has_trivial_constructor

template <class T>
struct has_trivial_constructor : public true_type-or-false_type {};

template <class T>
struct has_trivial_default_constructor : public true_type-or-false_type {};

Inherits: 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.

Compiler Compatibility: 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. In addition, in order to correctly handle private or deleted default-constructors then C++11's deltype is required. Currently (May 2015) 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.

C++ Standard Reference: 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.

Boost C++ Libraries

has_trivial_constructor