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

pganssle · web-flow · commit c3dd7e45cc5d · 2020-08-17T23:40:07.000+01:00
* 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).
diff --git a/Modules/_zoneinfo.c b/Modules/_zoneinfo.c
@@ -412,7 +412,6 @@ zoneinfo_clear_cache(PyObject *cls, PyObject *args, PyObject *kwargs)
         }
 
         clear_strong_cache(type);
-        ZONEINFO_STRONG_CACHE = NULL;
     }
     else {
         PyObject *item = NULL;
@@ -2471,6 +2470,7 @@ clear_strong_cache(const PyTypeObject *const type)
     }
 
     strong_cache_free(ZONEINFO_STRONG_CACHE);
+    ZONEINFO_STRONG_CACHE = NULL;
 }
 
 static PyObject *
@@ -2525,6 +2525,7 @@ zoneinfo_init_subclass(PyTypeObject *cls, PyObject *args, PyObject **kwargs)
     }
 
     PyObject_SetAttrString((PyObject *)cls, "_weak_cache", weak_cache);
+    Py_DECREF(weak_cache);
     Py_RETURN_NONE;
 }
 
@@ -2616,8 +2617,7 @@ module_free()
         Py_CLEAR(ZONEINFO_WEAK_CACHE);
     }
 
-    strong_cache_free(ZONEINFO_STRONG_CACHE);
-    ZONEINFO_STRONG_CACHE = NULL;
+    clear_strong_cache(&PyZoneInfo_ZoneInfoType);
 }
 
 static int

Original file line number	Diff line number	Diff line change
`@@ -412,7 +412,6 @@ zoneinfo_clear_cache(PyObject cls, PyObject args, PyObject *kwargs)`
`412`	`412`	`}`
`413`	`413`
`414`	`414`	`clear_strong_cache(type);`
`415`		`- ZONEINFO_STRONG_CACHE = NULL;`
`416`	`415`	`}`
`417`	`416`	`else {`
`418`	`417`	`PyObject *item = NULL;`
`@@ -2471,6 +2470,7 @@ clear_strong_cache(const PyTypeObject *const type)`
`2471`	`2470`	`}`
`2472`	`2471`
`2473`	`2472`	`strong_cache_free(ZONEINFO_STRONG_CACHE);`
	`2473`	`+ ZONEINFO_STRONG_CACHE = NULL;`
`2474`	`2474`	`}`
`2475`	`2475`
`2476`	`2476`	`static PyObject *`
`@@ -2525,6 +2525,7 @@ zoneinfo_init_subclass(PyTypeObject cls, PyObject args, PyObject **kwargs)`
`2525`	`2525`	`}`
`2526`	`2526`
`2527`	`2527`	`PyObject_SetAttrString((PyObject *)cls, "_weak_cache", weak_cache);`
	`2528`	`+ Py_DECREF(weak_cache);`
`2528`	`2529`	`Py_RETURN_NONE;`
`2529`	`2530`	`}`
`2530`	`2531`
`@@ -2616,8 +2617,7 @@ module_free()`
`2616`	`2617`	`Py_CLEAR(ZONEINFO_WEAK_CACHE);`
`2617`	`2618`	`}`
`2618`	`2619`
`2619`		`- strong_cache_free(ZONEINFO_STRONG_CACHE);`
`2620`		`- ZONEINFO_STRONG_CACHE = NULL;`
	`2620`	`+ clear_strong_cache(&PyZoneInfo_ZoneInfoType);`
`2621`	`2621`	`}`
`2622`	`2622`
`2623`	`2623`	`static int`