Using a UCS2 Python on a platform with a 32-bit wchar_t, the following code throws an exception (but should not):

>>> ctypes.c_wchar('\u10000')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: one character unicode string expected

The trouble is in the u_set() function in Modules/_ctypes/cfield.c.  The corresponding u_get() function looks correct.

On a UCS4 Python running on a system with a 16-bit wchar_t, u_set() will corrupt the data by silently truncating the character to 16-bits.

For reference, Linux and Mac OS use a 32-bit wchar_t while Windows uses a 16-bit wchar_t.