[Python-checkins] gh-96997: Clarify the contract of PyMem_SetAllocator() (GH-98977)
miss-islington
webhook-mailer at python.org
Wed Nov 2 17:56:20 EDT 2022
https://github.com/python/cpython/commit/6cf30c6cc464c428f454038b80c084d13475730d
commit: 6cf30c6cc464c428f454038b80c084d13475730d
branch: 3.10
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: miss-islington <31488909+miss-islington at users.noreply.github.com>
date: 2022-11-02T14:56:14-07:00
summary:
gh-96997: Clarify the contract of PyMem_SetAllocator() (GH-98977)
(cherry picked from commit c053284e3930027847d5adf99efcb1aa5ccbacd1)
Co-authored-by: Pablo Galindo Salgado <Pablogsal at gmail.com>
files:
M Doc/c-api/memory.rst
diff --git a/Doc/c-api/memory.rst b/Doc/c-api/memory.rst
index 1372dc45d782..046719c3790f 100644
--- a/Doc/c-api/memory.rst
+++ b/Doc/c-api/memory.rst
@@ -95,6 +95,8 @@ for the I/O buffer escapes completely the Python memory manager.
Allocator Domains
=================
+.. _allocator-domains:
+
All allocating functions belong to one of three different "domains" (see also
:c:type:`PyMemAllocatorDomain`). These domains represent different allocation
strategies and are optimized for different purposes. The specific details on
@@ -477,6 +479,25 @@ Customize Memory Allocators
debug hooks on top on the new allocator.
+ .. warning::
+
+ :c:func:`PyMem_SetAllocator` does have the following contract:
+
+ * It can be called after :c:func:`Py_PreInitialize` and before
+ :c:func:`Py_InitializeFromConfig` to install a custom memory
+ allocator. There are no restrictions over the installed allocator
+ other than the ones imposed by the domain (for instance, the Raw
+ Domain allows the allocator to be called without the GIL held). See
+ :ref:`the section on allocator domains <allocator-domains>` for more
+ information.
+
+ * If called after Python has finish initializing (after
+ :c:func:`Py_InitializeFromConfig` has been called) the allocator
+ **must** wrap the existing allocator. Substituting the current
+ allocator for some other arbitrary one is **not supported**.
+
+
+
.. c:function:: void PyMem_SetupDebugHooks(void)
Setup :ref:`debug hooks in the Python memory allocators <pymem-debug-hooks>`
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