changeset:   89657:e68f156ea0e6
user:        Benjamin Peterson <benjamin@python.org>
date:        Fri Mar 14 20:15:29 2014 -0500
files:       Include/objimpl.h Misc/NEWS
description:
cast negative numbers to size_t before shifting them (#20929)


diff -r 63d2d0c15b37 -r e68f156ea0e6 Include/objimpl.h
--- a/Include/objimpl.h	Fri Mar 14 23:13:00 2014 +0000
+++ b/Include/objimpl.h	Fri Mar 14 20:15:29 2014 -0500
@@ -265,7 +265,7 @@
 #define _PyGCHead_REFS(g) ((g)->gc.gc_refs >> _PyGC_REFS_SHIFT)
 #define _PyGCHead_SET_REFS(g, v) do { \
     (g)->gc.gc_refs = ((g)->gc.gc_refs & ~_PyGC_REFS_MASK) \
-        | (v << _PyGC_REFS_SHIFT); \
+        | (((size_t)(v)) << _PyGC_REFS_SHIFT);             \
     } while (0)
 #define _PyGCHead_DECREF(g) ((g)->gc.gc_refs -= 1 << _PyGC_REFS_SHIFT)
 
diff -r 63d2d0c15b37 -r e68f156ea0e6 Misc/NEWS
--- a/Misc/NEWS	Fri Mar 14 23:13:00 2014 +0000
+++ b/Misc/NEWS	Fri Mar 14 20:15:29 2014 -0500
@@ -8,6 +8,8 @@
 Core and Builtins
 -----------------
 
+- Issue #20929: Add a type cast to avoid shifting a negative number.
+
 - Issue #20731: Properly position in source code files even if they
   are opened in text mode. Patch by Serhiy Storchaka.