[PATCH] D30837: [libcxx] Support for shared_ptr<T()>

[Erik Pilkington via Phabricator via cfe-commits]

erik.pilkington created this revision.

This patch adds support for `shared_ptr<T()>` types, so that the following works:

  void Func();
  void Del(void (*)())
  std::shared_ptr<void()> x(Func, Del);

Where previously this would fail to compile. In PR27566, the use case described for this was a shared pointer to a dynamically loaded function, which seems reasonable enough to me. Both libstdc++ and MSVC support this use case as well, and I didn't notice any wording in the standard that disallowed it. This patch has 2 parts:

1. Don't try to instantiate an `allocator<T()>`
2. Fix `__enable_weak_this()` dummy overload to work with function pointers.

Number 1 is accomplished by passing in `allocator<void>` into `__shared_ptr_pointer` or `__shared_ptr_emplace` when no allocator was passed to the constructor of the `shared_ptr`, I believe this is correct because in this case the allocator is only used for a rebind, so any instantiation of std::allocator would work fine.

This is my first libc++ patch, so take it with a grain of salt! Thanks for taking a look,
Erik


https://reviews.llvm.org/D30837

Files:
  include/memory
  test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.create/make_shared.pass.cpp

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