GNU bug report logs - #24695
impossible to use weak hash tables inside gc hooks

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Stefan Israelsson Tampe <stefan.itampe <at> gmail.com>
To: bug-guile <at> gnu.org
Subject: impossible to use weak hash tables inside gc hooks
Date: Fri, 14 Oct 2016 20:54:56 +0200

[Message part 1 (text/plain, inline)]

For more advanced gc concepts it would be nice to keep a set a objects in a
weak key hash table and at gc loop over the alive ones the various gc hooks
that is available for the c coder.

The problem is that current guile data structure would hang on folding
because inside the guile weak folder gc is assumed to be prevented. Not
sure what to do here. This might be a feature request or a bug report
dependning on how you view it.

Regards

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Message #8 received at 24695 <at> debbugs.gnu.org (full text, mbox):

From: Andy Wingo <wingo <at> pobox.com>
To: Stefan Israelsson Tampe <stefan.itampe <at> gmail.com>
Cc: 24695 <at> debbugs.gnu.org
Subject: Re: bug#24695: impossible to use weak hash tables inside gc hooks
Date: Wed, 01 Mar 2017 13:49:53 +0100

On Fri 14 Oct 2016 20:54, Stefan Israelsson Tampe <stefan.itampe <at> gmail.com> writes:

> For more advanced gc concepts it would be nice to keep a set a objects
> in a weak key hash table and at gc loop over the alive ones the
> various gc hooks that is available for the c
> coder.
>
> The problem is that current guile data structure would hang on folding
> because inside the guile weak folder gc is assumed to be
> prevented. Not sure what to do here. This might be a
> feature request or a bug report dependning on how you view it.

What does "at GC" mean?  After GC?  Before GC is a pretty tense
situation as you can't allocate memory.  Also I suspect you could do
this with a weak vector (or other structure with disappearing links) and
a before_gc C hook.  WDYT?

I am tempted to just close this one as out of scope for Guile :)

Andy

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