longjmp (3)
Leading comments
Copyright (C) 2016 Michael Kerrisk <mtk.manpages@gmail.com> %%%LICENSE_START(GPLv2+_DOC_FULL) This is free documentation; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU General Public License's references to "object code" and "executables" are to be interpreted as the output of any document formatting or typesetting system,...
NAME
longjmp, siglongjmp - nonlocal jump to a saved stack contextSYNOPSIS
#include <setjmp.h> void longjmp(jmp_buf env, int val); void siglongjmp(sigjmp_buf env, int val);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
siglongjmp(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_C_SOURCE
DESCRIPTION
longjmp() and setjmp(3) are useful for dealing with errors and interrupts encountered in a low-level subroutine of a program. longjmp() restores the environment saved by the last call of setjmp(3) with the corresponding env argument. After longjmp() is completed, program execution continues as if the corresponding call of setjmp(3) had just returned the value val. longjmp() cannot cause 0 to be returned. If longjmp() is invoked with a second argument of 0, 1 will be returned instead. siglongjmp() is similar to longjmp() except for the type of its env argument. If, and only if, the sigsetjmp(3) call that set this env used a nonzero savesigs flag, siglongjmp() also restores the signal mask that was saved by sigsetjmp(3).RETURN VALUE
These functions never return.ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).| Interface | Attribute | Value |
| longjmp(), siglongjmp() | Thread safety | MT-Safe |
CONFORMING TO
longjmp(): POSIX.1-2001, POSIX.1-2008, C89, C99.siglongjmp(): POSIX.1-2001, POSIX.1-2008.
NOTES
POSIX does not specify whether longjmp() will restore the signal context (see setjmp(3) for some more details). If you want to portably save and restore signal masks, use sigsetjmp(3) and siglongjmp(). The values of automatic variables are unspecified after a call to longjmp() if they meet all the following criteria:- *
- they are local to the function that made the corresponding setjmp(3) call;
- *
- their values are changed between the calls to setjmp(3) and longjmp(); and
- *
- they are not declared as volatile. Analogous remarks apply for siglongjmp(). longjmp() and siglongjmp() make programs hard to understand and maintain. If possible, an alternative should be used.