Subject: 27.0.50; concurrent XML validation yields an invalid file

From: Vincent Lefevre <[email-masked]>
Date: Fri, 30 Aug 2019 09:25:01 +0200

Consider a big, valid XML file a.xml, e.g. using a vacuous schema, and
copy it to b.xml (thus a.xml and b.xml are the same file, though they
don't need to be identical for the test).

Open the files at the same time with: emacs -Q a.xml b.xml

Then one of them is regarded as invalid.

Note: This also works with "emacs -Q a.xml" then C-x 5 2 C-x f b.xml
while XML validation on a.xml hasn't finished.

The file a.xml must be big enough so that XML validation takes enough
time (or something like that). For instance, I can reproduce the bug
on my machine with a.xml being

<?xml version="1.0" encoding="utf-8"?>
<root>
  <a/>
  <a/>
  <a/>
  <a/>
  <a/>
  <a/>
  <a/>
...
  <a/>
  <a/>
</root>

where there are 3000 <a/>.

In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.10)
 of 2019-08-23 built on zira
Repository revision: 7b0d49854675eae962c6baf8ae6fd90a2c87889b
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description: Debian GNU/Linux bullseye/sid

Recent messages:
Loading /home/vinc17/share/emacs/site-lisp/mutteditor.el (source)...done
Loading time...done
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure --prefix=/usr/local/emacs-trunk'

Configured features:
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ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF XFT ZLIB
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GMP

Important settings:
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Load-path shadows:
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Features:
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Memory information:
((conses 16 65080 9343)
 (symbols 48 8743 1)
 (strings 32 20691 2807)
 (string-bytes 1 697512)
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