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[/
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 2011) compilers more recent than Visual C++ 8, GCC-4.3, Greenhills 6.0,
Intel-11.0, and Codegear have the necessary compiler __intrinsics to ensure that this
trait "just works". You may also test to see if the necessary __intrinsics are available
by checking to see if the macro `BOOST_HAS_TRIVIAL_CONSTRUCTOR` is defined.
__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]
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