1 files changed, 17 insertions, 11 deletions
diff --git a/src/fns.c b/src/fns.c
index c91710b7c10..b65f3f203f7 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -64,17 +64,23 @@ With argument t, set the random number seed from the current time and pid.")
    srandom (getpid () + time (0));
  if (XTYPE (limit) == Lisp_Int && XINT (limit) > 0)
    {
-      /* Try to take our random number from the higher bits of VAL,
+      if (XINT (limit) >= 0x40000000)
-         not the lower, since (says Gentzel) the low bits of `random'
+        /* This case may occur on 64-bit machines.  */
-         are less random than the higher ones.  We do this by using the
+        val = random () % XINT (limit);
-         quotient rather than the remainder.  At the high end of the RNG
+      else
-         it's possible to get a quotient larger than limit; discarding
+        {
-         these values eliminates the bias that would otherwise appear
+          /* Try to take our random number from the higher bits of VAL,
-         when using a large limit.  */
+             not the lower, since (says Gentzel) the low bits of `random'
-      denominator = (unsigned long)0x40000000 / XFASTINT (limit);
+             are less random than the higher ones.  We do this by using the
-      do
+             quotient rather than the remainder.  At the high end of the RNG
-        val = (random () & 0x3fffffff) / denominator;
+             it's possible to get a quotient larger than limit; discarding
-      while (val >= limit);
+             these values eliminates the bias that would otherwise appear
+             when using a large limit.  */
+          denominator = (unsigned long)0x40000000 / XFASTINT (limit);
+          do
+            val = (random () & 0x3fffffff) / denominator;
+          while (val >= limit);
+        }
    }
  else
    val = random ();

diff --git a/src/fns.c b/src/fns.c index c91710b7c10..b65f3f203f7 100644 --- a/src/fns.c +++ b/src/fns.c
@@ -64,17 +64,23 @@ With argument t, set the random number seed from the current time and pid.")
64	srandom (getpid () + time (0));	64	srandom (getpid () + time (0));
65	if (XTYPE (limit) == Lisp_Int && XINT (limit) > 0)	65	if (XTYPE (limit) == Lisp_Int && XINT (limit) > 0)
66	{	66	{
67	/* Try to take our random number from the higher bits of VAL,	67	if (XINT (limit) >= 0x40000000)
68	not the lower, since (says Gentzel) the low bits of `random'	68	/* This case may occur on 64-bit machines. */
69	are less random than the higher ones. We do this by using the	69	val = random () % XINT (limit);
70	quotient rather than the remainder. At the high end of the RNG	70	else
71	it's possible to get a quotient larger than limit; discarding	71	{
72	these values eliminates the bias that would otherwise appear	72	/* Try to take our random number from the higher bits of VAL,
73	when using a large limit. */	73	not the lower, since (says Gentzel) the low bits of `random'
74	denominator = (unsigned long)0x40000000 / XFASTINT (limit);	74	are less random than the higher ones. We do this by using the
75	do	75	quotient rather than the remainder. At the high end of the RNG
76	val = (random () & 0x3fffffff) / denominator;	76	it's possible to get a quotient larger than limit; discarding
77	while (val >= limit);	77	these values eliminates the bias that would otherwise appear
		78	when using a large limit. */
		79	denominator = (unsigned long)0x40000000 / XFASTINT (limit);
		80	do
		81	val = (random () & 0x3fffffff) / denominator;
		82	while (val >= limit);
		83	}
78	}	84	}
79	else	85	else
80	val = random ();	86	val = random ();