On Tue, Jan 21, 2014 at 11:03:43AM -0800, Andrew Honig wrote:
> > > In random.c the taviso() routine uses "rand() % rand()" which
> > > can cause a floating point exception if rand() returns 0.
> > > Add some tests to make sure that doesn't happen.
> > >
> > > Signed-off-by: Vince Weaver <vincent.weaver@xxxxxxxxx>
> > >
> > > diff --git a/random.c b/random.c
> > > index 7def9ff..a71fcea 100644
> > > --- a/random.c
> > > +++ b/random.c
> > > @@ -42,6 +42,7 @@ static unsigned long randbits(int limit)
> > > static unsigned long taviso(void)
> > > {
> > > unsigned long r = 0;
> > > + unsigned long temp;
> > >
> > > switch (rand() % 4) {
> > > case 0: r = rand() & rand();
> > > @@ -51,10 +52,14 @@ static unsigned long taviso(void)
> > > #endif
> > > break;
> > >
> > > - case 1: r = rand() % rand();
> > > + case 1: temp = rand();
> > > + r = rand();
> >
>
> Perhaps, I'm reading this wrong, but this looks backwards to me. This will
> perform the mod operation only when temp is 0. Shouldn't this be
> if (temp) r %= temp;
clang seems to agree.
random.c:57:16: warning: Division by zero
if (!temp) r %= temp;
~~^~~~~~~
random.c:62:26: warning: Division by zero
if (!temp) r |= rand() % temp;
~~~~~~~^~~~~~
Vince, want to send a follow-up fix ?
Dave
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