https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107622
--- Comment #4 from Wilhelm M <klaus.doldinger64 at googlemail dot com> ---
In the following class the static data member is accessible via explicit
template instantiation from the outside. So the compiler cannot reason that the
value is in [0,2]. But this does not hold for the function g(): here mState2 is
definitely not accessible from outside. But here the std::unreachable() is
still neccessary. here the optimization is missing.
struct FSM {
enum class State : uint8_t {A, B, C};
static void f() {
switch(mState) {
case State::A:
o = 10;
break;
case State::B:
o = 11;
break;
case State::C:
o = 12;
break;
default:
// std::unreachable();
break;
}
}
static void g() {
static State mState2{State::A}; // not accessible from outside
switch(mState2) {
case State::A:
o = 10;
break;
case State::B:
o = 11;
break;
case State::C:
o = 12;
break;
default:
// std::unreachable();
break;
}
}
private:
inline static State mState{State::A}; // still modifyable via explicit
template instantiation
};
