[xml/sgml-pkgs] Bug#993638: Bug#993638: libxml2: XHTML 1.0 validation is broken

[Vincent Lefevre]

Concerning the change in the libxml2 code, I found this:

  https://gitlab.gnome.org/GNOME/libxml2/-/commit/01411e7c5ea0fff181271e092f46a2138c3720ec
  "Check for invalid redeclarations of predefined entities"

with the example of the incorrect

   <!ENTITY lt "<">

which was in the old libxml2 testcases, BTW.

Thus this is intentional. But such a major change (since this breaks
official DTDs released in the past, something which should normally
*never* happen) should have at least been announced somewhere.
Otherwise one doesn't know what's going on (even a web search for the
error message led to nothing -- now, there's only my bug report...).

Now, I understand why there's nothing mentioned in the NEWS file,
which is a symlink to the changelog file: this file stops at
"v2.9.9: Jan 03 2019", while this version is 2.9.12.

The upstream release notes of libxml2 2.9.11

  https://mail.gnome.org/archives/xml/2021-May/msg00000.html

contain:

  - Check for invalid redeclarations of predefined entities (Nick Wellnhofer)

Note that this change is recent, so that most users (Debian or not)
have not upgraded yet. Whether the issue would be more visible once
most users have upgraded (in particular if the old DTDs have been
archived locally with the XML data), I don't know.

-- 
Vincent Lefèvre <vincent at vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)