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Re: [SG16] P2348: Feedback on r1 draft

From: Corentin <corentin.jabot_at_[hidden]>
Date: Mon, 13 Sep 2021 12:02:13 +0200
Here is a draft of changes as requested by SG16, Jens, and Hubert

I found it better for /whitespace/ to refer to a single whitespace instead
of describing a sequence. I have adjusted the pluralisation of everything

I've added some notes to clarify the intent in important places
I've used Hubert's excellent suggestion for phase 1 of translation
I've put back some prose to describe multi-line comments
I made sure whitespace does not appear at the start of a sentence
I introduced the grammar term line-break-character to describe
single-codepoint line-breaks (\n, \r) independently of line-breaks
sequences (like \r\n)

Hopefully we can take this of the hands of SG16!

Thanks again for the feedback,


On Fri, Sep 10, 2021 at 9:36 AM Jens Maurer <Jens.Maurer_at_[hidden]> wrote:

> On 09/09/2021 22.54, Hubert Tong wrote:
> > (2)
> > In the new [lex.whitespaces] subclause, the following is added:
> > whitespaces are ignored except as they serve to separate tokens
> >
> > This seems to have come from the text being removed out of
> [lex.token] (where it was excusable). Whitespace separation is significant
> in [cpp.replace.general], etc. This sentence should at best be a note in
> relation to phase 7 of translation.
> >
> >
> > I am happy to remove it entirely.
> > It's certainly not needed for phase 7. And I think phase 3
> wording says something similar.
> >
> > In [cpp.pre], Jens objected to my removal of
> >
> > > The only whitespace characters that shall appear between
> preprocessing tokens within a preprocessing directive (from just after the
> directive-introducing token through just before the terminating new-line
> character) are space and horizontal-tab (including spaces that have
> replaced comments or possibly other whitespace characters in translation
> phase 3).
> >
> > I am not able to convince myself than the grammar described at the
> start at [cpp.pre] allows line-breaks to appear between preprocessing
> tokens within a preprocessing directive,
> > but I'm happy to replaced the striked paragraph by
> >
> > Only /horizontal-whitespace/s shall appear between preprocessing
> tokens within a preprocessing directive.
> >
> >
> > This is neither necessary nor harmless. The term "preprocessing
> directive" is defined right after the grammar in [cpp.pre]. Its definition
> precludes the presence of line-breaks outside of /**/ between preprocessing
> tokens within the directive. We do want to allow comments in preprocessing
> directives.
> Good point; I was missing [cpp.pre] p1, which seems to say everything we
> want to say.
> So, I'm good with the removal now.
> > This seems to point to another problem with the wording:
> > (3)
> > The removal of the comment replacement in phase 3 means that the
> definition of preprocessing directives requires an update to qualify that
> it wants to talk about line-breaks (but not those that are inside /**/
> comments).
> Indeed, the status quo seems to allow new-lines within /* comments */
> inside a preprocessing-directive.
> Maybe it would be clearer/easier to retain the replacement of comments
> with a single space
> character in phase 3? While we do need to differentiate different kinds
> of whitespace
> (horizontal whitespace vs. new-lines) in phase 4, there's no point in
> talking about comments
> separately beyond phase 3.
> Jens

Received on 2021-09-13 05:02:27