[Bug sanitizer/80963] UBSAN false positive with visibility=hidden

["jengelh at inai dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80963

--- Comment #3 from Jan Engelhardt <jengelh at inai dot de> ---
The question is more like - can it be made to work even if (In reply to Andrew
Pinski from comment #1)
> 
> That is Archive in the shared library and in the main executable are
> considered two different classes.

If that is how UBSAN thinks, then it should say so by uniquely identifying each
"distinct" class, e.g.:

main.cpp:3:16: runtime error: member call on address 0x000000dcfc20 which does
not point to an object of type 'Archive.1234'
0x000000dcfc20: note: object is of type 'ArchiveImpl' [Archive.5678]


Secondly, I think that considering them two different classes is only valid in
C, but not under the ODR rules of C++.


Finally, nonwithstanding all the above, it would be nice to have some -f option
to always make UBSAN treat same-name classes as the same thing irrespective of
visibility. Reason: to make UBSAN "work" with this example meant having to edit
configure.ac+Makefile.am (of the particular real-world program) to not use
"-Wl,--version-script=foo.sym -fvisiblity=hidden" at all, and that was a little
more work than just slapping another -f into CXXFLAGS.