Issue #12102: Merge with 3.2.
diff --git a/Doc/ACKS.txt b/Doc/ACKS.txt
index e68826c..433c9ee 100644
--- a/Doc/ACKS.txt
+++ b/Doc/ACKS.txt
@@ -144,6 +144,7 @@
* Sjoerd Mullender
* Dale Nagata
* Michal Nowikowski
+ * Steffen Daode Nurpmeso
* Ng Pheng Siong
* Koray Oner
* Tomas Oppelstrup
diff --git a/Doc/library/mmap.rst b/Doc/library/mmap.rst
index 7708028..1598cb8 100644
--- a/Doc/library/mmap.rst
+++ b/Doc/library/mmap.rst
@@ -21,6 +21,12 @@
:func:`os.open` function, which returns a file descriptor directly (the file
still needs to be closed when done).
+.. note::
+ If you want to create a memory-mapping for a writable, buffered file, you
+ should :func:`~io.IOBase.flush` the file first. This is necessary to ensure
+ that local modifications to the buffers are actually available to the
+ mapping.
+
For both the Unix and Windows versions of the constructor, *access* may be
specified as an optional keyword parameter. *access* accepts one of three
values: :const:`ACCESS_READ`, :const:`ACCESS_WRITE`, or :const:`ACCESS_COPY`
diff --git a/Misc/NEWS b/Misc/NEWS
index 5d7f59f..c740b20 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -237,6 +237,9 @@
Library
-------
+- Issue #12102: Document that buffered files must be flushed before being used
+ with mmap. Patch by Steffen Daode Nurpmeso.
+
- Issue #12560: Build libpython.so on OpenBSD. Patch by Stefan Sperling.
- Issue #1813: Fix codec lookup under Turkish locales.