Page MenuHomePhabricator

Add pre-C++11 is_constructible wrappers for 3 arguments
ClosedPublic

Authored by dim on Jan 6 2018, 5:25 PM.

Details

Summary

After rL319736 for 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.

Diff Detail

Repository
rCXX libc++

Event Timeline

dim created this revision.Jan 6 2018, 5:25 PM
EricWF accepted this revision.Jan 7 2018, 12:43 AM

LGTM.

This revision is now accepted and ready to land.Jan 7 2018, 12:43 AM
This revision was automatically updated to reflect the committed changes.