<memory>: ~_Ref_count_base() should be non-virtual

[StephanTLavavej]

STL/stl/inc/memory

Line 620 in 6b0238d

virtual ~_Ref_count_base() noexcept {} // TRANSITION, should be non-virtual

shared_ptr's type-erasure machinery doesn't require the reference count control block to have a virtual destructor. Making this non-virtual would be a minor improvement, but it's an ABI-breaking change.

vNext note: Resolving this issue will require breaking binary compatibility. We won't be able to accept pull requests for this issue until the vNext branch is available. See #169 for more information.

[MikeGitb]

Is there going to be a branch, where all the vnext stuff can be put into / PR-d against or what is the planned procedure?

[StephanTLavavej]

#169 tracks that. Yes, it will be a branch alongside master (one of the only branches we plan to have in the repo).

[frederick-vs-ja]

While investigating future-related machineries, I found that _Deleter_base::~_Deleter_base seems never virtually called (see #3284 (comment)), and thus can be made implicitly declared and non-virtual. Perhaps such change is also ABI-breaking and should be done in vNext.