[Bug c++/81668] LTO ODR warnings are not helpful

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81668

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |msebor at gcc dot gnu.org

--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
(In reply to sgunderson from comment #2)

> file; how would I know which one to look
> through to find the two differing definitions?

One thing to try might be to add static_assert() statements to the header(s)
that define these allegedly incompatible symbols (such as struct st_vio) and
using C++ or GCC type traits verify that they and all their members are in fact
of the expected type, independent of any macros (like MYSQL_VIO).  If you can
then compile all the translation units successfully without LTO and still get
errors with LTO that would suggest a bug in GCC and might also give more
information to debug it.  Otherwise, errors without LTO should point to the
translation units that define the symbols in incompatible ways.