[Bug c++/86465] C++17 <optional> triggers: ‘<anonymous>’ may be used uninitialized in this function

[proski at gnu dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86465

--- Comment #2 from Pavel Roskin <proski at gnu dot org> ---
Created attachment 44761
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44761&action=edit
Heavily simplified example, g++-5 compatible

I'm attaching a dumbed down version of the previous example, which compiles
with gcc 5.5.0 and newer.

gcc 5.5.0 and gcc 6.4.0 don't produce any warning. gcc 7.3.0, 8.1.0 and the
today's gcc from the git master branch all produce the warning.

That suggests that the issue is indeed related to the one described in bug
#86485.

The implementation of optional in libstdc++ 7 doesn't trigger a warning, it's
the changes in libstdc++ 8 that started triggering it. However, gcc 7 appears
to have the same compiler issue.