Re: Cross-building GuixSD (and maybe using pre-built toolchains)

[ludo@gnu.org (Ludovic Courtès)]

Paul Boddie <paul@boddie.org.uk> skribis:

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

Yes.

> From previous questions, it appears that any compiler must have been built 
> specifically for Guix to use (and cannot be those those pre-built toolchains 
> provided by, say, Debian), so would these cross-compilers be the ones normally 
> used to generate the "bootstrap binaries" (that would normally be used to then 
> 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 system", 
> then generate special cross-compilers for my target architecture (that are 
> 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
“bootstrapped” for that platform.  There’s nothing special to be done.

I’m trying to find ways to rephrase this, but I can’t think of other
ways than what the “Bootstrapping” and “Porting” sections of the manuals
say.  :-)

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

No.

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