crash, alt + scroll on canvas two times, with tool change in-between

[Cojnel]

1. activate the selection tool,
2. with the cursor on the canvas,
hold down the alt modifier key and
turn the scroll wheel on the mouse,
3. switch to the node editing tool,
4. switch back to the selection tool,
5. repeat step 2,
6. crash with this terminal message:

Program received signal SIGSEGV, Segmentation fault.
0xb64debd0 in __dynamic_cast () from /usr/lib/i386-linux-gnu/libstdc++.so.6

It seams to crash quickly when switching to and from the node editing tool,
but it happens with all tools, sometimes it takes 2 or 3 tries when
switching to and from the other tools but eventually it crashes.

Tested with r12945
on linux mint 15 32bit

[su_v (suv-lp)]

> alt + scroll with the cursor on the canvas

I feel rather stupid - but could you explain in detail what I'm expected to do here?

[Alvin Penner (apenner)]

I was able to produce a crash, but only if an object was first drawn and selected while doing the test.
Then do steps 1 - 6
The scrolling was done with the middle mouse wheel

...............................

Emergency save document locations:
  C:\Documents and Settings\Alvin\New document 1.2014_01_18_07_07_38.0.svg
Emergency save completed. Inkscape will close now.
If you can reproduce this crash, please file a bug at www.inkscape.org
with a detailed description of the steps leading to the crash, so we can fix it.

C:\InkscapeBZR>inkscape\inkscape -V
Inkscape 0.48+devel r12936 (Jan 15 2014)

[Cojnel (cojnel)]

Sorry about that, i should have specifed that i ment
alt + turn the scroll wheel on the mouse,
ill fix it.

[jazzynico (jazzynico)]

Also reproduced on Crunchbang Waldorf, Inkscape trunk revision 12954.

GDB backtrace attached.

[Markus Engel (engelmarkus)]

This is really difficult to reproduce. It happenend once to me without anything drawn on the canvas, but it's easier if there's an object selected first. The part of the code that causes the segfault should reset the opacities of all the objects cycled through if the cursor is moved (as far as I understand). By cycling, the currently active tool isn't changed, is it? I don't quite get what this "prev_event_context" variable is good for.
Anyway, could you try the attached patch? Do these segfaults still occur? Does it change the behaviour in any way?

[Markus Engel (engelmarkus)]

I applied the patch and cleaned up the SelectTool a bit.
This should be fixed in r13088.