From 2fbada87f45985bb3e1ac7ec3f95d07d2f87c58b Mon Sep 17 00:00:00 2001
From: Petr Viktorin <encukou@gmail.com>
Date: Fri, 6 Jun 2025 16:51:40 +0200
Subject: [PATCH] gh-57089: Note _layout_ in the bitfield docs (GH-134148)

(cherry picked from commit b22b964a5c245e13ae0439c5efbb8984acf607ab)

Co-authored-by: Petr Viktorin <encukou@gmail.com>
Co-authored-by: Meador Inge <meadori@gmail.com>
Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>
---
 Doc/library/ctypes.rst | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/Doc/library/ctypes.rst b/Doc/library/ctypes.rst
index 8e74c6c9dee744..2ee4450698a107 100644
--- a/Doc/library/ctypes.rst
+++ b/Doc/library/ctypes.rst
@@ -714,10 +714,16 @@ item in the :attr:`~Structure._fields_` tuples::
    ...                 ("second_16", c_int, 16)]
    ...
    >>> print(Int.first_16)
-   <Field type=c_long, ofs=0:0, bits=16>
+   <ctypes.CField 'first_16' type=c_int, ofs=0, bit_size=16, bit_offset=0>
    >>> print(Int.second_16)
-   <Field type=c_long, ofs=0:16, bits=16>
-   >>>
+   <ctypes.CField 'second_16' type=c_int, ofs=0, bit_size=16, bit_offset=16>
+
+It is important to note that bit field allocation and layout in memory are not
+defined as a C standard; their implementation is compiler-specific.
+By default, Python will attempt to match the behavior of a "native" compiler
+for the current platform.
+See the :attr:`~Structure._layout_` attribute for details on the default
+behavior and how to change it.
 
 
 .. _ctypes-arrays: