I'm now very confused.
In trying to follow things of type wchar_t* around the Python source, I
discovered PyUnicode_FromWideChar in unicodebject.c. For OS X, the
conversion lands in the following code, where w is the incoming WideChar
array, declared as wchar_t *.
register Py_UNICODE *u;
register Py_ssize_t i;
u = PyUnicode_AS_UNICODE(unicode);
for (i = size; i > 0; i--)
*u++ = *w++;
But this looks wrong: on OS X, sizeof(wchar_t) is 4 and I think w is
encoded in UTF-32. So I was expecting to see some kind of explicit
conversion from UTF-32 to UCS-2 here. Instead, it looks as though the
incoming values are implicitly truncated from 32 bits to 16. Doesn't this
do the wrong thing for characters outside the BMP?
Should I open an issue for this, or am I simply misunderstanding?