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std::is_trivially_copyable(3)  C++ Standard Libary std::is_trivially_copyable(3)

NAME
     std::is_trivially_copyable - std::is_trivially_copyable

Synopsis
	Defined in header <type_traits>
	template< class T >		 (since C++11)
	struct is_trivially_copyable;

	std::is_trivially_copyable is a UnaryTypeTrait.

	If  T  is  a trivially copyable type, provides the member constant value
     equal to true.
	For any other type, value is false.

	If std::remove_all_extents_t<T> is an incomplete type and not (possibly
	cv-qualified) void, the behavior is undefined.

	If the program adds specializations for std::is_trivially_copyable or
	std::is_trivially_copyable_v, the behavior is undefined.

Template parameters
	T - a type to check

	Helper variable template

	template< class T >
	inline	     constexpr	     bool	is_trivially_copyable_v        =
     (since C++17)
	is_trivially_copyable<T>::value;

     Inherited from std::integral_constant

Member constants
	value	 true if T is a trivially copyable type, false otherwise
	[static] (public static member constant)

Member functions
	operator bool converts the object to bool, returns value
		      (public member function)
	operator()    returns value
	(C++14)       (public member function)

Member types
	Type	   Definition
	value_type bool
	type	   std::integral_constant<bool, value>

Notes
	Objects of trivially-copyable types that are not potentially-overlapping
     subobjects
	are  the  only C++ objects that may be safely copied with std::memcpy or
     serialized
	to/from   binary   files   with   std::ofstream::write()   /	std::if-
     stream::read().

Example
     // Run this code

      #include <type_traits>

      struct A { int m; };
      static_assert(std::is_trivially_copyable_v<A> == true);

      struct B { B(B const&) {} };
      static_assert(std::is_trivially_copyable_v<B> == false);

      struct C { virtual void foo(); };
      static_assert(std::is_trivially_copyable_v<C> == false);

      struct D
      {
	  int m;

	  D(D const&) = default; // -> trivially copyable
	  D(int x) : m(x + 1) {}
      };
      static_assert(std::is_trivially_copyable_v<D> == true);

      int main() {}

	Defect reports

	The  following	behavior-changing  defect  reports were applied retroac-
     tively to
	previously published C++ standards.

	   DR	 Applied to	  Behavior as published 	 Correct  behav-
     ior
	LWG 2015 C++11	    T could be an array of incomplete the behavior is
			    class  type with unknown bound     undefined in this
     case

See also
	is_trivial checks if a type is trivial
	(C++11)    (class template)

http://cppreference.com 	   2024.06.10	   std::is_trivially_copyable(3)
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