SD_EVENT_SOURCE_UNREF - Online Linux Manual PageSection : 3
Updated :
Source : systemd 250
Note : sd_event_source_unref

NAMEsd_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);

DESCRIPTIONsd_event_source_unref() may be used to decrement by one the 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 it is removed from its 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 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 VALUEsd_event_source_unref() and sd_event_source_disable_unref() always return NULL​. sd_event_source_ref() always returns the event source object passed in​.

NOTESThese APIs are implemented as a shared library, which can be compiled and linked to with the libsystemd ​pkg-config(1) file​.

SEE ALSOsd-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
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