ignore-value: clarify some comments

[gnulib.git] / lib / ignore-value.h

diff --git a/lib/ignore-value.h b/lib/ignore-value.h
index 5f97c91..7fd4772 100644 (file)
--- a/lib/ignore-value.h
+++ b/lib/ignore-value.h
@@ -1,6 +1,6 @@
-/* ignore a value to quiet a compiler warning
+/* ignore a function return without a compiler warning
 
-   Copyright (C) 2008 Free Software Foundation, Inc.
+   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
@@ -15,15 +15,9 @@
    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.  */
+/* Written by Jim Meyering, Eric Blake and Pádraig Brady.  */
 
-#ifndef __attribute__
-# if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 8)
-#  define __attribute__(x)
-# endif
-#endif
-
-/* Use this function to avoid a warning when using a function declared with
+/* 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,
@@ -38,8 +32,33 @@
    "copy.c:233: warning: ignoring return value of 'fchown',
    declared with attribute warn_unused_result".  */
 
-static inline void
-ignore_value (int i __attribute__ ((__unused__)))
-{
-  /* empty */
-}
+#ifndef _GL_IGNORE_VALUE_H
+# define _GL_IGNORE_VALUE_H
+
+# include <stdint.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