The following code raises an Assertion Failure under debug in r64518
running on Windows XP SP2:

<code>
import ctypes

class X (ctypes.Structure): pass

ctypes.POINTER (X)
</code>

Assertion failed: PyErr_Occurred(), file ..\Modules\_ctypes\_ctypes.c,
line 309

The comment just before _ctypes.c:309 indicates that when a NULL is
returned at that point, an error condition should already obtain.

From reading through PEP 3118 once I'm not entirely clear on the role 
stgdict->format is supposed to be taking here, but I did get comtypes to 
compile and run successfully by changing line 910 from

stgdict->format = alloc_format_string("&", itemdict->format);

to

stgdict->format = alloc_format_string("&", itemdict->format ? itemdict-
>format : "P");

(Where "P" is just struct.pack's void pointer format string.)

Thanks for the heads up.  Fixed in trunk (rev 64971) and py3k (rev 64972).

I used "&B" (pointer to bytes) as the format string for pointer to
incomplete structure, not "&P".