CPOs are specified as actual semiregular function objects that can be copied and constructed freely, so it seems a bit hostile to make them final/non-addressable? (It's debatable whether the type of a CPO is a type "specified in the C++ standard library" for which [derivation]/4 would apply.)
On Tue, Jun 15, 2021 at 1:34 PM Jonathan Wakely via Gcc-patches <gcc-patches@gcc.gnu.org> wrote: > > This restricts the API of the CPOs and other function objects so they > cannot be misused by deriving from them or taking their addresses. > > Signed-off-by: Jonathan Wakely <jwak...@redhat.com> > > libstdc++-v3/ChangeLog: > > * include/bits/ranges_base.h (ranges::begin, ranges::end) > (ranges::cbegin, ranges::cend, ranges::rbeing, ranges::rend) > (ranges::crbegin, ranges::crend, ranges::size, ranges::ssize) > (ranges::empty, ranges::data, ranges::cdata): Make types final. > Add deleted operator& overloads. > (ranges::advance, ranges::distance, ranges::next, ranges::prev): > Likewise. > * testsuite/std/ranges/headers/ranges/synopsis.cc: Replace > ill-formed & expressions with using-declarations. Add checks for > other function objects. > > Tested powerpc64le-linux. Committed to trunk. >
