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Re: srfi-18 and the vm

From: Andy Wingo
Subject: Re: srfi-18 and the vm
Date: Fri, 22 May 2009 18:20:22 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/23.0.92 (gnu/linux)

On Fri 22 May 2009 17:10, address@hidden (Ludovic Courtès) writes:

> ¡Hola!
> Andy Wingo <address@hidden> writes:
>> I'm catching up with mail. On my syncase-in-boot-9 branch, I enabled
>> compilation of srfi-18 and fixed a bug in it regarding multiple-value
>> returns. Now I just ran the srfi-18 test like 100 times in a row and it
>> didn't show any strange errors. Yaaaay!
> What kind of "strange errors" would it lead to before?

Random ones based on races, as code was lazily memoized from multiple
threads at once.

> When SRFI-18 wasn't compiled, I would expect multiple value returns
> would translate in a `value.c' struct that would then be passed along as
> a single value.

Indeed. The VM truncates multiple values, but here we were doing a (let
((x (values))) something x), which returned 0 values to a continuation
needing a value, raising a valid error. Fixed that in the original
source code.

In addition, we were sometimes getting 0 values in a for-effect context,
which the GHIL->GLIL compiler didn't support. Like this:

  (begin (call/cc (lambda (k) (k))) 10)

I've fixed this in the tree-il->glil compiler.



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