bpo-2122: Make mmap.flush() behave same on all platforms (GH-8692)

Previously, its behavior was platform-dependent and there was no error checking
under Windows.

2 files changed, 13 insertions, 4 deletions

diff --git a/Doc/library/mmap.rst b/Doc/library/mmap.rst
index ca09a6a..c8ae7a6 100644
--- a/Doc/library/mmap.rst
+++ b/Doc/library/mmap.rst
@@ -191,11 +191,13 @@ To map anonymous memory, -1 should be passed as the fileno along with the length
       changes to the given range of bytes will be flushed to disk; otherwise, the
       whole extent of the mapping is flushed.
 
-      **(Windows version)** A nonzero value returned indicates success; zero
-      indicates failure.
+      ``None`` is returned to indicate success.  An exception is raised when the
+      call failed.
 
-      **(Unix version)** A zero value is returned to indicate success. An
-      exception is raised when the call failed.
+      .. versionchanged:: 3.8
+         Previously, a nonzero value was returned on success; zero was returned
+         on error under Windows.  A zero value was returned on success; an
+         exception was raised on error under Unix.
 
 
    .. method:: move(dest, src, count)
diff --git a/Doc/whatsnew/3.8.rst b/Doc/whatsnew/3.8.rst
index 1f816a1..d07896b 100644
--- a/Doc/whatsnew/3.8.rst
+++ b/Doc/whatsnew/3.8.rst
@@ -265,6 +265,13 @@ Changes in the Python API
   task name is visible in the ``repr()`` output of :class:`asyncio.Task` and
   can also be retrieved using the :meth:`~asyncio.Task.get_name` method.
 
+* The :meth:`mmap.flush() <mmap.mmap.flush>` method now returns ``None`` on
+  success and raises an exception on error under all platforms.  Previously,
+  its behavior was platform-depended: a nonzero value was returned on success;
+  zero was returned on error under Windows.  A zero value was returned on
+  success; an exception was raised on error under Unix.
+  (Contributed by Berker Peksag in :issue:`2122`.)
+
 
 CPython bytecode changes
 ------------------------