[Lazarus] Weird object variables access [SOLVED] - Delphi mode bug!

Ondrej Pokorny lazarus at kluug.net
Wed Oct 25 10:49:31 CEST 2017

On 24.10.2017 23:18, Michael Van Canneyt via Lazarus wrote:
> On Tue, 24 Oct 2017, Giuliano Colla wrote:
>> Il 24/10/2017 14:10, Michael Van Canneyt via Lazarus ha scritto:
>>> A valid method can never be stored in a pointer, since the former is 
>>> actually 2 pointers (method/data) and the latter is just 1 pointer.
>>> That the assignment is valid is Delphi compatible: only the procedure
>>> address is copied. 
>> I can confirm it as an fpc bug.
> No, I'm sorry to say that IMO you did not. I looked at your code.
> It simply works by accident in Delphi, because you are calling a 
> method of the same object as the caller.

Yes, the code is wrong. But the reason is that myMethod is assigned in 
FormCreate. The later "@myMethod := pMethod;" assignment overwrites only 
half of the myMethod:TProc variable and so correct Self stays in the 
second half of myMethod.

Remove FormCreate and you get an AV.

Furthermore, "Format('0x%P',[@Myself])" doesn't make sense - it should 
be "Format('0x%P',[Pointer(Myself)])".

No bug at all - just wrong code.

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