SD_EVENT_SOURCE_UNREF(3)

NAME
sd_event_source_unref, sd_event_source_unrefp, sd_event_source_ref, sd_event_source_disable_unref, sd_event_source_disable_unrefp - Increase or decrease event source reference counters

SYNOPSIS

#include <systemd/sd-event.h>

sd_event_source* sd_event_source_unref(sd_event_source *source);

void sd_event_source_unrefp(sd_event_source **source);

sd_event_source* sd_event_source_ref(sd_event_source *source);

sd_event_source* sd_event_source_disable_unref(sd_event_source *source);

void sd_event_source_disable_unrefp(sd_event_source **source);

DESCRIPTION

sd_event_source_unref() may be used to decrement by one the internal reference counter of the event source object specified as source. The reference counter is initially set to one, when the event source is created with calls such as sd_event_add_io(3) or sd_event_add_time(3). When the reference counter reaches zero, the object is detached from the event loop object and destroyed.

sd_event_source_unrefp() is similar to sd_event_source_unref() but takes a pointer to a pointer to an sd_event_source object. This call is useful in conjunction with GCC's and LLVM's Clean-up Variable Attribute[1]. Note that this function is defined as inline function.

sd_event_source_ref() may be used to increase by one the internal reference counter of the event source object specified as source.

sd_event_source_unref(), sd_bus_creds_unrefp() and sd_bus_creds_ref() execute no operation if the passed event source object is NULL.

Note that event source objects stay alive and may be dispatched as long as they have a reference counter greater than zero. In order to drop a reference of an event source and make sure the associated event source handler function is not called anymore it is recommended to combine a call of sd_event_source_unref() with a prior call to sd_event_source_set_enabled() with SD_EVENT_OFF or call sd_event_source_disable_unref(), see below.

sd_event_source_disable_unref() combines a call to sd_event_source_set_enabled() with SD_EVENT_OFF with sd_event_source_unref(). This ensures that the source is disabled before the local reference to it is lost. The source parameter is allowed to be NULL.

sd_event_source_disable_unrefp() is similar to sd_event_source_unrefp(), but in addition disables the source first. This call is useful in conjunction with GCC's and LLVM's Clean-up Variable Attribute[1]. Note that this function is defined as inline function.

RETURN VALUE

sd_event_source_unref() and sd_event_source_disable_unref() always return NULL. sd_event_source_ref() always returns the event source object passed in.

NOTES

Functions described here are available as a shared library, which can be compiled against and linked to with the libsystemd pkg-config(1) file.

The code described here uses getenv(3), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not call setenv(3) from a parallel thread. It is recommended to only do calls to setenv() from an early phase of the program when no other threads have been started.

HISTORY

sd_event_source_unref(), sd_event_source_unrefp(), and sd_event_source_ref() were added in version 229.

sd_event_source_disable_unref() and sd_event_source_disable_unrefp() were added in version 243.

SEE ALSO

sd-event(3), sd_event_add_io(3), sd_event_add_time(3), sd_event_add_signal(3), sd_event_add_child(3), sd_event_add_inotify(3), sd_event_add_defer(3), sd_event_source_set_enabled(3)

NOTES

1.  Clean-up Variable Attribute
    https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html