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[Caml-list] Modifying heap from custom finalizers?
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Date: -- (:)
From: Nuutti Kotivuori <naked+caml@n...>
Subject: Re: [Caml-list] Modifying heap from custom finalizers?
Damien Doligez wrote:

[...]

>> And if zeroing the value at sweep phase makes the values pointed by
>> it garbage collected only at the next collection, is there any I
>> can speed up the process?
>
> What makes you think there is no other pointer to these values ?
> And to the things pointed by these values ?

These values are values in the global data array - which is allocated
separately. The only things (well, debugger and toplevel do some
hacks) accessing these are SETGLOBAL and GETGLOBAL instructions in the
actual code blocks. The only thing that can create new GETGLOBAL
instructions for the slots in future code is the ident table in
Symtable. So if no existing code block, nor the ident table,
references the global, it can be zeroed out - since nothing can read
it's value.

The globals for modules contain a pointer to an array which holds the
closures for the functions defined by the module. This array can then
be reclaimed by the garbage collector - and if all the closures for a
certain module stop existing, the code block in turn is garbage
collected.

This should all be briefly described in the mail I sent earlier about
the second phase of the approach.

>> I could find no documentation what you can and what you can't do in
>> the finalizers for custom blocks.
>
> You should enter this in the bug tracking system as a feature wish.

Indeed. I shall do that.

I managed to catch a rather nasty flu just before christmas, and some
personal issues came up recently - so I shall make no promises on the
time schedule with which I'm implementing all this.

-- Naked

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