51 lines
2.2 KiB
C
51 lines
2.2 KiB
C
/* ignore a function return without a compiler warning. -*- coding: utf-8 -*-
|
|
|
|
Copyright (C) 2008-2020 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 <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. */
|
|
#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
|