std::is_trivially_copyable - cppreference.com
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    std::is_trivially_copyable

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    Defined in header <type_traits> 
    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.

    Template parameters

    T - a type to check

    Helper variable template

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

    Inherited from std::integral_constant

    Member constants

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

    Member functions

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

    See also