C setjump and longjump

“Setjump” and “Longjump” are defined in setjmp.h, a header file in C standard library.

setjump(jmp_buf buf) : uses buf to remember the current position and returns 0.
longjump(jmp_buf buf, i) : Go back to the place buf is pointing to and return i.

// C program to demonstrate 
// working of setjmp() and
// longjmp()
#include <setjmp.h>
#include <stdio.h>
jmp_buf buf;
void func()
{
    printf("Welcome to GeeksforGeeks\n");

    // Jump to the point setup by setjmp
    longjmp(buf, 1);

    printf("Geek2\n");
}

int main()
{
    // Setup jump position using buf and return 0
    if (setjmp(buf))
        printf("Geek3\n");
    else {
        printf("Geek4\n");
        func();
    }
    return 0;
}

Output

Geek4
Welcome to GeeksforGeeks
Geek3

The main feature of these functions is to provide a way that deviates from standard call and return sequences. This is mainly used to implement exception handling in C. setjmp can be used like try (in languages like C++ and Java). The call to longjmp can be used like throw (Note that longjmp() transfers control to the point set by setjmp()).

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