stdaddressof

std::addressof is a utility in the C++ standard library that returns the actual memory address of an object, bypassing any overloaded address-of operator. It is designed to obtain a true pointer to an object even when a class defines a custom operator&.

The function is declared in the <memory> header and is available since C++11. Its signature is template<class T> constexpr T* addressof(T& r) noexcept. It yields a pointer to the referred object, regardless of any user-defined operator&. The operation is constexpr and noexcept, making it usable in constant expressions and in contexts where exceptions must be avoided.

std::addressof is particularly important when a class overloads operator& to return a proxy or otherwise alter the meaning of address taking. In such cases, using the built-in address operator (&) would invoke the overloaded operator, not the actual memory address. std::addressof provides a standard, portable way to obtain the real address of the object.

Typical usage is straightforward: given an lvalue obj of some type T, std::addressof(obj) yields a T* that points to the original object. This is commonly used in low-level code, in library implementations, or when interacting with APIs that require the true object address.

Notes: std::addressof requires an lvalue of type T; it cannot take a temporary. It is also useful in situations where operator& is deleted or unavailable. See also the built-in address-of operator and related utilities in <memory>.