bug#38407: 27.0.50; infinite loop with display of large file without newlines

[Eli Zaretskii]

> Cc: rpluim@gmail.com, pieter@vanoostrum.org, 38407@debbugs.gnu.org
> From: Phil Sainty <psainty@orcon.net.nz>
> Date: Sat, 7 Dec 2019 14:28:37 +1300
> 
> > In general, searching for a newline is very fast in Emacs, so if you
> > use the right primitives, you should be able to scan quite a lot of
> > text before the time begins affecting responsiveness.
> 
> `so-long-detected-long-line-p' is the provided predicate, and it
> relies on `forward-line' (which I've assumed is as quick as I'm going
> to get for finding newlines), along with narrowing to limit the amount
> of text scanned to the maximum value that we care about (i.e. the
> minimum length of a too-long line).
> 
> I've just done a bit of testing with much larger files and values, and
> suspect that we could indeed make these values quite dramatically
> bigger without any noticeable impact.

Yes, I'd expect that.

Thanks.