Path: utzoo!attcan!uunet!husc6!cmcl2!nrl-cmf!ames!elroy!cit-vax!jerbil
From: jerbil@cit-vax.Caltech.Edu (Joe Beckenbach)
Newsgroups: comp.software-eng
Subject: Re: Makefile Generators
Message-ID: <8963@cit-vax.Caltech.Edu>
Date: 22 Dec 88 16:39:46 GMT
References: <2472@mergvax>
Reply-To: joe@cit-vax.caltech.edu (Joe Beckenbach)
Organization: California Institute of Technology
Lines: 27


	[Tried replying to the original article but mailer bounced it]

	The X windows system has a 'makedepend' command which parses like a
C preprocessor to find dependencies which might be hidden by #defines,
other #includes, and #if/#ifdef/#ifndef sequences. There are tradeoffs
involved of course:
	1- In building 'makedepend' in X windows, apparently a section of
the cpp source code is needed to ensure proper decoding and handling of #if's.
	2- Each file is processed once. If included multiple times, it simply
reuses what information it has. This causes problems in the unfortunate case
where a #if/#else clause selects one of two #includes in one file, and the
other in another: the first time through will set the choice of dependencies
in stone.

	The man page says that the algorithm assumes that all the source files
for a given makefile use the roughly the same set of -I and -D flags. The 
mechanism is based at bottom on cobbling together a useful framework from a
Berkeley kernel-building makefile which modifies itself to add appropriate
dependencies. [Sorry, can't remember where it is. I think it's in a GENERIC
directory somewhere. (And I call myself a system manager. :-) ]

	Joe Beckenbach [aka jerbil; use joe@cit-vax.caltech.edu for mail]
-- 
Joe Beckenbach	joe@csvax.caltech.edu	Caltech 256-80, Pasadena CA 91125
PRINCIPLE OF LEAST ASTONISHMENT: a common-sense rule unknown to the
	worlds of systems and programming