.\" Written by Michael Haardt, Fri Nov 25 14:51:42 MET 1994
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.\" 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 "March 2, 1997" "" "Library functions"
.SH NAME
longjmp, siglongjmp \- non-local jump to a saved stack context
.SH SYNOPSIS
.ad l
.B #include <setjmp.h>
.sp
.nf
.BI "void longjmp(jmp_buf " env ", int " val );
.BI "void siglongjmp(sigjmp_buf " env ", int " val );
.fi
.ad b
.SH DESCRIPTION
\fBlongjmp()\fP and \fBsetjmp()\fP are useful for dealing with errors
and interrupts encountered in a low-level subroutine of a program.
\fBlongjmp()\fP restores the environment saved by the last call of
\fBsetjmp()\fP with the corresponding \fIenv\fP argument.  After
\fBlongjmp()\fP is completed, program execution continues as if the
corresponding call of \fBsetjmp()\fP had just returned the value
\fIval\fP.  \fBlongjmp()\fP cannot cause 0 to be returned.  If longjmp
is invoked with a second argument of 0, 1 will be returned instead.
.P
\fBsiglongjmp()\fP is similar to \fBlongjmp()\fP except for the type of
its \fIenv\fP argument.  If the \fBsigsetjmp()\fP call that set this
\fIenv\fP used a nonzero \fIsavesigs\fP flag, \fBsiglongjmp()\fP also
restores the set of blocked signals.
.SH "RETURN VALUE"
These functions never return.
.SH "CONFORMING TO"
POSIX
.SH NOTES
POSIX does not specify whether \fBlongjmp\fP will restore the signal
context.  If you want to save and restore signal masks, use
\fBsiglongjmp\fP.
.P
\fBlongjmp()\fP and \fBsiglongjmp()\fP make programs hard to
understand and maintain.  If possible an alternative should be used.
.SH "SEE ALSO"
.BR setjmp "(3), " sigsetjmp (3)