From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Thu, 18 Sep 2014 19:42:27 +0000 (-0400)
Subject: - Fixed an unlikely race condition observed in some exotic end-user
X-Git-Tag: rel_1_0_0b1~70^2~73
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c7ec21b29e926c40dd64eb2909d5f8b5e120ed94;p=thirdparty%2Fsqlalchemy%2Fsqlalchemy.git

- Fixed an unlikely race condition observed in some exotic end-user
setups, where the attempt to check for "duplicate class name" in
declarative would hit upon a not-totally-cleaned-up weak reference
related to some other class being removed; the check here now ensures
the weakref still references an object before calling upon it further.
fixes #3208
---

diff --git a/doc/build/changelog/changelog_09.rst b/doc/build/changelog/changelog_09.rst
index 56be5b38e7..c0d13e16db 100644
--- a/doc/build/changelog/changelog_09.rst
+++ b/doc/build/changelog/changelog_09.rst
@@ -13,6 +13,17 @@
 .. changelog::
     :version: 0.9.8
 
+    .. change::
+        :tags: bug, declarative
+        :versions: 1.0.0
+        :tickets: 3208
+
+        Fixed an unlikely race condition observed in some exotic end-user
+        setups, where the attempt to check for "duplicate class name" in
+        declarative would hit upon a not-totally-cleaned-up weak reference
+        related to some other class being removed; the check here now ensures
+        the weakref still references an object before calling upon it further.
+
     .. change::
         :tags: bug, orm
         :versions: 1.0.0
diff --git a/lib/sqlalchemy/ext/declarative/clsregistry.py b/lib/sqlalchemy/ext/declarative/clsregistry.py
index 4595b857a8..3ef63a5aeb 100644
--- a/lib/sqlalchemy/ext/declarative/clsregistry.py
+++ b/lib/sqlalchemy/ext/declarative/clsregistry.py
@@ -103,7 +103,12 @@ class _MultipleClassMarker(object):
                 self.on_remove()
 
     def add_item(self, item):
-        modules = set([cls().__module__ for cls in self.contents])
+        # protect against class registration race condition against
+        # asynchronous garbage collection calling _remove_item,
+        # [ticket:3208]
+        modules = set([
+            cls.__module__ for cls in
+            [ref() for ref in self.contents] if cls is not None])
         if item.__module__ in modules:
             util.warn(
                 "This declarative base already contains a class with the "