[libcxx] Fix LWG 2875: shared_ptr::shared_ptr(Y*, D, […]) constructors should be constrained.

Fixes LWG issue 2875.

Differential Revision: https://reviews.llvm.org/D81414

libcxx/docs/Cxx1zStatusIssuesStatus.csv

@@ -300,7 +300,7 @@
 "`2872 <https://wg21.link/LWG2872>`__","Add definition for direct-non-list-initialization","Kona","|Complete|",""
 "`2873 <https://wg21.link/LWG2873>`__","Add noexcept to several shared_ptr related functions","Kona","|Complete|",""
 "`2874 <https://wg21.link/LWG2874>`__","Constructor ``shared_ptr::shared_ptr(Y*)``\  should be constrained","Kona","",""
-"`2875 <https://wg21.link/LWG2875>`__","shared_ptr::shared_ptr(Y\*, D, [|hellip|\ ]) constructors should be constrained","Kona","",""
+"`2875 <https://wg21.link/LWG2875>`__","shared_ptr::shared_ptr(Y\*, D, [|hellip|\ ]) constructors should be constrained","Kona","|Complete|",""
 "`2876 <https://wg21.link/LWG2876>`__","``shared_ptr::shared_ptr(const weak_ptr<Y>&)``\  constructor should be constrained","Kona","",""
 "`2878 <https://wg21.link/LWG2878>`__","Missing DefaultConstructible requirement for istream_iterator default constructor","Kona","|Complete|",""
 "`2890 <https://wg21.link/LWG2890>`__","The definition of 'object state' applies only to class types","Kona","|Complete|",""

libcxx/include/memory

@@ -2620,6 +2620,24 @@ struct __compatible_with
     : is_convertible<_Tp*, _Up*> {};
 #endif // _LIBCPP_STD_VER > 14
 
+template <class _Dp, class _Pt,
+    class = decltype(_VSTD::declval<_Dp>()(_VSTD::declval<_Pt>()))>
+static true_type __well_formed_deleter_test(int);
+
+template <class, class>
+static false_type __well_formed_deleter_test(...);
+
+template <class _Dp, class _Pt>
+struct __well_formed_deleter : decltype(__well_formed_deleter_test<_Dp, _Pt>(0)) {};
+
+template<class _Dp, class _Tp, class _Yp>
+struct __shared_ptr_deleter_ctor_reqs
+{
+    static const bool value = __compatible_with<_Tp, _Yp>::value &&
+                              is_move_constructible<_Dp>::value &&
+                              __well_formed_deleter<_Dp, _Tp*>::value;
+};
+
 #if defined(_LIBCPP_ABI_ENABLE_SHARED_PTR_TRIVIAL_ABI)
 #  define _LIBCPP_SHARED_PTR_TRIVIAL_ABI __attribute__((trivial_abi))
 #else
@@ -2652,10 +2670,10 @@ public:
                             typename enable_if<__compatible_with<_Yp, element_type>::value, __nat>::type = __nat());
     template<class _Yp, class _Dp>
         shared_ptr(_Yp* __p, _Dp __d,
-                   typename enable_if<__compatible_with<_Yp, element_type>::value, __nat>::type = __nat());
+                   typename enable_if<__shared_ptr_deleter_ctor_reqs<_Dp, _Yp, element_type>::value, __nat>::type = __nat());
     template<class _Yp, class _Dp, class _Alloc>
         shared_ptr(_Yp* __p, _Dp __d, _Alloc __a,
-                   typename enable_if<__compatible_with<_Yp, element_type>::value, __nat>::type = __nat());
+                   typename enable_if<__shared_ptr_deleter_ctor_reqs<_Dp, _Yp, element_type>::value, __nat>::type = __nat());
     template <class _Dp> shared_ptr(nullptr_t __p, _Dp __d);
     template <class _Dp, class _Alloc> shared_ptr(nullptr_t __p, _Dp __d, _Alloc __a);
     template<class _Yp> _LIBCPP_INLINE_VISIBILITY shared_ptr(const shared_ptr<_Yp>& __r, element_type* __p) _NOEXCEPT;
@@ -2921,7 +2939,7 @@ shared_ptr<_Tp>::shared_ptr(_Yp* __p,
 template<class _Tp>
 template<class _Yp, class _Dp>
 shared_ptr<_Tp>::shared_ptr(_Yp* __p, _Dp __d,
-                            typename enable_if<__compatible_with<_Yp, element_type>::value, __nat>::type)
+                            typename enable_if<__shared_ptr_deleter_ctor_reqs<_Dp, _Yp, element_type>::value, __nat>::type)
     : __ptr_(__p)
 {
 #ifndef _LIBCPP_NO_EXCEPTIONS
@@ -2975,7 +2993,7 @@ shared_ptr<_Tp>::shared_ptr(nullptr_t __p, _Dp __d)
 template<class _Tp>
 template<class _Yp, class _Dp, class _Alloc>
 shared_ptr<_Tp>::shared_ptr(_Yp* __p, _Dp __d, _Alloc __a,
-                            typename enable_if<__compatible_with<_Yp, element_type>::value, __nat>::type)
+                            typename enable_if<__shared_ptr_deleter_ctor_reqs<_Dp, _Yp, element_type>::value, __nat>::type)
     : __ptr_(__p)
 {
 #ifndef _LIBCPP_NO_EXCEPTIONS

libcxx/test/libcxx/utilities/memory/util.smartptr/util.smartptr.shared/function_type_default_deleter.fail.cpp

@@ -44,11 +44,9 @@ int main(int, char**) {
     SPtr<2> s2(getFn<2>(), Deleter{}); // OK
     SPtr<3> s3(nullptr, Deleter{}); // OK
   }
-  // expected-error-re@memory:* 2 {{static_assert failed{{.*}} "default_delete cannot be instantiated for function types"}}
-  {
-    SPtr<4> s4(getFn<4>()); // expected-note {{requested here}}
-    SPtr<5> s5(getFn<5>(), std::default_delete<FnType<5>>{}); // expected-note {{requested here}}
-  }
+
+  // expected-error-re@memory:* {{static_assert failed{{.*}} "default_delete cannot be instantiated for function types"}}
+  std::default_delete<FnType<5>> deleter{}; // expected-note {{requested here}}
 
   return 0;
 }

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

@@ -28,6 +28,22 @@ struct A
 
 int A::count = 0;
 
+struct bad_ty { };
+
+struct bad_deleter
+{
+    void operator()(bad_ty) { }
+};
+
+struct no_move_deleter
+{
+    no_move_deleter(no_move_deleter const&) = delete;
+    no_move_deleter(no_move_deleter &&) = delete;
+    void operator()(int*) { }
+};
+
+static_assert(!std::is_move_constructible<no_move_deleter>::value, "");
+
 struct Base { };
 struct Derived : Base { };
 
@@ -65,6 +81,12 @@ int main(int, char**)
     assert(test_deleter<A>::dealloc_count == 1);
 
     {
+        // Make sure we can't construct with:
+        //    a) a deleter that doesn't have an operator ()(int*)
+        //    b) a deleter that doesn't have a move constructor.
+        static_assert(!std::is_constructible<std::shared_ptr<int>, int*, bad_deleter>::value, "");
+        static_assert(!std::is_constructible<std::shared_ptr<int>, int*, no_move_deleter>::value, "");
+
         // Make sure that we can construct a shared_ptr where the element type and pointer type
         // aren't "convertible" but are "compatible".
         static_assert(!std::is_constructible<std::shared_ptr<Derived[4]>, Base[4], test_deleter<Derived[4]> >::value, "");

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

@@ -28,6 +28,22 @@ struct A
 
 int A::count = 0;
 
+struct bad_ty { };
+
+struct bad_deleter
+{
+    void operator()(bad_ty) { }
+};
+
+struct no_move_deleter
+{
+    no_move_deleter(no_move_deleter const&) = delete;
+    no_move_deleter(no_move_deleter &&) = delete;
+    void operator()(int*) { }
+};
+
+static_assert(!std::is_move_constructible<no_move_deleter>::value, "");
+
 struct Base { };
 struct Derived : Base { };
 
@@ -115,6 +131,14 @@ int main(int, char**)
 #endif // TEST_STD_VER >= 11
 
     {
+        // Make sure we can't construct with:
+        //    a) a deleter that doesn't have an operator ()(int*)
+        //    b) a deleter that doesn't have a move constructor.
+        static_assert(!std::is_constructible<std::shared_ptr<int>, int*, bad_deleter,
+                                             test_allocator<A> >::value, "");
+        static_assert(!std::is_constructible<std::shared_ptr<int>, int*, no_move_deleter,
+                                             test_allocator<A> >::value, "");
+
         // Make sure that we can construct a shared_ptr where the element type and pointer type
         // aren't "convertible" but are "compatible".
         static_assert(!std::is_constructible<std::shared_ptr<Derived[4]>,