Re: gexps

[Ludovic Courtès]

David Craven <address@hidden> skribis:

>> 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?

That would make it a different derivation.

>> 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?

For downloads (origins).  The manual mentions it briefly.

Ludo’.