[mypyc] Make list get/set item more memory safe on free-threaded builds#21683
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p-sawicki
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Jul 6, 2026
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Use the CPython C API for list get item and set item, as direct item access is not memory safe in the presence of race conditions on a free-threaded Python.
Note that these operations are not necessarily atomic -- this only fixes memory safety. Explicit synchronization is still generally expected for correctness.
This still doesn't cover for loops over lists. I will fix them in a follow-up PR.
Preserve existing optimized primitives on non-free-threaded builds.
Work on mypyc/mypyc#1202.