procexec/exit_handlers.c

+/* 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);
 }