.\" Written by Michael Haardt, Fri Nov 25 14:51:42 MET 1994
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.\" "
.TH LONGJMP 3 2009-01-13 "" "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 \fIenv\fP argument.
After
.BR longjmp ()
is completed, program execution continues as if the
corresponding call of
.BR setjmp (3)
had just returned the value
\fIval\fP.
.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 \fIenv\fP argument.
If, and only if, the
.BR sigsetjmp (3)
call that set this
\fIenv\fP used a nonzero \fIsavesigs\fP flag,
.BR siglongjmp ()
also restores the signal mask that was saved by
.BR sigsetjmp (3).
.SH "RETURN VALUE"
These functions never return.
.SH "CONFORMING TO"
C89, C99, and POSIX.1-2001 specify
.BR longjmp ().
POSIX.1-2001 specifies
.BR siglongjmp ().
.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)
.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/.