[Python-3000] [Python-Dev] Stabilizing the C API of 2.6 and 3.0

Tue Jun 3 01:00:05 CEST 2008

On 6/2/08, Gregory P. Smith <greg at krypto.org> wrote:
> I believe those APIs are already there in the existing interface.  Why does
> that concern you?

Just because PyBytes_InternXXX are not in Py3K C API. Iff the whole
point of this patch is easier merges, then I believe there is a
problem here. Please note I'm definitely +1 for your patch, but the
string interning API seems to need a bit more of care. Am I wrong?

>
>
> On Mon, Jun 2, 2008 at 9:17 AM, Lisandro Dalcin <dalcinl at gmail.com> wrote:
>
> > Are you completelly sure of adding those guys:  PyBytes_InternXXX ???
> >
> >
> >
> >
> >
> > On 6/1/08, Gregory P. Smith <greg at krypto.org> wrote:
> > > On Fri, May 30, 2008 at 1:37 AM, M.-A. Lemburg <mal at egenix.com> wrote:
> > >  > On 2008-05-30 00:57, Nick Coghlan wrote:
> > >  >>
> > >  >> M.-A. Lemburg wrote:
> > >  >>>
> > >  >>> * Why can't we have both PyString *and* PyBytes exposed in 2.x,
> > >  >>> with one redirecting to the other ?
> > >  >>
> > >  >> We do have that - the PyString_* names still work perfectly fine in
> 2.x.
> > >  >> They just won't be used in the Python core codebase anymore -
> everything in
> > >  >> the Python core will use either PyBytes_* or PyUnicode_* regardless
> of which
> > >  >> branch (2.x or 3.x) you're working on. I think that's a good thing
> for ease
> > >  >> of maintenance in the future, even if it takes people a while to get
> their
> > >  >> heads around it right now.
> > >  >
> > >  > Sorry, I probably wasn't clear enough:
> > >  >
> > >  > Why can't we have both PyString *and* PyBytes exposed as C
> > >  > APIs (ie. visible in code and in the linker) in 2.x, with one
> redirecting
> > >  > to the other ?
> > >  >
> > >  >>> * Why should the 2.x code base turn to hacks, just because 3.x
> wants
> > >  >>> to restructure itself ?
> > >  >>
> > >  >> With the better explanation from Greg of what the checked in
> approach
> > >  >> achieves (i.e. preserving exact ABI compatibility for PyString_*,
> while
> > >  >> allowing PyBytes_* to be used at the source code level), I don't see
> what
> > >  >> has been done as being any more of a hack than the possibly more
> common
> > >  >> "#define <oldname> <newname>" (which *would* break binary
> compatibility).
> > >  >>
> > >  >> The only things that I think would tidy it up further would be to:
> > >  >> - include an explanation of the approach and its effects on API and
> ABI
> > >  >> backward and forward compatibility within 2.x and between 2.x and
> 3.x in
> > >  >> stringobject.h
> > >  >> - expose the PyBytes_* functions to the linker in 2.6 as well as 3.0
> > >  >
> > >  > Which is what I was suggesting all along; sorry if I wasn't
> > >  > clear enough on that.
> > >  >
> > >  > The standard approach is that you provide #define redirects from the
> > >  > old APIs to the new ones (which are then picked up by the compiler)
> > >  > *and* add function wrappers to the same affect (to make linkers,
> > >  > dynamic load APIs such ctypes and debuggers happy).
> > >  >
> > >  >
> > >  > Example from pythonrun.h|c:
> > >  > ---------------------------
> > >  >
> > >  > /* Use macros for a bunch of old variants */
> > >  > #define PyRun_String(str, s, g, l) PyRun_StringFlags(str, s, g, l,
> NULL)
> > >  >
> > >  > /* Deprecated C API functions still provided for binary compatiblity
> */
> > >  >
> > >  > #undef PyRun_String
> > >  > PyAPI_FUNC(PyObject *)
> > >  > PyRun_String(const char *str, int s, PyObject *g, PyObject *l)
> > >  > {
> > >  >        return PyRun_StringFlags(str, s, g, l, NULL);
> > >  > }
> > >  >
> > >
> > >
> > > Okay, how about this?
> http://codereview.appspot.com/1521
> > >
> > >  Using that patch, both PyString_ and PyBytes_ APIs are available using
> > >  function stubs similar to the above.  I opted to define the stub
> > >  functions right next to the ones they were stubbing rather than
> > >  putting them all at the end of the file or in another file but they
> > >  could be moved if someone doesn't like them that way.
> > >
> > >
> > >  > I still believe that we should *not* make "easy of merging" the
> > >  > primary motivation for backporting changes in 3.x to 2.x. Software
> > >  > design should not be guided by restrictions in the tool chain,
> > >  > if not absolutely necessary.
> > >  >
> > >  > The main argument for a backport needs to be general usefulness
> > >  > to the 2.x users, IMHO... just like any other feature that
> > >  > makes it into 2.x.
> > >  >
> > >  > If merging is difficult then this needs to be addressed, but
> > >  > there are more options to that than always going back to the
> > >  > original 2.x trunk code. I've given a few suggestions on how
> > >  > this could be approached in other emails on this thread.
> > >
> > >
> > > I am not the one doing the merging or working on merge tools so I'll
> > >  leave this up to those that are.
> > >
> > >  -gps
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> >
> >
> > >
> >
> >
> > --
> > Lisandro Dalcín
> > ---------------
> > Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
> > Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
> > Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
> > PTLC - Güemes 3450, (3000) Santa Fe, Argentina
> > Tel/Fax: +54-(0)342-451.1594
> >
>
>

-- 
Lisandro Dalcín
---------------
Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
PTLC - Güemes 3450, (3000) Santa Fe, Argentina
Tel/Fax: +54-(0)342-451.1594