On Sun, Jun 14, 2020 at 2:44 PM Jens Maurer <Jens.Maurer@gmx.net> wrote:

Supposed I'm on an EBCDIC-only system.

If I understand correctly, EBCDIC has a host of control characters
that can't be represented in Unicode (while preserving semantics);
the mapping that exists re-uses some Unicode control characters,
but with different semantics.

Suppose one of those EBCDIC control characters is mapped to \u1234.
What if \u1234 also appears as such in my source code, obviously
intending to mean the Unicode semantics?

I think I'd like
I can't speak to whether you have such a preference or not.  :)
 
to have at least the option of getting a
syntax error (I asked for a Unicode control character that
doesn't exist as such on EBCDIC), but it seems the mapping
will give me the EBCDIC control character with different
semantics.  (All of this in a string literal, of course,
so it hurts when performing output.)

Hubert, is my understanding above correct?
Yes. The possibility of such an option (to get an error) should not be ruled out by some "accident of wording" in the specification of C++.

As a point of information (from another thread), implementations are known that perform the "conventional" mapping.

The presence of a UCN for a C1 (non-EBCDIC) control character in a supposedly-EBCDIC string is not immediately indicative of an error. For example, the environment I use has SSH perform autoconversion (with the "conventional" mapping) from EBCDIC-1047 to ISO-8859-1.
 

Jens