Proposed resolution:

Change in 6.8.2 [basic.fundamental] paragraph 17 as follows:

The types described in this subclause are called fundamental types. The representation of a fundamental type is implementation-defined, subject to the constraints in this subclause.

CWG 2023-12-01

Since there is no requirement for "implementation-defined" in the specification, the representation is unspecified by omission. It was noted that "unspecified behavior" has well-defined (and narrow) meaning, whereas the not-specified property here is static throughout the instance of the abstract machine. In that sense, it is similar to implementation-defined, abent the documentation requirement. It might be worthwhile to have a defined term for such properties.

Proposed resolution [SUPERSEDED]:

Change in 6.8.2 [basic.fundamental] paragraph 17 as follows:

The types described in this subclause are called fundamental types. The representation of a fundamental type is unspecified except as stated in this subclause.

(From editorial issue 4893.)

It is unclear whether the representation of unsigned integral types is unspecified or implementation-defined.