setjmp - <setjmp.h>: Non-local goto

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AVR-LibC                                          Version 2.2.1                                     setjmp(3avr)

       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.

       Notesetjmp 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 Howtopermanentlybindavariabletoaregister?).

       For a very detailed discussion of setjmp/longjmp, see Chapter 7 of AdvancedProgrammingintheUNIXEnvironment, 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() somewhere ...
           }
       }

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

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

voidlongjmp(jmp_buf__jmpb,int__ret)[extern]
       Non-local jump to a saved stack context.

       #include <setjmp.h>

       longjmp() restores the environment saved by the last call of setjmp() with the corresponding __jmpb
       argument. After longjmp() is completed, program execution continues as if the corresponding call of
       setjmp() had just returned the value __ret.

       Notelongjmp() cannot cause 0 to be returned. If longjmp() is invoked with a second argument of 0, 1 will
           be returned instead.

       Parameters__jmpb Information saved by a previous call to setjmp().
           __ret Value to return to the caller of setjmp().

       Returns
           This function never returns.

   intsetjmp(jmp_buf__jmpb)[extern]
       Save stack context for non-local goto.

       #include <setjmp.h>

       setjmp() saves the stack context/environment in __jmpb for later use by longjmp(). The stack context will
       be invalidated if the function which called setjmp() returns.

       Parameters__jmpb Variable of type jmp_buf which holds the stack information such that the environment can be
           restored.

       Returnssetjmp() returns 0 if returning directly, and non-zero when returning from longjmp() using the saved
           context.

       setjmp - <setjmp.h>: Non-local goto

Functions
       int setjmp (jmp_buf __jmpb)
       void longjmp (jmp_buf __jmpb, int __ret)