bug#28455: 26.0.50; first M-x next-error is very slow

[Eli Zaretskii]

> From: Tom Tromey <tom@tromey.com>
> Date: Wed, 13 Sep 2017 20:24:49 -0600
> 
> I ran `make' using M-x compile.
> A number of errors appeared.
> 
> The very first M-x next-error took a long time -- 8 seconds by my
> count.
> 
> This seems to happen the first time after each compilation.

Does it have to be a compilation, or visiting a file with the error
messages, putting it in compilation-mode, then invoking next-error
exhibits the same problem?  If the latter, can you post an example
file which could be used to reproduce this?

Also, does the slow 1st time happen in "emacs -Q"?

Thanks.