* lib/ignore-value.h: New file.

2 files changed, 63 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 7b693be0694..df1d6bc2144 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,7 @@
         allow C code to suppress warnings about ignored return values
         * Makefile.in (GNULIB_MODULES): Add ignore-value.
         * configure, lib/Makefile.in, lib/gnulib.mk, m4/gl-comp.m4: Regenerate.
+        * lib/ignore-value.h: New file.
 
 2011-01-31  Chong Yidong  <cyd@stupidchicken.com>
 
diff --git a/lib/ignore-value.h b/lib/ignore-value.h
new file mode 100644
index 00000000000..5e683bbb533
--- /dev/null
+++ b/lib/ignore-value.h
@@ -0,0 +1,62 @@
+/* ignore a function return without a compiler warning
+
+   Copyright (C) 2008-2011 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, 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
+
+# ifndef ATTRIBUTE_DEPRECATED
+/* The __attribute__((__deprecated__)) feature
+   is available in gcc versions 3.1 and newer.  */
+#  if __GNUC__ < 3 || (__GNUC__ == 3 && __GNUC_MINOR__ < 1)
+#   define ATTRIBUTE_DEPRECATED /* empty */
+#  else
+#   define ATTRIBUTE_DEPRECATED __attribute__ ((__deprecated__))
+#  endif
+# endif
+
+/* The __attribute__((__warn_unused_result__)) feature
+   is available in gcc versions 3.4 and newer,
+   while the typeof feature has been available since 2.7 at least.  */
+# if __GNUC__ < 3 || (__GNUC__ == 3 && __GNUC_MINOR__ < 4)
+#  define ignore_value(x) ((void) (x))
+# else
+#  define ignore_value(x) (({ __typeof__ (x) __x = (x); (void) __x; }))
+# endif
+
+/* ignore_value works for scalars, pointers and aggregates;
+   deprecate ignore_ptr.  */
+static inline void ATTRIBUTE_DEPRECATED
+ignore_ptr (void *p) { (void) p; } /* deprecated: use ignore_value */
+
+#endif