[libcxx] Fix LWG 2876: shared_ptr::shared_ptr(const weak_ptr<Y>&) constructor should be constrained.

[zoecarver]

Summary

Fixes LWG 2876 and some issues with array types in weak_ptr.

[zoecarver]

I'm going to add a more comprehensive patch to fully support array types in weak_ptr later this week.

[zoecarver]

• Update 1z satus

[ldionne]

Can we add tests for these constructors with incompatible Yps too?

libcxx/include/memory

4533

I'm not seeing this change as part of LWG 2876.

Where does that come from? If we don't have proper support for array types in weak_ptr, we should add it separately (with tests too), not as part of fixing this simple LWG issue.

libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.const/weak_ptr.pass.cpp

85

STD_TEST_VERSION doesn't exist either. Please see my comment in another patch.

[zoecarver]

If we don't have proper support for array types in weak_ptr, we should add it separately (with tests too), not as part of fixing this simple LWG issue.

I was hoping to put together a patch for this today but I didn't have time. I should be able to implement this tomorrow or sometime later this week. We should put this patch on hold until that's done.