Sorry I'm jumping after being off the ball for a bit but I would point the finger at
MemorySleuth in this
instance.
> pMyObject = ^tMyObject;
> tMyObject = class
> ...
> end;
>
> I created objects and saved them in a StringGrid;
>
> var myObject : pMyObject;
> begin
> new(myObject);
> MyObject^ := tMyObject.create;
> MyObject^.Methodcalls
> MyStringGrid.Objects[Col,Row] := MyObject;
By requesting memory using New with the identifier 'myObject' then making the
assignment to an untyped pointer inside the StringGrid the memory tracker is likely
failing to follow the assignment of memory to a valid destination - most of the syntax
tracking methods require some fairly tight type binding to let them cross procedure
boundaries...
> then I disposed of the object in the end;
> tMyObject(MyStringGrid.Objects[Col,Row]).free;
> dispose(MyStringGrid.Objects[Col,Row])
It's likely that MemorySleuth hasn't associated the Dispose of the Stringgrid
pointer with the New used to allocate the memory... The Dispose would produce an
error if Disposing memory illegally so it's safe to say the memory there has been
correctly
handled.
> TurboSleuth reported an undisposed memory from the new line.
> When I recoded to use a tMyObject instead of a pMyObject (and dropped the
> associated new and dispose calls) the leak disappeared. I am more clever now,
> though no wiser. Any insights or explanations?
Part of your confusion will be Delphis assistance in dereferencing pointers for you...
> var myObject : pMyObject;
This creates [myObject] -> nil
> new(myObject);
this creates [myobject] -> [a TMyObject handle] -> nil
> MyObject^ := tMyObject.create;
this creates [myobject] -> [a TMyObject handle] -> [An actual object]
> MyStringGrid.Objects[Col,Row] := MyObject;
Syntactically this should be doing [MyStringGrid.Objects[Col,Row] -> [a TMyObject
Handle]
but then shouldn't
> tMyObject(MyStringGrid.Objects[Col,Row]).free;
produce an error since you've not dereferenced the pointer for access to Free. Delphi
is doing
this for you.
if you translate the above to remove the StringGrid
var
MyObject :pMyObject;
begin
new(MyObject);
MyObject^ := TMyObject.Create;
MyObject^.MethodCalls;
MyObject.Free; // Notice that there's no ^
dispose(MyObject);
end;
This helpful autodereference makes much of Delphis syntax easily readable but like all
things there's a downside too...
--
Aaron Scott-Boddendijk
Jump Productions
(07) 838-3371 Voice
(07) 838-3372 Fax
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