blob: 1f78ed79895b84754203e922bc1d2eeb1c100cb7 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
|
/* -*- 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_ */
|
