[Python-checkins] cpython (3.2): Issue #12973: Fix undefined-behaviour-inducing overflow check in list_repeat.

[mark.dickinson]

http://hg.python.org/cpython/rev/99b808c94834
changeset:   72417:99b808c94834
branch:      3.2
parent:      72414:7a41855b6196
user:        Mark Dickinson <mdickinson at enthought.com>
date:        Mon Sep 19 19:18:37 2011 +0100
summary:
  Issue #12973: Fix undefined-behaviour-inducing overflow check in list_repeat.

files:
  Misc/NEWS            |  4 ++++
  Objects/listobject.c |  6 +++---
  2 files changed, 7 insertions(+), 3 deletions(-)


diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,10 @@
 Core and Builtins
 -----------------
 
+- Issue #12973: Fix overflow check that relied on undefined behaviour in
+  list_repeat.  This bug caused test_list to fail with recent versions
+  of Clang.
+
 - Issue #12802: the Windows error ERROR_DIRECTORY (numbered 267) is now
   mapped to POSIX errno ENOTDIR (previously EINVAL).
 
diff --git a/Objects/listobject.c b/Objects/listobject.c
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -58,7 +58,7 @@
     if (newsize == 0)
         new_allocated = 0;
     items = self->ob_item;
-    if (new_allocated <= ((~(size_t)0) / sizeof(PyObject *)))
+    if (new_allocated <= (PY_SIZE_MAX / sizeof(PyObject *)))
         PyMem_RESIZE(items, PyObject *, new_allocated);
     else
         items = NULL;
@@ -510,9 +510,9 @@
     PyObject *elem;
     if (n < 0)
         n = 0;
+    if (n > 0 && Py_SIZE(a) > PY_SSIZE_T_MAX / n)
+        return PyErr_NoMemory();
     size = Py_SIZE(a) * n;
-    if (n && size/n != Py_SIZE(a))
-        return PyErr_NoMemory();
     if (size == 0)
         return PyList_New(0);
     np = (PyListObject *) PyList_New(size);

-- 
Repository URL: http://hg.python.org/cpython