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longjmp
setjmp

Usage

   #include <setjmp.h>
   void longjmp(jmp_buf env, int value);
   int setjmp(jmp_buf env);

   ANSI

Description

   These functions allow a goto between functions. They are good for dealing
   with errors or interrupts encountered in low-level subroutines of a
   program.

   setjmp saves the stack environment in the variable env for later use by
   longjmp.

   longjmp restores the environment previously saved by setjmp in jmp_buf
   and is pointed to by envp. The return value is that of setjmp.

   NOTE: The environment must have been previously saved using setjmp by a
   function that is currently active, and which is the same function or a
   parent of the function containing the call to longjmp.

   After completion of longjmp, program execution continues just as if the
   corresponding call to setjmp had just returned with value. The value will
   never be 0. If value is passed as 0, the value 1 will be returned.

Return Value

   setjmp returns a 0. There is no return value for longjmp.

Example 

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

   void docall(void);
   jmp_buf environment;
   int error_val = -1;

   int main()
   {
       int error_code;
       error_code = setjmp(environment);
       if(error_code != 0)

           {
               printf("Longjmp called\n");
               exit(EXIT_FAILURE);
           }
       printf("Setjmp called\n");
       docall();
       return EXIT_SUCCESS;
   }

   void docall(void)
   {
       longjmp(environment,error_val);
   }