mfbt/Unused.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_unused_h
   8 #define mozilla_unused_h
   9
  10 #include "mozilla/Attributes.h"
  11 #include "mozilla/Types.h"
  12
  13 #ifdef __cplusplus
  14
  15 namespace mozilla {
  16
  17 //
  18 // Suppress GCC warnings about unused return values with
  19 //   Unused << SomeFuncDeclaredWarnUnusedReturnValue();
  20 //
  21 struct unused_t {
  22   template <typename T>
  23   MOZ_ALWAYS_INLINE_EVEN_DEBUG void operator<<(const T& /*unused*/) const {}
  24 };
  25
  26 extern MFBT_DATA const unused_t Unused;
  27
  28 }  // namespace mozilla
  29
  30 #endif  // __cplusplus
  31
  32 // An alternative to mozilla::Unused for use in (a) C code and (b) code where
  33 // linking with unused.o is difficult.
  34 #define MOZ_UNUSED(expr) \
  35   do {                   \
  36     if (expr) {          \
  37       (void)0;           \
  38     }                    \
  39   } while (0)
  40
  41 #endif  // mozilla_unused_h