Stefan Monnier <monnier@iro.umontreal.ca> writes:

>>>> Error in post-command-hook: (wrong-type-argument listp (nil DEAD . 18764377))
>>> 
>>> Oh yes, the live_deleted_processes variable needs to be gcpro'd.
>
>> I'm not  familiar with Emacs C code,  so I don't know  how to proceed.
>> Can you send a patch, or at least, the lines that have to be modified,
>> and how ?
>
> Add something like
>
>    staticpro (&live_deleted_processes);
>
> in syms_of_process

Works fine!

I used two tests:

  1) (original test) Quick switching between two flyspellized buffers
     that have different dictionaries,

  2) 

(let (processes)
  (dotimes (i 100)
    (push (start-process "bug" nil "/tmp/sleep") processes))
  (dotimes (i 50)
    (if (zerop (mod i 2))
	(delete-process (pop processes))
      (kill-process (pop processes))))
  (message "%S" (call-process "/tmp/sleep"))
  (dotimes (i 50)
    (delete-process (pop processes)))
  (message "%S" (call-process "/tmp/sleep")))

None of them succeeded before, but now it's OK.

(Final ?) patch attached.

Agustin, can you check that you can't trigger the bug anymore?