bug#74357: c-mode: Some syntactic constructs cause unreasonable typing lag

[Alan Mackenzie]

Hello, Björn.

On Sat, Nov 30, 2024 at 21:07:06 +0100, Björn Lindqvist wrote:
> Hello Alan,

> Now I rebuilt emacs from scratch with patches. Though there is still
> some lag, on my degenerate test case there is a substantial
> improvement! I can't try the patches on my slow computer since
> building emacs on it takes too long. But I'll try it on the next emacs
> release.

That's good news!

I've committed the patch to the Emacs master branch, after having done a
little more optimisation on it.  I haven't closed the bug, yet, though.

The question is, is the patch good enough to close the bug?  What do you
think?  On my timings, typing in 20 y's at Line 328 of your test file,
with the patch was approximately three times as fast as before it.

On my (new, fast) machine, the final test run had Emacs taking ~50 ms
per keystroke.  I appreciate that is not so good, given that 50 ms is
only slightly faster than a fast typist can type, and most machines are
slower than mine.

You said you may be able to try out the patch on your slower machine.
That would be most appreciated.

Further optimisation for the test case is going to be difficult, if it's
possible at all.

So, again the question, is the current improvement enough to justify
closing the bug?

Thanks again for taking the trouble to submit the bug report, and even
more for doing it in such an easy to reproduce way.

> -- 
> mvh/best regards Björn Lindqvist

-- 
Alan Mackenzie (Nuremberg, Germany).