Problem mit symlinks, locate-library and load-history [Was: <Something else>]

[Alan Mackenzie]

Hi, Emacs!

On Tue, 14 Mar 2006, Alan Mackenzie wrote in an article with Subject: "CC
Mode: File mode specification error: (void-variable
c-font-lock-keywords-3)":

>Hi, Emacs and CC Mode!
>
>Start Emacs 22 with -Q, then visit a file.c.
>
>Emacs displays the message:
>
>  File mode specification error: (void-variable c-font-lock-keywords-3)
>
>.  Probably that variable needs an autoload on it, or something like
>that.  Please consider the bug as noted by CC Mode, and that it will be
>fixed in the next (minor) release.

This problem happens with the form

    (eval-after-load "font-lock" '(require cc-fonts))

in cc-mode.el.  eval-after-load calls (locate-library "font-lock"), which
returns

    "/home/acm/emacs/emacs/lisp/font-lock.elc"

, which it then tries, with (assoc (locate-library file) load-history), to
match against

    "/mnt/hda7/emacs/lisp/font-lock.el"

, and fails.  There are two distinct problems here:

(i) locate-library gives a .elc, but there's a .el in load-history.

(ii) /home/acm/emacs is actually a symbolic link pointing at /mnt/hda7.

My reactions:

(i) The dumped lisp files are byte compiled, so it seems strange indeed
that font-lock.el is record in load-history rather than font-lock.elc.
Is this a bug?

(ii) Why on earth is eval-after-load converting "font-lock" to a full
filename and then searching for that?  Surely it is sufficient that any
old font-lock has been loaded at some time (e.g., at dump time)?

On the other hand, if absolute pathnames are to be used, shouldn't they
first be filtered with file-truename, like this:

*** subr.el     Sun Feb 19 12:50:45 2006
--- subr.acm.el Sun Mar 19 22:00:15 2006
***************
*** 1378,1384 ****
            ;; Emacs for the case that FILE is one of them.
            ;; (load-symbol-file-load-history)
            (when (locate-library file)
!             (assoc (locate-library file) load-history)))
          (eval form))))
    form)
  
--- 1378,1384 ----
            ;; Emacs for the case that FILE is one of them.
            ;; (load-symbol-file-load-history)
            (when (locate-library file)
!             (assoc (file-truename (locate-library file)) load-history)))
          (eval form))))
    form)
  
There are approximately 45 places in ..../lisp where locate-library is
used, and approximately none of them use file-truename.  3 of these are
assoc'king the result with load-history.
 
-- 
Alan Mackenzie (Munich, Germany)