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[thirdparty/man-pages.git] / man3 / setjmp.3

.\" Written by Michael Haardt, Fri Nov 25 14:51:42 MET 1994
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.\" 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)