Repair widespread misuse of _PyString_Resize. Since it's clear people don't understand how this function works, also beefed up the docs. The most common usage error is of this form (often spread out across gotos): if (_PyString_Resize(&s, n) < 0) { Py_DECREF(s); s = NULL; goto outtahere; } The error is that if _PyString_Resize runs out of memory, it automatically decrefs the input string object s (which also deallocates it, since its refcount must be 1 upon entry), and sets s to NULL. So if the "if" branch ever triggers, it's an error to call Py_DECREF(s): s is already NULL! A correct way to write the above is the simpler (and intended) if (_PyString_Resize(&s, n) < 0) goto outtahere; Bugfix candidate.

--- a/Modules/cdmodule.c	Sat Apr 27 18:03:26 2002 +0000
+++ b/Modules/cdmodule.c	Sat Apr 27 18:44:32 2002 +0000
@@ -251,8 +251,7 @@
 		return NULL;
 	}
 	if (n < numframes)
-		if (_PyString_Resize(&result, n * sizeof(CDFRAME)))
-			return NULL;
+		_PyString_Resize(&result, n * sizeof(CDFRAME));
 
 	return result;
 }