Namespaces
Variants
Views
Actions

std::addressof

From cppreference.com
< cpp‎ | memory
Revision as of 08:10, 7 December 2012 by Cubbi (Talk | contribs)

 
 
 
 

Template:ddcl list begin <tr class="t-dsc-header">

<td>
Defined in header <memory>
</td>

<td></td> <td></td> <tr class="t-dcl ">

<td >
template< class T >
T* addressof(T& arg);
</td>

<td class="t-dcl-nopad"> </td> <td > (since C++11) </td> </tr> Template:ddcl list end

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

Contents

Parameters

arg - lvalue object or function

Return value

Pointer to arg.

Exceptions

noexcept specification:  
noexcept
  

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:

#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

Template:cpp/memory/dcl list allocatorTemplate:cpp/memory/dcl list pointer traits