Proposed resolution:

This wording is relative to N4727.

1. Edit [new.delete.single] as indicated:

   void operator delete(void* ptr) noexcept;
   void operator delete(void* ptr, std::size_t size) noexcept;
   void operator delete(void* ptr, std::align_val_t alignment) noexcept;
   void operator delete(void* ptr, std::size_t size, std::align_val_t alignment) noexcept;
   

   -10- Effects: […]

   -11- Replaceable: A C++ program may define functions with any of these function signatures, and thereby displace the default versions defined by the C++ standard library. If a function without a size parameter is defined, the program should also define the corresponding function with a size parameter. If a function with a size parameter is defined, the program shall also define the corresponding version without the size parameter; no diagnostic is required. [Note: The default behavior below may change in the future, which will require replacing both deallocation functions when replacing the allocation function. — end note]

2. Edit [new.delete.array] as indicated:

   void operator delete[](void* ptr) noexcept;
   void operator delete[](void* ptr, std::size_t size) noexcept;
   void operator delete[](void* ptr, std::align_val_t alignment) noexcept;
   void operator delete[](void* ptr, std::size_t size, std::align_val_t alignment) noexcept;
   

   -9- Effects: […]

   -10- Replaceable: A C++ program may define functions with any of these function signatures, and thereby displace the default versions defined by the C++ standard library. If a function without a size parameter is defined, the program should also define the corresponding function with a size parameter. If a function with a size parameter is defined, the program shall also define the corresponding version without the size parameter; no diagnostic is required. [Note: The default behavior below may change in the future, which will require replacing both deallocation functions when replacing the allocation function. — end note]

[ 2018-06-18 after reflector discussion ]

Priority set to 3

[ 2018-04-03; Thomas Köppe and Tim Song suggest wording ]

In general requirements on a whole program, as opposed to a single translation unit, generally specify "no diagnostic required", since we don't want to require implementations to do multi-translation-unit analysis. However, [new.delete.single] paragraph 11 says,

If a function with a size parameter is defined, the program shall also define the corresponding version without the size parameter.

This is clearly not restricted to a single translation unit; should "no diagnostic required" be added?