The Tor Browser / file comparison
comparison: mfbt/DebugOnly.h
mfbt/DebugOnly.h
- branch
- TOR_BUG_9701
- changeset 8
- 97036ab72558
equal
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| -1:000000000000 | 0:1f239531ca8c |
|---|---|
| 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 /* | |
| 8 * Provides DebugOnly, a type for variables used only in debug builds (i.e. by | |
| 9 * assertions). | |
| 10 */ | |
| 11 | |
| 12 #ifndef mozilla_DebugOnly_h | |
| 13 #define mozilla_DebugOnly_h | |
| 14 | |
| 15 namespace mozilla { | |
| 16 | |
| 17 /** | |
| 18 * DebugOnly contains a value of type T, but only in debug builds. In release | |
| 19 * builds, it does not contain a value. This helper is intended to be used with | |
| 20 * MOZ_ASSERT()-style macros, allowing one to write: | |
| 21 * | |
| 22 * DebugOnly<bool> check = func(); | |
| 23 * MOZ_ASSERT(check); | |
| 24 * | |
| 25 * more concisely than declaring |check| conditional on #ifdef DEBUG, but also | |
| 26 * without allocating storage space for |check| in release builds. | |
| 27 * | |
| 28 * DebugOnly instances can only be coerced to T in debug builds. In release | |
| 29 * builds they don't have a value, so type coercion is not well defined. | |
| 30 * | |
| 31 * Note that DebugOnly instances still take up one byte of space, plus padding, | |
| 32 * when used as members of structs. | |
| 33 */ | |
| 34 template<typename T> | |
| 35 class DebugOnly | |
| 36 { | |
| 37 public: | |
| 38 #ifdef DEBUG | |
| 39 T value; | |
| 40 | |
| 41 DebugOnly() { } | |
| 42 DebugOnly(const T& other) : value(other) { } | |
| 43 DebugOnly(const DebugOnly& other) : value(other.value) { } | |
| 44 DebugOnly& operator=(const T& rhs) { | |
| 45 value = rhs; | |
| 46 return *this; | |
| 47 } | |
| 48 void operator++(int) { | |
| 49 value++; | |
| 50 } | |
| 51 void operator--(int) { | |
| 52 value--; | |
| 53 } | |
| 54 | |
| 55 T* operator&() { return &value; } | |
| 56 | |
| 57 operator T&() { return value; } | |
| 58 operator const T&() const { return value; } | |
| 59 | |
| 60 T& operator->() { return value; } | |
| 61 const T& operator->() const { return value; } | |
| 62 | |
| 63 #else | |
| 64 DebugOnly() { } | |
| 65 DebugOnly(const T&) { } | |
| 66 DebugOnly(const DebugOnly&) { } | |
| 67 DebugOnly& operator=(const T&) { return *this; } | |
| 68 void operator++(int) { } | |
| 69 void operator--(int) { } | |
| 70 #endif | |
| 71 | |
| 72 /* | |
| 73 * DebugOnly must always have a destructor or else it will | |
| 74 * generate "unused variable" warnings, exactly what it's intended | |
| 75 * to avoid! | |
| 76 */ | |
| 77 ~DebugOnly() {} | |
| 78 }; | |
| 79 | |
| 80 } | |
| 81 | |
| 82 #endif /* mozilla_DebugOnly_h */ |
