Generate a warning if the return value of FilePath::Append is ignored.

base/compiler_specific.h

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_COMPILER_SPECIFIC_H_
 #define BASE_COMPILER_SPECIFIC_H_
 
 #include "build/build_config.h"
 
 #if defined(COMPILER_MSVC)
@@ skipping 32 matching lines @@
 //
 // Example usage:
 // Foo::Foo() : x(NULL), ALLOW_THIS_IN_INITIALIZER_LIST(y(this)), z(3) {}
 //
 // Compiler warning C4355: 'this': used in base member initializer list:
 // http://msdn.microsoft.com/en-us/library/3c594ae3(VS.80).aspx
 #define ALLOW_THIS_IN_INITIALIZER_LIST(code) MSVC_PUSH_DISABLE_WARNING(4355) \
                                              code \
                                              MSVC_POP_WARNING()
 
-#else  // COMPILER_MSVC
+#else  // Not MSVC
 
 #define MSVC_SUPPRESS_WARNING(n)
 #define MSVC_PUSH_DISABLE_WARNING(n)
 #define MSVC_PUSH_WARNING_LEVEL(n)
 #define MSVC_POP_WARNING()
 #define ALLOW_THIS_IN_INITIALIZER_LIST(code) code
 
 #endif  // COMPILER_MSVC
 
+
+#if defined(COMPILER_GCC)
+#define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
+#else  // Not GCC
+#define WARN_UNUSED_RESULT
+#endif
+
 #endif  // BASE_COMPILER_SPECIFIC_H_
-