https://bugs.gentoo.org/879715
https://github.com/net-snmp/net-snmp/commit/ddec5fa0ed1c76fde5eea9b974442faeec008526
https://github.com/net-snmp/net-snmp/commit/fec0f9ee59d5d89c28d70bb35fad29a0013d048c
https://github.com/net-snmp/net-snmp/commit/f362b354ce993d7394bf77db41bb27cfe8d1e307

From ddec5fa0ed1c76fde5eea9b974442faeec008526 Mon Sep 17 00:00:00 2001
From: Sam James <sam@gentoo.org>
Date: Thu, 17 Nov 2022 00:10:09 +0000
Subject: [PATCH] configure.d: fix compatibility with Clang 16

Clang 16 makes -Wimplicit-function-declaration and -Wimplicit-int an error by
default. Unfortunately, this can lead to misconfiguration or miscompilation of
software as configure tests may then return the wrong result.

We also fix -Wstrict-prototypes while here as it's easy to do and it prepares
us for C23.

For more information, see LWN.net [0] or LLVM's Discourse [1], the Gentoo wiki
[2], or the (new) c-std-porting mailing list [3].

[0] https://lwn.net/Articles/913505/
[1] https://discourse.llvm.org/t/configure-script-breakage-with-the-new-werror-implicit-function-declaration/65213
[2] https://wiki.gentoo.org/wiki/Modern_C_porting
[3] hosted at lists.linux.dev.

Bug: https://bugs.gentoo.org/879715
Signed-off-by: Sam James <sam@gentoo.org>
[ bvanassche: removed two header file guards ]
--- a/configure
+++ b/configure
@@ -28483,7 +28483,14 @@ else
 #ifdef HAVE_SYS_FS_TYPES_H
 #include <sys/fs_types.h>
 #endif
-int main ()
+#ifdef HAVE_SYS_STATFS_H
+#include <sys/statfs.h>
+#endif
+#ifdef HAVE_SYS_STATVFS_H
+#include <sys/statvfs.h>
+#endif
+
+int main(void)
 {
 struct fs_data fsd;
 /* Ultrix's statfs returns 1 for success,
@@ -31851,8 +31858,10 @@ else
 #if HAVE_SYS_SYSCTL_H
 # include <sys/sysctl.h>
 #endif
+#include <stddef.h>
+#include <stdlib.h>
 
-int main(int argc, char **argv)
+int main(void)
 {
   int                 mib[2];
   size_t              len;
--- a/configure.d/config_os_functions
+++ b/configure.d/config_os_functions
@@ -216,7 +216,14 @@ AC_CACHE_VAL(
 #ifdef HAVE_SYS_FS_TYPES_H
 #include <sys/fs_types.h>
 #endif
-int main ()
+#ifdef HAVE_SYS_STATFS_H
+#include <sys/statfs.h>
+#endif
+#ifdef HAVE_SYS_STATVFS_H
+#include <sys/statvfs.h>
+#endif
+
+int main(void)
 {
 struct fs_data fsd;
 /* Ultrix's statfs returns 1 for success,
--- a/configure.d/config_os_misc4
+++ b/configure.d/config_os_misc4
@@ -185,8 +185,10 @@ else
 #if HAVE_SYS_SYSCTL_H
 # include <sys/sysctl.h>
 #endif
+#include <stddef.h>
+#include <stdlib.h>
 
-int main(int argc, char **argv)
+int main(void)
 {
   int                 mib[2];
   size_t              len;

From fec0f9ee59d5d89c28d70bb35fad29a0013d048c Mon Sep 17 00:00:00 2001
From: Sam James <sam@gentoo.org>
Date: Thu, 17 Nov 2022 00:13:55 +0000
Subject: [PATCH] agent/mibgroup: fix -Wstrict-prototypes

Clang 16 warns on this. Fix it in preparation for C23.

Signed-off-by: Sam James <sam@gentoo.org>
[ bvanassche: minor formatting changes ]
--- a/agent/mibgroup/agentx/protocol.c
+++ b/agent/mibgroup/agentx/protocol.c
@@ -1895,7 +1895,7 @@ agentx_parse(netsnmp_session * session, netsnmp_pdu *pdu, u_char * data,
 
 #ifdef TESTING
 
-testit(netsnmp_pdu *pdu1)
+void testit(netsnmp_pdu *pdu1)
 {
     char            packet1[BUFSIZ];
     char            packet2[BUFSIZ];
@@ -1964,7 +1964,7 @@ testit(netsnmp_pdu *pdu1)
 
 
 
-main()
+int main(void)
 {
     netsnmp_pdu     pdu1;
     oid             oid_buf[] = { 1, 3, 6, 1, 2, 1, 10 };
--- a/agent/mibgroup/header_complex.c
+++ b/agent/mibgroup/header_complex.c
@@ -569,7 +569,7 @@ header_complex_dump(struct header_complex_index *thestuff)
     }
 }
 
-main()
+int main(void)
 {
     oid             oidsave[MAX_OID_LEN];
     int             len = MAX_OID_LEN, len2;

From f362b354ce993d7394bf77db41bb27cfe8d1e307 Mon Sep 17 00:00:00 2001
From: Sam James <sam@gentoo.org>
Date: Thu, 17 Nov 2022 00:20:04 +0000
Subject: [PATCH] agent: fix -Wincompatible-function-pointer-types

Clang 16 makes -Wincompatible-function-pointer-types an error by default.

Fixes the following error:
```
mibgroup/if-mib/data_access/interface_linux.c:159:23: error: incompatible function pointer types assigning to 'void (*)(char *, ...) __attribute__((noreturn))' from 'void (char *, ...)' [-Wincompatible-function-pointer-types]
    pci_access->error = netsnmp_pci_error;
                      ^ ~~~~~~~~~~~~~~~~~
1 error generated.
```

Signed-off-by: Sam James <sam@gentoo.org>
--- a/agent/mibgroup/if-mib/data_access/interface_linux.c
+++ b/agent/mibgroup/if-mib/data_access/interface_linux.c
@@ -31,7 +31,7 @@ static struct pci_access *pci_access;
 /* Avoid letting libpci call exit(1) when no PCI bus is available. */
 static int do_longjmp =0;
 static jmp_buf err_buf;
-static void
+PCI_NONRET static void
 netsnmp_pci_error(char *msg, ...)
 {
     va_list args;