Re: Fwd: Bug#1050663: dar option --on-fly-isolate creates catalogue with broken slice_layout

On Wed, Aug 30 2023, Denis Corbin wrote:

>> Summary
>> =======
>> g++ 10 works fine with optimization.
>> g++ 11 or newer work only without optimization.
>> Hope this helps.
>
> Thanks for confirming this is a gcc issue. I don't know what should be the next
> step, if someone fills a bug report to gcc Debian maintainer?

Well, to be sure, we have a couple of possibilities:

1) This is a gcc bug,

or 2) There is something in dar (or, for that matter, bzip2 or some
other library) that is relying on some sort of C/C++ undefined behavior
(UB) that the optimizer is taking in a different direction.  Other
possibilities could include race conditions, etc.

I have seen a lot of things fall into bucket #2, but that doesn't mean
we conclusively rule out bucket #1 either.

I wonder if the backtrace is helpful at all, or if your ability to
reproduce it might be able to help narrow down which situation is the
case?  Before taking a bug report to gcc, I am sure they will want to
know we have ruled out #2, and hopefully have a concise case for
reproduction of the issue.

- John