From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: Cross-building GuixSD (and maybe using pre-built toolchains)
Date: Thu, 01 Sep 2016 21:43:38 +0200
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References: <201608302326.38349.paul@boddie.org.uk>
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To: Paul Boddie <paul@boddie.org.uk>
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Paul Boddie <paul@boddie.org.uk> skribis:

> When you write "cross-compile from x86_64" do you mean run a cross-compil=
er on=20
> an x86_64 host that targets another architecture? (I'm guessing "yes".)

Yes.

> From previous questions, it appears that any compiler must have been buil=
t=20
> specifically for Guix to use (and cannot be those those pre-built toolcha=
ins=20
> provided by, say, Debian), so would these cross-compilers be the ones nor=
mally=20
> used to generate the "bootstrap binaries" (that would normally be used to=
 then=20
> build packages on the target system)?

Yes, Guix packages only depend on other Guix packages; there cannot be
dependencies on external packages.

> Or do I first bootstrap Guix on my (x86_64, in this example) "build syste=
m",=20
> then generate special cross-compilers for my target architecture (that ar=
e=20
> then exposed via offloading)?

Offloading and cross-compilation are unrelated.  Offloading is just a
mechanism that allows distributed builds.

Guix supports x86_64-linux-gnu, so, IOW, the distro is already
=E2=80=9Cbootstrapped=E2=80=9D for that platform.  There=E2=80=99s nothing =
special to be done.

I=E2=80=99m trying to find ways to rephrase this, but I can=E2=80=99t think=
 of other
ways than what the =E2=80=9CBootstrapping=E2=80=9D and =E2=80=9CPorting=E2=
=80=9D sections of the manuals
say.  :-)

> And can I provide a foreign architecture build daemon on the same machine=
 as=20
> the one performing the build?

No.

> Sorry if this is all obvious or if I'm not assuming that what is possible=
 is=20
> actually possible! I'm used to discovering limitations with build systems=
. (To=20
> me it is remarkable that given all the portable things like shell scripts=
 that=20
> do a lot of the lifting in build processes, many build systems have an=20
> unreasonable affinity to the build host's architecture.)
>
> Thanks for all the help!

No problem!  I realize it can be difficult to convey the big picture of
Guix here to someone already familiar with other build systems.

Ludo=E2=80=99.