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std::is_trivially_copyable(3) C++ Standard Libarystd::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 (pos- sibly 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-over- lapping 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 be- havior 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)
NAME | Synopsis | Template parameters | Member constants | Member functions | Member types | Notes | Example | See also
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