On 6/15/20 11:38 AM, Corentin wrote:

On Mon, 15 Jun 2020 at 17:17, Tom Honermann <tom@honermann.net> wrote:
On 6/15/20 7:14 AM, Corentin via SG16 wrote:

Hubert has specifically requested better support for unmappable characters, so I don't agree with the parenthetical.

I don't think that's a fair characterisation. Again there is a mapping for all characters in ebcdic. That mapping is prescriptive rather than semantic, but both Unicode and IBM agree on that mapping ( the codepoints they map to do not have associated semantic whatsoever and are meant to be used that way). The wording trick will be to make sure we don't prevent that mapping.

The claim that Unicode and IBM agree on this mapping seems overreaching to me.  Yes, there is a specification for how EBCDIC code pages can be mapped to Unicode code points in a way that preserves round tripping.  I don't think that should be read as an endorsement for conflating the semantic meanings of those characters that represent distinct abstract characters before/after such a mapping.  I believe there have been requests to be able to differentiate the presence of one of these control characters in the source input and the mapped Unicode code point being written as a UCN.