Comment on WARN_UNUSED_RESULT about how to defeat it.

base/compiler_specific.h

 // Copyright (c) 2011 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_
 #pragma once
 
 #include "build/build_config.h"
 
@@ skipping 93 matching lines @@
 #define OVERRIDE override
 #elif defined(__clang__)
 #define OVERRIDE override
 #else
 #define OVERRIDE
 #endif
 
 // Annotate a function indicating the caller must examine the return value.
 // Use like:
 //   int foo() WARN_UNUSED_RESULT;
+// To explicitly ignore a result, see |ignore_result()| in <base/basictypes.h>.
 #if defined(COMPILER_GCC)
 #define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
 #else
 #define WARN_UNUSED_RESULT
 #endif
 
 // Tell the compiler a function is using a printf-style format string.
 // |format_param| is the one-based index of the format string parameter;
 // |dots_param| is the one-based index of the "..." parameter.
 // For v*printf functions (which take a va_list), pass 0 for dots_param.
 // (This is undocumented but matches what the system C headers do.)
 #if defined(COMPILER_GCC)
 #define PRINTF_FORMAT(format_param, dots_param) \
     __attribute__((format(printf, format_param, dots_param)))
 #else
 #define PRINTF_FORMAT(format_param, dots_param)
 #endif
 
 // WPRINTF_FORMAT is the same, but for wide format strings.
 // This doesn't appear to yet be implemented in any compiler.
 // See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38308 .
 #define WPRINTF_FORMAT(format_param, dots_param)
 // If available, it would look like:
 //   __attribute__((format(wprintf, format_param, dots_param)))
 
 #endif  // BASE_COMPILER_SPECIFIC_H_