[slime-devel] CMUCL raises emacs debugger

Raymond Toy toy.raymond at gmail.com
Fri Mar 4 18:23:05 UTC 2011

On 3/4/11 3:00 AM, Helmut Eller wrote:
> * Raymond Toy [2011-03-03 20:26] writes:
>> On 3/3/11 7:47 AM, Desmond O. Chang wrote:
>>> Hi,
>>> If slime-net-coding-system is utf-8-unix, emacs will enter backtrace
>>> buffer after cmucl startup.  Here is my operation:
>>> 1. (setq slime-net-coding-system 'utf-8-unix)
>>> 2. C-u M-x slime
>>> 3. input "lisp -noinit"
>>> 4. cmucl starting...
>>> 5. cmucl started, but raises emacs debugger
>>> This error doesn't occur every time.  If everything is ok, please quit
>>> cmucl then restart it, the error should occur now.
>> FWIW, I can reproduce this.  I don't have such problems with cmucl and
>> xemacs, though.  I don't what the cause is, but a backtrace would be useful.
> The problem seems to be that (format stream "~6,'0x" length) triggers a
> gc-hook which writes something to the stream in the middle of the length
> field.  I was able to reproduce it with the March snapshot but not 
> with the one from December.
> Quick workaround: add
> (setq swank-backend::*install-gc-hooks* nil)
> to ~/.swank.lisp.
> We could write the length to a private buffer before writing it to the
> stream.  That would probably work most of the time.  I guess, tho, that
> any kind of writing to a stream can potentially trigger gc.

How about disabling gc in write-message?  Or at least on cmucl, binding
ext:*gc-verbose* to NIL in write-message?

That seems to work for me.


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