longjmp

 

C

Language

Standard Library

Type support

Dynamic memory management

Error handling

Program utilities

Date and time utilities

Strings library

Algorithms

Numerics

Input/output support

Localization support

Thread support (C11)

Atomic operations (C11)

 

Program support utilities

Program termination
abort exit quick_exit (C++11) _Exit (C++11)	atexit at_quick_exit (C++11) EXIT_SUCCESSEXIT_FAILURE
Communicating with the environment
system	getenv
Signals
signal raise sig_atomic_t	SIG_DFLSIG_IGN SIG_ERR
Signal types
SIGABRTSIGFPESIGILLSIGINTSIGSEGVSIGTERM
Non-local jumps
setjmp
longjmp
Types
jmp_buf

 

Defined in header <setjmp.h>
void longjmp( jmp_buf env, int status );

Loads the execution context env saved by a previous call to setjmp. This function does not return. Control is transferred to the call site of the macro setjmp that set up env. That setjmp then returns the value, passed as the status.

If the function that called setjmp has exited, the behavior is undefined (in other words, only long jumps up the call stack are allowed).

Parameters

env	-	variable referring to the execution state of the program saved by setjmp
status	-	the value to return from setjmp. If it is equal to ​0​, 1 is used instead

Return value

(none)

Example

Typical usage: exception mechanism

Run this code

#include <stdio.h>
#include <setjmp.h>
 
static jmp_buf call_env;
 
void f_2(void)
{
    printf("Enter f_2()\n");
 
    /* Restore calling environment:                             */
    /*   - "return" to the program state when setjmp was called */
    /*   - setjmp will return second arg of longjmp (1)         */
    longjmp(call_env,1);   /* declare an exception with code 1 */
}
 
void f_1(void)
{
    printf("Enter f_1()\n");
    f_2();
    printf("In f_1()\n");   /* never executed */
}
 
int main(void)
{
    int rtn;
    if (!(rtn=setjmp(call_env)))  /* save calling environment; return 0 */
    {  /* normal processing here */
       printf("In main(): %d\n", rtn);   /* 0 */
       f_1();
    }
    else   /* exception mechanism here */
       /* when longjmp jumps back, setjmp returns second arg of longjmp */
       printf("In main(): %d\n", rtn);   /* 1 */
 
    return 0;
}

Output:

In main(): 0
Enter f_1()
Enter f_2()
In main(): 1

See also

setjmp	saves the context (function macro)
C++ documentation for longjmp