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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.

CONFORMING TO

       C89,  C99,  and  POSIX.1-2001 specify setjmp().  POSIX.1-2001 specifies
       sigsetjmp().

NOTES

       POSIX does not specify whether setjmp() will save the signal mask.   In
       System  V  it  will  not.   In  4.3BSD it will, and there is a function
       _setjmp that will not.  By default, Linux/glibc follows  the  System  V
       behavior,  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.

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

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

SEE ALSO

       longjmp(3), siglongjmp(3)

COLOPHON

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                                  2009-06-26                         SETJMP(3)