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5dc7a1d2 PE |
1 | /* ignore a function return without a compiler warning |
2 | ||
caf8a9b2 | 3 | Copyright (C) 2008-2012 Free Software Foundation, Inc. |
5dc7a1d2 PE |
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 | ||
e765a388 PE |
35 | #ifndef _GL_IGNORE_VALUE_H |
36 | # define _GL_IGNORE_VALUE_H | |
5dc7a1d2 | 37 | |
5dc7a1d2 PE |
38 | /* The __attribute__((__warn_unused_result__)) feature |
39 | is available in gcc versions 3.4 and newer, | |
40 | while the typeof feature has been available since 2.7 at least. */ | |
41 | # if __GNUC__ < 3 || (__GNUC__ == 3 && __GNUC_MINOR__ < 4) | |
42 | # define ignore_value(x) ((void) (x)) | |
43 | # else | |
44 | # define ignore_value(x) (({ __typeof__ (x) __x = (x); (void) __x; })) | |
45 | # endif | |
46 | ||
5dc7a1d2 | 47 | #endif |