[Python-3000] [Python-Dev] Stabilizing the C API of 2.6 and 3.0 (original) (raw)

M.-A. Lemburg mal at egenix.com
Wed May 28 12:12:27 CEST 2008

I'm beginning to wonder whether I'm the only one who cares about the Python 2.x branch not getting cluttered up with artifacts caused by a broken forward merge strategy.

How can it be that we allow major C API changes such as the renaming of the PyString APIs to go into the trunk without discussion or a PEP ?

We're having lengthy discussions about the addition of single method to an object, but such major changes just go in like that and nobody seems to really care.

Puzzled,

Marc-Andre Lemburg eGenix.com

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On 2008-05-27 12:10, M.-A. Lemburg wrote:

On 2008-05-26 23:34, Christian Heimes wrote:

M.-A. Lemburg schrieb:

Isn't that an awefuly confusing approach ?

Wouldn't it be better to keep PyString APIs and definitions in stringobject.c|h and only add a new bytesobject.h header file that #defines the PyBytes APIs in terms of PyString APIs ? That maintains backwards compatibility and allows Python internals to use the new API names. With your approach, you've basically backported the confusing notion in Py3k that str() maps PyUnicode, only that in Py2 str() will now map to PyBytes. The last time I brought up the topic, I had a lengthy discussion with Guido. At first I wanted to rename the API in Python 3.0 only. Guido argued that it's going to cause too much merge conflicts. He then suggested the approach I implemented today. That's the same argument that came up in the module renaming discussion. I have a feeling that we should be looking for better merge tools, rather than implement code changes that cause more trouble than do good, just because our existing tools aren't smart enough. Wouldn't it be possible to have a 2to3.py converter take the 2.x code (including the C code), convert it and then apply any changes to the 3.x branch ? This wouldn't be merging in the classical sense, it would be automated forward porting. I find the approach less confusing than your suggestion and my initial idea. I disagree on that. Renaming old APIs to use the new names by adding a header file with #define is standard practice. Renaming the old APIs in the source code and undoing the renaming with a header file is not. The internal API names are consistent for Python 2.6 and 3.0. The byte string C API is prefixed PyBytes and the unicode C API is prefixed PyUnicode. A core developer has just to remember that 'str' is a byte string in 2.x but an unicode object in 3.0. So you've solved part of the problem for 3.x by moving the naming mixup back to 2.x. Extension developers don't have to worry at all. The ABI and external API is mostly the same and still exposes the 'str' functions as PyString. Well, yes, but only due to a preprocessor hack that turns the names used in bytesobject.c back into names you'd normally look for in stringobject.c. And all this, just because Subversion can't handle merging of symbol renaming. You'd have to add an aliase bytes -> str to the builtins to at least reduce the confusion a bit. Python 2.6 already has an alias bytes -> str Yes, but please let's first discuss this some more. I don't think that the timing was right.... you started this thread just yesterday and the patches are already checked in. I'm sorry if I was too hasty for you. I got +1 from a couple of developers and it's basically Guido's suggestion. Please discuss any changes of the 2.x code base on python-dev. Such major changes do need more discussion and possibly a PEP as well. Thanks,

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