计算VMT的长度

function GetVirtualMethodCount(AClass: TClass): Integer;
begin
  Result := (PInteger(Integer(AClass) + vmtClassName)^ - 
    (Integer(AClass) + vmtParent) - SizeOf(Pointer)) div SizeOf(Pointer);
end;

http://stackoverflow.com/questions/760513/where-can-i-find-information-on-the-structure-of-the-delphi-vmt