>From the thread on the dar support mailing list:
https://sourceforge.net/p/dar/mailman/message/37890758/
On Sat, Sep 02 2023, Thomas wrote:
> On Wed, Aug 30, 2023 at 03:24:12PM -0500, John Goerzen wrote:
>> 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.
>
> To find the root cause why the optimizer does something harmfull in our
> case is way over my head.
>
> But...
> I have found a workaround for dar. The appended patch works for me with
> dar v2.7.11 and g++ v13.2.0, v12.3.0 and v11.4.0. Means, files generated
> with OnFlyIsolation are readable again with default optimizations
> activated.
> It seems the optimizer does not like the used ternary operator.
>
> I tested the patch with g++ v10.4.0 and 9.3.0, too without problems but
> these versions are working with or without this patch anyway.
>
> Hope this helps.
>
> Tom
>
> [2. text/x-diff; slice_layout.cpp-remove_ternary_operator.patch]...
diff -rupN DAR_a/src/libdar/slice_layout.cpp DAR_b/src/libdar/slice_layout.cpp
--- DAR_a/src/libdar/slice_layout.cpp 2023-09-02 09:08:49.657051708 +0200
+++ DAR_b/src/libdar/slice_layout.cpp 2023-09-02 09:11:39.240669572 +0200
@@ -54,7 +54,11 @@ namespace libdar
void slice_layout::write(generic_file & f) const
{
- char tmp = older_sar_than_v8 ? OLDER_THAN_V8 : V8;
+ char tmp = V8;
+ if(older_sar_than_v8)
+ {
+ tmp = OLDER_THAN_V8;
+ }
first_size.dump(f);
other_size.dump(f);
first_slice_header.dump(f);
