Re: [PATCH/RFC] "Recursive Make considered harmful"

From: Sam Ravnborg <sam@ravnborg.org>
Date: Jul 29, 2005, 07:31 UTC
Message-ID: <20050729073134.GA6507@mars.ravnborg.org>
In-Reply-To: <20050729065335.GA32263@mythryan2.michonline.com>

Show 5 quoted lines

> > While I do not have strong objections to make the build process
> > go faster, it is somewhat disturbing that the Makefile pieces
> > maintained in subdirectories need to name things they touch
> > using paths that include the subdirectory names.  I do not have
> > a better alternative to suggest, though...

If the goal is to speed up the build process the only sane way is to fix the dependencies. In kbuild fixdep is used to parse the .c file and it locates all references to .h files (recursive) and also detects any usage of CONFIG_ symbols. This part should be relative straightforward to include in git.

Show 11 quoted lines

> I think I'm going to rethink this, a bit more.  I'm unhappy with how I
> had to edit the sub-dir Makefiles to include directory names.  Sam, if
> you happen to be reading this, feel free to help out!
> 
> I'm almost thinking that something like:
> 
> 	PROGS := 
> 	SCRIPTS :=
> 	include x/Makefile.inc
> 	PROGRAMS += $(addprefix x/,$PROGS)
> 	ALL_SCRIPTS += $(addprefix x/,$SCRIPTS)

That is doable for sure. But it hits you hard when you have to create some special rules in a subdirectory - then you need to know in what directory you are placed. You could assing sub := x before including x/Makefile.inc.

On the other hand. The recursive make considered harmful is IMHO a bit overaggregated. See the kernel where it is used extensively. And it works with no hassle. For a small project like git it should be possible to keep the dependencies in proper shape so there is no cross directory boundaries to worry about - or at least only a few.

Sam