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