Usage of setjmp(buf) and longjmp?

[shwetha_siddu]

Dear All,
First time i read above two functions. what is the function of those two?

int main()  
{    
 volatile  int b;    
 int a;
 b =3;
 a = 3; 
 if(setjmp(buf)!=0)      
   {      

      printf("A = %d ", a);        
      printf("\n\nB = %d ", b);        
      exit(0);    
   }    
  b = 5;
  a = 5;    
 longjmp(buf , 1);  
 return 0;
}

[matsp]

To jump in the code. It's pretty pointless in this example, since it's within a function, and we may just as well use some of the more common control-flow terms, e.g. do-while, while, if, goto.

It is very useful to get back to a lower level of call-stack when something has gone horribly wrong - e.g. do setjmp() somewhere, and longjmp when an error occurs. It also works for signal handling in Linux/Unix. [Early versions of try/catch in C++ tended to use setjmp/longjmp, but nowadays, it is generally done via direct code generation in the compiler].

It is a very BAD pair of functions, since it's goto but 3 times worse, since it can "goto" out of the current function.

--
Mats