bpo-41344: Raise ValueError when creating shared memory of size 0 (GH-21556)

diff --git a/Lib/multiprocessing/shared_memory.py b/Lib/multiprocessing/shared_memory.py
index a3a5fcf4aba1e7d76fa1cc66baaf011de65d0a6a..122b3fcebf3fedd29ece099d1a64b2ef771e29f6 100644 (file)
--- a/Lib/multiprocessing/shared_memory.py
+++ b/Lib/multiprocessing/shared_memory.py
@@ -76,6 +76,8 @@ class SharedMemory:
             raise ValueError("'size' must be a positive integer")
         if create:
             self._flags = _O_CREX | os.O_RDWR
+            if size == 0:
+                raise ValueError("'size' must be a positive number different from zero")
         if name is None and not self._flags & os.O_EXCL:
             raise ValueError("'name' can only be None if create=True")
 

diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py
index 6a0e1016aff8d0391d8dbe701191a9311cb17804..fd3b4303f034c1f068c1cccd2954c21ee58cdb1e 100644 (file)
--- a/Lib/test/_test_multiprocessing.py
+++ b/Lib/test/_test_multiprocessing.py
@@ -3880,6 +3880,18 @@ class _TestSharedMemory(BaseTestCase):
 
         sms.close()
 
+        # Test creating a shared memory segment with negative size
+        with self.assertRaises(ValueError):
+            sms_invalid = shared_memory.SharedMemory(create=True, size=-1)
+
+        # Test creating a shared memory segment with size 0
+        with self.assertRaises(ValueError):
+            sms_invalid = shared_memory.SharedMemory(create=True, size=0)
+
+        # Test creating a shared memory segment without size argument
+        with self.assertRaises(ValueError):
+            sms_invalid = shared_memory.SharedMemory(create=True)
+
     def test_shared_memory_across_processes(self):
         # bpo-40135: don't define shared memory block's name in case of
         # the failure when we run multiprocessing tests in parallel.

diff --git a/Misc/NEWS.d/next/Library/2020-07-20-13-27-48.bpo-41344.iKipNd.rst b/Misc/NEWS.d/next/Library/2020-07-20-13-27-48.bpo-41344.iKipNd.rst
new file mode 100644 (file)
index 0000000..475bc9b
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-07-20-13-27-48.bpo-41344.iKipNd.rst
@@ -0,0 +1 @@
+Prevent creating :class:`shared_memory.SharedMemory` objects with :code:`size=0`.