[pywin32-checkins] /hgrepo/p/py/pywin32/pywin32: fix some refcount edge cases, from...

[<pyw...@li...>]

changeset 95b4f896b100 in /hgrepo/p/py/pywin32/pywin32
details: http://pywin32.hg.sourceforge.net/hgweb/pywin32/pywin32/hgrepo/p/py/pywin32/pywin32?cmd=changeset;node=95b4f896b100
summary: fix some refcount edge cases, from kxroberto via #3440738

diffstat:

 Pythonwin/win32assoc.cpp |  6 ++++--
 Pythonwin/win32cmd.cpp   |  7 +++++--
 2 files changed, 9 insertions(+), 4 deletions(-)

diffs (46 lines):

diff -r dbbfddbcc824 -r 95b4f896b100 Pythonwin/win32assoc.cpp
--- a/Pythonwin/win32assoc.cpp	Sun Jan 01 14:01:21 2012 -0500
+++ b/Pythonwin/win32assoc.cpp	Mon Jan 02 12:40:31 2012 +1100
@@ -225,14 +225,16 @@
 	// decref of the instance may trigger instance delete,
 	// which may trigger AttachObject(None), which will
 	// attempt to decref etc.  
-	// So set the instance to NULL _before_ we decref it!
+	// So set the instance to NULL _before_ we decref it, and only
+	// do the decref after we've incref'd the new object - if it is the
+	// same object we may otherwise transition it via a refcount of 0.
 	PyObject *old = pAssoc->virtualInst;
 	pAssoc->virtualInst = NULL;
-	XDODECREF(old);
 	if (ob!=Py_None) {
 		pAssoc->virtualInst = ob;
 		DOINCREF(ob);
 	}
+	XDODECREF(old);
 	RETURN_NONE;
 }
 
diff -r dbbfddbcc824 -r 95b4f896b100 Pythonwin/win32cmd.cpp
--- a/Pythonwin/win32cmd.cpp	Sun Jan 01 14:01:21 2012 -0500
+++ b/Pythonwin/win32cmd.cpp	Mon Jan 02 12:40:31 2012 +1100
@@ -208,8 +208,10 @@
 		RETURN_ERR("The parameter must be a callable object or None");
 
 	void *oldMethod = NULL;
-	// note I maybe decref, then maybe incref.  I assume object wont be destroyed
-	// (ie, ref go to zero) between the 2 calls!)
+	// note I maybe decref, then maybe incref.  To ensure the object will
+	// not be destroyed (ie, ref go to zero) between the 2 calls), I
+	// add a temporary reference first.
+	DOINCREF(hookedObject);
 	if (pList->Lookup(message, oldMethod)) {
 		pList->RemoveKey(message);
 		// oldMethod is returned - don't drop its reference.
@@ -220,6 +222,7 @@
 		pList->SetAt(message,method);
 		Py_INCREF(hookedObject);
 	}
+	DODECREF(hookedObject); // remove temp reference added above.
 	if (oldMethod)
 		return (PyObject *)oldMethod;
 	else