CPython current temporarily changes `PYMEM_DOMAIN_RAW` to the default allocator during initialization and shutdown. The motivation is to ensure that core runtime structures are allocated and freed using the same allocator. However, modifying the current allocator changes global state and is not thread-safe even with the GIL. Other threads may be allocating or freeing objects use PYMEM_DOMAIN_RAW; they are not required to hold the GIL to call PyMem_RawMalloc/PyMem_RawFree. This adds new internal-only functions like `_PyMem_DefaultRawMalloc` that aren't affected by calls to `PyMem_SetAllocator()`, so they're appropriate for Python runtime initialization and finalization. Use these calls in places where we previously swapped to the default raw allocator.
The Python C API ================ The C API is divided into these sections: 1. ``Include/``: Limited API 2. ``Include/cpython/``: CPython implementation details 3. ``Include/cpython/``, names with the ``PyUnstable_`` prefix: API that can change between minor releases 4. ``Include/internal/``, and any name with ``_`` prefix: The internal API Information on changing the C API is available `in the developer guide`_ .. _in the developer guide: https://devguide.python.org/c-api/