Are const parameters dangerous?
Marco Cantu's recent blog post The Case of Delphi Const String Parameters opened a can of worms. A very, very old can... The presented behavior is not something new, and it is certainly not a compiler bug. It is just the way reference counting works. A pure ARC problem—one instance of something is destroyed when the other one is created and assigned, because the const parameter did not trigger the reference counting mechanism—this is why const is used for speed optimization in the first place. The same thing that happens with strings happens with reference-counted objects, but it is easier to see what happens with objects in the same kind of code. You will need a form with a memo and a button to test the following code: type IFoo = interface function GetCount: Integer; function GetNumber: Integer; end; TFoo = class(TInterfacedObject, IFoo) private FNumber: Integer; public constructor Create(ANumber: Integer); destructor Destroy; override; f...