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__has_trivial_default_constructor
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Type Trait Functions

Syntax

bool __has_trivial_default_constructor (typename T )

Returns true if and only if T has a trivial default constructor.

Errorif T is an incomplete type.

False (but well-formed) if a class type does not have a default constructor.

According to the definition from Section 20.4.4.3 of the Working Draft notes, a type T has a trivial copy assignment operator if:

- a scalar type (or array thereof)
- an array of class type with a trivial default constructor
- a class type with a trivial default constructorr

Especially note false for reference types.

According to Section 21.1 p5 of the Working Draft, a default constructor is trivial if:

- It is not user provided
- Its class has no virtual functions
- Its class has no virtual base classes
- Each direct base class of X has a trivial copy assignment operator.
- All the direct base classes of its class have trivial default constructors.
- For all the non-static data members of its class that are of class type (or array thereof), each such class has a trivial default constructor.

A default consructor is not user provided if it is implicitly declared, or defined inline as = default;.

Ox interaction if the copy assign operator is defined as deleted.

Ox interaction false if the default constructor is defined as deleted.

Ox interaction with default function definitions.

See Also

C++0x Features (C++Builder 2009)

Type Trait Functions Overview

Working Draft - Standard for Programming Language C++ - http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2588.pdf

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