On Fri, Jun 24, 2016 at 09:20:32AM +0000, David Laight wrote:
> From: Phil Sutter
> > Sent: 23 June 2016 18:34
> >
> > By directly comparing the value of both unsigned variables, casting to
> > signed becomes unnecessary.
> >
> > This also fixes for compiling with older versions of gcc (at least
> > <=3.4.6) which emit the following warning:
> >
> > | ifstat.c: In function `update_db':
> > | ifstat.c:542: warning: comparison is always false due to limited range of
> > data type
> >
> > Signed-off-by: Phil Sutter <p...@nwl.cc>
> > ---
> > misc/ifstat.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/misc/ifstat.c b/misc/ifstat.c
> > index abbb4e732fcef..9a44da487599e 100644
> > --- a/misc/ifstat.c
> > +++ b/misc/ifstat.c
> > @@ -539,7 +539,7 @@ static void update_db(int interval)
> > int i;
> >
> > for (i = 0; i < MAXS; i++) {
> > - if ((long)(h1->ival[i] - n->ival[i]) <
> > 0) {
> > + if (h1->ival[i] < n->ival[i]) {
> > memset(n->ival, 0,
> > sizeof(n->ival));
> > break;
>
> That isn't the same check.
> The original code is using modulo arithmetic.
Oh, right! The code behaves differently if h1->ival[i] is close to
ULONG_MAX and n->ival[i] is very small. Though I don't see where this
becomes relevant. Am I missing another scenario?
Thanks, Phil
