bug#55230: CC Mode 5.35.1 (C++//l); Cache inconsistency

Hello again, Michael.

On Tue, May 03, 2022 at 18:10:36 +0000, Alan Mackenzie wrote:
> On Mon, May 02, 2022 at 15:30:09 -0400, Michael Welsh Duggan wrote:
> > Package: cc-mode

> > From emacs -Q:

> > C-x C-f /tmp/foo.cpp RET
> > M-x c-toggle-parse-state-debug RET
> > "{}

> > After typing the close brace, I get the following:
> > c-parse-state inconsistency at 3: using cache: (2), from scratch: nil.  POINT-MIN: 1
> > Old state:
> > (setq c-state-cache '(2)  c-state-cache-good-pos 1  c-state-nonlit-pos-cache nil  c-state-nonlit-pos-cache-limit 0  c-state-brace-pair-desert nil  c-state-point-min 1  c-state-point-min-lit-type nil  c-state-point-min-lit-start nil  c-state-min-scan-pos 1  c-state-old-cpp-beg nil  c-state-old-cpp-end nil  c-parse-state-point 3)

> > I have not noticed any indentation errors due to this, but any cache
> > inconsistency might lead to errors down the line, hence this report.

> Many thanks for the bug report.

> This time it is not the cache mechanism itself which is at fault.
> Instead, it is the first character ", which since it is unbalanced by
> another ", has had its syntax is temporarily "commented out" by giving
> it a syntax-table property of "punctuation".  The parse-state cache was
> generated whilst in this state, but used when it no longer was, hence
> the inconsistency.

> There are somewhere between 10 and 20 occurrences of c-parse-state in
> the source code which will need to be "protected" against this fault.  I
> hope to be able to finish this work in the next two or three days, when
> I'll get back to you again.

There were actually 32 such occurrences, and they have generated a rather
large patch which I am taking the liberty of just sending to you.  The
vast bulk of this patch is just putting (c-with-string-fences ....)
around these functions, reindenting them.

I've attached the patch as a separate file because it is so big.  It
should apply cleanly to the CC Mode in the Emacs savannah master version.
Would you please apply it and try it out a bit, and let me know how well
it works.  Thanks!

> > Emacs  : GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo version 1.16.0)
> >  of 2022-04-09
> > Package: CC Mode 5.35.1 (C++//l)
> > Buffer Style: gnu
> > c-emacs-features: (pps-extended-state col-0-paren posix-char-classes gen-string-delim gen-comment-delim syntax-properties 1-bit)

> > -- 
> > Michael Welsh Duggan
> > ([email protected])

-- 
Alan Mackenzie (Nuremberg, Germany).