[slime-devel] Re: make swank safe if loaded into an image with an older version of swank in the image

[Madhu]

* Marco Baringer <87ir17m6mo.fsf at arsenic.bese.it> :
Wrote on Sat, 02 Feb 2008 21:43:27 +0100:

|   It can happen (though i admit it's a rare occurance) that you build an
|   image with swank, update swank and then try to load swank into the
|   existing image. hard to debug/understand errors ensue, this simple
|   patch protects against that.
|
| Index: swank-loader.lisp
[...]
| +(eval-when (:compile-toplevel :load-toplevel :execute)
| +  (when (find-package :swank)
| +    (delete-package :swank)
| +    (delete-package :swank-io-package)
| +    (delete-package :swank-loader)
| +    (delete-package :swank-backend)))
| +
|  (cl:defpackage :swank-loader
|    (:use :cl)
|    (:export :load-swank

This is a bad idea. In general, packages should not be automatically
deleted[1], and I would prefer if package deletion was provided in a
function called reload-swank-loader or something that the user can
call when he knows what is happening

Secondly, this breaks a common[2] strategy to put swank fasl files in a
different location: For example in my lisp's init file I may have have

(eval-when (:load-toplevel :execute :compile-toplevel)
(unless (find-package :swank-loader)
  (make-package :swank-loader)))

(defparameter swank-loader::*fasl-directory* "/user11/madhu/build/swank/")

(load "/path/toswank-loader.lisp")

- To override the defvar in swank-loader.lisp

The logic propsed in the patch would break this usage completely by
deleting the package the variable belongs to
--
Madhu

[1] I hear some implementations may leak objects in deleted packages
[2] By common, I mean I use this idiom and have seen others use this to
customize defvars.