[3.13] gh-87595: Support mmap.size() for anonymous mapping on Unix (GH-24781) by miss-islington · Pull Request #138405 · python/cpython

…thonGH-24781)

Previously, the size would be returned on Windows and an OSError would
be raised on Unix.

Also, raise ValueError instead of OSError for trackfd=False.
(cherry picked from commit 32032ee)

Co-authored-by: Zackery Spytz <zspytz@gmail.com>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

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