c++ get address of variable without operator&

Question

I have got a class that has overloaded unary operator&. The objects of that type were created using new, so address of variable was accessible but now I need to use static object. Is it possible to get its address?

@FredLarson I was surprised too look at: http://en.wikipedia.org/wiki/Operators_in_C_and_C%2B%2B#Member_and_pointer_operators — KugBuBu, Oct 30 '14 at 13:55
@KugBuBu: Yes, I saw that it can be overloaded. But the question is not explicit on which actually is overloaded in this case. I've seen classes overload binary `operator&` (say, for string concatenation). It's unusual to overload the unary operator. — Fred Larson, Oct 30 '14 at 13:57
@FredLarson: The question would be rather trivial if it weren't about the unary operator. — Mike Seymour, Oct 30 '14 at 14:01
Essentially the same question http://stackoverflow.com/q/1142607/57428 — sharptooth, Oct 30 '14 at 15:32
@MikeSeymour Nvm, I was being silly. This is why staying up for more than 20 hours is never a good idea. — Pharap, Oct 31 '14 at 14:18

Mike Seymour · Answer 1 · 2014-10-30T14:21:41.773

In C++11 or later, std::addressof(object), declared by the <memory> header.

Historically, it was more grotesque, especially if you wanted to deal with const and volatile qualifiers correctly. One possibility used by Boost's implementation of addressof is

reinterpret_cast<T*>(
    &const_cast<char&>(
        reinterpret_cast<const volatile char &>(object)))

first adding qualifers while converting to char& so that reinterpret_cast would work however object were qualified; then removing them so that the final conversion would work; then finally taking the address and converting that to the correct type. As long as T has the same qualifiers as object (which it will as a template parameter deduced from object), the resulting pointer will be correctly qualified.

This is also how `std::addressof` is implemented by GCC – Brian Bi Oct 30 '14 at 19:10 — Brian Bi, Oct 30 '14 at 19:10
And pretty much the same implementation for VC++. – Niall Oct 31 '14 at 08:33 — Niall, Oct 31 '14 at 08:33

score 31 · Accepted Answer · edited Oct 30 '14 at 13:57

31

Since C++11, you may use the function std::addressof

edited Oct 30 '14 at 13:57

Jonathan Wakely

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answered Oct 30 '14 at 13:49

Jarod42

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c++ get address of variable without operator&

2 Answers2