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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #ifndef BASE_TEMPLATE_UTIL_H_ | 5 #ifndef BASE_TEMPLATE_UTIL_H_ |
6 #define BASE_TEMPLATE_UTIL_H_ | 6 #define BASE_TEMPLATE_UTIL_H_ |
7 | 7 |
8 #include <stddef.h> | 8 #include <stddef.h> |
9 #include <iosfwd> | 9 #include <iosfwd> |
10 #include <type_traits> | 10 #include <type_traits> |
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119 // TODO(crbug.com/554293): Remove this when all platforms have this in the std | 119 // TODO(crbug.com/554293): Remove this when all platforms have this in the std |
120 // namespace. | 120 // namespace. |
121 #if defined(CR_USE_FALLBACKS_FOR_OLD_GLIBCXX) | 121 #if defined(CR_USE_FALLBACKS_FOR_OLD_GLIBCXX) |
122 template <class T> | 122 template <class T> |
123 using is_trivially_destructible = std::has_trivial_destructor<T>; | 123 using is_trivially_destructible = std::has_trivial_destructor<T>; |
124 #else | 124 #else |
125 template <class T> | 125 template <class T> |
126 using is_trivially_destructible = std::is_trivially_destructible<T>; | 126 using is_trivially_destructible = std::is_trivially_destructible<T>; |
127 #endif | 127 #endif |
128 | 128 |
129 #undef CR_USE_FALLBACKS_FOR_OLD_GLIBCXX | |
Ilya Sherman
2016/08/30 21:06:39
nit: Why did you move this? If you don't need to
Sidney San Martín
2016/08/30 21:18:13
I did have to move it, sadly. It needs the underly
Sidney San Martín
2016/08/30 21:30:32
Sorry, just figured out what you meant. Fixed!
| |
130 | |
131 // underlying_value | |
132 // Casts an enum to its underlying integral type, leaves other values alone. | |
133 // Useful for scoped enums, which don't cast implicitly. | |
134 | |
135 // Enums, taken by value. This specialization is necessary because creating an | |
136 // std::underlying_type with a non-enum is UB (and usually a compile error). | |
137 template <typename T, | |
138 typename std::enable_if<std::is_enum<T>::value, int>::type = 0> | |
139 constexpr typename underlying_type<T>::type underlying_value(T val) { | |
140 return static_cast<typename underlying_type<T>::type>(val); | |
141 } | |
142 | |
143 // Non-enum scalars, taken by value. This specialization is necessary due to an | |
144 // interesting case where a static const integral or enum data member can have | |
145 // an inline initializer and no out-of-line definition, but then may only be | |
146 // used in constant expressions. The catch-all specialization below would try | |
147 // to form a const reference. Discussion here: | |
148 // http://stackoverflow.com/questions/3792412/const-and-static-specifiers-in-c/3 792427#3792427 | |
149 template <typename T, | |
150 typename std::enable_if<std::is_fundamental<T>::value, int>::type = 0> | |
151 constexpr T underlying_value(T val) { | |
152 return val; | |
153 } | |
154 | |
155 // Non-scalars, taken by rvalue reference. T must be copyable or moveable, just | |
156 // like a static_cast. | |
157 template <typename T, | |
158 typename std::enable_if< | |
159 !std::is_scalar<typename std::remove_reference<T>::type>::value, | |
160 int>::type = 0> | |
161 constexpr T underlying_value(T&& val) { | |
162 return std::forward<T>(val); | |
163 } | |
164 | |
129 } // namespace base | 165 } // namespace base |
130 | 166 |
131 #undef CR_USE_FALLBACKS_FOR_OLD_GLIBCXX | |
132 | |
133 #endif // BASE_TEMPLATE_UTIL_H_ | 167 #endif // BASE_TEMPLATE_UTIL_H_ |
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