sd_event_source_unref - Man Page

#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);

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​.

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​.

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

All functions listed here are thread-agnostic and only a single thread may operate on a given object at any given time​. Different threads may access the same object at different times​. Multiple independent objects may be used from different threads in parallel​.

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​.

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​.

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)

1.

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

sd-event(3), sd_event_add_child(3), sd_event_add_defer(3), sd_event_add_inotify(3), sd_event_add_io(3), sd_event_add_memory_pressure(3), sd_event_add_signal(3), sd_event_add_time(3), sd_event_source_get_pending(3), sd_event_source_set_enabled(3), systemd.directives(7), systemd.index(7).

The man pages sd_event_source_disable_unref(3), sd_event_source_disable_unrefp(3), sd_event_source_ref(3) and sd_event_source_unrefp(3) are aliases of sd_event_source_unref(3).