Cross-compiling git (was: [PATCHv2] add Android support)

From: Jakub Narebski <jnareb@gmail.com>
To: Jeff King <peff@peff.net>
Cc: Rafael Gieschke <rafael@gieschke.de>,
	Junio C Hamano <gitster@pobox.com>,
	git@vger.kernel.org
Subject: Cross-compiling git (was: [PATCHv2] add Android support)
Date: Mon, 23 May 2011 00:04:44 -0700 (PDT)	[thread overview]
Message-ID: <m3k4dhzynr.fsf_-_@localhost.localdomain> (raw)
In-Reply-To: <20110519122026.GA30240@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:
> On Thu, May 19, 2011 at 01:37:53PM +0200, Rafael Gieschke wrote:
> 
> > > (3) Add uname_S = Android (Makefile).
> > > 
> > > The first two would become much easier to justify if presented that
> > > way. At least you won't hear from anybody "we don't want that much code to
> > > not to run git on a phone!", as it is not entirely implausible to imagine
> > > environments without support for one or both of these two facilities.
> > 
> > So, you would prefer to leave out ANDROID and use something like "ifeq
> > ($(uname_S),Android)", so you will have to compile using make
> > uname_S=Android? I would be fine with that, too. But I would also be
> > fine with having to specify the build options on the command line or
> > using a config.mak if you want to keep Android out of the Makefile.
> 
> The point of uname_S is that it would be found automatically. Sadly,
> There is nothing helpful in uname to tell us that we are on android:
> 
>   $ uname -a
>   Linux localhost 2.6.37.4-cyanogenmod-01332-g7f230e8 #1 PREEMPT Tue Apr
>   12 12:54:14 EDT 2011 armv7l GNU/Linux
> 
> You could obviously guess from Linux on that architecture, but that
> seems flaky to me. You can also figure it out by looking around the
> filesystem, but that is not something I'm excited about having the
> Makefile do.
> 
> So I think we are probably stuck either with the user setting an ANDROID
> meta-flag that sets the other flags appropriately, or leaving it up to
> the user to provide a sane config.mak.

By the way, how well Git supports cross-compiling (which from the
thread is necessity to generate binaries for Android)?  `uname -a`
trick works only when compiling on same machine.

./configure supports --host and --build options, but I don't know if
it pass them down to make somehow.  ANDROID=YesPlease seems wasteful:
what about setting HOST or MACHINE, or even uname_* variables, or just
using Autoconf's `host` (in the form of CPU-VENDOR-OS)?

-- 
Jakub Narebski
Poland
ShadeHawk on #git