[fpc-devel] Newbie question: how does the compiler know the class type of an object ( the Is operator)

Dennis Poon dennis at avidsoft.com.hk
Fri Aug 22 19:53:53 CEST 2014

Howard Page-Clark wrote:
> program Project1;
> uses classes;
> begin
>   WriteLn('InstanceSize of TObject=',TObject.InstanceSize);
>   ReadLn;
> end.

I tried and it says the instancesize is 4 (on win 32 bit).
My question actually was how does the "as" and "is" get the class type 
of an object.
So, does that imply the 4 byte is used to store a pointer to the class 
type and Virtual Method table?


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