| [/ |
| Copyright 2007 John Maddock. |
| Distributed under the Boost Software License, Version 1.0. |
| (See accompanying file LICENSE_1_0.txt or copy at |
| http://www.boost.org/LICENSE_1_0.txt). |
| ] |
| |
| [section:has_trivial_constructor has_trivial_constructor] |
| |
| template <class T> |
| struct has_trivial_constructor : public __tof {}; |
| |
| template <class T> |
| struct has_trivial_default_constructor : public __tof {}; |
| |
| __inherit If T is a (possibly cv-qualified) type with a trivial default-constructor |
| then inherits from __true_type, otherwise inherits from __false_type. |
| |
| These two traits are synonyms for each other. |
| |
| If a type has a trivial default-constructor then the constructor have no effect: |
| calls to the constructor can be safely omitted. Note that using meta-programming |
| to omit a call to a single trivial-constructor call is of no benefit whatsoever. |
| However, if loops and/or exception handling code can also be omitted, then some |
| benefit in terms of code size and speed can be obtained. |
| |
| __compat If the compiler does not support partial-specialization of class |
| templates, then this template can not be used with function types. |
| |
| Without some (as yet unspecified) help from the compiler, |
| has_trivial_constructor will never report that a user-defined class or struct has a |
| trivial constructor; this is always safe, if possibly sub-optimal. Currently |
| (May 2005) only MWCW 9 and Visual C++ 8 have the necessary compiler __intrinsics to detect |
| user-defined classes with trivial constructors. |
| |
| __std_ref 12.1p6. |
| |
| __header ` #include <boost/type_traits/has_trivial_constructor.hpp>` or ` #include <boost/type_traits.hpp>` |
| |
| __examples |
| |
| [:`has_trivial_constructor<int>` inherits from `__true_type`.] |
| |
| [:`has_trivial_constructor<char*>::type` is the type `__true_type`.] |
| |
| [:`has_trivial_constructor<int (*)(long)>::value` is an integral constant |
| expression that evaluates to /true/.] |
| |
| [:`has_trivial_constructor<MyClass>::value` is an integral constant |
| expression that evaluates to /false/.] |
| |
| [:`has_trivial_constructor<T>::value_type` is the type `bool`.] |
| |
| [endsect] |
| |