Re: 02/04: monads, gexp: Prevent redefinition of syntax parameters.

[Ricardo Wurmus]

address@hidden writes:

> civodul pushed a commit to branch master
> in repository guix.
>
> commit 8245bb74fc7bdcdc2f9d458057cefc9cd982e489
> Author: Ludovic Courtès <address@hidden>
> Date:   Wed Feb 6 21:58:43 2019 +0100
>
>     monads, gexp: Prevent redefinition of syntax parameters.
>
>     Fixes <https://bugs.gnu.org/27476>.
>
>     This fixes multi-threaded compilation of this code where syntax
>     parameters could end up being redefined and where a race condition could
>     lead a thread to see the "wrong" value of the syntax parameter.
>
>     * guix/monads.scm (define-syntax-parameter-once): New macro.
>     (>>=, return): Use it.
>     * guix/gexp.scm (define-syntax-parameter-once): New macro.
>     (current-imported-modules, current-imported-extensions): Use it.

Oh yeah!

Thank you so much for squashing this bug (and all of those it was merged
with)!

--
Ricardo