[slime-devel] Re: slime-edit-definition woes

[Edi Weitz]

On 05 Mar 2005 23:58:28 +0100, Luke Gorrie <luke at synap.se> wrote:

> I have narrowed the test case down far enough to take slime out of
> the picture:
>
>   $ rm *.x86f
>   $ lisp
>   * (asdf:oos 'asdf:load-op :foo)
>   * (let ((*read-suppress* t))
>       (with-open-file (s "foo1.lisp")
>         (dotimes (i 4) (read s))))
>   ...hits the error...

Same here.

> i.e. it looks like a bug where clsql's reader syntax doesn't work
> with *READ-SUPPRESS* but just looking at the code I don't see why
> this is so.

I think I've found the answer:

Usually, LISP::TOKEN-DELIMITERP returns NIL for #\[, but after CLSQL
has modified the readtable this macro returns T:

  edi at vmware:/tmp$ cmucl
  ; Loading #p"/home/edi/.cmucl-init".
  CMU Common Lisp CVS release-19a 19a-release-20040728 + minimal debian patches, running on vmware
  With core: /usr/lib/cmucl/lisp.core
  Dumped on: Thu, 2005-02-10 19:05:48+01:00 on vmware
  For support see http://www.cons.org/cmucl/support.html Send bug reports to the debian BTS.
  or to pvaneynd at debian.org
  type (help) for help, (quit) to exit, and (demo) to see the demos

  Loaded subsystems:
      Python 1.1, target Intel x86
      CLOS based on Gerd's PCL 2004/04/14 03:32:47
  * (asdf:oos 'asdf:load-op :clsql)

  ; [blabla]

  NIL
  * (lisp::token-delimiterp #\[)

  NIL
  * (clsql:locally-enable-sql-reader-syntax)

  * (lisp::token-delimiterp #\[)

  T

Now, when *READ-SUPPRESS* is true then CMUCL's LISP::READ-TOKEN will
call LISP::INTERNAL-READ-EXTENDED-TOKEN which in this case (i.e. when
looking at #\[) will unread the character from the stream and return
immediately.  At that point the reader is stuck and will try
indefinitely to get past the opening bracket.

Something like that...

> NB: I want buffer-local syntax as much as the next guy but I think
> this clsql #.(hack-read-syntax) ... #.(unhack-read-syntax) trick is
> a bit fragile -- I don't think that tools like SLIME or the CMUCL
> debugger can really do the right thing with it.

Yep, everything works fine if I use EVAL-WHEN and a copy of the
readtable instead so the case is closed for me.  Thanks for your help!

> BTW, on my machine it also hangs Emacs but that's just due to
> swappage as the lisp heap expands. I don't have much ram though.

Get more RAM, it's fun... :)

Cheers,
Edi.