P0019R8 atomic_ref

[StephanTLavavej]

P0019R8 atomic_ref
P1960R0 atomic_ref Cleanup (note: this paper made minor changes to other wording)

LWG-3160 atomic_ref() = delete; should be deleted

Feature-test macro as of WG21-N4842, added by WG21-P1902:
#define __cpp_lib_atomic_ref 201806L

[AlexGuteniev]

I have a question on this one.

It appears that atomic_ref is "the same as atomic, but reference". So easy way of implementing it could be adding support for references in _Atomic_storage and other classes. But on the other hand, ABI should be preserved, to avoid making this vNext.

So I guess the best way to implement atomic_ref is to re-use existing _Atomic_storage so that it is both extended to support atomic_ref and ABI-unchanged for atomic.

Want you to confirm that.

[AlexGuteniev]

Also I believe that #694 should be merged prior to starting work on this, as they may be changing overlapping parts actually no, changes are merge-able.

[AlexGuteniev]

I think simple change (the way which I put it in draft PR) is possible.

Standard defines:

T* ptr; // exposition only

But as it defines no way to reassign the pointer:

atomic_ref& operator = (const atomic_ref&) = delete

So it may be implemented as reference:

T& ptr; // exposition only

This replacement of value with reference allows for transparent reuse atomic machinery for atomic_ref.