[Cython] More concerns over extern ctypedefs

[Dag Sverre Seljebotn]

Consider this code:

cdef extern from "t.h":
     ctypedef long hullo

def foo(hullo h): pass

I noticed that it creates code like this:
PyArg_ParseTupleAndKeywords(__pyx_args, __pyx_kwds, "l", __pyx_argnames, 
&__pyx_v_h))

Which could probably destroy the stack if we don't have the exact 
typedef, right? Which means: One should either write our own parsing 
code instead (generate for each parameter signature), or generate the 
typestring at runtime, or insert C checks for the sizeof(the typedefs). 
The latter will destroy the current approach for numpy.int64 and friends 
and remove what I consider a nice feature.

Just as I took all that care to allow approximate typedefs for buffers :-)

Just noting it down, I suppose for now we'll live with it. But need to 
be more careful about recommending approximate typedefs.

-- 
Dag Sverre