bug#45248: 28.0.50; Emacs freezes with big C functions

[Alan Mackenzie]

Hello, Ravine.

On Wed, Dec 23, 2020 at 08:48:26 +0530, Ravine Var wrote:
> Alan Mackenzie <acm@muc.de> writes:
> > Sorry it's taken a little while to reply.  I've been preoccupied with
> > another bug in the meantime.

> No problem.

> > By "scrolling becomes slower", do you mean (1) that the time for an
> > isolated single full screen scroll becomes longer, the further you are
> > through that struct?  Or do you mean (2) that on auto-repeat of the C-v
> > or PageDown key, the scrolling becomes slower?

> The second behavior. Opening the file and scrolling from the
> the beginning with C-v becomes progressively slower.

> > If you mean (2), from emacs -Q without enabling
> > fast-but-imprecise-scrolling, then you are just seeing the normal
> > expected, but unfortunate behaviour of Emacs: Emacs will not redisplay a
> > screen as long as there is keyboard input unprocessed, but Emacs is
> > spending its time fontifying the intermediate screens (which are not
> > about to be displayed) as part of processing that input.  30 characters
> > per second is faster than CC Mode can paint a single screen.

> Ok.

> > For problem (2) I recommend, again, enabling
> > fast-but-imprecise-scrolling.

> Without the patch in message 11, scrolling is bad
> even when fast-but-imprecise-scrolling is enabled.

> With the patch, things are much better and there
> is no lockup, once fast-but-imprecise-scrolling is enabled.

> I think this is enough for this bug - thanks for
> looking into this issue.

Thanks!  I've found some infinite loops, which I've also corrected.  And
I've committed the patch to the savannah master branch.

So, I'm closing the bug with this post.  Thanks for all the testing and
profiling in sorting out this bug.

-- 
Alan Mackenzie (Nuremberg, Germany).