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Revision 1.17, Sat May 31 16:15:07 2008 UTC (7 years, 2 months ago) by enami
Refer sigprocmask(2) instead of non existing sigmask(2). Also, xref sigprocmask(2) and pthread_sigmask(3).
.\" $NetBSD: setjmp.3,v 1.17 2008/05/31 16:15:07 enami Exp $ .\" .\" Copyright (c) 1990, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" This code is derived from software contributed to Berkeley by .\" the American National Standards Committee X3, on Information .\" Processing Systems. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)setjmp.3 8.1 (Berkeley) 6/4/93 .\" .Dd June 1, 2008 .Dt SETJMP 3 .Os .Sh NAME .Nm sigsetjmp , .Nm siglongjmp , .Nm setjmp , .Nm longjmp , .Nm _setjmp , .Nm _longjmp , .Nm longjmperror .Nd non-local jumps .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In setjmp.h .Ft int .Fn sigsetjmp "sigjmp_buf env" "int savemask" .Ft void .Fn siglongjmp "sigjmp_buf env" "int val" .Ft int .Fn setjmp "jmp_buf env" .Ft void .Fn longjmp "jmp_buf env" "int val" .Ft int .Fn _setjmp "jmp_buf env" .Ft void .Fn _longjmp "jmp_buf env" "int val" .Ft void .Fn longjmperror void .Sh DESCRIPTION The .Fn sigsetjmp , .Fn setjmp , and .Fn _setjmp functions save their calling environment in .Fa env . Each of these functions returns 0. .Pp The corresponding .Fn longjmp functions restore the environment saved by the most recent invocation of the respective .Fn setjmp function. They then return so that program execution continues as if the corresponding invocation of the .Fn setjmp call had just returned the value specified by .Fa val , instead of 0. .Pp Pairs of calls may be intermixed, i.e., both .Fn sigsetjmp and .Fn siglongjmp as well as .Fn setjmp and .Fn longjmp combinations may be used in the same program. However, individual calls may not, e.g., the .Fa env argument to .Fn setjmp may not be passed to .Fn siglongjmp . .Pp The .Fn longjmp routines may not be called after the routine which called the .Fn setjmp routines returns. .Pp All accessible objects have values as of the time .Fn longjmp routine was called, except that the values of objects of automatic storage invocation duration that do not have the .Li volatile type and have been changed between the .Fn setjmp invocation and .Fn longjmp call are indeterminate. .Pp The .Fn setjmp Ns / Ns Fn longjmp function pairs save and restore the signal mask while .Fn _setjmp Ns / Ns Fn _longjmp function pairs save and restore only the register set and the stack. (See .Fn sigprocmask 2 . ) .Pp The .Fn sigsetjmp Ns / Ns Fn siglongjmp function pairs save and restore the signal mask if the argument .Fa savemask is non-zero. Otherwise, only the register set and the stack are saved. .Pp In other words, .Fn setjmp Ns / Ns Fn longjmp are functionally equivalent to .Fn sigsetjmp Ns / Ns Fn siglongjmp when .Fn sigsetjmp is called with a non-zero .Fa savemask argument. Conversely, .Fn _setjmp Ns / Ns Fn _longjmp are functionally equivalent to .Fn sigsetjmp Ns / Ns Fn siglongjmp when .Fn sigsetjmp is called with a zero-value .Fa savemask . .Pp The .Fn sigsetjmp Ns / Ns Fn siglongjmp interfaces are preferred for maximum portability. .Sh ERRORS If the contents of the .Fa env are corrupted or correspond to an environment that has already returned, the .Fn longjmp routine calls the routine .Xr longjmperror 3 . If .Fn longjmperror returns, the program is aborted (see .Xr abort 3 ) . The default version of .Fn longjmperror prints the message .Dq Li longjmp botch to standard error and returns. User programs wishing to exit more gracefully should write their own versions of .Fn longjmperror . .Sh SEE ALSO .Xr sigaction 2 , .Xr sigaltstack 2 , .Xr sigprocmask 2 , .Xr pthread_sigmask 3 , .Xr signal 3 .Sh STANDARDS The .Fn setjmp and .Fn longjmp functions conform to .St -ansiC . The .Fn sigsetjmp and .Fn siglongjmp functions conform to .St -p1003.1-90 . .Sh CAVEATS Historically, on .At V , the .Fn setjmp Ns / Ns Fn longjmp functions have been equivalent to the .Bx .Fn _setjmp Ns / Ns Fn _longjmp functions and do not restore the signal mask. Because of this discrepancy, the .Fn sigsetjmp Ns / Ns Fn siglongjmp interfaces should be used if portability is desired. .Pp Use of .Fn longjmp or .Fn siglongjmp from inside a signal handler is not as easy as it might seem. Generally speaking, all possible code paths between the .Fn setjmp and .Fn longjmp must be signal race safe. Furthermore, the code paths must not do resource management (such as .Xr open 2 or .Xr close 2 ) without blocking the signal in question, or resources might be mismanaged. Obviously this makes .Fn longjmp much less useful than previously thought.