[Bug c++/80635] std::optional and bogus -Wmaybe-uninitialized warning

[palves at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80635

--- Comment #2 from Pedro Alves <palves at redhat dot com> ---
Looks like a regression at some point:

There are no warnings with g++ 5.3.1, either reduced testcase, or with the
obvious change to use std::experimental::optional instead of std::optional.

Also no warnings with g++ 8.0.0 20170428 + -fno-lifetime-dse or
-flifetime-dse=1, perhaps unsurprisingly.

The original bug supposedly triggers with g++ 6.3.1 too, though I haven't
confirmed with the reduced testcase there.  (It's an s390 gdb buildbot, I don't
have access to it.)