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
42