Subject: bug#9313: 24.0.50; Emacs 24 cannot load byte-compiled code from Emacs 23.3 when using EIEIO's defmethod

From: David Engster <[email-masked]>
Date: Wed, 17 Aug 2011 17:52:03 +0200

This is a very late followup to an older message from emacs-devel,
regarding the issue that Emacs24 after the lexbind merge cannot run
byte-compiled code from Emacs23.3 if that is using EIEIO's 'defmethod':

http://thread.gmane.org/gmane.emacs.devel/138030/focus=78338

In that message Stefan Monnier says that this is considered a bug, so
I'm writing this report. Also, this issue is popping up more frequently
now as people are migrating to Emacs24-bzr, but still have compiled Gnus
or CEDET sources with Emacs23, so I think this should be fixed before a
release.

Here's a recipe:

* Create a file ~/eieio-test/eieio-test.el with the following contents:

 (require 'eieio)

 (defclass someclass ()
   ((astring :initarg :astring
             :initform ""))
   "Some test class.")

 (defmethod somemethod ((arg someclass))
   "Some method."
   (message "Somemethod called."))

 (provide 'eieio-test)

* Byte-compile the file using Emacs 23.3:

  emacs23 --batch -f batch-byte-compile eieio-test.el

* Load Emacs24-bzr with

  emacs24 -Q -L ~/eieio-test

  and evaluate

  (require 'eieio-test)

* The following backtrace will appear:

Debugger entered--Lisp error: (void-function eieio-defmethod)
  (eieio-defmethod (quote somemethod) (quote (((arg someclass)) #[(arg) "\300\301!\207" [message "Somemethod called."] 2 "Some method."])))
  require(eieio-test)
  eval((require (quote eieio-test)) nil)

* Note that the following setups work:

  - Byte compile with Emacs23, require with Emacs23
  - Byte compile with Emacs24, require with Emacs24
  - Require uncompiled el-file.

* This issue is occuring since the lexbind merge.

Cheers,
David