NAME

       setjmp, sigsetjmp - save stack context for nonlocal goto

SYNOPSIS

       #include <setjmp.h>

       int setjmp(jmp_buf env);

       int sigsetjmp(sigjmp_buf env, int savesigs);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       setjmp(): see NOTES.
       sigsetjmp(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_C_SOURCE

DESCRIPTION

       setjmp() and longjmp(3) are useful for dealing with errors and interrupts encountered in a
       low-level subroutine of a program.  setjmp() saves the stack  context/environment  in  env
       for  later use by longjmp(3).  The stack context will be invalidated if the function which
       called setjmp() returns.

       sigsetjmp() is similar to setjmp().  If, and only if, savesigs is nonzero,  the  process's
       current  signal  mask  is  saved  in  env and will be restored if a siglongjmp(3) is later
       performed with this env.

RETURN VALUE

       setjmp() and sigsetjmp() return 0 if returning directly, and nonzero when  returning  from
       longjmp(3) or siglongjmp(3) using the saved context.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌──────────────────────┬───────────────┬─────────┐
       │Interface             │ Attribute     │ Value   │
       ├──────────────────────┼───────────────┼─────────┤
       │setjmp(), sigsetjmp() │ Thread safety │ MT-Safe │
       └──────────────────────┴───────────────┴─────────┘

CONFORMING TO

       setjmp(): POSIX.1-2001, POSIX.1-2008, C89, C99.

       sigsetjmp(): POSIX.1-2001, POSIX.1-2008.

NOTES

       POSIX  does  not  specify whether setjmp() will save the signal mask (to be later restored
       during longjmp(3)).  In System V it will not.  In 4.3BSD it will, and there is a  function
       _setjmp  that  will  not.   On Linux with glibc versions before 2.19, setjmp() follows the
       System V behavior by default, but the BSD behavior is provided if the _BSD_SOURCE  feature
       test   macro  is  defined  and  none  of  _POSIX_SOURCE,  _POSIX_C_SOURCE,  _XOPEN_SOURCE,
       _XOPEN_SOURCE_EXTENDED, _GNU_SOURCE,  or  _SVID_SOURCE  is  defined.   Since  glibc  2.19,
       <setjmp.h>  exposes  only  the  System  V version of setjmp().  Programs that need the BSD
       semantics should replace calls to setjmp()  with  calls  to  sigsetjmp()  with  a  nonzero
       savesigs argument.

       If you want to portably save and restore signal masks, use sigsetjmp() and siglongjmp(3).

       setjmp()  and  sigsetjmp() make programs hard to understand and maintain.  If possible, an
       alternative should be used.

SEE ALSO

       longjmp(3), siglongjmp(3)

COLOPHON

       This page is part of release 4.04 of the Linux man-pages project.  A  description  of  the
       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at http://www.kernel.org/doc/man-pages/.

                                            2015-08-08                                  SETJMP(3)