2 <setjmp.h>: Non-local goto

While the C language has the dreaded goto statement, it can only be used to jump to a label in the same (local) function. In order to jump directly to another (non-local) function, the C library provides the setjmp() and longjmp() functions. setjmp() and longjmp() are useful for dealing with errors and interrupts encountered in a low-level subroutine of a program.

Note:

setjmp() and longjmp() make programs hard to understand and maintain. If possible, an alternative should be used.

longjmp() can destroy changes made to global register variables (see How to permanently bind a variable to a register?).

For a very detailed discussion of setjmp()/longjmp(), see Chapter 7 of Advanced Programming in the UNIX Environment, by W. Richard Stevens.

Example:

    #include <setjmp.h>

    jmp_buf env;

    int main (void)
    {
        if (setjmp (env))
        {
            ... handle error ...
        }

        while (1)
        {
           ... main processing loop which calls foo() some where ...
        }
    }

    ...

    void foo (void)
    {
        ... blah, blah, blah ...

        if (err)
        {
            longjmp (env, 1);
        }
    }