/*************************************************************************\
*                  Copyright (C) Michael Kerrisk, 2026.                   *
*                                                                         *
* This program is free software. You may use, modify, and redistribute it *
* under the terms of the GNU General Public License as published by the   *
* Free Software Foundation, either version 3 or (at your option) any      *
* later version. This program is distributed without any warranty.  See   *
* the file COPYING.gpl-v3 for details.                                    *
\*************************************************************************/

/* exit_handlers.c

   Demonstrate the use of atexit(3) and on_exit(3), which can be used to
   register functions (commonly known as "exit handlers") to be called at
   normal process exit. (These functions are not called if the process does
   an _exit(2) or if it is terminated by a signal.)
*/
#define _BSD_SOURCE     /* Get on_exit() declaration from <stdlib.h> */
#include <stdlib.h>
#include "tlpi_hdr.h"

#ifdef __linux__        /* Few UNIX implementations have on_exit() */
#define HAVE_ON_EXIT
#endif

static void
atexitFunc1(void)
{
    printf("atexit function 1 called\n");
}

static void
atexitFunc2(void)
{
    printf("atexit function 2 called\n");
}

#ifdef HAVE_ON_EXIT
static void
onexitFunc(int exitStatus, void *arg)
{
    printf("on_exit function called: status=%d, arg=%ld\n",
                exitStatus, (long) arg);
}
#endif

int
main(int argc, char *argv[])
{
#ifdef HAVE_ON_EXIT
    if (on_exit(onexitFunc, (void *) 10) != 0)
        fatal("on_exit 1");
#endif
    if (atexit(atexitFunc1) != 0)
        fatal("atexit 1");
    if (atexit(atexitFunc2) != 0)
        fatal("atexit 2");
#ifdef HAVE_ON_EXIT
    if (on_exit(onexitFunc, (void *) 20) != 0)
        fatal("on_exit 2");
#endif

    exit(2);
}