Search notes:

libc: setjmp - longjmp

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

jmp_buf env;

void func() {
    printf("func, calling longjmp\n");
 
    longjmp(env, 42);
 // longjmp does not return
    printf("func, after calling longjmp\n");
}

int main() {

    switch (setjmp(env)) {
 // setjmp returns twice, once with 0
 // and one with the value passed to longjmp
    case 0:
       printf("call func()\n");
       func();
       break;
    case 42:
       printf("setjmp evaluated to 42\n");
       break;
    default:
       printf("setjmp evaluated to neither 42 nor 0\n");
    }
}

When run, this program prints

call func()
func, calling longjmp
setjmp evaluated to 42

GCC built-in functions __builtin_setjmp and __builtin_setjmp

GCC provides the built-in functions __builtin_setjmp and __builtin_longjmp which are similar to, but not interchangeable with setjmp and longjmp.

The built-in versions are used internally by GCC's libraries to implement exception handling on some targets.

The standard C library functions (<setjmp.h>) are preferred in regular user code.

libc: setjmp - longjmp

GCC built-in functions __builtin_setjmp and __builtin_setjmp

See also