[Bug sanitizer/70147] [6 Regression] testcase from hana testsuite gets miscompiled with -fsanitize=undefined

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70147

--- Comment #18 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Bernd Edlinger from comment #17)
> > As the compromise I meant this instead (incremental patch).
> > Though, in that case the -flifetime-dse=2 clobbers are also wrong in the
> > subobject ctors, because they should not overlap the vtable pointers of the
> > virtual bases if we rely on them from the caller, otherwise when those are
> > inlined could be DSEd, even when we actually rely on them.
> 
> However that sounds more or less like a P1-BUG !
> 
> If the virtual base has already initialized the base object,
> maybe it has put it into a linked list, or so all that code will
> silently be removed again, and the list would be left in an
> inconsistent state.
> 
> Do you see a way, how to conditionalize the clobber on the in_charge?

Very easily, by wrapping the CLOBBER into an conditional testing
current_in_charge_parm if that is non-NULL or something similar.
Or by using a different CLOBBER for the subobject ctors (e.g. one that does
clobber just the data fields and not the vtable pointers in there, whatever).