sigsetjmp(3)



SETJMP(3)                  Linux Programmer's Manual                 SETJMP(3)

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 inter-
       rupts 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  con-
       text.

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  (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
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                                  2014-01-07                         SETJMP(3)

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