GH-89988: Fix memory leak in pickle.Pickler dispatch_table lookup (GH-94298)

(cherry picked from commit 01ef1f95dab9c9930ce1a23634a3e5a8331bf3c7)

Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>

diff --git a/Lib/test/test_pickle.py b/Lib/test/test_pickle.py
index 057af21e71fe474529a90f11103fecdf9173c958..44fdca7a6b1688b796483e8e4873eb0bf9b246e5 100644 (file)
--- a/Lib/test/test_pickle.py
+++ b/Lib/test/test_pickle.py
@@ -154,6 +154,29 @@ class PyIdPersPicklerTests(AbstractIdentityPersistentPicklerTests,
                 return obj
         check(PersPickler)
 
+    @support.cpython_only
+    def test_custom_pickler_dispatch_table_memleak(self):
+        # See https://github.com/python/cpython/issues/89988
+
+        class Pickler(self.pickler):
+            def __init__(self, *args, **kwargs):
+                self.dispatch_table = table
+                super().__init__(*args, **kwargs)
+
+        class DispatchTable:
+            pass
+
+        table = DispatchTable()
+        pickler = Pickler(io.BytesIO())
+        self.assertIs(pickler.dispatch_table, table)
+        table_ref = weakref.ref(table)
+        self.assertIsNotNone(table_ref())
+        del pickler
+        del table
+        support.gc_collect()
+        self.assertIsNone(table_ref())
+
+
     @support.cpython_only
     def test_unpickler_reference_cycle(self):
         def check(Unpickler):

diff --git a/Misc/NEWS.d/next/Library/2022-06-26-10-59-15.gh-issue-89988.K8rnmt.rst b/Misc/NEWS.d/next/Library/2022-06-26-10-59-15.gh-issue-89988.K8rnmt.rst
new file mode 100644 (file)
index 0000000..811a8d6
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-06-26-10-59-15.gh-issue-89988.K8rnmt.rst
@@ -0,0 +1 @@
+Fix memory leak in :class:`pickle.Pickler` when looking up :attr:`dispatch_table`. Patch by Kumar Aditya.

diff --git a/Modules/_pickle.c b/Modules/_pickle.c
index 23d26f6d608ff3a30eef4352517eddb13a7142e0..b4b1dda199c23a41a8db27672b6a29dfef88ac1f 100644 (file)
--- a/Modules/_pickle.c
+++ b/Modules/_pickle.c
@@ -4773,7 +4773,9 @@ _pickle_Pickler___init___impl(PicklerObject *self, PyObject *file,
     {
         return -1;
     }
-
+    if (self->dispatch_table != NULL) {
+        return 0;
+    }
     if (_PyObject_LookupAttr((PyObject *)self, &_Py_ID(dispatch_table),
                              &self->dispatch_table) < 0) {
         return -1;