Issue 3160: atomic_ref() = delete; should be deleted

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3160. `atomic_ref() = delete;` should be deleted

Section: 32.5.7 [atomics.ref.generic] Status: C++20 Submitter: Tim Song Opened: 2018-10-01 Last modified: 2021-02-25

Priority: 0

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Discussion:

atomic_ref has a deleted default constructor, which causes pointless ambiguities in cases like:

void meow(atomic_ref<int>);
void meow(some_default_constructible_struct);

meow({});

It should have no default constructor rather than a deleted one. (Note that it has other user-defined constructors and so cannot be an aggregate under any definition.)

[2018-10-06 Status to Tentatively Ready after seven positive votes on the reflector.]

[2018-11, Adopted in San Diego]

Proposed resolution:

This wording is relative to N4762.

Edit 32.5.7 [atomics.ref.generic], class template atomic_ref synopsis, as indicated:

[…]
atomic_ref() = delete;
atomic_ref& operator=(const atomic_ref&) = delete;
[…]

Edit 32.5.7.3 [atomics.ref.int], class template specialization atomic_ref<integral> synopsis, as indicated:
```
[…]
atomic_ref() = delete;
atomic_ref& operator=(const atomic_ref&) = delete;
[…]
```
Edit 32.5.7.4 [atomics.ref.float], class template specialization atomic_ref<floating-point> synopsis, as indicated:
```
[…]
atomic_ref() = delete;
atomic_ref& operator=(const atomic_ref&) = delete;
[…]
```
Edit 32.5.7.5 [atomics.ref.pointer], class template specialization atomic_ref<T*> synopsis, as indicated:
```
[…]
atomic_ref() = delete;
atomic_ref& operator=(const atomic_ref&) = delete;
[…]
```

3160. atomic_ref() = delete; should be deleted

3160. `atomic_ref() = delete;` should be deleted