> If I redefine the string function, I encounter another, perhaps more
> serious problem leading to a segfault. I've defined my string function
> to be extremely simple:
> >>> def printer(arr):
> ... return str(arr[0])
>
> Now, if I try to print an element of the array:
> >>> mxArr[0]
>
> I get to this stack trace:
> #0 scalar_value (scalar=0x814be10, descr=0x5079e0) at
> scalartypes.inc.src:68
> #1 0x0079936a in PyArray_Scalar (data="" descr=0x5079e0,
> base=0x814e7a8) at arrayobject.c:1419
> #2 0x007d259f in array_subscript_nice (self=0x814e7a8, op=0x804eb8c)
> at arrayobject.c:1985
> #3 0x00d17dde in PyObject_GetItem (o=0x814e7a8, key=0x804eb8c) at
> Objects/abstract.c:94
>
> (Note: for some reason gdb claims that arrayobject.c:1985 is
> array_subscript_nice, but looking at my source this line is actually
> in array_item_nice. *boggle*)
>
> But scalar_value returns NULL for all non-native types. So, destptr in
> PyArray_Scalar is set to NULL, and the call the copyswap segfaults.
>
> Perhaps scalar_value should be checking the scalarkind field of
> PyArray_Descr, or using the elsize and alignment fields to figure out
> the pointer to return if scalarkind isn't set?
Hmmm... It looks like the modifications to scalar_value did not take
into account user-defined types. I've added a correction so that
user-defined types will use setitem to set the scalar value into the
array. Presumably your setitem function can handle setting the array
with scalars of your new type?
I've checked the changes into SVN.
Do there also need to be changes in scalartypes.inc.src to use getitem if a user-defined type does not inherit from a Numpy scalar? i.e. at scalartypes.inc.src:114 we should return some pointer calculated from the PyArray_Descr's elsize and alignment field to get the destination for the "custom scalar" type to be copied.
As it stands, if the user-defined type does not inherit from a Numpy scalar, lots of things continue to break. Furthermore it seems like the scalar conversions prefer the builtin types, but it seems to me that the user-defined type should be preferred.
i.e. if I try to get an element from my mxDateTime array, I get a float back:
>>> mxArr[0] = DateTime.now()
>>> mxArr[0][0]
732610.60691268521
But what I really want is the mxDateTime, which, oddly enough, is what happens if I use tolist():
>>> mxArr.tolist()[0]
[<DateTime object for '2006-10-27 14:33:57.25' at a73c60>]
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