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 6d3ad2cb83fb2f4517d6f514d4a08aea03d90232..480a1ec1eb0cdf9a15917f30ee99968086dd726e 100644 (file)
--- 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 ff20b43eeba47061233c750e00bc04b7686cb594..ea7d75302238d5e81eea50e781885bce8c462e6c 100644 (file)
--- 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;