Hi David,
this looks very similar to a problem that we are trying to
debug for a while, and that I recently submitted as a bug report:
https://gitlab.com/freepascal.org/fpc/source/-/issues/41439
The problem has been nicely simplified by alligator in
https://gitlab.com/freepascal.org/fpc/source/-/issues/41444
There is some problem related to PPU writing...
I hope to be able using this simplified example t understand better this
issue,
but I am currently still busy with the previous issue, also raised by alligator:
https://gitlab.com/freepascal.org/fpc/source/-/issues/41443
for which I hope to have found a fix.
Pierre
Le 17/10/2025 à 19:35, David Jenkins via fpc-devel a écrit :
What is the best way to check if a virtual function in a base class has
been overridden by a class that inherits the base class?
In LCL TPrinter.pas the following check is used:
procedure TPrinter.NewPage;
begin
Inc(fPageNumber);
if TMethod(@Self.DoNewPage).Code = Pointer(@TPrinter.DoNewPage) then
begin
..
end
..
end
We have run across an optimization problem with the TCocoaPrinter class
and that TPrinter code.
TCocoaPrinter = class(TPrinter)
with no override of DeNewPage
Sometime with Level2 or Level3 optimization,
TMethod(@Self.DoNewPage).Code is changed to point to systemh.inc
EmptyMethod instead of TPrinter.DoNewPage and the check no longer works
appropriately.
Is there another way to make that check that is not affected by
optimization?
I will eventually throw a fix to the LCL folks but we use a similar
formulation in our code and are concerned that it might also be affected
by optimization at some point. Right now it is not because none of the
base functions are completely empty, but they are trivial functions that
match each other and could be optimized in the future by coalescing them.
Thanks
David Jenkins
Scooter Software.
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