On Tue, Jul 16, 2024 at 10:50 AM Jason Merrill <ja...@redhat.com> wrote: > > On 7/16/24 10:31 AM, Eric Gallager wrote: > > On Mon, Jul 15, 2024 at 10:37 PM Patrick Palka <ppa...@redhat.com> wrote: > >> > >> Bootstrapped andrregtested on x86_64-pc-linux-gnu, does this look > >> OK for trunk? > >> > >> -- >8 -- > >> > >> Here we're neglecting to emit a -Wunused-value for eligible ! operator > >> expressions, and in turn for != operator expressions that are rewritten > >> as !(x == y), only because we don't call warn_if_unused_value on > >> TRUTH_NOT_EXPR since its class is tcc_expression. This patch makes us > >> consider warning for TRUTH_NOT_EXPR as well. > >> > > > > Eh, I think I've seen the ! operator recommended as a way to silence > > -Wunused-value previously in cases where an actual fix isn't > > practical; some people might be mad about this... > > That sounds like weird advice to me; I'd expect the result of ! to be > used, and we already warn if the operand is something other than bool. > Clang also warns for the bool case. >
It's possible that I was getting -Wunused-value confused with -Wunused-result when I was remembering the advice I'd heard: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66425 > Seems like ADDR_EXPR is another tcc_expression that could use handling > here, e.g. > > struct A { int i; }; > A& f(); > int main() { > &f().i; // missed warning > } > > Jason >
