mirror of https://github.com/axmolengine/axmol.git
78 lines
2.0 KiB
C++
78 lines
2.0 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/*
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* Provides DebugOnly, a type for variables used only in debug builds (i.e. by
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* assertions).
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*/
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#ifndef mozilla_DebugOnly_h_
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#define mozilla_DebugOnly_h_
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namespace mozilla {
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/**
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* DebugOnly contains a value of type T, but only in debug builds. In release
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* builds, it does not contain a value. This helper is intended to be used with
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* MOZ_ASSERT()-style macros, allowing one to write:
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*
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* DebugOnly<bool> check = func();
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* MOZ_ASSERT(check);
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*
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* more concisely than declaring |check| conditional on #ifdef DEBUG, but also
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* without allocating storage space for |check| in release builds.
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*
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* DebugOnly instances can only be coerced to T in debug builds. In release
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* builds they don't have a value, so type coercion is not well defined.
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*/
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template<typename T>
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class DebugOnly
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{
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public:
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#ifdef DEBUG
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T value;
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DebugOnly() { }
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DebugOnly(const T& other) : value(other) { }
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DebugOnly(const DebugOnly& other) : value(other.value) { }
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DebugOnly& operator=(const T& rhs) {
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value = rhs;
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return *this;
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}
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void operator++(int) {
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value++;
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}
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void operator--(int) {
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value--;
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}
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T* operator&() { return &value; }
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operator T&() { return value; }
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operator const T&() const { return value; }
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T& operator->() { return value; }
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#else
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DebugOnly() { }
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DebugOnly(const T&) { }
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DebugOnly(const DebugOnly&) { }
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DebugOnly& operator=(const T&) { return *this; }
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void operator++(int) { }
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void operator--(int) { }
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#endif
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/*
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* DebugOnly must always have a destructor or else it will
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* generate "unused variable" warnings, exactly what it's intended
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* to avoid!
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*/
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~DebugOnly() {}
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};
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}
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#endif /* mozilla_DebugOnly_h_ */
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