1 /* ignore a function return without a compiler warning 2 3 Copyright (C) 2008-2012 Free Software Foundation, Inc. 4 5 This program is free software: you can redistribute it and/or modify 6 it under the terms of the GNU General Public License as published by 7 the Free Software Foundation; either version 3 of the License, or 8 (at your option) any later version. 9 10 This program is distributed in the hope that it will be useful, 11 but WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 GNU General Public License for more details. 14 15 You should have received a copy of the GNU General Public License 16 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 17 18 /* Written by Jim Meyering, Eric Blake and Pádraig Brady. */ 19 20 /* Use "ignore_value" to avoid a warning when using a function declared with 21 gcc's warn_unused_result attribute, but for which you really do want to 22 ignore the result. Traditionally, people have used a "(void)" cast to 23 indicate that a function's return value is deliberately unused. However, 24 if the function is declared with __attribute__((warn_unused_result)), 25 gcc issues a warning even with the cast. 26 27 Caution: most of the time, you really should heed gcc's warning, and 28 check the return value. However, in those exceptional cases in which 29 you're sure you know what you're doing, use this function. 30 31 For the record, here's one of the ignorable warnings: 32 "copy.c:233: warning: ignoring return value of 'fchown', 33 declared with attribute warn_unused_result". */ 34 35 #ifndef _GL_IGNORE_VALUE_H 36 # define _GL_IGNORE_VALUE_H 37 38 # ifndef _GL_ATTRIBUTE_DEPRECATED 39 /* The __attribute__((__deprecated__)) feature 40 is available in gcc versions 3.1 and newer. */ 41 # if __GNUC__ < 3 || (__GNUC__ == 3 && __GNUC_MINOR__ < 1) 42 # define _GL_ATTRIBUTE_DEPRECATED /* empty */ 43 # else 44 # define _GL_ATTRIBUTE_DEPRECATED __attribute__ ((__deprecated__)) 45 # endif 46 # endif 47 48 /* The __attribute__((__warn_unused_result__)) feature 49 is available in gcc versions 3.4 and newer, 50 while the typeof feature has been available since 2.7 at least. */ 51 # if __GNUC__ < 3 || (__GNUC__ == 3 && __GNUC_MINOR__ < 4) 52 # define ignore_value(x) ((void) (x)) 53 # else 54 # define ignore_value(x) (({ __typeof__ (x) __x = (x); (void) __x; })) 55 # endif 56 57 #endif 58