longjmp.c

/* longjmp.c

   Demonstrate the use of setjmp() and longjmp() to perform a nonlocal goto.

   Usage: longjmp [x]

   The presence or absence of a command-line argument determines which of two
   functions (f1() or f2()) we will longjmp() from.
*/
#include <setjmp.h>
#include "tlpi_hdr.h"

static jmp_buf env;
static void
f2(void)
{
    longjmp(env, 2);
}
static void
f1(int argc)
{
    if (argc == 1)
        longjmp(env, 1);
    f2();
}
int
main(int argc, char *argv[])
{
    switch (setjmp(env)) {
    case 0:     /* This is the return after the initial setjmp() */
        printf("Calling f1() after initial setjmp()\n");
        f1(argc);               /* Never returns... */
        break;                  /* ... but this is good form */

    case 1:
        printf("We jumped back from f1()\n");
        break;

    case 2:
        printf("We jumped back from f2()\n");
        break;
    }

    exit(EXIT_SUCCESS);
}