[maemo-developers] [maemo-developers] build system

[From: Timo Savola]

Gustavo Barbieri wrote:

> While trying to build it by hand and also create an ebuild (Gentoo),
> I've found out that many other things are hard coded and the build
> process is not that usual (ie: doesn't use autotools and stuff like
> that). There is any reason?

Scratchbox is a complex piece of software; it's actually closer to an
operating system than an application.  There are a few reasons why
things are like they are:

Scratchbox's host tools (including compilers) are dynamic binaries that
need to work in the sandbox where the root filesystem is dominated by
the contents of the target filesystem.  The host tools are linked so
that they find correct host libraries from under /scratchbox instead of
trying to link against ARM/whatever libraries found in /lib and
/usr/lib.  The host tools can also be used outside the sandbox
environment, so the library location must be the same in either case for
that to work.  Being able to use the toolchains from outside is handy,
but moving the Scratchbox installation directory to a more suitable
place is often more important.  I have done some preliminary work for
making the installation and login process work even when /scratchbox
doesn't exist outside the sandbox; the work should be fairly simple to
complete.

A bigger problem (from my perspective) is the fact that Scratchbox can
only be built directly to its installation directory.  The tools fail to
configure and/or build when things are not in correct places.  I worked
on this problem last year, but in the end it seemed next to impossible
to fix--I don't remember the specific problems anymore.  This problem
could also be solved by building most of the tools inside the sandbox
(like sb-perl-devkit and sb-toolchains are built), but then we'd also
have to build all libraries and tools that are used during the build
(i.e. Linux from scratch).

Using autotools for building Scratchbox would be a bit pointless because
the Scratchbox build procedure is not something automake or autoconf
solve.  Scratchbox is mostly just a set of upstream packages that
already have autotools-based build systems; we just have to build them
with correct settings (and patches) in the correct order.  We use the
GAR system[1] which is specifically designed for this.  (GAR is a bit
messy because it uses make; I'd one day like to replace it with a
scons[2]-based build system...)

[1] http://www.lnx-bbc.org/garchitecture.html
[2] http://www.scons.org/

We (Lauri Leukkunen, Veli Mankinen and myself) have plans[3] for a
complete redesign of Scratchbox which (among other things) solves all of
the problems you mentioned.  We're hoping to write a more elaborate
Scratchbox 2.0 design document in near future.  But any help in
improving the existing versions is naturally welcome. :)

[3] http://scratchbox.org/~tsavola/sb2-outline.txt

I'm posting this message to scratchbox-devel so that we can continue the
discussion on a more suitable mailing list.

timo