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

[Alexander Meyer]

* Thomas Dickey <dickey at his.com> [2018-12-31 20:32]:

> On Mon, Dec 31, 2018 at 06:11:23PM +0100, Alexander Meyer wrote:
>> * Thomas Dickey <dickey at his.com> [2018-12-31 00:51]:
>> 
>>> Can you make a backtrace for #341, please?
>> 
>> Here it is:

[...]

Thanks a lot for taking the time to investigate the issue and for
providing the fontconfig patch! I've been away from home and couldn't
reply earlier.

As the issue has now been solved xterm-wise, just a few remarks:

>> Reading symbols from /usr/bin/xterm...Reading symbols from /usr/lib/debug/.build-id/b8/d462fb6f4969a6a228262ceff981af02a1a4d5.debug...done.
>> done.
>> (gdb) run -fa 'Noto Mono'
> 
> fwiw, my Debian/testing machine has these fonts (with "noto" in their names):
> 
> ii  fonts-noto                                    20181130-1                            all          metapackage to pull in all Noto fonts
> ii  fonts-noto-cjk                                1:20170601+repack1-3                  all          "No Tofu" font families with large Unicode coverage (CJK regular and bold)
> ii  fonts-noto-color-emoji                        0~20180810-1                          all          color emoji font from Google
> ii  fonts-noto-hinted                             20181130-1                            all          "No Tofu" font families with large Unicode coverage (hinted)
> ii  fonts-noto-mono                               20181130-1                            all          "No Tofu" monospaced font family with large Unicode coverage
> ii  fonts-noto-unhinted                           20181130-1                            all          "No Tofu" font families with large Unicode coverage (unhinted)

Exactly the same on my system. fonts-noto-color-emoji was only recently
installed via a dependency at the same time as xterm was upgraded from
337 to 338.

It turns out that simply removing the package fonts-noto-color-emoji
eliminates the issue! So that's probably the best workaround right now
for anyone with the same problem, until your patch is incorporated into
fontconfig.

[...]

> This part is in the newer function which handles fallback fonts.
> Since your trace shows line-numbers, I'm assuming it's not the Debian package.
> (Actually the trace seems to show that you've compiled fontconfig -- turning
> off the optimization might help pinpoint the details).

For the record, no, the trace had been made with the provided
xterm-dbgsym and libfontconfig1-dbgsym packages.

Best
Alex