu.org. All of [28]our lists have public archives. Copyright (C) [29]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [30]maintained by the GCC team. Last modified 2022-10-26. References 1. https://gcc.gnu.org/gcc-4.3/changes.html#4.3.5 2. https://gmplib.org/ 3. https://www.mpfr.org/ 4. https://gcc.gnu.org/install/prerequisites.html 5. https://gcc.gnu.org/ml/gcc-announce/2001/msg00000.html 6. https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#Warning-Options 7. https://gcc.gnu.org/gcc-4.3/porting_to.html 8. https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html 9. https://gcc.gnu.org/gcc-4.3/cxx0x_status.html 10. https://gcc.gnu.org/gcc-4.3/cxx0x_status.html 11. https://gcc.gnu.org/onlinedocs/libstdc++/manual/parallel_mode.html 12. https://gcc.gnu.org/onlinedocs/gfortran/Code-Gen-Options.html#Code-Gen-Options 13. https://gcc.gnu.org/onlinedocs/gfortran/Code-Gen-Options.html#index-g_t_0040code_007bfinit-local-zero_007d-167 14. https://gcc.gnu.org/onlinedocs/gcc-4.3.0/gfortran/GAMMA.html 15. https://gcc.gnu.org/onlinedocs/gcc-4.3.0/gfortran/LGAMMA.html 16. https://gcc.gnu.org/onlinedocs/gfortran/Fortran-Dialect-Options.html 17. https://gcc.gnu.org/onlinedocs/gfortran/BOZ-literal-constants.html 18. https://gcc.gnu.org/onlinedocs/libstdc++/ 19. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.3.1 20. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.3.2 21. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.3.3 22. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.3.4 23. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.3.5 24. https://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.3.6 25. https://gcc.gnu.org/onlinedocs/ 26. mailto:gcc-help@gcc.gnu.org 27. mailto:gcc@gcc.gnu.org 28. https://gcc.gnu.org/lists.html 29. https://www.fsf.org/ 30. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.2/index.html GCC 4.2 Release Series (This release series is no longer supported.) May 19, 2008 The [1]GNU project and the GCC developers are pleased to announce the release of GCC 4.2.4. This release is a bug-fix release, containing fixes for regressions in GCC 4.2.3 relative to previous releases of GCC. Release History GCC 4.2.4 May 19, 2008 ([2]changes) GCC 4.2.3 February 1, 2008 ([3]changes) GCC 4.2.2 October 7, 2007 ([4]changes) GCC 4.2.1 July 18, 2007 ([5]changes) GCC 4.2.0 May 13, 2007 ([6]changes) References and Acknowledgements GCC used to stand for the GNU C Compiler, but since the compiler supports several other languages aside from C, it now stands for the GNU Compiler Collection. A list of [7]successful builds is updated as new information becomes available. The GCC developers would like to thank the numerous people that have contributed new features, improvements, bug fixes, and other changes as well as test results to GCC. This [8]amazing group of volunteers is what makes GCC successful. For additional information about GCC please refer to the [9]GCC project web site or contact the [10]GCC development mailing list. To obtain GCC please use [11]our mirror sites or [12]our version control system. For questions related to the use of GCC, please consult these web pages and the [13]GCC manuals. If that fails, the [14]gcc-help@gcc.gnu.org mailing list might help. Comments on these web pages and the development of GCC are welcome on our developer list at [15]gcc@gcc.gnu.org. All of [16]our lists have public archives. Copyright (C) [17]Free Software Foundation, Inc. Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved. These pages are [18]maintained by the GCC team. Last modified 2022-10-26. References 1. http://www.gnu.org/ 2. https://gcc.gnu.org/gcc-4.2/changes.html 3. https://gcc.gnu.org/gcc-4.2/changes.html 4. https://gcc.gnu.org/gcc-4.2/changes.html 5. https://gcc.gnu.org/gcc-4.2/changes.html 6. https://gcc.gnu.org/gcc-4.2/changes.html 7. https://gcc.gnu.org/gcc-4.2/buildstat.html 8. https://gcc.gnu.org/onlinedocs/gcc/Contributors.html 9. https://gcc.gnu.org/index.html 10. mailto:gcc@gcc.gnu.org 11. https://gcc.gnu.org/mirrors.html 12. https://gcc.gnu.org/git.html 13. https://gcc.gnu.org/onlinedocs/ 14. mailto:gcc-help@gcc.gnu.org 15. mailto:gcc@gcc.gnu.org 16. https://gcc.gnu.org/lists.html 17. https://www.fsf.org/ 18. https://gcc.gnu.org/about.html ====================================================================== http://gcc.gnu.org/gcc-4.2/changes.html GCC 4.2 Release Series Changes, New Features, and Fixes Caveats * GCC no longer accepts the -fshared-data option. This option has had no effect in any GCC 4 release; the targets to which the option used to apply had been removed before GCC 4.0. General Optimizer Improvements * New command-line options specify the possible relationships among parameters and between parameters and global data. For example, -fargument-noalias-anything specifies that arguments do not alias any other storage. Each language will automatically use whatever option is required by the language standard. You should not need to use these options yourself. New Languages and Language specific improvements * [1]OpenMP is now supported for the C, C++ and Fortran compilers. * New command-line options -fstrict-overflow and -Wstrict-overflow have been added. -fstrict-overflow tells the compiler that it may assume that the program follows the strict signed overflow semantics permitted for the language: for C and C++ this means that the compiler may assume that signed overflow does not occur. For example, a loop like for (i = 1; i > 0; i *= 2) is presumably intended to continue looping until i overflows. With -fstrict-overflow, the compiler may assume that signed overflow will not occur, and transform this into an infinite loop. -fstrict-overflow is turned on by default at -O2, and may be disabled via -fno-strict-overflow. The -Wstrict-overflow option may be used to warn about cases where the compiler assumes that signed overflow will not occur. It takes five different levels: -Wstrict-overflow=1 to 5. See the [2]documentation for details. -Wstrict-overflow=1 is enabled by -Wall. * The new command-line option -fno-toplevel-reorder directs GCC to emit top-level functions, variables, and asm statements in the same order that they appear in the input file. This is intended to support existing code which relies on a particular ordering (for example, code which uses top-level asm statements to switch sections). For new code, it is generally better to use function and variable attributes. The -fno-toplevel-reorder option may be used for most cases which currently use -fno-unit-at-a-time. The -fno-unit-at-a-time option will be removed in some future version of GCC. If you know of a case which requires -fno-unit-at-a-time which is not fixed by -fno-toplevel-reorder, please open a bug report. C family * The pragma redefine_extname will now macro expand its tokens for compatibility with SunPRO. * In the next release of GCC, 4.3, -std=c99 or -std=gnu99 will direct GCC to handle inline functions as specified in the C99 standard. In preparation for this, GCC 4.2 will warn about any use of non-static inline functions in gnu99 or c99 mode. This new warning may be disabled with the new gnu_inline function attribute or the new -fgnu89-inline command-line option. Also, GCC 4.2 and later will define one of the preprocessor macros __GNUC_GNU_INLINE__ or __GNUC_STDC_INLINE__ to indicate the semantics of inline functions in the current compilation. * A new command-line option -Waddress has been added to warn about suspicious uses of memory addresses as, for example, using the address of a function in a conditional expression, and comparisons against the memory address of a string literal. This warning is enabled by -Wall. C++ * C++ visibility handling has been overhauled. Restricted visiblity is propagated from classes to members, from functions to local statics, and from templates and template arguments to instantiations, unless the latter has explicitly declared visibility. The visibility attribute for a class must come between the class-key and the name, not after the closing brace. Attributes are now allowed for enums and elaborated-type-specifiers that only declare a type. Members of the anonymous namespace are now local to a particular translation unit, along with any other declarations which use them, though they are still treated as having external linkage for language semantics. * The (undocumented) extension which permitted templates with default arguments to be bound to template template parameters with fewer parameters has been removed. For example: template