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authorRichard Maw <richard.maw@codethink.co.uk>2012-01-11 10:45:00 +0000
committerRichard Maw <richard.maw@codethink.co.uk>2012-01-11 10:45:00 +0000
commit24d1733e78a17d71aea6912144394ed7d3a82d50 (patch)
tree069608d934a8716d55a94c62c4bd75c1152f868c /tests/gnu/ignore-value.h
parentd7b9fe130c2305d44fa1023283d3c2fcd389ba93 (diff)
downloadm4-24d1733e78a17d71aea6912144394ed7d3a82d50.tar.gz
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+/* ignore a function return without a compiler warning
+
+ Copyright (C) 2008-2010 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. */
+
+/* Use these functions 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". */
+
+static inline void ignore_value (int i) { (void) i; }
+static inline void ignore_ptr (void* p) { (void) p; }
+/* FIXME: what about aggregate types? */