Path: utzoo!utgpu!watmath!uunet!tut.cis.ohio-state.edu!gem.mps.ohio-state.edu!csd4.csd.uwm.edu!mailrus!ames!fxgrp!news
From: grady@fxgrp.fx.com (Steven Grady)
Newsgroups: gnu.utils.bug
Subject: Re: make 3.55 infinite loop
Message-ID: <1989Aug31.080610.20127@fxgrp.fx.com>
Date: 31 Aug 89 08:06:10 GMT
References: <1989Aug31.014333.18904@fxgrp.fx.com>
Reply-To: grady@fxgrp.UUCP (Steven Grady)
Organization: FX Development Group, Inc., Mountain View, CA
Lines: 44

[Sorry these are so long.]
Hmm.  On looking at this further, I see a more insidious problem.
Consider the siuation where you want to include one makefile
in another, but you want to provide the opportunity for
overriding productions (which is what I want to do).  This
requires using a ".DEFAULT" rule (as recommended in the "Overriding
Makefiles" section of the texinfo document).  But consider the
following makefile:
	a: b
		@echo making a
	
	.DEFAULT:
		$(MAKE) -f OtherMakefile $@

The default production, a, depends on b.  Assume b exists.  Well,
since there is a default production, b has commands associated with it 
(namely, the commands in the default production which are used whenever
no other productions can be found).  Since b has commands but no dependencies,
the default rule will be executed.  So it's going to invoke another
make just because it can't find any production on what to do for a file
that already exists.

If there were an additional line up there: "include a", then even if
some other production were invoked, it would still check if "a" was
up-to-date (since all include files are checked), and therefore the
default rule would fire to try to update "b".

It also seems to be the case that gnumake always checks to see if
the makefile being used is up-to-date.  Again, if there's a default 
production, gnumake will try to use it to update the makefile itself,
meaning that gnumake will _always_ be invoked at least twice if there's
a DEFAULT production.

I think I've made my point that firing off commands if there are no 
dependencies, combined with DEFAULT productions, is a bad thing.  I'm 
not sure what the right fix would be, but it seems that if there are 
no dependencies, commands should only be executed if the target is PHONY.

	Steven
	...!ucbvax!grady
	grady@postgres.berkeley.edu

"But Calvin is no kind and loving god!  He's one of
the _old_ gods!  He demands sacrifice!"