Concept of setjump and longjump in C

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

  • setjump(jmp_buf buf) : uses buf to remember current position and returns 0.
  • longjump(jmp_buf buf, i) : Go back to place buf is pointing to and return i .
// A simple C program to demonstrate working of setjmp() and longjmp()
jmp_buf buf;
void func()
    printf("Welcome to GeeksforGeeks ");
    // Jump to the point setup by setjmp
    longjmp(buf, 1);
    printf("Geek2 ");
int main()
    // Setup jump position using buf and return 0
    if (setjmp(buf))
        printf("Geek3 ");
        printf("Geek4 ");
    return 0;

Output :

Welcome to GeeksforGeeks

The main feature of these function is to provide a way that deviates from standard call and return sequence. 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()).

This article is attributed to GeeksforGeeks.org

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