bug#20272: Support reproducible builds

[Ludovic Courtès]

Hi!

Andy Wingo <address@hidden> skribis:

> On Thu 22 Dec 2016 00:53, address@hidden (Ludovic Courtès) writes:
>
>> +(define (module-generate-unique-id! m)
>> +  (let ((i (module-next-unique-id m)))
>> +    (set-module-next-unique-id! m (+ i 1))
>> +    i))
>
> This introduces a race condition when expanding from multiple threads at
> once.  Any plan here?

Good point!  We could grab a per-module mutex for that, though that’s
again a fat mutex.

Thoughts?

Ludo’.