std::copy_constructible

template< class T >
concept copy_constructible =
    std::move_constructible<T> &&
    std::constructible_from<T, T&> && std::convertible_to<T&, T> &&
    std::constructible_from<T, const T&> && std::convertible_to<const T&, T> &&
    std::constructible_from<T, const T> && std::convertible_to<const T, T>;

The concept copy_constructible is satisfied if T is an lvalue reference type, or if it is a move_constructible object type where an object of that type can constructed from a (possibly const) lvalue or const rvalue of that type in both direct- and copy-initialization contexts with the usual semantics (a copy is constructed with the source unchanged).

Semantic requirements

If T is an object type, then copy_constructible<T> is modeled only if given

• v, an lvalue of type (possibly const) T or an rvalue of type const T,

the following are true:

• After the definition T u = v;, u is equal to v and v is not modified;
• T(v) is equal to v and does not modify v.

References

• C++23 standard (ISO/IEC 14882:2024):
• 18.4.14 Concept copy_constructible [concept.copyconstructible]
• C++20 standard (ISO/IEC 14882:2020):
• 18.4.14 Concept copy_constructible [concept.copyconstructible]

See also