Samba 4 buildsystem; patch in progress

[James Peach]

On 05/01/2008, at 5:32 PM, Jelmer Vernooij wrote:

> After discussing this with various people over the last week, I  
> decided
> to try and see how hard it would be to get Samba 4 to use a simple
> Makefile again.
>
> I've now got something partially working, heavily based on the  
> "include"

Is "include" portable? According to <http://www.freebsd.org/cgi/man.cgi?query=make&sektion=1 
 >, BSD make uses ".include".

> and double-colon features in make (portable across all makes we build
> on, afaik).

This is a weird one. <http://www.freebsd.org/cgi/man.cgi?query=make&sektion=1 
 > describes :: in a way that conflicts with your use of it to  
accumulate target dependencies and rules. However, <http://www.opengroup.org/onlinepubs/009695399/utilities/make.html 
 > claims that the accumulation behaviour is a BSD make-ism.

> So far I've managed to avoid most beartraps; it should work portably
> across all platforms, doesn't use recursive make, doesn't use libtool
> and variables and rules don't use a lot of magic.

I have to say that I don't think a truly portable Makefile is a good  
idea.

First, I'm not convinced that the portable subset of make has the  
features we would want to use in the build.

Second, even if we narrow the scope to 3 or 4 make implementations, I  
think there will be a continual support cost from folks building on  
platforms without these implementation, as well as the likelihood of  
GNU make-isms constantly leaking in from the 99% of Samba developers  
who use GNU make exclusively.

Finally, I think that using the full vocabulary of a single make  
implementation (particularly GNU make), is too useful to ignore, eg.  
"$^".

> A nice advantage of this system is that you never have to run
> config.status if you include one of the files included by the  
> Makefile.
> Only when config.status changes do you have to update anything.
>
> Another advantage is that we can include the config.mk for tdb, talloc
> and ldb within the Samba build and the standalone builds (and
> potentially the Samba 3 makefile). So, only one place where the rules
> are and thus harder to break.

With the above caveats, I rather like the approach. It's simple and  
obvious and easy for people to dig into.

You could include a GNU make download/bootstrap script with installs a  
temporary copy of GNU make automatically if configure doesn't find it.  
Then you could use GNU make features like per-target variables. Would  
this make a GNU make dependency more acceptable?

--
James Peach | jpeach at samba.org