mirror of https://github.com/mkerrisk/man-pages
150 lines
3.5 KiB
Groff
150 lines
3.5 KiB
Groff
.\" Written by Michael Haardt, Fri Nov 25 14:51:42 MET 1994
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.\"
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.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\"
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.\" The GNU General Public License's references to "object code"
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.\" and "executables" are to be interpreted as the output of any
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.\" document formatting or typesetting system, including
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.\" intermediate and printed output.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public
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.\" License along with this manual; if not, see
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.\" <http://www.gnu.org/licenses/>.
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.\" %%%LICENSE_END
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.\"
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.\" Added siglongjmp, Sun Mar 2 22:03:05 EST 1997, jrv@vanzandt.mv.com
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.\" Modifications, Sun Feb 26 14:39:45 1995, faith@cs.unc.edu
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.\" "
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.TH LONGJMP 3 2015-08-08 "" "Linux Programmer's Manual"
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.SH NAME
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longjmp, siglongjmp \- nonlocal jump to a saved stack context
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.SH SYNOPSIS
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.nf
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.B #include <setjmp.h>
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.BI "void longjmp(jmp_buf " env ", int " val );
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.BI "void siglongjmp(sigjmp_buf " env ", int " val );
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.fi
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.BR siglongjmp ():
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_POSIX_C_SOURCE\ >=\ 1 || _XOPEN_SOURCE || _POSIX_C_SOURCE
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.SH DESCRIPTION
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.BR longjmp ()
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and
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.BR setjmp (3)
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are useful for dealing with errors
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and interrupts encountered in a low-level subroutine of a program.
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.BR longjmp ()
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restores the environment saved by the last call of
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.BR setjmp (3)
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with the corresponding
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.I env
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argument.
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After
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.BR longjmp ()
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is completed, program execution continues as if the
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corresponding call of
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.BR setjmp (3)
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had just returned the value
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.IR val .
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.BR longjmp ()
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cannot cause 0 to be returned.
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If
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.BR longjmp ()
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is invoked with a second argument of 0, 1 will be returned instead.
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.P
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.BR siglongjmp ()
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is similar to
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.BR longjmp ()
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except for the type of
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its
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.I env
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argument.
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If, and only if, the
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.BR sigsetjmp (3)
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call that set this
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.I env
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used a nonzero
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.I savesigs
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flag,
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.BR siglongjmp ()
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also restores the signal mask that was saved by
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.BR sigsetjmp (3).
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.SH RETURN VALUE
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These functions never return.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.TS
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allbox;
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lbw23 lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR longjmp (),
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.BR siglongjmp ()
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T} Thread safety MT-Safe
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.TE
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.SH CONFORMING TO
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.BR longjmp ():
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POSIX.1-2001, POSIX.1-2008, C89, C99.
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.BR siglongjmp ():
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POSIX.1-2001, POSIX.1-2008.
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.SH NOTES
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POSIX does not specify whether
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.BR longjmp ()
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will restore the signal context (see
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.BR setjmp (3)
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for some more details).
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If you want to portably save and restore signal masks, use
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.BR sigsetjmp (3)
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and
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.BR siglongjmp ().
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.P
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The values of automatic variables are unspecified after a call to
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.BR longjmp ()
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if they meet all the following criteria:
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.IP \(bu 3
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they are local to the function that made the corresponding
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.BR setjmp (3)
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call;
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.IP \(bu
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their values are changed between the calls to
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.BR setjmp (3)
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and
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.BR longjmp ();
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and
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.IP \(bu
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they are not declared as
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.IR volatile .
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.P
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Analogous remarks apply for
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.BR siglongjmp ().
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.P
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.BR longjmp ()
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and
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.BR siglongjmp ()
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make programs hard to
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understand and maintain.
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If possible, an alternative should be used.
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.SH SEE ALSO
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.BR setjmp (3),
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.BR sigsetjmp (3)
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