[mercury-users] GC / Guile

Julien Fischer juliensf at csse.unimelb.edu.au
Sun Jun 12 16:42:46 AEST 2011

On Sun, 12 Jun 2011, Paul Bone wrote:

> On Fri, Jun 10, 2011 at 07:32:44PM +0200, Tomas By wrote:
>> Hi all,
>> After various upgrades, including to Guile 2.0.1, I am having new
>> problems with the Mercury - Guile combination.
>> | $ ./test
>> | 0xac44040 is not a GC visible pointer location
>> | GC_is_visible test failed
>> | Aborted
>> | $
>> As far as I can tell, the `test' binary uses the Mercury version of the
>> Boehm GC. All source files shown below.
>> Any help appreciated.
> It looks like Guile also uses the BoehmGC (although I don't know).  We haven't
> tried combining different versions of BoehmGC in the same process like this.
> I expect that this is the cause of your problems.

The issue here is: will Guile work with the modified version of Boehm GC
that is supplied with Mercury**?  I don't think Mercury specific
modifications should cause trouble per se -- they are additions to the
existing API rather than modifications of it.

(** I'm pretty sure it must be Mercury's version of the GC being linked
in since if it was the unmodified one then I don't think linking would

Based on a quick browse of the Guile mailing list I note that the above
error has occurred before with Guile.  The things I suggest checking
here are:

(1) Are the compile time settings used by Mercury for the Boehm GC
suitable for Guile?

(2) Are the runtime settings used by Mercury for the Boehm GC suitable
for Guile?

(3) Is there some conflict between Mercury and Guile when it comes
to setting runtime parameters in the Boehm GC?

>   + Mercury's version of BoehmGC is slightly modified, so replacing it with
>     guile's version of BoehmGC may not be easy.

As I mentioned above, I think this unlikely.

>   + Mercury and Guile may also use different compilation options for BoehmGC.
>     However this is just my speculation.

This should be the starting point for any investigation IMO.

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