SD_EVENT_SOURCE_UNREF(3)

  .SH "NAME" sd_event_source_unref, sd_event_source_unrefp, sd_event_source_ref - Increase or decrease event source reference counters
  .SH "SYNOPSIS"

#include <systemd/sd-event.h>

      .HP u sd_event_source* sd_event_source_unref(sd_event_source *source);
      .HP u void sd_event_source_unrefp(sd_event_source **source);
      .HP u sd_event_source* sd_event_source_ref(sd_event_source *source);

  .SH "DESCRIPTION"

    .PP sd_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.
    .PP 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.
    .PP sd_event_source_ref() may be used to increase by one the reference counter of the event source object specified as source.
    .PP sd_event_source_unref(), sd_bus_creds_unrefp() and sd_bus_creds_ref() execute no operation if the passed event source object is NULL.
    .PP 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.

  .SH "RETURN VALUE"

    .PP sd_event_source_unref() always returns NULL. sd_event_source_ref() always returns the event source object passed in.

  .SH "NOTES"

  .PP These APIs are implemented as a shared library, which can be compiled and linked to with the libsystemd pkg-config(1) file.
  .SH "SEE ALSO"

    .PP 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