Mercurial > gnulib
view lib/ignore-value.h @ 37246:5cfb3a67238d
regex: avoid glibc deadlock during configure
glibc has a known bug where certain corruptions of the heap can
cause malloc to default to printing a debug message that includes
a backtrace, but the act of getting the backtrace uses dlopen
which in turn calls into malloc, causing a recursive lock ending
in deadlock. Thus, when configure is probing for a known glibc
heap corruption bug, the overall configure would hang.
The solution suggested by glibc developers is to force malloc
to quit printing debug messages, which avoids recursive malloc.
* m4/regex.m4 (gl_REGEX): Avoid recursive malloc deadlock when
glibc bug 15078 in turn triggers bug 16159.
Reported by Michal Privoznik.
Signed-off-by: Eric Blake <eblake@redhat.com>
author | Eric Blake <eblake@redhat.com> |
---|---|
date | Tue, 03 Dec 2013 10:34:13 -0700 |
parents | 0f5e6eb69134 |
children | 344018b6e5d7 |
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/* ignore a function return without a compiler warning Copyright (C) 2008-2013 Free Software Foundation, Inc. This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. */ /* Written by Jim Meyering, Eric Blake and Pádraig Brady. */ /* Use "ignore_value" to avoid a warning when using a function declared with gcc's warn_unused_result attribute, but for which you really do want to ignore the result. Traditionally, people have used a "(void)" cast to indicate that a function's return value is deliberately unused. However, if the function is declared with __attribute__((warn_unused_result)), gcc issues a warning even with the cast. Caution: most of the time, you really should heed gcc's warning, and check the return value. However, in those exceptional cases in which you're sure you know what you're doing, use this function. For the record, here's one of the ignorable warnings: "copy.c:233: warning: ignoring return value of 'fchown', declared with attribute warn_unused_result". */ #ifndef _GL_IGNORE_VALUE_H #define _GL_IGNORE_VALUE_H /* Normally casting an expression to void discards its value, but GCC versions 3.4 and newer have __attribute__ ((__warn_unused_result__)) which may cause unwanted diagnostics in that case. Use __typeof__ and __extension__ to work around the problem, if the workaround is known to be needed. */ #if 3 < __GNUC__ + (4 <= __GNUC_MINOR__) # define ignore_value(x) \ (__extension__ ({ __typeof__ (x) __x = (x); (void) __x; })) #else # define ignore_value(x) ((void) (x)) #endif #endif