>>> patrick keshishian 31-Aug-17 20:40 >>>
>
> On Thu, Aug 31, 2017 at 12:13:19PM -0700, William Ahern wrote:
> > On Thu, Aug 31, 2017 at 02:08:07PM +0200, Otto Moerbeek wrote:
> > > Hi,
> > >
> > > /usr/src/usr.sbin/sasyncd/carp.c:157:12: warning: comparison of
> > > unsigned enum expression < 0 is always false [-Wtautological-compare]
> > > if (state < 0 || state > FAIL)
> > > ~~~~~ ^ ~
> > > /usr/src/usr.sbin/sasyncd/carp.c:166:20: warning: comparison of
> > > unsigned enum expression < 0 is always false [-Wtautological-compare]
> > > if (current_state < 0 || current_state > FAIL) {
> > > ~~~~~~~~~~~~~ ^ ~
>
> if (!(state >= INIT && state <= FAIL))
> state = FAIL;
> and
> if (!(current_sate >= INIT && current_state <= FAIL) {
> log_err ...
> ...
> return;
> }
>
> More better?
If the compiler is using an unsigned underlying type for the enum, the
comparison
state >= INIT
will give something along the lines of "expression >= 0 is always true"
I don't know what the best solution is here; I would defer to Otto!
Tom
> --patrick
>
> > >
> > > this warning is a tiny bit interesting. A compiler is free to choose
> > > the type of the enum, as long as it can represent all given values.
> > > So another compiler might choose not to make it unsigned. So I came up
> > > with this fix that is not depending on the signedness of the type. But
> > > most of the time avoiding enum is better, I suppose.
> >
> > It's free to choose the integer type of the enum, but enumeration members
> > (i.e. the constant identifiers) have int type.
> >
> > The identifiers in an enumerator list are declared as constants that have
> > type int and may appear wherever such are permitted.
> >
> > C11 (N1570) 6.7.2.2p3.
> >
> > Furthermore, the defining expression of the constant must be representable
> > as an int. 6.7.2.2p2.
> >
> > I've always vascillated about which operand to cast, and to which type, when
> > silencing compilers' annoying warnings. But now that I've read the section
> > more closely I think I'll just cast the operand with enum type to int, all
> > things being equal.
> >
