#19 Stack smash error on selection drag.

[tlhonmey]

Running on Gentoo, 17.0 profile enables stack smash protection by default.
gcc 7.3.0.
glibc 2.26

Editing a .bmp file, attempting to drag a selected chunk of picture results in the program being killed for a stack violation.

Backtrace:

     Normal images (color-mapped, 8-bit grayscale, 24-bit true-color)
     will not lose any color info, but non-true-color images may be
     promoted to 24-bit mode.

*** stack smashing detected ***: <unknown> terminated

Program received signal SIGABRT, Aborted.
0x00007ffff5b47060 in raise () from /lib64/libc.so.6
(gdb) bt
#0  0x00007ffff5b47060 in raise () from /lib64/libc.so.6
#1  0x00007ffff5b48c3d in abort () from /lib64/libc.so.6
#2  0x00007ffff5b8d37f in ?? () from /lib64/libc.so.6
#3  0x00007ffff5c25f8c in ?? () from /lib64/libc.so.6
#4  0x00007ffff5c25f22 in __stack_chk_fail () from /lib64/libc.so.6
#5  0x00005555555d85c6 in ?? ()
#6  0x00007ffff7976cb3 in XtDispatchEventToWidget () from /usr/lib64/libXt.so.6
#7  0x00007ffff79772a9 in _XtDefaultDispatcher () from /usr/lib64/libXt.so.6
#8  0x00007ffff7977398 in XtDispatchEvent () from /usr/lib64/libXt.so.6
#9  0x000055555557e1c9 in main ()

Core dump attached.

If it's not immediately obvious where the problem is, let me know and I'll see about rebuilding with full debugging symbols to generate a more precise trace.