Re: gexps

[David Craven]

> If we force use of the host system type (say x86_64-linux), independent
> of (%current-system) (say mips64el-linux), we approach what you want.
> However, that would give us different derivations depending on the host
> system type.  That is, ‘guix system build -s mips64el-linux -d’ on
> x86_64 would return something different from ‘guix system build -d’ on
> mips64.  This is not desirable.

Maybe an option would be if %current-system != host-system run guile
using qemu-arm?

> An option would to have ‘gexp->file’ produce a fixed-output derivation
> (it can compute the hash of the output on the host side).
>
> Or maybe we need another mechanism similar to fixed-output derivations
> to define equivalence classes of derivations.

I'll have to read up on fixed-output derivations. Can you give me an
example of where they are used currently?