Define the rename method conditionally

Author: aisk

Lib/multiprocessing/shared_memory.py

@@ -254,28 +254,26 @@ def unlink(self):
             if self._track:
                 resource_tracker.unregister(self._name, "shared_memory")
 
-    def rename(self, newname, flags=0):
-        """Renames a shared memory block.
-
-        The policy how the operation is handled depends on the flag passed.
-        The default behavior is if the newname already exists, it will
-        be unlinked beforehand.
-        With the SHM_RENAME_EXCHANGE flag, the old and new name will
-        be exchanged.
-        With the SHM_RENAME_NOREPLACE flag, an error will be returned
-        if the new name exists.
-        """
-        if not hasattr(_posixshmem, "shm_rename"):
-            raise OSError("Unsupported operation on this platform")
-
-        oldname = self._name
-        if _USE_POSIX and self._prepend_leading_slash:
-            newname = "/" + newname
-        self._fd = _posixshmem.shm_rename(self._name, newname, flags)
-        if self._track:
-            resource_tracker.unregister(oldname, "shared_memory")
-            resource_tracker.register(newname, "shared_memory")
-        self._name = newname
+    if hasattr(_posixshmem, "shm_rename"):
+        def rename(self, newname, flags=0):
+            """Renames a shared memory block.
+
+            The policy how the operation is handled depends on the flag passed.
+            The default behavior is if the newname already exists, it will
+            be unlinked beforehand.
+            With the SHM_RENAME_EXCHANGE flag, the old and new name will
+            be exchanged.
+            With the SHM_RENAME_NOREPLACE flag, an error will be returned
+            if the new name exists.
+            """
+            oldname = self._name
+            if _USE_POSIX and self._prepend_leading_slash:
+                newname = "/" + newname
+            self._fd = _posixshmem.shm_rename(self._name, newname, flags)
+            if self._track:
+                resource_tracker.unregister(oldname, "shared_memory")
+                resource_tracker.register(newname, "shared_memory")
+            self._name = newname
 
 
 _encoding = "utf8"

Lib/test/_test_multiprocessing.py

@@ -4376,11 +4376,8 @@ def test_shared_memory_recreate(self):
             self.addCleanup(shm2.unlink)
             self.assertEqual(shm2._name, names[1])
 
+    @unittest.skipUnless(hasattr(shared_memory, "rename"), "requires SharedMomery.rename")
     def test_shared_memory_rename(self):
-        _posixshmem = import_helper.import_module("_posixshmem")
-        if not hasattr(_posixshmem, "shm_rename"):
-            raise unittest.SkipTest('requires _posixshmem.shm_rename')
-
         name1 = self._new_shm_name('testrename01_tsmb')
         name2 = self._new_shm_name('testrename02_tsmb')
         sms = shared_memory.SharedMemory(name1, create=True, size=512)