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

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

[Tom Tromey]

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.
However if I C-u M-x next-error to restart from the beginning, then that
is fast.

Tom


In GNU Emacs 26.0.50 (build 18, x86_64-pc-linux-gnu, GTK+ Version 3.22.17)
 of 2017-09-09 built on bapiya
Repository revision: 4131f9785e30f2a31745125c714e922892113c62
Windowing system distributor 'Fedora Project', version 11.0.11903000
System Description:	Fedora release 25 (Twenty Five)

Recent messages:
syntax: ((statement 4143)), indent: 4
syntax: ((statement 4143) (comment-intro)), indent: 4 [7 times]
syntax: ((statement 4750)), indent: 8
C-x C-g is undefined
Saving file /home/tromey/gcc/gcc/libcpp/macro.c...
Wrote /home/tromey/gcc/gcc/libcpp/macro.c
Saving file /home/tromey/gcc/gcc/libcpp/macro.c...
Wrote /home/tromey/gcc/gcc/libcpp/macro.c
Mark set
Compilation exited abnormally with code 2

Configured using:
 'configure --prefix=/home/tromey/Emacs/install'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS NOTIFY
LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11

Important settings:
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  value of $XMODIFIERS: @im=ibus
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Major mode: C/*l

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Load-path shadows:
/home/tromey/.emacs.d/elpa/bubbles-0.5/bubbles hides /home/tromey/Emacs/install/share/emacs/26.0.50/lisp/play/bubbles

Features:
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gnus-cite smiley shr-color url-util shr svg xml dom browse-url
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Memory information:
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 (symbols 48 56689 1)
 (miscs 40 9756 5605)
 (strings 32 514129 71833)
 (string-bytes 1 14329693)
 (vectors 16 245436)
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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.