On Mon, 2015-02-09 at 15:11 -0800, Ian Romanick wrote:
> On 02/09/2015 01:39 PM, Jan Vesely wrote:
> > This is more consistent with the rest, and avoids potential undefined
> > behavior (signed overflow) in drmRandom()
> >
> > Signed-off-by: Jan Vesely <jan.vesely@xxxxxxxxxxx>
> > ---
> > xf86drmRandom.c | 14 +++++++-------
> > 1 file changed, 7 insertions(+), 7 deletions(-)
> >
> > diff --git a/xf86drmRandom.c b/xf86drmRandom.c
> > index ecab9e2..a084b86 100644
> > --- a/xf86drmRandom.c
> > +++ b/xf86drmRandom.c
> > @@ -98,7 +98,7 @@ typedef struct RandomState {
> > unsigned long q; /* m div a */
> > unsigned long r; /* m mod a */
> > unsigned long check;
> > - long seed;
> > + unsigned long seed;
> > } RandomState;
> >
> > #if RANDOM_MAIN
> > @@ -147,13 +147,13 @@ int drmRandomDestroy(void *state)
> > unsigned long drmRandom(void *state)
> > {
> > RandomState *s = (RandomState *)state;
> > - long hi;
> > - long lo;
> > + unsigned long hi;
> > + unsigned long lo;
> >
> > hi = s->seed / s->q;
> > lo = s->seed % s->q;
> > s->seed = s->a * lo - s->r * hi;
> > - if (s->seed <= 0) s->seed += s->m;
> > + if ((s->a * lo) <= (s->r * hi)) s->seed += s->m;
>
> This seems like an unrelated change.
This change is necessary. since s->seed is unsigned now it cannot be <
0. also the result of s->seed op s->q is unsigned.
>
> >
> > return s->seed;
> > }
> > @@ -166,7 +166,7 @@ double drmRandomDouble(void *state)
> > }
> >
> > #if RANDOM_MAIN
> > -static void check_period(long seed)
> > +static void check_period(unsigned long seed)
> > {
> > unsigned long count = 0;
> > unsigned long initial;
> > @@ -178,7 +178,7 @@ static void check_period(long seed)
> > while (initial != drmRandom(state)) {
> > if (!++count) break;
> > }
> > - printf("With seed of %10ld, period = %10lu (0x%08lx)\n",
> > + printf("With seed of %10lu, period = %10lu (0x%08lx)\n",
> > seed, count, count);
> > drmRandomDestroy(state);
> > }
> > @@ -195,7 +195,7 @@ int main(void)
> > }
> > printf("After 10000 iterations: %lu (%lu expected): %s\n",
> > rand, state->check,
> > - rand - state->check ? "*INCORRECT*" : "CORRECT");
> > + rand != state->check ? "*INCORRECT*" : "CORRECT");
>
> So does this.
I'll drop this one in v2, it shouldn't have been included
>
> > drmRandomDestroy(state);
> >
> > printf("Checking periods...\n");
> >
>
--
Jan Vesely <jan.vesely@xxxxxxxxxxx>
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