[Numpy-discussion] numpy 2.0, what else to do?

[Charles R Harris]

On Mon, Feb 15, 2010 at 10:19 PM, David Cournapeau <david at silveregg.co.jp>wrote:

> Charles R Harris wrote:
> >
> >
> > On Mon, Feb 15, 2010 at 8:13 PM, David Cournapeau <david at silveregg.co.jp
> > <mailto:david at silveregg.co.jp>> wrote:
> >
> >     Charles R Harris wrote:
> >      >
> >      >
> >      > On Mon, Feb 15, 2010 at 3:58 PM, Charles R Harris
> >      > <charlesr.harris at gmail.com <mailto:charlesr.harris at gmail.com>
> >     <mailto:charlesr.harris at gmail.com
> >     <mailto:charlesr.harris at gmail.com>>> wrote:
> >      >
> >      >
> >      >
> >      >     On Mon, Feb 15, 2010 at 3:34 PM, David Cournapeau
> >      >     <cournape at gmail.com <mailto:cournape at gmail.com>
> >     <mailto:cournape at gmail.com <mailto:cournape at gmail.com>>> wrote:
> >      >
> >      >         On Tue, Feb 16, 2010 at 7:04 AM, Charles R Harris
> >      >         <charlesr.harris at gmail.com
> >     <mailto:charlesr.harris at gmail.com> <mailto:charlesr.harris at gmail.com
> >     <mailto:charlesr.harris at gmail.com>>>
> >      >         wrote:
> >      >          >
> >      >          >
> >      >          > On Mon, Feb 15, 2010 at 2:46 PM, David Cournapeau
> >      >         <cournape at gmail.com <mailto:cournape at gmail.com>
> >     <mailto:cournape at gmail.com <mailto:cournape at gmail.com>>>
> >      >          > wrote:
> >      >          >>
> >      >          >> On Tue, Feb 16, 2010 at 4:08 AM, Charles R Harris
> >      >          >> <charlesr.harris at gmail.com
> >     <mailto:charlesr.harris at gmail.com>
> >      >         <mailto:charlesr.harris at gmail.com
> >     <mailto:charlesr.harris at gmail.com>>> wrote:
> >      >          >>
> >      >          >> >
> >      >          >> > I was wondering about that. Why do we have a private
> >      >         include directory?
> >      >          >> > Would it make more sense to move it to
> >      >         core/include/numpy/private.
> >      >          >>
> >      >          >> No, the whole point is to avoid other packages to
> include
> >      >         that by
> >      >          >> mistake, to avoid namespace pollution.
> >      >          >
> >      >          > Isn't that what the npy prefix is for?
> >      >
> >      >         No, npy_ is for public symbols. Anything in private should
> be
> >      >         private :)
> >      >
> >      >          > In any case, if it needs to be at a
> >      >          > higher level for easy inclusion, then it should move
> up.
> >      >
> >      >         It is not that easy - we should avoid putting this code
> into
> >      >         core/include, because then we have to keep it compatible
> >     across
> >      >         releases, but there is no easy way to share headers
> >     between modules
> >      >         without making it public.
> >      >
> >      >
> >      >     Py_TYPE, Py_Size, etc. are unlikely to cause compatibility
> >     problems
> >      >     across releases.
> >      >
> >      >
> >      >
> >      > In particular, I think
> >      >
> >      > #if (PY_VERSION_HEX < 0x02060000)
> >      > #define Py_TYPE(o)    (((PyObject*)(o))->ob_type)
> >      > #define Py_REFCNT(o)  (((PyObject*)(o))->ob_refcnt)
> >      > #define Py_SIZE(o)    (((PyVarObject*)(o))->ob_size)
> >      > #endif
> >      >
> >      > belongs somewhere near the top, maybe with a prefix (cython seems
> to
> >      > define them also)
> >
> >     The rule is easy: one should put in core/include/numpy whatever is
> >     public, and put in private what is not.
> >
> >     Note that defining those macros above publicly is very likely to
> cause
> >     trouble because I am sure other people do define those macros,
> without
> >     caring about polluting the namespace as well. Given that it is
> >     temporary, and is small, I think copying the compat header is better
> >     than making it public, the best solution being to add something in
> >     distutils to share it between submodules,
> >
> >
> > You would prefer to fix the macros in ndarrayobject.h using #ifdef's
> then?
>
> In case what I am worried about is not clear: if ndarrayobject.h defines
> Py_TYPE, it means that every C extensions using the numpy C API will
> have Py_TYPE in the public namespace. Now, if another python extension
> with a C API does the same, you have issues. Having #ifdef/#endif around
> only make it worse because then you have strange interactions depending
> on the order of header inclusion (I really hate that behavior from the
> python headers).
>
> The numpy C headers are already pretty messy, let's not make it worse.
> Especially since the workaround is trivial.
>
>
What is the work around? Mind, I think those macros need to be compatible
with py3k just to make porting other applications easier. I still think we
should call it NPY_Py_TYPE or some such. We also have some stray ob_refcnt.
Note that the gnu headers also have implementation stuff hidden away in a
folder. Whatever we do, I think it needs to be easy discover for anyone
coming new to the code, it shouldn't be hidden away in somewhere in the
distutils. That's like burying it on a small Caribbean island along with all
the witnesses.

Chuck
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