SAS/C Library Reference, Vol. 1

setjmp -- Define Label for Nonlocal goto

SYNOPSIS

 #include <setjmp.h>

 int setjmp(jmp_buf env);

DESCRIPTION

setjmp defines a target for a nonlocal goto. The call to setjmp always returns 0. If another routine, called later by the caller of setjmp, issues the call longjmp(env, code), the earlier call to setjmp is resumed. This time, setjmp returns the value contained in the code argument to longjmp.

RETURN VALUE

A true return from setjmp always produces a 0. When control returns from setjmp because longjmp was used, the return value is nonzero.

CAUTION

Variables of storage class auto and register, whose values have been changed between the setjmp and longjmp calls, have indeterminate values on return to setjmp unless declared volatile.

EXAMPLE

  #include <stdio.h>
  #include <setjmp.h>
  #include <stdlib.h>

  jmp_buf env;
  void dummy();

  main()
  {
     int ret;

     if ((ret = setjmp(env)) != 0) {
        fprintf(stderr, "longjmp called with value %dn", ret);
        exit(1);
     }
     dummy();
     fprintf(stderr, "longjmp was not called.n");
  }

  void dummy()
  {
     puts("Entering dummy routine.");
     longjmp(env, 3);
     puts("Never reached.");
  }

RELATED FUNCTIONS

longjmp, sigsetjmp