Recompiling elisp files (Re: Taking over production of emacs20 package.)

[Christian Lynbech <lynbech@daimi.aau.dk>]

I am not quite so pessimistic about the possibilities of recompiling
installed elisp files.

I see three situations where makefile do special things in order to
compile elisp files:

1) generating/editing .el files (gnats and tm are examples of this) at
   build-time. This is not a problem since the generated .el file is
   installed as part of the .deb file.

2) .elc file is generated through other means than simple
   compilation. VM (at least at some point) had the option to
   concatenate all the little .elc files into one big .elc file. But I
   am pretty sure that (unless something really sick is going on in
   the .elc file generation) one would always be able to use the
   little files instead, perhaps with the appropriate amount of
   additional autoloads in the site-start.d file.

3) specific order of compilation is required. The problem here is (as
   I remember) mainly with macro expansion. Different solutions
   exists. Requiring the maintainer to extract a canonical compilation
   order from the build process is one (should then be handed to the
   elisp service handler). Fixing the source is another (if all files
   has the correct set of `requires', the bytecompiler should be able
   to figure out the rest on it self). A simple hack that probably
   would work quite a long bit of the way would be to sort the set of
   .el files according to the timestamps of the existing .elc and the
   compile in that order, though this certainly is less than robust.


Does anybody know of a concrete example where recompiling a set of
installed .el files in some specific (say alphabetic) order will fail?
Gnus in the emacs distribution used to have this problem, I seem to
remember, but it does not seem to be a problem in 19.34 (I maintain
emacs under CVS which by default ignores .elc files and thus want to
recompile lisp/).

---------------------------+--------------------------------------------------
Christian Lynbech          | Computer Science Department, University of Aarhus
Office: R0.32              | Ny Munkegade, Building 540, DK-8000 Aarhus C
Phone: +45 8942 3218       | lynbech@daimi.aau.dk -- www.daimi.aau.dk/~lynbech
---------------------------+--------------------------------------------------
Hit the philistines three times over the head with the Elisp reference manual.
                                        - petonic@hal.com (Michael A. Petonic)


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