http://hg.python.org/cpython/file/be5f1f0bea09/Modules/_ctypes/cfield.c#l1235

CID 486657 (#1 of 1): Unchecked return value (CHECKED_RETURN)
5. check_return: Calling function "PyUnicode_AsWideChar(PyObject *, wchar_t *, Py_ssize_t)" without checking return value (as is done elsewhere 7 out of 8 times).
1263    PyUnicode_AsWideChar(value, (wchar_t *)ptr, size);

Re msg193703: A little before that, 'value' is INCREF'ed, and then:

    wstr = PyUnicode_AsUnicodeAndSize(value, &size);
    if (wstr == NULL)
        return NULL;

Shouldn't 'value' be DECREF'ed before returning?

New changeset 78e8980ec9f7 by Brett Cannon in branch '3.3':
Issue #18556: Check the return value for PyUnicode_AsWideChar() in
http://hg.python.org/cpython/rev/78e8980ec9f7

New changeset 2f4c4db9aee5 by Brett Cannon in branch 'default':
merge for issue #18556
http://hg.python.org/cpython/rev/2f4c4db9aee5

Thanks for the check, Matthew, but if you look at the other *_set() methods they do not necessarily DECREF their 'value' argument. Plus if PyUnicode_AsWideChar() fails it means memory is full or a fatal error has triggered, so there are bigger worries. =)