[PATCH] D41805: Add pre-C++11 is_constructible wrappers for 3 arguments

[Dimitry Andric via Phabricator via cfe-commits]

dim created this revision.
dim added reviewers: EricWF, mclow.lists.
Herald added a subscriber: krytarowski.

After https://reviews.llvm.org/rL319736 for https://reviews.llvm.org/D28253 (which fixes PR28929), gcc cannot compile `<memory>` anymore in pre-C+11 modes, complaining:

  In file included from /usr/include/c++/v1/memory:648:0,
                   from test.cpp:1:
  /usr/include/c++/v1/memory: In static member function 'static std::__1::shared_ptr<_Tp> std::__1::shared_ptr<_Tp>::make_shared(_A0&, _A1&, _A2&)':
  /usr/include/c++/v1/memory:4365:5: error: wrong number of template arguments (4, should be at least 1)
       static_assert((is_constructible<_Tp, _A0, _A1, _A2>::value), "Can't construct object in make_shared" );
       ^
  In file included from /usr/include/c++/v1/memory:649:0,
                   from test.cpp:1:
  /usr/include/c++/v1/type_traits:3198:29: note: provided for 'template<class _Tp, class _A0, class _A1> struct std::__1::is_constructible'
   struct _LIBCPP_TEMPLATE_VIS is_constructible
                               ^~~~~~~~~~~~~~~~
  In file included from /usr/include/c++/v1/memory:648:0,
                   from test.cpp:1:
  /usr/include/c++/v1/memory:4365:5: error: template argument 1 is invalid
       static_assert((is_constructible<_Tp, _A0, _A1, _A2>::value), "Can't construct object in make_shared" );
       ^
  /usr/include/c++/v1/memory: In static member function 'static std::__1::shared_ptr<_Tp> std::__1::shared_ptr<_Tp>::allocate_shared(const _Alloc&, _A0&, _A1&, _A2&)':
  /usr/include/c++/v1/memory:4444:5: error: wrong number of template arguments (4, should be at least 1)
       static_assert((is_constructible<_Tp, _A0, _A1, _A2>::value), "Can't construct object in allocate_shared" );
       ^
  In file included from /usr/include/c++/v1/memory:649:0,
                   from test.cpp:1:
  /usr/include/c++/v1/type_traits:3198:29: note: provided for 'template<class _Tp, class _A0, class _A1> struct std::__1::is_constructible'
   struct _LIBCPP_TEMPLATE_VIS is_constructible
                               ^~~~~~~~~~~~~~~~
  In file included from /usr/include/c++/v1/memory:648:0,
                   from test.cpp:1:
  /usr/include/c++/v1/memory:4444:5: error: template argument 1 is invalid
       static_assert((is_constructible<_Tp, _A0, _A1, _A2>::value), "Can't construct object in allocate_shared" );
       ^

This is also reported in https://bugs.freebsd.org/224946 (FreeBSD is apparently one of the very few projects that regularly builds programs against libc++ with gcc).

The reason is that the static assertions are invoking `is_constructible` with three arguments, while gcc does not have the built-in `is_constructible` feature, and the pre-C++11 `is_constructible` wrappers in `<type_traits>` only provide up to two arguments.

I have added additional wrappers for three arguments, modified the `is_constructible` entry point to take three arguments instead, and added a simple test to is_constructible.pass.cpp.


Repository:
  rCXX libc++

https://reviews.llvm.org/D41805

Files:
  include/type_traits
  test/std/utilities/meta/meta.unary/meta.unary.prop/is_constructible.pass.cpp

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