From: Jan Vesely <jan.vesely@rutgers.edu>
To: dri-devel@lists.freedesktop.org
Subject: [libdrm][PATCH 1/2] random: Use unsigned long for seed
Date: Mon, 9 Feb 2015 16:39:54 -0500 [thread overview]
Message-ID: <1423517995-28251-1-git-send-email-jan.vesely@rutgers.edu> (raw)
This is more consistent with the rest, and avoids potential undefined
behavior (signed overflow) in drmRandom()
Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>
---
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;
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");
drmRandomDestroy(state);
printf("Checking periods...\n");
--
2.1.0
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next reply other threads:[~2015-02-09 21:40 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-09 21:39 Jan Vesely [this message]
2015-02-09 21:39 ` [libdrm][PATCH 2/2] Fix gcc -Wextra warnings Jan Vesely
2015-02-09 23:12 ` Ian Romanick
2015-02-09 23:32 ` Emil Velikov
2015-02-10 0:02 ` Jan Vesely
2015-02-10 0:27 ` Emil Velikov
2015-02-10 21:37 ` Jan Vesely
2015-02-10 22:55 ` Emil Velikov
2015-02-09 23:11 ` [libdrm][PATCH 1/2] random: Use unsigned long for seed Ian Romanick
2015-02-09 23:26 ` Jan Vesely
2015-02-09 23:28 ` [libdrm][PATCH v2 " Jan Vesely
2015-02-10 18:21 ` Ian Romanick
2015-02-10 0:10 ` [libdrm][PATCH 3/2] Fix always true comparison Jan Vesely
2015-02-25 17:11 ` Jan Vesely
2015-02-25 18:41 ` Emil Velikov
2015-03-02 20:01 ` Jan Vesely
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