Issue #11675: Zero-out newly-created multiprocessing.[Raw]Array objects.

2 files changed, 18 insertions, 1 deletions

diff --git a/Lib/multiprocessing/sharedctypes.py b/Lib/multiprocessing/sharedctypes.py
index e83ce58..1e694da 100644
--- a/Lib/multiprocessing/sharedctypes.py
+++ b/Lib/multiprocessing/sharedctypes.py
@@ -80,7 +80,9 @@ def RawArray(typecode_or_type, size_or_initializer):
     type_ = typecode_to_type.get(typecode_or_type, typecode_or_type)
     if isinstance(size_or_initializer, int):
         type_ = type_ * size_or_initializer
-        return _new_value(type_)
+        obj = _new_value(type_)
+        ctypes.memset(ctypes.addressof(obj), 0, ctypes.sizeof(obj))
+        return obj
     else:
         type_ = type_ * len(size_or_initializer)
         result = _new_value(type_)
diff --git a/Lib/test/test_multiprocessing.py b/Lib/test/test_multiprocessing.py
index f4031de..1136ab2 100644
--- a/Lib/test/test_multiprocessing.py
+++ b/Lib/test/test_multiprocessing.py
@@ -914,6 +914,21 @@ class _TestArray(BaseTestCase):
         self.assertEqual(list(arr[:]), seq)
 
     @unittest.skipIf(c_int is None, "requires _ctypes")
+    def test_array_from_size(self):
+        size = 10
+        # Test for zeroing (see issue #11675).
+        # The repetition below strengthens the test by increasing the chances
+        # of previously allocated non-zero memory being used for the new array
+        # on the 2nd and 3rd loops.
+        for _ in range(3):
+            arr = self.Array('i', size)
+            self.assertEqual(len(arr), size)
+            self.assertEqual(list(arr), [0] * size)
+            arr[:] = range(10)
+            self.assertEqual(list(arr), list(range(10)))
+            del arr
+
+    @unittest.skipIf(c_int is None, "requires _ctypes")
     def test_rawarray(self):
         self.test_array(raw=True)