Rules governing stack purging
dave at looktowindward.com
Tue Oct 31 14:27:53 EST 2006
If all that is required is to read a property from a stack, couldn't
there be some way of loading is "read-only"? e.g. load stack (read
put the cp of stack <long_name> into x
Just a thought.
On 31 Oct 2006, at 17:48, Dave Cragg wrote:
> On 30 Oct 2006, at 22:43, Richard Gaskin wrote:
>> Consider your subsequent post:
>>> I just remembered something (third time this week, must be the
>>> new pills). Aren't "unused" stacks purged from memory by the
>>> engine when it needs to reclaim memory? I think I'm referring to
>>> stacks without the destryStack set, but which have been closed.
>>> I seem to recall reading this somewhere, either in the old
>>> Metacard docs, or the MC mailing list from long ago. If it's
>>> true, I wonder if it applies to "unopened" stacks in memory too.
>> This implies the engine introduces a "sometimes" rule ("sometime
>> it does one thing, sometimes something else"), which is generally
>> bad news.
> If this purging actually happens, which I don't know for sure, I
> don't think it's such a bad thing. It would only affect stacks that
> have been specifically closed, or that have been put in memory as a
> result of a direct reference to the stack file. Any subsequent
> reference just requires the engine to load the stack again. Nothing
> I'm still don't see how your suggestion will produce something more
> "consistent" than the current behavior. Going back to my set and
> save example:
> set the cProp of stack "C:/myStack.rev" to tData
> save stack "C:/myStack.rev"
> Under your proposal, if the stack's destroyStack property is true,
> nothing will have changed in the stack. I don't see how this can be
> considered consistent with anything.
> You say you were caught by this, but I'm still not clear what
> problems it causes. The only situation I can think of is if a
> second app changed the stack on disk while the first app had it in
> memory, and the first app expected subsequent references to load
> the stack from disk again. If this is the case, I don't think it is
> a normal situation, and we know we have to take care when two apps
> are mucking around with files. But under your suggestion, if I want
> to use a stack as a data file, I have to be sure to set it's
> destroyStack to false. I suspect more people will be caught by that.
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