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.\" Written by Michael Haardt, Fri Nov 25 14:51:42 MET 1994
.\"
.\" 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, including
.\" intermediate and printed output.
.\"
.\" This manual is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public
.\" License along with this manual; if not, write to the Free
.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
.\" USA.
.\"
.\" Added sigsetjmp, Sun Mar 2 22:03:05 EST 1997, jrv@vanzandt.mv.com
.\" Modifications, Sun Feb 26 14:39:45 1995, faith@cs.unc.edu
.\" "
.TH SETJMP 3 2009-06-26 "" "Linux Programmer's Manual"
.SH NAME
setjmp, sigsetjmp \- save stack context for nonlocal goto
.SH SYNOPSIS
.B #include <setjmp.h>
.sp
.nf
.BI "int setjmp(jmp_buf " env );
.BI "int sigsetjmp(sigjmp_buf " env ", int " savesigs );
.fi
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.BR setjmp ():
see NOTES.
.br
.BR sigsetjmp ():
_POSIX_C_SOURCE\ >=\ 1 || _XOPEN_SOURCE || _POSIX_C_SOURCE
.SH DESCRIPTION
.BR setjmp ()
and
.BR longjmp (3)
are useful for dealing with errors
and interrupts encountered in a low-level subroutine of a program.
.BR setjmp ()
saves the stack context/environment in \fIenv\fP for
later use by
.BR longjmp (3).
The stack context will be invalidated
if the function which called
.BR setjmp ()
returns.
.P
.BR sigsetjmp ()
is similar to
.BR setjmp ().
If, and only if, \fIsavesigs\fP is nonzero,
the process's current signal mask is saved in \fIenv\fP
and will be restored if a
.BR siglongjmp (3)
is later performed with this \fIenv\fP.
.SH "RETURN VALUE"
.BR setjmp ()
and
.BR sigsetjmp ()
return 0 if returning directly, and
nonzero when returning from
.BR longjmp (3)
or
.BR siglongjmp (3)
using the saved context.
.SH "CONFORMING TO"
C89, C99, and POSIX.1-2001 specify
.BR setjmp ().
POSIX.1-2001 specifies
.BR sigsetjmp ().
.SH NOTES
POSIX does not specify whether
.BR setjmp ()
will save the signal mask.
In System V it will not.
In 4.3BSD it will, and there
is a function \fB_setjmp\fP that will not.
By default, Linux/glibc follows the System V behavior,
but the BSD behavior is provided if the
.BR _BSD_SOURCE
feature test macro is defined and none of
.BR _POSIX_SOURCE ,
.BR _POSIX_C_SOURCE ,
.BR _XOPEN_SOURCE ,
.BR _XOPEN_SOURCE_EXTENDED ,
.BR _GNU_SOURCE ,
or
.B _SVID_SOURCE
is defined.
If you want to portably save and restore signal masks, use
.BR sigsetjmp ()
and
.BR siglongjmp (3).
.P
.BR setjmp ()
and
.BR sigsetjmp ()
make programs hard to understand
and maintain.
If possible an alternative should be used.
.SH "SEE ALSO"
.BR longjmp (3),
.BR siglongjmp (3)
.SH COLOPHON
This page is part of release 3.44 of the Linux
.I man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.
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