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1 | [/ |
2 | Copyright 2007 John Maddock. | |
3 | Copyright 2013 Antony Polukhin. | |
4 | Distributed under the Boost Software License, Version 1.0. | |
5 | (See accompanying file LICENSE_1_0.txt or copy at | |
6 | http://www.boost.org/LICENSE_1_0.txt). | |
7 | ] | |
8 | ||
9 | [section:has_trivial_move_assign has_trivial_move_assign] | |
10 | template <class T> | |
11 | struct has_trivial_move_assign : public __tof {}; | |
12 | ||
13 | __inherit If T is a (possibly cv-qualified) type with a trivial move assignment-operator | |
14 | then inherits from __true_type, otherwise inherits from __false_type. | |
15 | ||
16 | If a type has a trivial move assignment-operator then the operator has the same effect | |
17 | as copying the bits of one object to the other: | |
18 | calls to the operator can be safely replaced with a call to `memcpy`. | |
19 | ||
20 | __compat Without some (as yet unspecified) help from the compiler, | |
21 | has_trivial_move_assign will never report that a user-defined class or struct has a | |
22 | trivial move assign; this is always safe, if possibly sub-optimal. | |
23 | In addition, in order to correctly handle private or deleted move assignment | |
24 | operators then c++11's `decltype` is required. | |
25 | Currently (June 2015) compilers that have the necessary __intrinsics to ensure that this | |
26 | trait "just works" include Clang, GCC-5.1 and MSVC-12.0. | |
27 | You may also test to see if the necessary __intrinsics are available | |
28 | by checking to see if the macro `BOOST_HAS_TRIVIAL_MOVE_ASSIGN` is defined. | |
29 | ||
30 | ||
31 | __header ` #include <boost/type_traits/has_trivial_move_assign.hpp>` or ` #include <boost/type_traits.hpp>` | |
32 | ||
33 | __examples | |
34 | ||
35 | [:`has_trivial_move_assign<int>` inherits from `__true_type`.] | |
36 | ||
37 | [:`has_trivial_move_assign<char*>::type` is the type `__true_type`.] | |
38 | ||
39 | [:`has_trivial_move_assign<int (*)(long)>::value` is an integral constant | |
40 | expression that evaluates to /true/.] | |
41 | ||
42 | [:`has_trivial_move_assign<MyClass>::value` is an integral constant | |
43 | expression that evaluates to /false/.] | |
44 | ||
45 | [:`has_trivial_move_assign<T>::value_type` is the type `bool`.] | |
46 | ||
47 | [endsect] | |
48 |