[Fontconfig] Strange problem of fonts alias preference setting

[甘全]

Hi, guys!

After I installed two font packages, ttf-arphic-gkai00mp and
ttf-arphic-gbsn00lp, the fonts alias preference setting of san-serif
family in my .fonts.conf just stop working.

The specific section of my .fonts.conf file:
<alias>
  <family>serif</family>
  <prefer>
    <family>Bitstream Vera Serif</family>
    <family>Georgia</family>
    <family>Times New Roman</family>
  </prefer>
</alias>
<alias>
  <family>san-serif</family>
  <prefer>
    <family>Tahoma</family>
    <family>Bitstream Vera Sans</family>
    <family>Verdana</family>
    <family>Arial</family>
  </prefer>
</alias>
<alias>
  <family>monospace</family>
  <prefer>
    <family>Courier New</family>
    <family>Bitstream Vera Sans Mono</family>
  </prefer>
</alias>

The default san-serif fonts should be "Tahoma", but it was set to "AR
PL KaitiM GB", came with ttf-arphic-gkai00mp package, in both Gnome
2.12.3 and FVWM 2.5.16. But serif and monospace are not effected.

Both /etc/fonts/fonts.conf and my $HOME/.fonts.conf are not edited. I
tried to change some settings in .fonts.conf, and everything works
fine except the san-serif family alias. No matter what font is on top
of that list, "AR PL KaitiM GB" is displayed.

My distro is Debian/Unstable, the versions of fontconfig and
libfontconfig are 2.3.2-1.1, and the version of libxft2 is 2.1.8.2-3

I'm totally lost here, any help would be greatly appreciated.