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Showing content from https://en.cppreference.com/w/cpp/algorithm/../ranges/../../cpp/types/is_trivially_copyable.html below:

std::is_trivially_copyable - cppreference.com

template< class T > struct is_trivially_copyable;

(since C++11)

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.

[edit] Template parameters [edit] Helper variable template

template< class T > constexpr bool is_trivially_copyable_v = is_trivially_copyable<T>::value;

(since C++17) Inherited from std::integral_constant Member constants true if T is a trivially copyable type, false otherwise
(public static member constant) Member functions converts the object to bool, returns value
(public member function) returns value
(public member function) Member types [edit] 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::ifstream::read().

[edit] Example

#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() {}

[edit] Defect reports

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

DR Applied to Behavior as published Correct behavior LWG 2015 C++11 T could be an array of incomplete
class type with unknown bound the behavior is
undefined in this case [edit] See also

(C++11)(deprecated in C++26)

checks if a type is trivial
(class template) [edit]

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