Debugging an existing error

[Gary Palter]

Thanks for the hint.

After you connect Slime to the remote Lisp, use m-x slime-iist-threads. In the buffer listing all the threads in the remote Lisp, type “d” on the line of the thread you’re interested in and SLDB will activate on that thread. (Typing “d” runs slime-debug-thread which gets which thread to debug based on the current line in the thread list.)

  - Gary


> On May 2, 2023, at 1:13 AM, Christopher Stacy <cstacy at dtpq.com> wrote:
> 
> Hi there!
> 
> I am no slime expert.
> 
> 
> As a baseline, here's what happens when
> I use slime from Emacs 28.2, CCL 1.12 DarwinX8664.
> 
> ; SLIME 2.26.1
> CL-USER> (ql:quickload "bt-semaphore")
> CL-USER> (not (null (member :thread-support *features*)))
> T
> CL-USER>  bt:*supports-threads-p*
> T
> CL-USER> (defvar *loser
>        (bt:make-thread
>         (lambda ()
>               (sleep 5)
>               (error "tired of you"))))
> *LOSER
> CL-USER>
> 
> That subsequently pops up an sldb window
> in the erring thread. This is what we want
> to happen remotely, too.
> 
> What I've read suggests that it's supposed to
> automagically work remotely, too.
> Your standalone app should call
> swank:create-server
> before calling bc:make-thread.
> 
> I tried that (with the same program above)
> from a shell:
> 
>   % ccl64 --load /tmp/test.lisp
>   ;; Swank started at port: 4006.
>   ?
>   > Error: tired of you
>   > While executing: #<Anonymous Function #x302000C99B6F>, in process Anonymous thread(4).
>   ;;;
>   ;;; #<PROCESS Anonymous thread(4) [Active] #x302000C996ED> requires access to Shared Terminal Input
>   ;;; Type (:y 4) to yield control to this thread.
>   ;;;
> 
> Back in Emacs I did:  m-x slime-connect.
> 
> That worked, but warned me that I had
> a different version of slime than the
> remote end. I can see the erring thread
> over there (I have no local inferior lisp):
> 
> ; SLIME 2.26.1
> CL-USER> *loser
> #<PROCESS Anonymous thread(4) [semaphore wait] #x302000C996ED>
> 
> Then I did:      m-x slime-thread-debug
> which is a command I discovered from
> emacs command completion fishing.
> 
> That blew me into the debugger in Emacs.
> There was no corresponding visible output
> on the remote test/erring program in bash.
> Here are the slime events:
> 
> (swank:debug-nth-thread nil)
>  "COMMON-LISP-USER" :repl-thread 5)
> (:debug 12 1
>     ("The value NIL is not of the expected type UNSIGNED-BYTE." "   [Condition of type TYPE-ERROR]" nil)
>     (("USE-VALUE" "Use a new value of type UNSIGNED-BYTE instead of NIL.")
> 
> which I imagine is due to the incompatible
> versions of slime/swank I was trying to use.
> Or maybe I am using the wrong command.
> But it looked like it was supposed to work!
> 
> THat's the first time I've tried anything
> like this in many years, and it's all I know.
> Hopefully someone with a clue will come
> along here shortly.
> 
> One final note. Apparently there is a wrinkle for sbcl threads.
> https://stackoverflow.com/questions/41502921/handling-an-exception-in-a-thread
> 
> Hope my experiment helps you at all.
> 
> 

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