NAME

       sd_event_source_set_destroy_callback, sd_event_source_get_destroy_callback, sd_event_destroy_t - Define
       the callback function for resource cleanup

SYNOPSIS

       #include <systemd/sd-event.h>

       typedef int (*sd_event_destroy_t)(void *userdata);

       int sd_event_source_set_destroy_callback(sd_event_source *source, sd_event_destroy_t callback);

       int sd_event_source_get_destroy_callback(sd_event_source *source, sd_event_destroy_t *callback);

DESCRIPTION

       sd_event_source_set_destroy_callback() sets callback as the callback function to be called right before
       the event source object source is deallocated. The userdata pointer from the event source object will be
       passed as the userdata parameter. This pointer can be set by an argument to the constructor functions,
       see sd_event_add_io(3), or directly, see sd_event_source_set_userdata(3). This callback function is
       called even if userdata is NULL. Note that this callback is invoked at a time where the event source
       object itself is already invalidated, and executing operations or taking new references to the event
       source object is not permissible.

       sd_event_source_get_destroy_callback() returns the current callback for source in the callback parameter.

RETURN VALUE

       On success, sd_event_source_set_destroy_callback() returns 0 or a positive integer. On failure, it
       returns a negative errno-style error code.

       sd_event_source_get_destroy_callback() returns positive if the destroy callback function is set, 0 if
       not. On failure, returns a negative errno-style error code.

   Errors
       Returned errors may indicate the following problems:

       -EINVAL
           The source parameter is NULL.

NOTES

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

SEE ALSO

       systemd(1), 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_userdata(3)