How can I set architecture/system-specific origin sources?

How can I set architecture/system-specific origin sources?

[Pierre Neidhardt]

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Hi!

I'd like to write a package definition whose source is different
depending on the system / arch it is built for.

I thought of writing something like this:

--8<---------------cut here---------------start------------->8---
(source (origin
         (method url-fetch)
         (uri
          (string-append "http://foo.bar/"
                         version "-" 
                         (match (or (%current-target-system)
                                    (%current-system))
                           ("i686-linux" "x86")
                           ("x86_64-linux" "x86_64"))
                         ".tgz"))
         (sha256
          (base32
           (match (or (%current-target-system)
                      (%current-system))
             ("x86_64-linux"
              "0y4qms4lm9xiix93g45337rx5nrp0y3gb0x0avyv7l9qrkk03zz8")
             ("i686-linux"
              "0yc8n6vpqyb6qhcv5kwvr3h21ya271fi930fvd98hlkg8cg5kwyf"))))))
--8<---------------cut here---------------end--------------->8---

My laptop is a x86_64-linux and the above definition always uses the
x86_64 source, even with

  guix build --system=i686-linux foo

In Nix, the following works:

--8<---------------cut here---------------start------------->8---
  src =
    if stdenv.hostPlatform.system == "x86_64-linux" then
      fetchurl {
        url = "http://foo.bar/...";
        sha256 = "e8ff01e6cc38d1b3fd56a083f5860737dbd2f319a39037528fb1a74a89ae9878";
      }
    else if stdenv.hostPlatform.system == "i686-linux" then
      fetchurl {
        url = "http://foo.bar/...";
        sha256 = "cef3591e436f528852db0e8c145d3842f920e0c89bcfb219c466797cb7b18879";
      }
    else throw "foo does not support platform ${stdenv.hostPlatform.system}";
--8<---------------cut here---------------end--------------->8---

Is this a Guix bug?

-- 
Pierre Neidhardt
https://ambrevar.xyz/

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Re: How can I set architecture/system-specific origin sources?

[Mathieu Othacehe]

Hello Pierre,

>
> My laptop is a x86_64-linux and the above definition always uses the
> x86_64 source, even with
>
>   guix build --system=i686-linux foo
>
> In Nix, the following works:
>
> --8<---------------cut here---------------start------------->8---
>   src =
>     if stdenv.hostPlatform.system == "x86_64-linux" then
>       fetchurl {
>         url = "http://foo.bar/...";
>         sha256 = "e8ff01e6cc38d1b3fd56a083f5860737dbd2f319a39037528fb1a74a89ae9878";
>       }
>     else if stdenv.hostPlatform.system == "i686-linux" then
>       fetchurl {
>         url = "http://foo.bar/...";
>         sha256 = "cef3591e436f528852db0e8c145d3842f920e0c89bcfb219c466797cb7b18879";
>       }
>     else throw "foo does not support platform ${stdenv.hostPlatform.system}";
> --8<---------------cut here---------------end--------------->8---
>
> Is this a Guix bug?

Well, it's not really a bug, but quite suprising at first. If you look
at the definition of <package> in (guix packages), you'll see that some
fields are (thunked). %current-system and %current-target-system will
only return valid results in (thunked) fields.

As "source" is not thunked, you can make it thunked, but it can hurt
performances. You can also make multiple packages for each architecture,
and use them as inputs conditionned by %current-system and
%current-target-system.

Mathieu

Re: How can I set architecture/system-specific origin sources?

[Pierre Neidhardt]

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Hi Mathieu!

Thanks for the details, this makes much more sense now! :)
So how can I thunk the source field then?

-- 
Pierre Neidhardt
https://ambrevar.xyz/

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Re: How can I set architecture/system-specific origin sources?

[Efraim Flashner]

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On Tue, Dec 31, 2019 at 03:00:50PM +0100, Pierre Neidhardt wrote:
> Hi Mathieu!
> 
> Thanks for the details, this makes much more sense now! :)
> So how can I thunk the source field then?
> 

There's computed-origin-method that's floating around a couple of
package modules or you can look at something like ghc which has a
different blessed binary per-architecture.

-- 
Efraim Flashner   <efraim@flashner.co.il>   אפרים פלשנר
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Confidentiality cannot be guaranteed on emails sent or received unencrypted

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Re: How can I set architecture/system-specific origin sources?

[Pierre Neidhardt]

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Thank you Efraim, this is exactly what I needed.  I've applied the trick
used by GHC (simpler in my opinion), it works perfectly.

As Mathieu pointed out, this is a bit unsettling at first.  Is this
(thunked) behaviour documented anywhere?  If not, shall we documented
it?  Where?

Cheers!

-- 
Pierre Neidhardt
https://ambrevar.xyz/

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Re: How can I set architecture/system-specific origin sources?

[Ludovic Courtès]

Hi,

Mathieu Othacehe <m.othacehe@gmail.com> skribis:

> Well, it's not really a bug, but quite suprising at first. If you look
> at the definition of <package> in (guix packages), you'll see that some
> fields are (thunked). %current-system and %current-target-system will
> only return valid results in (thunked) fields.
>
> As "source" is not thunked, you can make it thunked, but it can hurt
> performances. You can also make multiple packages for each architecture,
> and use them as inputs conditionned by %current-system and
> %current-target-system.

I should say that it’s because source is architecture-independent.  :-)

The package definition for ‘mit-scheme’, for example, passes the
bootstrap binaries, which are architecture-dependent, as inputs.

Ludo’.

Re: How can I set architecture/system-specific origin sources?

[Pierre Neidhardt]

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Ludovic Courtès <ludo@gnu.org> writes:

> I should say that it’s because source is architecture-independent.  :-)
>
> The package definition for ‘mit-scheme’, for example, passes the
> bootstrap binaries, which are architecture-dependent, as inputs.

Yes, that makes sense! :)

-- 
Pierre Neidhardt
https://ambrevar.xyz/

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