[fedora-arm] Linaro toolchains and Fedora

[Michael Hope]

On Tue, Nov 29, 2011 at 2:17 PM, Brendan Conoboy <blc at redhat.com> wrote:
> On 11/23/2011 06:59 PM, Michael Hope wrote:
>>
>> Hi Jon.  I've cc'ed Marcin and Ricardo who are working on the Linaro
>> platform side.
>
>
> Hi Michael, Marcin and Ricardo.  I'm working with Jon on or ARM endeavors
> and thought I'd follow-up since compilers are one of the few areas where I
> have more expertise than he.  Comments inline below.
>
>> Currently we have a Linaro + Ubuntu sauce cross compiler, plain Linaro
>> cross compiler, and plain Linaro native compiler.  We're working on a
>> plain tarball cross compiler that runs on generic Linux or Windows as
>> well.
>
> Fedora sauce is essentially the rpm packaging.  It's actually quite
> straight-forward to turn a basic build script (configure; make all install)
> into an rpm, so the technical effort needed in this endeavor may be minor.

Sounds good.  Note that Linaro produce a drop in replacement for FSF
GCC so we should be able to re-use your existing packaging.

How about splitting things up, such as gcc vs g++ vs Fortran vs
binutils packages?

>> The Linaro + Ubuntu sauce cross compiler is in the Ubuntu archive from
>> at least Natty onwards and Marcin is working on making these available
>> in Debian.  The plain Linaro compilers are in a PPA, don't include the
>> Ubuntu specific patches, and are more up to date.
>>
>> You probably want your default cross compiler to be the same as the
>> native compiler to reduce surprises so you'll probably want both a FSF
>> and Linaro cross compiler.
>
>
> One of the more complicated elements of Fedora Linaro integration that
> Fedora maintains its own gcc.  This is essentially FSF stable plus rpm
> sauce.  There is definitely room for a Linaro cross compiler.  There might
> be room for a Linaro native compiler.
>
> There are a few avenues we would like to explore:
>
> 1. Making the Linaro cross package set available for i686, x86_64, armv7hl
> and possibly armv5tel rpm-based distributions such as Fedora and RHEL.
>  These same packages would likely work on SuSE, Mandriva, etc. The end goal
> is to get a wider audience able to use the same tool set, regardless of
> their Linux distribution.  This wouldn't need to be limited to gcc and
> binutils- any package that makes sense to run on a non-arm system might be a
> valid candidate including qemu, cross-gdb, etc as you mentioned below.  My
> general assumption is that this would be a pure-Linaro set of packages so
> that the libc linaro-gcc links with would be linaro-libc, rather than
> Fedora-arm libc- that sort of thing.

We don't have a libc as there hasn't been the need.  The cross
compiler could either target the Fedora ARM port or the Linaro LEBs.

> 2. Making the Linaro native package set available on Fedora ARM.  This is
> tricky and will be both technically interesting and perhaps controversial.
>  Questions to be answered include things like: Should linaro gcc replace the
> system gcc? Whose libc should be used?

Marcin is working on a gcc-linaro package that you can install
alongside the native compiler.  The other question of 'could Fedora
switch to Linaro GCC' is a big one but we do support ARMv7, ARMv5,
x86_64, and i386, will investigate bugs found on other platforms, and
have been used by Ubuntu for some time.  Those should help calm some
nerves :)

>> Regarding next steps, I'm afraid we don't have much Fedora packaging
>> knowledge in Linaro but are happy to help when you run into problems
>> and do any bug triage.  Any thoughts on where the scripts or binaries
>> would be hosted, or who would keep it up to date?
>
> That's the big question- who would support this endeavor?  We have precedent
> for #1 in Fedora with the mingw cross compiler, but that is very
> Fedora-centric.  To bring in the wider rpm-based community, Linaro is the
> logical place to host as it is the "source."  With that in mind, what would
> we need to do to make rpms automagicaly build any time debs are produced?
>  Once packages are in rpm format it's very straight-forward for anybody to
> start using them, pulling updates, etc.

I'd have to bring that up with management.  We'll support you if you
use it but producing and maintaining the packaging is an overhead.

>> You might want Linaro GDB, QEMU, and the work that's going on into
>> libjpeg-turbo as well.  We do the changes in Ubuntu to demonstrate the
>> improvements, but I wonder if there's a way of sharing the whats and
>> whys so other distros can consider making the same changes.
>
>
> Fedora generally pulls from the official upstream so anything that gets
> pushed there trickles back down eventually.  It's not exactly ideal for
> cooperating on multi-package architecture-specific distribution such as
> Linaro produces, but the changes do make their way eventually.  In Fedora
> ARM we've reinvented the wheel a few times, as it were, and would like to
> bridge the upstream gap wherever feasible.
>
> Would you all be interested in a conference call to discuss?

That would be good.  I'm travelling next week so the week of the 12th
is best.  Let's see where we go over email and organise a call past
that.

-- Michael