Specifies that an instance of the type can be copy-constructed from an lvalue expression.
[edit] RequirementsThe type T satisfies CopyConstructible if
T satisfies MoveConstructible, andGiven
T or const T or an rvalue expression of type const T,The following expressions must be valid and have their specified effects:
Expression Post-conditions T u = v; The value of u is equivalent to the value of v.The value of v is unchanged.
T(v) The value of T(v) is equivalent to the value of v.The value of v is unchanged.
The expression v.~T() also must be valid, and, for lvalue v, the expression &v must have the type T* or const T* and must evaluate to the address of v.
Until C++11, classes that overloaded operator& were not CopyConstructible and thus were not usable in the standard library containers. This is a design decision in C++98 (instead of a defect, see LWG issue 390).
Since C++11, the standard library uses std::addressof whenever the address of an object is needed.
Extended contentBeing a CopyConstructible class implies std::is_copy_constructible but not vice versa since std::is_copy_constructible will only check for the ability to call the constructor with the correct arguments, and, e.g., not a MoveConstructible requirement.
Run this code
#include <type_traits>
#include <utility>
struct S
{
S() = default;
S(S&&) = delete;
S(const S&) = default;
};
static_assert(std::is_copy_constructible_v<S>);
int main()
{
S s1;
// Class `S` doesn't satisfy MoveConstructible requirement,
// hence doesn't satisfy CopyConstructible requirement
[[maybe_unused]] S s2{std::move(s1)}; // ill-formed, use of deleted function
}[edit] References Extended content
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