This patch addresses two main issues: (1) There exist some non-fatal

errors in some of the hash algorithms. For exmaple, in float_hash and
complex_hash a certain part of the value is not included in the hash
calculation. See Tim's, Guido's, and my discussion of this on
python-dev in May under the title "fix float_hash and complex_hash for
64-bit *nix"

(2) The hash algorithms that use pointers (e.g. func_hash, code_hash)
are universally not correct on Win64 (they assume that sizeof(long) ==
sizeof(void*))

As well, this patch significantly cleans up the hash code. It adds the
two function _Py_HashDouble and _PyHash_VoidPtr that the various
hashing routine are changed to use.

These help maintain the hash function invariant: (a==b) =>
(hash(a)==hash(b))) I have added Lib/test/test_hash.py and
Lib/test/output/test_hash to test this for some cases.

1 files changed, 9 insertions, 28 deletions

diff --git a/Objects/complexobject.c b/Objects/complexobject.c
index 42709ee..1a15a27 100644
--- a/Objects/complexobject.c
+++ b/Objects/complexobject.c
@@ -285,8 +285,7 @@ complex_hash(v)
 	PyComplexObject *v;
 {
 	double intpart, fractpart;
-	int expo;
-	long hipart, x;
+	long x;
 	/* This is designed so that Python numbers with the same
 	   value hash to the same value, otherwise comparisons
 	   of mapping keys will turn out weird */
@@ -302,7 +301,7 @@ complex_hash(v)
 #endif
 
 	if (fractpart == 0.0 && v->cval.imag == 0.0) {
-		if (intpart > 0x7fffffffL || -intpart > 0x7fffffffL) {
+		if (intpart > LONG_MAX || -intpart > LONG_MAX) {
 			/* Convert to long int and use its hash... */
 			PyObject *w = PyLong_FromDouble(v->cval.real);
 			if (w == NULL)
@@ -314,36 +313,18 @@ complex_hash(v)
 		x = (long)intpart;
 	}
 	else {
-		fractpart = frexp(fractpart, &expo);
-		fractpart = fractpart * 2147483648.0; /* 2**31 */
-		hipart = (long)fractpart; /* Take the top 32 bits */
-		fractpart = (fractpart - (double)hipart) * 2147483648.0;
-						/* Get the next 32 bits */
-		x = hipart + (long)fractpart + (long)intpart + (expo << 15);
-						/* Combine everything */
+		x = _Py_HashDouble(v->cval.real);
+		if (x == -1)
+			return -1;
 
 		if (v->cval.imag != 0.0) { /* Hash the imaginary part */
 			/* XXX Note that this hashes complex(x, y)
 			   to the same value as complex(y, x).
 			   Still better than it used to be :-) */
-#ifdef MPW
-			{
-				extended e;
-				fractpart = modf(v->cval.imag, &e);
-				intpart = e;
-			}
-#else
-			fractpart = modf(v->cval.imag, &intpart);
-#endif
-			fractpart = frexp(fractpart, &expo);
-			fractpart = fractpart * 2147483648.0; /* 2**31 */
-			hipart = (long)fractpart; /* Take the top 32 bits */
-			fractpart =
-				(fractpart - (double)hipart) * 2147483648.0;
-						/* Get the next 32 bits */
-			x ^= hipart + (long)fractpart +
-				(long)intpart + (expo << 15);
-						/* Combine everything */
+			long y = _Py_HashDouble(v->cval.imag);
+			if (y == -1)
+				return -1;
+			x += y;
 		}
 	}
 	if (x == -1)