Bug#968756: inkscape: Inkscape crash on multiple undo-redo actions

[Bernhard Übelacker <bernhardu@mailbox.org>]

Hello Jason,

> #0  0x00007efbfb5f3204 n/a (libgtk-3.so.0)
> #1  0x00007efbfb779a53 n/a (libgtk-3.so.0)
> #2  0x00007efbfb779b11 n/a (libgtk-3.so.0)
> #3  0x00007efbfb779ff1 n/a (libgtk-3.so.0)
> #4  0x00007efbf96c38ee ffi_call_unix64 (libffi.so.6)
> ...

I assume you updated inkscape to current version 1.0-5~bpo10+1 ?

The above part of your backtrace would translate to this
when debug symbols are installed.

(gdb) bt
#0  0x00007f5ab0050204 in _gtk_gesture_get_pointer_emulating_sequence () at ../../../../gtk/gtkgesture.c:1811
#1  0x00007f5ab01d6a53 in _gtk_widget_get_emulating_sequence () at ../../../../gtk/gtkwidget.c:4183
#2  0x00007f5ab01d6b11 in _gtk_widget_set_sequence_state_internal () at ../../../../gtk/gtkwidget.c:4245
#3  0x00007f5ab01d6ff1 in event_controller_sequence_state_changed () at ../../../../gtk/gtkwidget.c:17330
#4  0x00007f5aae1208ee in ffi_call_unix64 () from /lib/x86_64-linux-gnu/libffi.so.6
...

The instruction at this address originates from following location
and tries to read memory from the address the variable "data->event"
points to. The data variable is retrieved before by g_hash_table_iter_next.

https://sources.debian.org/src/gtk+3.0/3.24.5-1/gtk/gtkgesture.c/#L1811

Also this location is quite different from what the original segfault
lines in the first message was showing for the previous bpo version.


Unfortunately I guess this will not be sufficient for the maintainer
to find out the problem or create a fix.

If you receive such crashes multiple times, are the backtraces always
different? If yes you might consider to check for memory faults.

Also running inkscape through "valgrind --undef-value-errors=no inkscape"
might reveal something, but might be too slow to work long enough with it,
if there are no exact steps known to reproduce it.

Also you might add the debug symbols to your system to generate
backtraces with more information, like described here:

https://wiki.debian.org/HowToGetABacktrace#Installing_the_debugging_symbols

Kind regards,
Bernhard