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authorJörg Frings-Fürst <debian@jff.email>2022-01-08 11:51:07 +0100
committerJörg Frings-Fürst <debian@jff.email>2022-01-08 11:51:07 +0100
commitbe8efac78d067c138ad8dda03df4336e73f94887 (patch)
tree5f5254a628ba0ef72065b93d949d1c985742ea8e /tests/ignore-value.h
parent7b65dbd4ebade81d504cfe5e681292a58ad1fdf0 (diff)
New upstream version 1.0upstream/1.0
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+/* ignore a function return without a compiler warning. -*- coding: utf-8 -*-
+
+ Copyright (C) 2008-2022 Free Software Foundation, Inc.
+
+ This file is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Lesser General Public License as
+ published by the Free Software Foundation; either version 2.1 of the
+ License, or (at your option) any later version.
+
+ This file 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 Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with this program. If not, see <https://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.
+ The workaround is not needed with clang. */
+#if (3 < __GNUC__ + (4 <= __GNUC_MINOR__)) && !defined __clang__
+# define ignore_value(x) \
+ (__extension__ ({ __typeof__ (x) __x = (x); (void) __x; }))
+#else
+# define ignore_value(x) ((void) (x))
+#endif
+
+#endif