[xml/sgml-pkgs] Bug#994795: w3-dtd-mathml: invalid redeclaration of predefined entities amp and lt yields failures with libxml2 2.9.12

[Vincent Lefevre]

Package: w3-dtd-mathml
Version: 2.0.0.0-5.1
Severity: grave
Tags: patch
Justification: renders package unusable

The incorrect amp and lt entity redefinition yields failures with
libxml2 2.9.12, which is now in Debian. This introduces a major
regression.

Here's a testcase for one of the buggy files.

$ cat test.xml
<?xml version="1.0"?>
<!DOCTYPE root [
<!ENTITY % ent-isonum
      PUBLIC "-//W3C//ENTITIES Numeric and Special Graphic for MathML 2.0//EN"
             "http://www.w3.org/TR/MathML2/dtd/isonum.ent">
%ent-isonum;
]>
<root/>

$ xmllint --nonet --noout --noent test.xml
error : xmlAddEntity: invalid redeclaration of predefined entity
error : xmlAddEntity: invalid redeclaration of predefined entity

The attached patch fixes this bug.

See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=993638 about a
similar problem in the old w3c-dtd-xhtml package (no longer in Debian)
and the behavior of libxml2 2.9.12.

-- System Information:
Debian Release: bookworm/sid
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'stable-updates'), (500, 'stable-security'), (500, 'unstable'), (500, 'testing'), (500, 'stable'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 5.10.0-8-amd64 (SMP w/8 CPU threads)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=POSIX, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages w3-dtd-mathml depends on:
ii  sgml-base  1.30
ii  xml-core   0.18+nmu1

w3-dtd-mathml recommends no packages.

Versions of packages w3-dtd-mathml suggests:
ii  docbook-mathml  1.1CR1-2.1

-- no debconf information

-- 
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)
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