RE: class gc (fwd)

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From: Parmelan, Edouard (EP510777@exchange.FRANCE.NCR.com)
Date: Thu Dec 17 1998 - 03:54:00 EST

Godmar,

> I tied all the loose ends together and implemented class garbage
> collection.
Good news.

> A particular problem are
> the 512 byte arrays in the callMethod methods. We might want
> to consider alloca allocation here.
Don't use alloca, it use the stack pointer to know
if it can free a previous allocated block. Don't
forget that Threads have different stacks: alloca()
should be broken for this situation:

Thread-A, Stack 0x1000 to 0x3FFF
Thread-B, Stack 0x4000 to 0x7FFF

Thread-A call alloca() with sp == 0x2000.

jthread switch to Thead-B and call alloca() with
sp == 0x4000, so memory allocated by Thread-A is
freed.

jthread switch back to Thread-A and use the freed
alloca() memory...

Not so good :(

Edouard.

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