Bug#917034: xterm crashes on certain Unicode characters when font was selected with -fa

[Sven Joachim <svenjoac@gmx.de>]

Control: unmerge -1
Control: reopen -1

On 2018-12-30 18:26 +0100, Alexander Meyer wrote:

> * Sven Joachim <svenjoac@gmx.de> [2018-12-29 19:20]:
>> 
>> If you still get a segfault in xterm 341 (uploaded today), please tell
>> me and I will unmerge and reopen your bug.
>
> Unfortunately, I still get the same segfault with 341. But I've just
> noticed that the behaviour changes depending on whether I have a
> fonts.conf file enabled or not.
>
> I normally use the fonts.conf file from
> https://gist.github.com/dcrystalj/d1c1ceacf0d6fc9a0556
> installed in ~/.config/fontconfig/fonts.conf
>
> This is the behaviour I get across xterm versions:
> (everything with libfontconfig1 2.13.1-2)
>
> fonts.conf enabled:
> 337: works
> 338: segfault
> 340: segfault
> 341: segfault
>
> fonts.conf disabled:
> 337: works
> 338: aborts with error message "BadLength (poly request too large or
>      internal Xlib length error)" as described in bug 916349
> 340: works! (as opposed to what is reported in bug 916349)
> 341: works
>
>
> So the segfault only happens with that fonts.conf.

Thanks, that explains why others did not see it - and possibly also why
I could still reproduce #916349 in xterm 340, as I have my own
fonts.conf, albeit a much shorter and simpler one than yours.

Alas, with your file (saved as /tmp/fonts.conf) xterm does not even start
here, although I have fonts-noto-mono and fonts-noto-color-emoji
installed:

,----
| $ FONTCONFIG_FILE=/tmp/foo/fonts.conf xterm -fa 'Noto Mono'      
| xterm: cannot match normal font "Noto Mono"
| xterm: Selected font has no non-zero height for ISO-8859-1 encoding
`----

So I am a bit at a loss here.  And I am definitely not a an expert on
fontconfig (or fonts in general) either.

Cheers,
       Sven