Hi,

TFile.ReadAllBytes (in System.IOUtils) seems to alwasy return TBytes filled with zero's.

It's implemented as
(See: https://gitlab.com/freepascal.org/fpc/source/-/blob/fixes_3_2/packages/vcl-compat/src/system.ioutils.pp?ref_type=heads)

class function TFile.ReadAllBytes(const aPath: string): TBytes;
begin
  Result:=[];
  With OpenRead(aPath) do
    try
       SetLength(Result,Size);
       ReadBuffer(Result,0);  << second param should be "Size"
    finally
      Free;
    end;
end;

This is fixed in main.
https://gitlab.com/freepascal.org/fpc/source/-/commit/9eb77599e18c89bbe426bf272233540206893271

I think it's not been merged to fixes branch,

Shoud I file a bugreport about it?

ReadBuffer(Result,0); << second param should be "Size"

Not sure, but this (ReadBuffer(Result,Size);) seems to crash then (memory corruption)?

This:

     ReadBuffer(Result[0],Size);

seems to work OK though.
(Should be save even if Size is zero, since ReadBuffer does nothing then)

Actually, the ReadBuffer(Result,SIze) is broken due to ReadBuffer(TBytes,Count) being broken.
Compiler does not select the correct overload, but the fix for that has not been backported.
The solution would be to add offset zero.

Michael.

Should I open a ticket?

Yes, please.
Note that AFAIK the compiler fix will not be backported, we just need to fix the call to ReadBuffer.

Michael.

Done: https://gitlab.com/freepascal.org/fpc/source/-/issues/41479