commit c3dd7e45cc5d36bbe2295c2840faabb5c75d83e4
author Paul Ganssle <paul@ganssle.io> Mon Aug 17 18:40:07 2020 -0400
committer GitHub <noreply@github.com> Mon Aug 17 23:40:07 2020 +0100
tree a92a7e7f05f129d762220707719b15665ed5f634
parent 8aa163eea6b0fb4693f6c0a314d4f2ccada51d70

bpo-41568: Fix refleaks in zoneinfo subclasses (GH-21907)

* Fix refleak in C module __init_subclass__

This was leaking a reference to the weak cache dictionary for every
ZoneInfo subclass created.

* Fix refleak in ZoneInfo subclass's clear_cache

The previous version of the code accidentally cleared the global
ZONEINFO_STRONG_CACHE variable (and inducing `ZoneInfo` to create a new
strong cache) on calls to a subclass's `clear_cache()`. This would not
affect guaranteed behavior, but it's still not the right thing to do
(and it caused reference leaks).

Modules/_zoneinfo.c

diff --git a/Modules/_zoneinfo.c b/Modules/_zoneinfo.c
index 12b3969..2cee65f 100644
--- a/Modules/_zoneinfo.c
+++ b/Modules/_zoneinfo.c
@@ -412,7 +412,6 @@
         }
 
         clear_strong_cache(type);
-        ZONEINFO_STRONG_CACHE = NULL;
     }
     else {
         PyObject *item = NULL;
@@ -2471,6 +2470,7 @@
     }
 
     strong_cache_free(ZONEINFO_STRONG_CACHE);
+    ZONEINFO_STRONG_CACHE = NULL;
 }
 
 static PyObject *
@@ -2525,6 +2525,7 @@
     }
 
     PyObject_SetAttrString((PyObject *)cls, "_weak_cache", weak_cache);
+    Py_DECREF(weak_cache);
     Py_RETURN_NONE;
 }
 
@@ -2616,8 +2617,7 @@
         Py_CLEAR(ZONEINFO_WEAK_CACHE);
     }
 
-    strong_cache_free(ZONEINFO_STRONG_CACHE);
-    ZONEINFO_STRONG_CACHE = NULL;
+    clear_strong_cache(&PyZoneInfo_ZoneInfoType);
 }
 
 static int