Merged revisions 69582-69583 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk
........
r69582 | antoine.pitrou | 2009-02-13 14:52:33 +0100 (ven., 13 févr. 2009) | 4 lines
Issue #5186: Reduce hash collisions for objects with no __hash__ method by
rotating the object pointer by 4 bits to the right.
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r69583 | antoine.pitrou | 2009-02-13 14:57:40 +0100 (ven., 13 févr. 2009) | 3 lines
Fix compiler warning (gcc)
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diff --git a/Objects/object.c b/Objects/object.c
index ee18bc3..8583797 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -699,23 +699,15 @@
long
_Py_HashPointer(void *p)
{
-#if SIZEOF_LONG >= SIZEOF_VOID_P
- return (long)p;
-#else
- /* convert to a Python long and hash that */
- PyObject* longobj;
long x;
-
- if ((longobj = PyLong_FromVoidPtr(p)) == NULL) {
- x = -1;
- goto finally;
- }
- x = PyObject_Hash(longobj);
-
-finally:
- Py_XDECREF(longobj);
+ size_t y = (size_t)p;
+ /* bottom 3 or 4 bits are likely to be 0; rotate y by 4 to avoid
+ excessive hash collisions for dicts and sets */
+ y = (y >> 4) | (y << (8 * SIZEOF_VOID_P - 4));
+ x = (long)y;
+ if (x == -1)
+ x = -2;
return x;
-#endif
}
long