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[gnu-emacs] / lib / ignore-value.h

diff --git a/lib/ignore-value.h b/lib/ignore-value.h
index 2e344350946e8a4cd5170f764a2621e8caa9de8f..6713d96f84e6b4444a8ac1cb4867ba38a7d010b0 100644 (file)
--- a/lib/ignore-value.h
+++ b/lib/ignore-value.h
@@ -1,6 +1,6 @@
-/* ignore a function return without a compiler warning
+/* ignore a function return without a compiler warning.  -*- coding: utf-8 -*-
 
-   Copyright (C) 2008-2012 Free Software Foundation, Inc.
+   Copyright (C) 2008-2016 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
@@ -33,15 +33,18 @@
    declared with attribute warn_unused_result".  */
 
 #ifndef _GL_IGNORE_VALUE_H
-# define _GL_IGNORE_VALUE_H
-
-/* 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
+#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