From: Christian Heimes <christian@cheimes.de>
Date: Thu, 28 Feb 2008 11:18:49 +0000 (+0000)
Subject: The empty tuple is usually a singleton with a much higher refcnt than 1
X-Git-Tag: v2.6a1~28
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=cdddf187685cde1b2dba3d37aa180191bc254e58;p=thirdparty%2FPython%2Fcpython.git

The empty tuple is usually a singleton with a much higher refcnt than 1
---

diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
index 4efde75b6280..2ee947dcffa2 100644
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -2111,8 +2111,11 @@ combinations_next(combinationsobject *co)
 			}
 			Py_DECREF(old_result);
 		}
-		/* Now, we've got the only copy so we can update it in-place */
-		assert (Py_REFCNT(result) == 1);
+		/* Now, we've got the only copy so we can update it in-place 
+		 * CPython's empty tuple is a singleton and cached in 
+		 * PyTuple's freelist. 
+		 */
+		assert(r == 0 || Py_REFCNT(result) == 1);
 
                 /* Scan indices right-to-left until finding one that is not
                    at its maximum (i + n - r). */