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fix(dereference NULL ptr): Also tests "impl" in gdk_x11_device_xi2_window_at_position

Thibaud CANALE requested to merge (removed):fix_derefence_fault_gdk_x11_device_xi2_window_at_position into gtk-3-24

Sporadically an applet from Desktop Environment MATE crashes with a segmentation fault issue. Thanks to core dump and debugging symbols, I was able to pinpoint the place where the segmentation fault occurs.

From my (light) experience, it looks like a de-referencing issue when accessing value in "impl" object as "GdkWindowImplX11" type (structure) when equals to 0x0 (NULL), set from this instruction:

impl = GDK_WINDOW_IMPL_X11 (window->impl);

gdb_backtrace_core_wnck-applet_1642889923_5383.txt

As we can see in this full backtrace, we confirm with "impl = 0x0".

Unfortunately I wasn’t able to test my patch, since I can’t reproduce simply this issue (it just happens when it does). Don’t hesitate to ask me for more content and tests.

Best regards,

Signed-off-by: Thibaud CANALE thican@thican.net

Edited by Thibaud CANALE

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