BUG: Potential memory leak in function `get_all_cast_information` (a static analyzer report)

Reproducing code example:

Static analysis results, no POC. This static analysis report has been manually verified as a real bug.

Error message:

The path provided by the static analyzer is as follows.

1. A new reference is returned from PyList_New and pointed to by result. https://github.com/numpy/numpy/blob/e49478c74282bc8f9cb86816897302724d95d5ab/numpy/core/src/multiarray/_multiarray_tests.c.src#L1031

2. Assume result is not NULL. https://github.com/numpy/numpy/blob/e49478c74282bc8f9cb86816897302724d95d5ab/numpy/core/src/multiarray/_multiarray_tests.c.src#L1032

3. Call function PyObject_CallMethod, assign return value to classes. https://github.com/numpy/numpy/blob/e49478c74282bc8f9cb86816897302724d95d5ab/numpy/core/src/multiarray/_multiarray_tests.c.src#L1035

4. Assume classes is NULL, https://github.com/numpy/numpy/blob/e49478c74282bc8f9cb86816897302724d95d5ab/numpy/core/src/multiarray/_multiarray_tests.c.src#L1037

5. Function returns without decreasing the refcnt of result. https://github.com/numpy/numpy/blob/e49478c74282bc8f9cb86816897302724d95d5ab/numpy/core/src/multiarray/_multiarray_tests.c.src#L1038

NumPy/Python version information:

Static analysis carried out on commit 04ab04d.

Internal bug report ID: NumPy-86c782

[Snape3058]

Thanks a lot. If you do not think such reports are spamming, I will submit them later in recent days in just one issue. And if there are any important reports, I will submit them in separate unique issues or PRs. Thank you again for your support of my research.

… I do not think these are particularly problematic in practice

It is the problem of static analysis. Since such a technique is good at finding bugs that usually will not be triggered. The reason why I did not report them at the very beginning is that I also thought such paths would be seldom executed. However, to make the paper reviewers believe my tool is helpful to find real bugs, I need to submit all of them.

[seberg]

Btw. in case you are manually getting out all those “steps” with links to the lines. I think it would be good enough to have only the first link and then some summary of what follows.