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## addressof

### Authors

- Brad King
- Douglas Gregor
- Peter Dimov
- Glen Fernandes

### Header <boost/core/addressof.hpp>

The header `<boost/core/addressof.hpp>` defines the function template `boost::addressof`. `boost::addressof(x)` returns the address of `x`. Ordinarily, this address can be obtained by `&x`, but the unary `&` operator can be overloaded. `boost::addressof` avoids calling used-defined `operator&()`.

`boost::addressof` was originally contributed by Brad King based on ideas from discussion with Doug Gregor.

#### Synopsis

    namespace boost
    {
        template<class T> T* addressof( T& x );
    }

#### Example

    #include <boost/core/addressof.hpp>

    struct useless_type { };

    class nonaddressable {
        useless_type operator&() const;
    };

    void f() {
        nonaddressable x;
        nonaddressable* xp = boost::addressof(x);
        // nonaddressable* xpe = &x; /* error */
    }

#### Notes

In C++11 and above, `boost::addressof` is conditionally `constexpr` when possible. This is indicated by `BOOST_CORE_NO_CONSTEXPR_ADDRESSOF` not being defined.

With supported compilers, `boost::addressof` is always `constexpr` by leveraging compiler intrinsics. This is indicated by `BOOST_CORE_HAS_BUILTIN_ADDRESSOF` being defined.