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

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.

Reviewers: EricWF, mclow.lists

Reviewed By: EricWF

Subscribers: krytarowski, cfe-commits, emaste

Differential Revision: https://reviews.llvm.org/D41805

llvm-svn: 321963

1 files changed, 12 insertions, 0 deletions

diff --git a/libcxx/test/std/utilities/meta/meta.unary/meta.unary.prop/is_constructible.pass.cpp b/libcxx/test/std/utilities/meta/meta.unary/meta.unary.prop/is_constructible.pass.cpp
index 1f7c32a8cc0..b90363a5c38 100644
--- a/libcxx/test/std/utilities/meta/meta.unary/meta.unary.prop/is_constructible.pass.cpp
+++ b/libcxx/test/std/utilities/meta/meta.unary/meta.unary.prop/is_constructible.pass.cpp
@@ -30,6 +30,7 @@ struct A
 {
     explicit A(int);
     A(int, double);
+    A(int, long, double);
 #if TEST_STD_VER >= 11
 private:
 #endif
@@ -106,6 +107,16 @@ void test_is_constructible()
 #endif
 }
 
+template <class T, class A0, class A1, class A2>
+void test_is_constructible()
+{
+    static_assert(( std::is_constructible<T, A0, A1, A2>::value), "");
+    LIBCPP11_STATIC_ASSERT((std::__libcpp_is_constructible<T, A0, A1, A2>::type::value), "");
+#if TEST_STD_VER > 14
+    static_assert(( std::is_constructible_v<T, A0, A1, A2>), "");
+#endif
+}
+
 template <class T>
 void test_is_not_constructible()
 {
@@ -146,6 +157,7 @@ int main()
     test_is_constructible<int, const int> ();
     test_is_constructible<A, int> ();
     test_is_constructible<A, int, double> ();
+    test_is_constructible<A, int, long, double> ();
     test_is_constructible<int&, int&> ();
 
     test_is_not_constructible<A> ();