This is related to the recent changes to xfdesktop icon orientation and primary display changes. I think I've hit a corner case. All components built from git. On a multi-monitor setup (laptop, secondary, on left / monitor, primary, on right) with the desktop-settings option "Show icons on primary display" enabled, attempting to drag and drop an icon from the primary (external) display to the secondary (laptop) display results in an xfdesktop crash. Running xfdesktop through gdb yields the following message: Thread 1 “xfdesktop” received signal SIGBUS, Bus error. 0x000055555558216c in xfdesktop_icon_get_allowed_drop_actions (icon=0x7ffff7669ab0, suggested_action=0x0) at xfdesktop-icon.c:272 272 g_return_val_if_fail(XFDESKTOP_IS_ICON(icon), FALSE); I am unable to get a backtrace as this results in a hard lockup of my system. Of interest, when I uncheck the "Show icons on primary display" option, I don't get a crash and the icon is successfully moved to the secondary display. If the intent of this option is to force icons to the primary display, we may be missing a check.
One further note. If I change the primary/secondary designation (laptop, primary, on left / monitor, secondary, on right) and check the option, icons are handled well. If I try to drag an icon from the primary to secondary monitor, it snaps back.
Andre Miranda referenced this bugreport in commit c7c894fea51c8c2a7d2f776e7e313be59a5a0284 Avoid invalid memory access (Bug #15299) https://git.xfce.org/xfce/xfdesktop/commit?id=c7c894fea51c8c2a7d2f776e7e313be59a5a0284
Andre Miranda referenced this bugreport in commit 4ae6e0b9e3b2752d56a12f68a1e3f383bee830c8 Avoid invalid memory access (Bug #15299) https://git.xfce.org/xfce/xfdesktop/commit?id=4ae6e0b9e3b2752d56a12f68a1e3f383bee830c8
This is bug also present in 4.12.x, the array index is derived from row/column which may be negative! The crash happens even when "Show icons on primary display" is disabled, the icons just have to somehow end up on the external display. After the fix no more crashes, but the icons go back the primary monitor... Can you please file another bug requesting an improvement for this? (remember to mention this one)