https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67795
--- Comment #10 from frankhb1989 at gmail dot com --- (In reply to Marc Glisse from comment #7) > Hmm, with the static_cast, the front-end produces: > > <<cleanup_point return <retval> = (struct string_view &) (struct string_view > *) NON_LVALUE_EXPR <(struct string_view &) &(n != 0 ? > std::experimental::fundamentals_v1::basic_string_view<char>::remove_prefix > ((struct string_view *) s, n);, *s; : *s)>>>; > > while without it, I get: > > <<cleanup_point return <retval> = (struct string_view &) (n != 0 ? > std::experimental::fundamentals_v1::basic_string_view<char>::remove_prefix > ((struct string_view *) s, n);, (struct string_view *) s; : (struct > string_view *) s)>>; > > I also find it fishy. > > (note that you need -O2 or more for the warning) Thank you for the suggestion. I find these diagnostics exist with -O2 or -O3. Then the output is empty ... clang++ -Weverything with -O2/-O3 still behaves as I expect. (Only [-Wmissing-prototypes].)