From: Raymond Hettinger <python@rcn.com>
Date: Thu, 10 Jun 2004 18:42:15 +0000 (+0000)
Subject: Add a final permutation step to the tuple hash function.
X-Git-Tag: v2.4a1~212
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=57c2d930f688ca50248241919bd815c85bf39939;p=python

Add a final permutation step to the tuple hash function.

Prevents a collision pattern that occurs with nested tuples.
(Yitz Gale provided code that repeatably demonstrated the weakness.)
---

diff --git a/Misc/ACKS b/Misc/ACKS
index 6d3ad2cb83..480a1ec1eb 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -190,6 +190,7 @@ Gyro Funch
 Peter Funk
 Geoff Furnish
 Lele Gaifax
+Yitzchak Gale
 Raymund Galvin
 Nitin Ganatra
 Fred Gansevles
diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
index ff20b43eeb..ea7d753022 100644
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -280,6 +280,7 @@ tuplehash(PyTupleObject *v)
 		x = (x ^ y) * mult;
 		mult += 82520L + len + len;
 	}
+	x += 97531L;
 	if (x == -1)
 		x = -2;
 	return x;