ULTS 22,24: FontConfig broken by including ".conf" file

[Peter Grandi]

This happens to me on both ULTS 22 and ULKTS 24 on FotnConfig in somewhat different ways:

* In ULTS 24 if there is a file '/etc/fonts/local.conf' then all fonts are rendered as if the font were not hinted or 'hinting' were 'false'. This is not noticeable if antialiasing is on, and most users default to antialiasing.

* In ULTS 22 if there is a file '$XDG_CONFIG_HOME/fontconfig/fonts.conf' then some fonts are no longer found, or get rendered with rectangular shapes. I guess not many users customize their font settings.

A telling example from ULTS 22:

$ cat /etc/fonts/conf.d/10-antialias.conf
<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
<!-- Use the Antialiasing -->
  <match target="pattern">
    <edit name="antialias" mode="append"><bool>false</bool></edit>
  </match>
</fontconfig>
$ cp -p /etc/fonts/conf.d/10-antialias.conf $XDG_CONFIG_HOME/fontconfig/fonts.conf
$ fc-list 'dejavu sans mono' family
$ rm $XDG_CONFIG_HOME/fontconfig/fonts.conf
$ fc-list 'dejavu sans mono' family
DejaVu Sans Mono

This happens also with a skeleton '$XDG_CONFIG_HOME/fontconfig/fonts.conf' (or '/etc/fonts/local.conf') too:

$ cat > $XDG_CONFIG_HOME/fontconfig/fonts.conf
<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
</fontconfig>
$ fc-list 'dejavu sans mono' family
$ rm $XDG_CONFIG_HOME/fontconfig/fonts.conf
$ fc-list 'dejavu sans mono' family
DejaVu Sans Mono

None of these anomalies happen under ULST 20.

My impression: symptoms vary and are weird, so probably it is something like a buffer overflow when reading the ".conf" files or the use of not-initialized memory.

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Libera.chat.

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