ldd.1, sprof.1, accept.2, alarm.2, bind.2, chdir.2, clock_nanosleep.2, close.2, conne...

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

.\" Written by Michael Haardt, Fri Nov 25 14:51:42 MET 1994
.\"
.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
.\" 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, see
.\" <http://www.gnu.org/licenses/>.
.\" %%%LICENSE_END
.\"
.\" Added siglongjmp, 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 LONGJMP 3 2015-08-08 "" "Linux Programmer's Manual"
.SH NAME
longjmp, siglongjmp \- nonlocal jump to a saved stack context
.SH SYNOPSIS
.nf
.B #include <setjmp.h>

.BI "void longjmp(jmp_buf " env ", int " val );

.BI "void siglongjmp(sigjmp_buf " env ", int " val );
.fi
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.BR siglongjmp ():
_POSIX_C_SOURCE\ >=\ 1 || _XOPEN_SOURCE || _POSIX_C_SOURCE
.SH DESCRIPTION
.BR longjmp ()
and
.BR setjmp (3)
are useful for dealing with errors
and interrupts encountered in a low-level subroutine of a program.
.BR longjmp ()
restores the environment saved by the last call of
.BR setjmp (3)
with the corresponding
.I env
argument.
After
.BR longjmp ()
is completed, program execution continues as if the
corresponding call of
.BR setjmp (3)
had just returned the value
.IR val .
.BR longjmp ()
cannot cause 0 to be returned.
If
.BR longjmp ()
is invoked with a second argument of 0, 1 will be returned instead.
.P
.BR siglongjmp ()
is similar to
.BR longjmp ()
except for the type of
its
.I env
argument.
If, and only if, the
.BR sigsetjmp (3)
call that set this
.I env
used a nonzero
.I savesigs
flag,
.BR siglongjmp ()
also restores the signal mask that was saved by
.BR sigsetjmp (3).
.SH RETURN VALUE
These functions never return.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbw23 lb lb
l l l.
Interface	Attribute	Value
T{
.BR longjmp (),
.BR siglongjmp ()
T}	Thread safety	MT-Safe
.TE

.SH CONFORMING TO
.BR longjmp ():
POSIX.1-2001, POSIX.1-2008, C89, C99.

.BR siglongjmp ():
POSIX.1-2001, POSIX.1-2008.
.SH NOTES
POSIX does not specify whether
.BR longjmp ()
will restore the signal context (see
.BR setjmp (3)
for some more details).
If you want to portably save and restore signal masks, use
.BR sigsetjmp (3)
and
.BR siglongjmp ().
.P
The values of automatic variables are unspecified after a call to
.BR longjmp ()
if they meet all the following criteria:
.IP \(bu 3
they are local to the function that made the corresponding
.BR setjmp (3)
call;
.IP \(bu
their values are changed between the calls to
.BR setjmp (3)
and
.BR longjmp ();
and
.IP \(bu
they are not declared as
.IR volatile .
.P
Analogous remarks apply for
.BR siglongjmp ().
.P
.BR longjmp ()
and
.BR siglongjmp ()
make programs hard to
understand and maintain.
If possible, an alternative should be used.
.SH SEE ALSO
.BR setjmp (3),
.BR sigsetjmp (3)