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;

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

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

The behavior of a program that adds specializations for is_trivially_copyable
or is_trivially_copyable_v
(since C++17) 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::ifstream::read().

Example¶

// Run this code

#include <iostream>
#include <type_traits>

struct A
{
int m;
};

struct B
{
B(B const&) {}
};

struct C
{
virtual void foo();
};

struct D
{
int m;

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

int main()
{
std::cout << std::boolalpha;
std::cout << std::is_trivially_copyable<A>::value << '\n';
std::cout << std::is_trivially_copyable<B>::value << '\n';
std::cout << std::is_trivially_copyable<C>::value << '\n';
std::cout << std::is_trivially_copyable<D>::value << '\n';
}

Output:¶

true
false
false
true

See also¶

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