python / python/pythoncapi-compat

upgrade_pythoncapi.py: Wrong transformations for Py_Is

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Dominant language
C
Stars
110
Forks
39
Avg merge
8m
Merged PRs (30d)
2

Description

Consider an example:

if (((PyObject*)obj)->data == Py_None) {
    111;
}
if (Py_None == ((PyObject*)obj)->data) {
    111;
}

After upgrade_pythoncapi.py I got:

#include "pythoncapi_compat.h"

if (((PyObject*)obj)->Py_IsNone(data)) {
    111;
}
if (Py_None == ((PyObject*)obj)->data) {
    111;
}

Real world example:
https://github.com/aleaxit/gmpy/blob/eb8dfcbd84abcfcb36b4adcb0d5c6d050731dd75/src/gmpy2_xmpz_misc.c#L237

I'm not sure if this is a bug. This kind of issues is not easy to avoid, using regexps for code transformations. Have you considered to use something like the pycparser?

Thanks for the project.

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  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with upgrade_pythoncapi.py and reproduce both C examples from the issue, then compare the output with the referenced gmpy2_xmpz_misc.c case. Check whether the transformation handles both operand orders without corrupting member access; done means valid C is produced with the intended Py_IsNone transformation.

Written by the indexing model from the issue text.

Assessment

Tech stack
c, python
Domain
tooling
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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