getauxval.3: wfix

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

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.\" Added sigsetjmp, Sun Mar  2 22:03:05 EST 1997, jrv@vanzandt.mv.com
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.\" "
.TH SETJMP 3 2015-08-08 "" "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
.I env
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,
.I savesigs
is nonzero,
the process's current signal mask is saved in
.I env
and will be restored if a
.BR siglongjmp (3)
is later performed with this
.IR env .
.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 ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbw21 lb lb
l l l.
Interface	Attribute	Value
T{
.BR setjmp (),
.BR sigsetjmp ()
T}	Thread safety	MT-Safe
.TE

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

.BR sigsetjmp ():
POSIX.1-2001, POSIX.1-2008.
.SH NOTES
POSIX does not specify whether
.BR setjmp ()
will save the signal mask
(to be later restored during
.BR longjmp (3)).
In System V it will not.
In 4.3BSD it will, and there
is a function
.B _setjmp
that will not.
On Linux with glibc versions before 2.19,
.BR setjmp ()
follows the System V behavior by default,
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.
Since glibc 2.19,
.IR <setjmp.h>
exposes only the System V version of
.BR setjmp ().
Programs that need the BSD semantics should replace calls to
.BR setjmp ()
with calls to
.BR sigsetjmp ()
with a nonzero
.I savesigs
argument.

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)