sd_event_source_set_destroy_callback, sd_event_source_get_destroy_callback, sd_event_destroy_t — Define the callback function for resource cleanup
#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) ; |
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.
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.
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.
sd_event_destroy_t()
,
sd_event_source_set_destroy_callback()
, and
sd_event_source_get_destroy_callback()
were added in version 239.