[Moved to DR at the November, 2014 meeting.]

Proposed resolution (February, 2014):

Change 11.4.5.3 [class.copy.ctor] paragraph 28 as follows:

...It is unspecified whether subobjects representing virtual base classes are assigned more than once by the implicitly-defined copy/move assignment operator. [Example:

  struct V { };
  struct A : virtual V { };
  struct B : virtual V { };
  struct C : B, A { };

It is unspecified whether the virtual base class subobject V is assigned twice by the implicitly-defined copy/move assignment operator for C. —end example] [Note: This does not apply to move assignment, as a defaulted move assignment operator is deleted if the class has virtual bases. —end note]

The proposed resolution for issue 1402 overlooked some needed changes in 11.4.5.3 [class.copy.ctor] paragraph 28.