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