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From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: [PATCH 1/7] build-system: Add cargo build system.
Date: Tue, 13 Dec 2016 23:11:46 +0100
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	(David Craven's message of "Tue, 13 Dec 2016 19:07:17 +0100")
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To: David Craven <david@craven.ch>
Cc: guix-devel <guix-devel@gnu.org>

David Craven <david@craven.ch> skribis:

>> Hmm why is there a second one?  =E2=80=98gnu-build-system=E2=80=99 alrea=
dy provides gcc
>> and gcc:lib as implicit inputs, so maybe it=E2=80=99s just a matter of r=
emoving
>> =E2=80=98gcc=E2=80=99 from Rust=E2=80=99s =E2=80=98inputs=E2=80=99?
>
> So we do have an implicit gcc:lib package as an input. But I have to patc=
helf
> the rustc binaries and libraries so I need a way to retrieve the gcc lib =
output.
> I can do (assoc-ref inputs "gcc") but how do I get a reference to the
> lib output?
> (assoc-ref* inputs "gcc" "lib") doesn't work... So I add ("gcc:lib"
> ,gcc "lib") explicitly
> to the inputs so that I can retrieve it. This results in slightly
> different versions
> being included.

OK, got it.

Then you should probably be able to do:

  (inputs `(("gcc:lib" ,(canonical-package gcc) "lib") =E2=80=A6))

>> When you do =E2=80=98guix build rust -s i686-linux=E2=80=99, you get 32-=
bit packages.
>> Is that enough or am I missing something?
>
> The problem here is that we are patching precompiled binaries for i686 to=
 get
> them to run with guix. So I need to get a reference to a 32-bit glibc
> from within the package definition. I think that we'd have to --enable-mu=
ltilib.
> I don't know if we can make it a separate output and how we can prevent it
> from being added to %final-inputs by default. And then we need a way of
> obtaining it from within a package definition which amounts to the same
> problem as with gcc:lib.

We don=E2=80=99t currently --enable-multilib, but you could force a referen=
ce to
a 32-bit libc with this hack:

  (inputs `(("glibc32" ,(package (inherit glibc)
                          (arguments '(#:system "i686-linux" =E2=80=A6))))))

That=E2=80=99s unnecessary when the system is already "i686-linux", of cour=
se.

Would that help?

Cheers,
Ludo=E2=80=99.