Python 3.12 is leaky and python3-debug crashes on assertions

[jiridanek]

We test skrouterd binary (which embeds Python) with Address Sanitizer. To detect leaks in the router code, it is best when Python does not leak. Sadly, in Python 3.12 there appeared quite a number of leaks

• Leaks on Python's standard library at runtime shutdown python/cpython#100911

this has a quick command to visualize leaks

$ python3-debug -X showrefcount -c 'import ctypes'
[1670 refs, 1210 blocks]

• Memory leak on executables embedded with 3.12 and later python/cpython#113055
• python3.12 introduces numerous memory leaks (as reported by ASAN) python/cpython#113190 (comment)
• sub-interpreters: significant memory leak on shutdown python/cpython#110411 (comment)
• memory leak in _PyPathConfig_UpdateGlobal python/cpython#113442

In previous versions of python, setting PYTHONMALLOC="malloc_debug" used to make it stop leaking (as reported by asan).

Wanting to use python3-debug, I found that the version currently in Fedora 39 crashes due to

• Crashes and errors in test_embed with PYTHONUOPS=1 python/cpython#111339

and I also saw this, it has been tamed somewhat now so it only prints scary messages and does not crash

• 3.12.0b2: "Assertion failed: immortal object has less refcnt than expected _Py_IMMORTAL_REFCNT" python/cpython#105587

and this, when changing PYTHONMALLOC to either malloc or pymalloc

• Possible heap-use-after-free in ctypes in Python 3.12 python/cpython#113576