sd_event_source_set_destroy_callback(3) — Linux manual page


SD_EV...LBACK(3)  sd_event_source_set_destroy_callback  SD_EV...LBACK(3)

NAME         top

       sd_event_source_get_destroy_callback, sd_event_destroy_t - Define
       the callback function for resource cleanup

SYNOPSIS         top

       #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         top

       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         top

       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.

       Returned errors may indicate the following problems:

           The source parameter is NULL.

NOTES         top

       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

HISTORY         top

       sd_event_destroy_t(), sd_event_source_set_destroy_callback(), and
       sd_event_source_get_destroy_callback() were added in version 239.

SEE ALSO         top

       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)

COLOPHON         top

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       This page was obtained from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
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systemd 255                                             SD_EV...LBACK(3)

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