Proposed Resolution for LWG 2415: Inconsistency between unique_ptr and shared_ptr

[mclow.lists]

Summary

http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-active.html#2415

This change should really be applied to the shared_ptr in LFTS as well- and I have let Jeffrey know.

[EricWF]

LGTM.

[mclow.lists]

Committed as r236953

include/memory

 struct __rebind_alloc_helper
 {
 #ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
-  typedef typename _Traits::template rebind_alloc<_Tp>        type;
+    typedef typename _Traits::template rebind_alloc<_Tp>        type;
 #else
     typedef typename _Traits::template rebind_alloc<_Tp>::other type;
 #endif

                             >::type)
     : __ptr_(__r.get())
 {
-    typedef __shared_ptr_pointer<_Yp*, _Dp, allocator<_Yp> > _CntrlBlk;
-    __cntrl_ = new _CntrlBlk(__r.get(), __r.get_deleter(), allocator<_Yp>());
-    __enable_weak_this(__r.get());
+#if _LIBCPP_STD_VER > 11
+    if (__ptr_ == nullptr)
+        __cntrl_ = nullptr;
+    else
+#endif
+    {
+        typedef __shared_ptr_pointer<_Yp*, _Dp, allocator<_Yp> > _CntrlBlk;
+        __cntrl_ = new _CntrlBlk(__r.get(), __r.get_deleter(), allocator<_Yp>());
+        __enable_weak_this(__r.get());
+    }
     __r.release();
 }
 

                             >::type)
     : __ptr_(__r.get())
 {
-    typedef __shared_ptr_pointer<_Yp*,
-                                 reference_wrapper<typename remove_reference<_Dp>::type>,
-                                 allocator<_Yp> > _CntrlBlk;
-    __cntrl_ = new _CntrlBlk(__r.get(), ref(__r.get_deleter()), allocator<_Yp>());
-    __enable_weak_this(__r.get());
+#if _LIBCPP_STD_VER > 11
+    if (__ptr_ == nullptr)
+        __cntrl_ = nullptr;
+    else
+#endif
+    {
+        typedef __shared_ptr_pointer<_Yp*,
+                                     reference_wrapper<typename remove_reference<_Dp>::type>,
+                                     allocator<_Yp> > _CntrlBlk;
+        __cntrl_ = new _CntrlBlk(__r.get(), ref(__r.get_deleter()), allocator<_Yp>());
+        __enable_weak_this(__r.get());
+    }
     __r.release();
 }
 

test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.assign/unique_ptr_Y.pass.cpp

             pB = std::move(pA);
             assert(B::count == 0);
             assert(A::count == 0);
-            assert(pB.use_count() == 1);
+//          assert(pB.use_count() == 1); // no longer true due to LWG 2415
             assert(pA.get() == 0);
             assert(pB.get() == ptrA);
         }

             pB = std::move(pA);
             assert(B::count == 0);
             assert(A::count == 0);
-            assert(pB.use_count() == 1);
+//          assert(pB.use_count() == 1); // no longer true due to LWG 2415
             assert(pA.get() == 0);
             assert(pB.get() == ptrA);
         }

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

 void fn ( const std::shared_ptr<int> &) {}
 void fn ( const std::shared_ptr<B> &) { assert (false); }
 
+template <typename T>
+void assert_deleter ( T * ) { assert(false); }
+
 int main()
 {
     {

     throw_next = false;
     fn(std::unique_ptr<int>(new int));
     }
+
+#if __cplusplus >= 201402L
+    // LWG 2415
+    {
+    std::unique_ptr<int, void (*)(int*)> p(nullptr, assert_deleter<int>);
+    std::shared_ptr<int> p2(std::move(p)); // should not call deleter when going out of scope
+    }
+#endif
+    
 }