"""
r263026496">https://github.com/python/cpython/pull/12073/files#r263026496
"""

Oh wow, that's really strange. I'm sure that I wrote "https://..." URL but my URL became "r263026496">https://..." !?

3rd attempt to post the link:
https://github.com/python/cpython/pull/12073/files#r263026496

Anyway, my link points to my comment:

"""


PyMem_Free(m_obj->tagname) is called below without holding the GIL: that's illegal. Other move the call to free when the GIL is hold again, or use PyMem_RawFree().

"Warning: The GIL must be held when using these functions. "
https://docs.python.org/dev/c-api/memory.html#memory-interface

Note: You can use PYTHONMALLOC=debug or -X dev to reproduce the issue on a Python compiled in release mode.
"""

On the #ifdef MS_WINDOWS path of mmap_object_dealloc().