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gh-105766: Document that Custom Allocators Must Be Thread-Safe #107519

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Jul 31, 2023
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gh-105766: Document that Custom Allocators Must Be Thread-Safe #107519

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e6d16ca
Document that custom allocators must be thread-safe.
ericsnowcurrently Jul 31, 2023
c268cf2
Add a What's New entry.
ericsnowcurrently Jul 31, 2023
c2c7735
Fix a typo.
ericsnowcurrently Jul 31, 2023
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6 changes: 6 additions & 0 deletions Doc/c-api/memory.rst
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Expand Up @@ -476,6 +476,10 @@ Customize Memory Allocators
thread-safe: the :term:`GIL <global interpreter lock>` is not held when the
allocator is called.

For the remaining domains, the allocator must also be thread-safe:
the allocator may be called in different interpreters that do not
share a ``GIL``.

If the new allocator is not a hook (does not call the previous allocator),
the :c:func:`PyMem_SetupDebugHooks` function must be called to reinstall the
debug hooks on top on the new allocator.
Expand All @@ -500,6 +504,8 @@ Customize Memory Allocators
**must** wrap the existing allocator. Substituting the current
allocator for some other arbitrary one is **not supported**.

.. versionchanged:: 3.12
All allocators must be thread-safe.


.. c:function:: void PyMem_SetupDebugHooks(void)
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7 changes: 7 additions & 0 deletions Doc/whatsnew/3.12.rst
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Expand Up @@ -1876,6 +1876,13 @@ Porting to Python 3.12
* :c:func:`PyUnstable_Long_IsCompact`
* :c:func:`PyUnstable_Long_CompactValue`

* Custom allocators, set via :c:func:`PyMem_SetAllocator`, are now
required to be thread-safe, regardless of memory domain. Allocators
that don't have their own state, including "hooks", are not affected.
If your custom allocator is not already thread-safe and you need
guidance then please create a new GitHub issue
and CC ``@ericsnowcurrently``.

Deprecated
----------

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