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Fyodor:
> BlackBox, F1, What's New:
>
> . Procedure types can pose considerable implementation difficulties
> concerning the safe unloading of code. ..
>
> That is, a procedure variable may contain a dynamically created reference
> to a procedure in the module being unloaded, even if the latter is not
> related by import with the variable's module.
Is the same not true with objects as well?
MODULE TestLower;
TYPE hookType* = POINTER TO EXTENSIBLE RECORD END;
VAR hook* : hookType;
END TestLower.
MODULE TestUpper;
IMPORT TestLower;
TYPE myHook = POINTER TO RECORD (TestLower.hookType) END;
VAR hook: myHook;
BEGIN
NEW (hook);
TestLower.hook := hook;
END TestUpper.
As you see, I have installed a "hook object" in a module Lower.
I can now unload module Upper because it does not have clients.
What happens if TestUpper.hook uses resources from module Upper?
Naturally, one should take care of this in the CLOSE section of module
TestUpper, but what if there is no CLOSE section? Can you guarantee there
are no safety problems if one unloads such a sloppy module, even though I
have not used procedure variables?
What I am driving at is that possibly procedure variables are no more
dangerous than the O-O solution would have been, in the hands of a sloppy
programmer of course.
Comments?
W.
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Received on Thu Nov 18 2004 - 23:42:14 UTC