Re: [PATCH] libcpp, v2: Implement C++23 P1949R7 - C++ Identifier Syntax using Unicode Standard Annex 31

[Jakub Jelinek <jakub@redhat.com>]

On Mon, Aug 16, 2021 at 07:45:55PM -0400, Jason Merrill wrote:
> On 8/16/21 4:51 PM, Jakub Jelinek wrote:
> > On Mon, Aug 16, 2021 at 04:21:00PM -0400, Jason Merrill wrote:
> > > > I see for the UTF-8 chars we have:
> > > >         switch (ucn_valid_in_identifier (pfile, *cp, nst))
> > > >           {
> > > >           case 0:
> > > >             /* In C++, this is an error for invalid character in an identifier
> > > >                because logically, the UTF-8 was converted to a UCN during
> > > >                translation phase 1 (even though we don't physically do it that
> > > >                way).  In C, this byte rather becomes grammatically a separate
> > > >                token.  */
> > > >             if (CPP_OPTION (pfile, cplusplus))
> > > >               cpp_error (pfile, CPP_DL_ERROR,
> > > >                          "extended character %.*s is not valid in an identifier",
> > > >                          (int) (*pstr - base), base);
> > > >             else
> > > >               {
> > > >                 *pstr = base;
> > > >                 return false;
> > > >               }
> > > > So, shall we behave the same as C for cxx23_identifiers here?  And shall we
> > > > do something similar for the UCNs in \uxxxx and \Uxxxxxxxx forms?
> > > > Confused...
> > > 
> > > I tend to agree with Joseph's comment on your followup patch about this
> > > issue; do you?
> > 
> > It isn't clear to me if it is ok that it is an error even with just -E,
> > i.e. whether
> > "If a single universal-character-name does not match any of the other
> > preprocessing token categories, the program is ill-formed."
> > applies already in translation phase 4 which is what -E emits (or some other
> > one?), or only in phase 7 when converting preprocessing tokens to tokens.
> 
> I read it as applying in phase 3.

Ok, follow-up patch withdrawn.

	Jakub