Can & (address-of-operator) ever return nullptr?

Question

Sounds like a trivial question judging from typical usage of & operator, but is there a guarantee from the standard that address-of-operator cannot return nullptr when trying to get an address?

Answer 1

There is no guarantee that the operator& can't return nullptr, for instance by overloading this operator.

Here is a contrived example:

#include <iostream>

struct foo  { foo* operator& ()  { return nullptr; }  };

int main()
{
    foo f;
    
    if (&f == nullptr) {  std::cout << "nullptr detected\n";  }
    
    std::cout << "the true address is " << std::addressof(f) << "\n";
}

Demo