Guaranteed copy elision paper's use of void in a constructor

Question

In the paper P0135R0 there is an example:

struct NonMoveable {
  NonMoveable(int);
  NonMoveable(NonMoveable&) = delete;
  void NonMoveable(NonMoveable&) = delete;
  std::array<int, 1024> arr;
};
NonMoveable make() {
  return NonMoveable(42); // ok, directly constructs returned object
}
auto nm = make(); // ok, directly constructs 'nm'

This confused me:

void NonMoveable(NonMoveable&) = delete;

What is it? How constructor can be void?

UPD. Someone linked probable answer - No! This question is totally different.

*"No! This question is totally different."* How so? If you are not asking what `=delete` does, then what are you asking? — Baum mit Augen, Jul 16 '16 at 22:17
But the constructor is *alive and kicking* and is called `NonMoveable(int)`. — hgiesel, Jul 16 '16 at 22:18
Well that is an error, constructors and deconstructors don't have return types. — hgiesel, Jul 16 '16 at 22:22
@MarcGlisse Doesn't look like a typo. It would make at least 2 changes to make it legit. One removing `void` and second changing argument to `&&` — xinaiz, Jul 16 '16 at 22:26
Note that the current version of the paper, [P0135R1](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0135r1.html), does not contain such an example. — ildjarn, Jul 17 '16 at 00:22

Nicol Bolas · Accepted Answer · 2016-07-16T22:50:14.577

6

That "void" is what we would call a "typo". The intent was likely to remove the move assignment operator (though not strictly necessary, since deleting the copy constructor would do that). Considering that the person wrote "void", it's not surprising that the person also missed the && part, and forgot the const in the copy constructor's parameter (also not strictly necessary).

Basically, there's a lot wrong there; someone wrote it in a hurry.

edited Jul 16 '16 at 22:50

answered Jul 16 '16 at 22:28

Nicol Bolas

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6

It's likely meant to delete the copy assignment. Just deleting the copy constructor won't do the job. – T.C. Jul 16 '16 at 23:19
1

You misspelled Typevoido – Yakk - Adam Nevraumont Jul 17 '16 at 09:52

Guaranteed copy elision paper's use of void in a constructor

1 Answers1