LeakSanitizer detects memory leaks in test_import with _testsinglephase module in subinterpreter

Bug report

Bug description:

LeakSanitizer detects memory leaks when running test_import with the _testsinglephase module loaded in a subinterpreter.

How to Reproduce

Build:

CC=clang CXX=clang++ ./configure --disable-optimizations --with-pydebug --with-address-sanitizer && make -j$(nproc)

Run:

./python -X dev -X showrefcount -m test test_import -j0

Leak Summary

==643791==ERROR: LeakSanitizer: detected memory leaks
SUMMARY: AddressSanitizer: 6709 byte(s) leaked in 45 allocation(s).

Code Locations

The leaks originate from:

Subinterpreter execution:

• https://github.com/python/cpython/blob/e8e0f411bae1dde634fb152a81e1db1ad1cd2eaa/Modules/_testcapimodule.c#L1223
  (run_in_subinterp)

Module initialization:

• https://github.com/python/cpython/blob/e8e0f411bae1dde634fb152a81e1db1ad1cd2eaa/Modules/_testsinglephase.c#L516
  (init__testsinglephase_basic)
• https://github.com/python/cpython/blob/e8e0f411bae1dde634fb152a81e1db1ad1cd2eaa/Modules/_testsinglephase.c#L303
  (init_state with PyErr_NewException)

Import machinery:

• https://github.com/python/cpython/blob/e8e0f411bae1dde634fb152a81e1db1ad1cd2eaa/Python/importdl.c#L429
  (_PyImport_RunModInitFunc)

Leaked Objects

• Type objects (1016 bytes × 2): via type_new → PyErr_NewException
• Dictionary keys (424 bytes × 2): via new_keys_object → PyDict_SetItemString
• PyCMethod objects (384 bytes × 2 groups): via PyModule_AddFunctions
• Additional: Unicode strings, tuples, dictionaries

Full Output

See attached .log files for complete LeakSanitizer output for each version.

312.log
313.log
314.log
main.log

CPython versions tested on:

3.12, 3.13, 3.14, 3.15, CPython main branch

Operating systems tested on:

Linux

Reproduce the leak with the documented ASan build and ./python -X dev -X showrefcount -m test test_import -j0. Then inspect Modules/_testcapimodule.c (run_in_subinterp), Modules/_testsinglephase.c (init__testsinglephase_basic and init_state), and Python/importdl.c (_PyImport_RunModInitFunc). Done means the test completes without LeakSanitizer reporting the listed leaks.