[slime-devel] Re: CMUCL 19a: NIL is not of type SWANK::CONNECTION

[Helmut Eller]

Chisheng Huang <cph at chi-square-works.com> writes:

>   (defun send-to-emacs (object)
>     "Send OBJECT to Emacs."
>     (when *emacs-connection*
>       (funcall (connection.send *emacs-connection*) object)))
>
> If you think this fix is O.K., would you please merge it into swank.lisp?

That's not the best place for the test because *emacs-connection*
_should_ never be nil here.  Adding the test here makes finding bugs
harder, as it would be a kind of fail silent behavior.

I added the test in the gc-hooks instead.  There's also new variable
*install-gc-hooks* to disable the gc hooks for SLIME entirely.

> Of course, it's entirely logical to ask why *EMACS-CONNECTION* is NIL in
> the first place, which is totally beyond me.

Yes, that's a good question.  It can be nil if a you disconnect and a
GC happens afterwards or if you do some asynchronous processing, e.g.,
in a fd-handler or a thread.  It should never be nil if the GC is
(indirectly) triggered by a SLIME request.

Helmut.