std::addressof

 

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Defined in header <memory>
template< class T > T* addressof(T& arg);		(since C++11)

Obtains the actual address of the object or function arg, even in presence of overloaded operator&

Parameters

arg

-

lvalue object or function

Return value

Pointer to arg.

Exceptions

noexcept specification:  

noexcept

  (since C++11)

Possible implementation

template< class T > T* addressof(T& arg) { return reinterpret_cast<T*>( &const_cast<char&>( reinterpret_cast<const volatile char&>(arg))); }

Example

operator& may be overloaded for a pointer wrapper class to obtain a pointer to pointer:

run this code

#include <iostream>
#include <memory>
 
template<class T>
struct Ptr {
   T* data;
   Ptr(T* arg) : data(arg) {}
   ~Ptr() {delete data;}
   T** operator&() { return &data; }
};
 
template<class T>
void f(Ptr<T>* p) {
    std::cout << "Ptr overload called with p = " << p << '\n';
}
 
void f(int** p) {
    std::cout << "int** overload called with p = " << p << '\n';
}
 
int main()
{
    Ptr<int> p(new int(42));
    f(&p);                 // calls int** overload
    f(std::addressof(p));  // calls Ptr<int>* overload
}

Output:

int** overload called with p = 0012FF64
Ptr overload called with p = 0012FF64

See also

allocator	the default allocator (class template)
pointer_traits (C++11)	provides information about pointer-like types (class template)