NAME

setjmp, longjmp − non-local goto

SYNOPSIS

#include <setjmp.h>

int setjmp (env)
jmp_buf env;

void longjmp (env, val)
jmp_buf env;
int val;

DESCRIPTION

These functions are useful for dealing with errors and interrupts encountered in a low-level subroutine of a program. 

Setjmp saves its stack environment in env (whose type, jmp_buf, is defined in the <setjmp.h> header file), for later use by longjmp. It returns the value 0.

Longjmp restores the environment saved by the last call of setjmp with the corresponding env argument.  After longjmp is completed program execution continues as if the corresponding call of setjmp (which must not itself have returned in the interim) had just returned the value val. Longjmp cannot cause setjmp to return the value 0.  If longjmp is invoked with a second argument of 0, setjmp will return 1.  All accessible data have values as of the time longjmp was called. 

SEE ALSO

signal(2). 

WARNING

If longjmp is called when env was never primed by a call to setjmp, or when the last such call is in a function which has since returned, absolute chaos is guaranteed.

Version 2.5r1  —  October 29, 1986