bug#29554: 25.3; 100% CPU spinning, while parsing compile output.

[Eli Zaretskii <eliz@gnu.org>]

> From: Sam Varshavchik <mrsam@courier-mta.com>
> Date: Sun, 03 Dec 2017 12:55:49 -0500
> 
> Attached is simple makefile with a bunch of echo statements that reproduce  
> the output of an actual compilation. I had to gzip and attach it, in order  
> to avoid the large lines getting messed up by E-mail formatting.
> 
> Saving this makefile, and hitting F5, or executing "compile" makes emacs  
> spin with 100% CPU utilization for about five seconds, before it starts  
> responding again. Then, going to the compilation output buffer, and M-> to  
> go the end of the buffer, that also pegs emacs for another 4-5 seconds, at  
> 100% cpu.
> 
> Yup, these are very long lines. But that's the end result from automake and  
> libtool. This is the real world, when it comes to C++ development these  
> days...

Maybe my machine is much faster than yours (although it's a 6-year old
box), but I don't see such long delays, the responses are sub-second
here (something like 0.2 sec or so).  Did you visit the file in
Makefile mode or in some other mode?