CPP11 — _var types for fixed-length underlying types

the spec currently is extremely vague about how _var types for fixed-length
underlying types are supposed to work. The only words are:

The T_var types are also produced for fixed-length structured
types for reasons of consistency. These types have the same
semantics as T_var types for variable-length types. This allows
applications to be coded in terms of T_var types regardless of
whether the underlying types are fixed- or variable-length.

This has long been a source of confusion to me. In particular, it doesn't
answer questions such as

• Can a _var for a fixed-length type be initialized with a pointer
  to the fixed-length type? If so, does the _var adopt it?

• Can a _var for fixed-length type be initialized with a value?

• What does assignment between _vars for fixed-length types do?

• Does the _var for a fixed-length type work like a reference
  and remain bound to the same block of memory?

• What does default-initialization of such a _var do?

• etc, etc.

duplicate of issdue 1521...close issue