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bug#27476: libguile/memoize.c is not thread safe, so syntax parameter ex
From: |
Ludovic Courtès |
Subject: |
bug#27476: libguile/memoize.c is not thread safe, so syntax parameter expansion is not thread-safe |
Date: |
Wed, 06 Feb 2019 23:09:23 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) |
Hi!
Andy Wingo <address@hidden> skribis:
> To be clear, here's the series of events. Firstly, know that defining a
> syntax parameter is like:
Thanks for the clear explanation!
>> So I came up with ‘define-syntax-parameter-once’, which is like
>> ‘define-once’ but for syntax parameters (note that we can’t use
>> ‘define-once’ in ‘define-syntax-parameter-once’ because it expands to a
>> reference to NAME, which doesn’t work for a macro):
>
> Your fix is good! But, it prevents redefinition of syntax parameters.
Yes. It’s acceptable in this case, so I’ve pushed it as a workaround as
commit 8245bb74fc7bdcdc2f9d458057cefc9cd982e489 in Guix.
> I would like to work on a solution that instead of using this
> double-lookup, simply adds an association between P and F* in the
> environment, instead of doing the double-lookup thing. Probably that
> will be 3.0-only.
>
> For 2.2, we can probably update the compiler to trampoline through some
> kind of "redefine-syntax" or something that will do (set-car! B F**)
> instead of (define P (stx-param B*)). I.e. redefinition keeps the
> unique key there.
Sounds good. Are you taking a look at this?
Perhaps that’d be a good excuse to release 2.2.5.
Thank you!
Ludo’.