US061 09.04.4 p10 Coroutine allocation should consider std::align_val_t P2014

[wg21bot]

Coroutine allocation does not consider std::align_val_t overloads introduced in C++17

Proposed change:
Add them to the sequence of operator new calls that are attempted using wording similar to 7.6.2.7/18

[jfbastien]

From #62 (closed as duplicate):

The construction of the argument list for the call to the allocation function to allocate the 'coroutine state' does not call the overload of operator new() that accepts a std::align_val_t in the case that the allocation required for the coroutine has 'new-extended alignment'. This means that allocations of coroutine frames may not be correctly aligned in cases where the coroutine state contains overaligned types.

Proposed change:
Apply similar wording from [expr.new]p18:
Insert
"If the coroutine state has new-extended alignment then the next argument is std::align_val_t." after "has type size_t."

Insert at end of paragraph:
If no matching function is found and the allocated coroutine state has new-extended alignment, the alignment argument is removed from the argument list, and overload resolution is performed again.

[jfbastien]

EWG Tuesday: http://wiki.edg.com/bin/view/Wg21belfast/US061

US061 Does EWG want to consider this for C++20

F	A
7	2

Gor and Lewis to work on wording.

[jfbastien]

See cplusplus/papers#750

[jfbastien]

Based on discussion of P2014, no consensus for change.

[jensmaurer]

EWG in Prague: Rejected. There was no consensus to adopt this change.