6.12.3 setjmp Function

A macro that saves the current state of the program for later use by the longjmp function.

Include

<setjmp.h>

Prototype

int setjmp(jmp_buf env)

Argument

env

the array where the environment will be stored

Return Value

If the return is from a direct call, setjmp returns zero. If the return is from a call to longjmp, setjmp returns a non-zero value, even if longjmp was called with its val argument set to 0, in which case setjmp will return 1.

Remarks

The setjmp function can return as a result of a direct call, when the environment is stored, or from a subsequent call to longjmp, which uses the stored environment to continue execution from the saved instance of the previously called setjmp function.

Example

See the notes at the beginning of this chapter or section for information on using printf() or scanf() (and other functions reading and writing the stdin or stdout streams) in the example code.

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

jmp_buf jb;

void inner (void)
{
    longjmp(jb, 5);
}

int main (void)
{
  int i;
  if((i = setjmp(jb))) {
    printf("setjmp returned %d\n", i);
    exit(0);
  }
  printf("setjmp returned 0 - good\n");
  printf("calling inner...\n");
  inner();
  printf("inner returned - bad!\n");
}

Example Output

setjmp returned 0 - good
calling inner...
setjmp returned 5