Re: x-dnd (drag and drop) fails on x86_64

[Jan D.]

Reiner Steib wrote:

> Please describe exactly what actions triggered the bug
> and the precise symptoms of the bug:
>
> Open www.gnu.org in the Firefox browser.  Select some text
> (e.g. "Welcome to the GNU Project web server") with the mouse.
> Dragging the text over the Emacs frame leads to the following
> backtrace:
>
> --8<---------------cut here---------------start------------->8---
> Debugger entered--Lisp error: (wrong-type-argument listp 0)
>  x-dnd-handle-xdnd((drag-n-drop (#<window 3 on *scratch*> 1 (351 .
>  375) 0 nil 1 (50 . 0) nil (351 . 375) (7 . 14)) ["XdndEnter" #<frame
>  address@hidden 0xe2f4d0> 32 [... 0 ... 0 0 0 0
>  0 0 0]]) #<frame address@hidden 0xe2f4d0>
>  #<window 3 on *scratch*> "XdndEnter" 32 [(1344 . 62806) 0 (768 . 1)
>  0 0 0 0 0 0 0])
>  x-dnd-handle-drag-n-drop-event((drag-n-drop (#<window 3 on
>  *scratch*> 1 (351 . 375) 0 nil 1 (50 . 0) nil (351 . 375) (7 . 14))
>  ["XdndEnter" #<frame address@hidden 0xe2f4d0>
>  32 [... 0 ... 0 0 0 0 0 0 0]]))
>  call-interactively(x-dnd-handle-drag-n-drop-event)
> --8<---------------cut here---------------end--------------->8---
>
> Emacs was built on x86_64 (AMD 64 bit) and started with "emacs -Q",
> then I did `M-x toggle-debug-on-error RET'.  Drag and drop to an Emacs
> built on i686 (same source) works fine.

I don't have access to any 64-bit processors, so if you could debug a 
bit, that would be helpful.

Start emacs in gdb and set a breakpoint:
% cd emacs/src
% gdb emacs
(gdb) b x_handle_dnd_message
(gdb) r -Q

Then do the same drop and when the breakpoint is reached:
(gdb) p *event
(gdb) p sizeof(event->data)
(gdb) p sizeof(event->data.l[0])



There is obviously some 32/64 bit mixup somewhere.  If I can get the raw 
event data and those sizes I can probably track it down.

Thanks,

   Jan D.