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

std::is_copy_constructible, std::is_trivially_copy_constructible, std::is_nothrow_copy_constructible - cppreference.com

template< class T > struct is_copy_constructible;

(1) (since C++11)

template< class T > struct is_trivially_copy_constructible;

(2) (since C++11)

template< class T > struct is_nothrow_copy_constructible;

(3) (since C++11)

If T is not a complete type, (possibly cv-qualified) void, or an array of unknown bound, the behavior is undefined.

If an instantiation of a template above depends, directly or indirectly, on an incomplete type, and that instantiation could yield a different result if that type were hypothetically completed, the behavior is undefined.

If the program adds specializations for any of the templates described on this page, the behavior is undefined.

[edit] Helper variable templates template< class T > inline constexpr bool is_copy_constructible_v = is_copy_constructible<T>::value; (since C++17) template< class T > inline constexpr bool is_trivially_copy_constructible_v = is_trivially_copy_constructible<T>::value; (since C++17) template< class T > inline constexpr bool is_nothrow_copy_constructible_v = is_nothrow_copy_constructible<T>::value; (since C++17) Inherited from std::integral_constant Member constants true if T is copy-constructible, 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] Possible implementation [edit] Notes

In many implementations, is_nothrow_copy_constructible also checks if the destructor throws because it is effectively noexcept(T(arg)). Same applies to is_trivially_copy_constructible, which, in these implementations, also requires that the destructor is trivial: GCC bug 51452, LWG issue 2116.

[edit] Example

#include <string>
#include <type_traits>
 
struct S1
{
    std::string str; // member has a non-trivial copy constructor
};
static_assert(std::is_copy_constructible_v<S1>);
static_assert(!std::is_trivially_copy_constructible_v<S1>);
 
struct S2
{
    int n;
    S2(const S2&) = default; // trivial and non-throwing
};
static_assert(std::is_trivially_copy_constructible_v<S2>);
static_assert(std::is_nothrow_copy_constructible_v<S2>);
 
struct S3
{
    S3(const S3&) = delete; // explicitly deleted
};
static_assert(!std::is_copy_constructible_v<S3>);
 
struct S4
{
    S4(S4&) {}; // cannot bind const, hence not a copy-constructible
};
static_assert(!std::is_copy_constructible_v<S4>);
 
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 2196 C++11 the behavior was unclear if const T& cannot be formed the value produced is false in this case [edit] See also

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