[Python-Dev] Tagged integers (original) (raw)

Phillip J. Eby pje at telecommunity.com
Fri Jul 16 06:08:22 CEST 2004

At 01:41 PM 7/16/04 +1200, Greg Ewing wrote:

James Y Knight <foom at fuhm.net>:

> The only thing you can do with an arbitrary PyObject * is access its > obtype or obrefcnt. Anything else will break with objects today. One other thing that would break is testing whether an object is an integer and then accessing fields of the integer object directly. Not that this seems a likely thing for people to do, though.

I guess we'd need to XXX-ify ob_ival as well, then. There's already a PyInt_AS_LONG macro that should be used for that purpose.

So far, the -1000 from Guido makes it seem unlikely this'll get accepted, though.

I am sort of curious, though, as to how many extension modules would actually require changes to support this. A bit of grepping through the source of several I use, seems to indicate that it isn't that common to use ob_type, and it's most likely to appear:

  1. in the setup of a type object, setting the type's type to type :) (by far the most common, and not a usage that needs to be changed)

  2. in the definition of a macro that verifies the type of an extension object

  3. in allocation/deallocation routines

Only uses 2 and 3 would need to be changed, and they tend to be quite isolated.

By contrast, I didn't find any ob_ival uses, and the only place I saw direct use of ob_refcnt was in some Pyrex-generated tp_dealloc code.

Of course, my sampling was hardly statistically valid. I imagine the real extensions to check out would be things like SciPy, Numeric, PIL, wxPython, Boost::Python, win32all, PyCrytpo, etc. That is, widely used packages of very large size.

If I understand correctly, extensions have to be recompiled to move between Python versions anyway, and compared to some previous C API changes, this one actually seems pretty minor. Extensions like 'kjbuckets' that were written for early 1.x Python versions definitely needed work to make them build with the later 1.x and 2.x versions.

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