Hi Florin,

I believe there are 2 primitives for 2 different use-cases:
primitiveArrayBecomeOneWayNoCopyHash 248
- primitiveArrayBecomeOneWayCopyHash 249

The difference between both is which hash is preserved. I think for your use-case you should use the other primitive.

On Mon, Jan 24, 2022 at 5:04 AM Florin Mateoc <florin.mateoc@gmail.com> wrote:
 
Hi,

I am a bit surprised by the #becomeForward: behavior in Squeak. This is a one way become, where the target of the operation is the receiver, which sheds its identity/existence. Nobody points to it after the primitive execution, so it is discarded. This understanding also conforms to the method comment.
As such, I remember a pattern of usage in VisualAge Smalltalk, where one way become was used as a cheap cleanup/avoidance of memory leaks, by doing oneWayBecome: nil. It's not that I advocate for it, but this works in Squeak too, except in Squeak #becomeForward: does an additional thing to the pointers redirection, it changes the identityHash of the argument, the non (obvious) target. While I understand this may be useful in certain situations, I think it is a dangerous conflation of activities. A new primitive that sets the identity hash could be used (VA has it) explicitly instead when such behavior is desired.
As it is, if I do "Object new becomeForward: nil", it succeeds and it changes nil's identityHash.

Sorry if this has been debated before,

Cheers,
Florin


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Clément Béra
https://clementbera.github.io/