[squeak-dev] RE: [Pharo-project] [FFI] ExternalStructure ownership (or not) of memory

Schwab,Wilhelm K bschwab at anest.ufl.edu
Sat Apr 3 03:37:42 UTC 2010


So ExternalStructure>>free is not invoked by default?  Sady to say, I never even considered that possibility.


-----Original Message-----
From: pharo-project-bounces at lists.gforge.inria.fr [mailto:pharo-project-bounces at lists.gforge.inria.fr] On Behalf Of Andreas Raab
Sent: Friday, April 02, 2010 8:24 PM
To: The general-purpose Squeak developers list
Cc: Pharo-project at lists.gforge.inria.fr
Subject: Re: [Pharo-project] [FFI] ExternalStructure ownership (or not) of memory

I would suggest that you only register a finalizer for objects where you
*do* have responsibility to reclaim them. There are no implicit finalizers registered for any subclasses of ExternalObject by default - the only thing that happens is that all handles are cleared when the image is restarted.

   - Andreas

On 4/2/2010 5:17 PM, Schwab,Wilhelm K wrote:
> Hello all,
> Suppose I have a pointer to a structure and I do or do not have the responsibility of reclaiming the memory when a corresponding ExternalStructure sub-instance is finalized.  How do I distinguish the two cases?  One idea I had is to explicitly set the handle to nil if I do not own the memory, but (please correct me if I'm wrong), I can't do that while I'm still using the instance because it will presumably use the handle in accessing the fields, right?
> Looking at implementors of #isExternalAddress, maybe the idea is to use a byte array to make a copy of memory and an address to refer to it.
> What should I be asking? :)
> Bill

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