Index: Python/getargs.c
===================================================================
--- Python/getargs.c	(révision 81783)
+++ Python/getargs.c	(copie de travail)
@@ -1311,13 +1311,16 @@
         int temp=-1;
         Py_buffer view;
 
-        if (pb && pb->bf_releasebuffer && *format != '*')
-            /* Buffer must be released, yet caller does not use
-               the Py_buffer protocol. */
-            return converterr("pinned buffer", arg, msgbuf, bufsize);
+        if (*format++ != '*' && *format++ != '#')
+            return converterr(
+                "invalid use of 'w' format character",
+                arg, msgbuf, bufsize);
 
+        if (pb == NULL || pb->bf_getbuffer == NULL)
+            return converterr("single-segment read-write buffer",
+                              arg, msgbuf, bufsize);
 
-        if (pb && pb->bf_getbuffer && *format == '*') {
+        if (*format == '*') {
             /* Caller is interested in Py_buffer, and the object
                supports it directly. */
             format++;
@@ -1332,29 +1335,28 @@
             }
             if (!PyBuffer_IsContiguous((Py_buffer*)p, 'C'))
                 return converterr("contiguous buffer", arg, msgbuf, bufsize);
-            break;
-        }
+        } else /* if (*format == '#') */ {
+            if (pb->bf_releasebuffer)
+                /* Buffer must be released, yet caller does not use
+                   the Py_buffer protocol. */
+                return converterr("pinned buffer", arg, msgbuf, bufsize);
 
-        /* Here we have processed w*, only w and w# remain. */
-        if (pb == NULL ||
-            pb->bf_getbuffer == NULL ||
-            ((temp = PyObject_GetBuffer(arg, &view,
-                                        PyBUF_SIMPLE)) != 0) ||
-            view.readonly == 1) {
-            if (temp==0) {
-                PyBuffer_Release(&view);
+            format++;
+            temp = PyObject_GetBuffer(arg, &view, PyBUF_SIMPLE);
+            if (temp != 0 || view.readonly == 1) {
+                if (temp==0)
+                    PyBuffer_Release(&view);
+                return converterr("single-segment read-write buffer",
+                                  arg, msgbuf, bufsize);
             }
-            return converterr("single-segment read-write buffer",
-                              arg, msgbuf, bufsize);
-        }
 
-        if ((count = view.len) < 0)
-            return converterr("(unspecified)", arg, msgbuf, bufsize);
-        *p = view.buf;
-        if (*format == '#') {
+            count = view.len;
+            if (count < 0)
+                return converterr("(unspecified)", arg, msgbuf, bufsize);
+            *p = view.buf;
+
             FETCH_SIZE;
             STORE_SIZE(count);
-            format++;
         }
         break;
     }
Index: Doc/c-api/arg.rst
===================================================================
--- Doc/c-api/arg.rst	(révision 81783)
+++ Doc/c-api/arg.rst	(copie de travail)
@@ -156,21 +156,17 @@
    single-segment buffer objects are accepted; :exc:`TypeError` is raised for all
    others.
 
-``w`` (read-write character buffer) [char \*]
-   Similar to ``s``, but accepts any object which implements the read-write buffer
-   interface.  The caller must determine the length of the buffer by other means,
-   or use ``w#`` instead.  Only single-segment buffer objects are accepted;
-   :exc:`TypeError` is raised for all others.
-
 ``w*`` (read-write byte-oriented buffer) [Py_buffer]
-   This is to ``w`` what ``s*`` is to ``s``.
+   This format accepts any object which implements the read-write buffer
+   interface. It fills a :ctype:`Py_buffer` structure provided by the caller.
+   The buffer may contain embedded null bytes.
 
 ``w#`` (read-write character buffer) [char \*, int]
-   Like ``s#``, but accepts any object which implements the read-write buffer
-   interface.  The :ctype:`char \*` variable is set to point to the first byte
-   of the buffer, and the :ctype:`int` is set to the length of the buffer.
-   Only single-segment buffer objects are accepted; :exc:`TypeError` is raised
-   for all others.
+   Like ``w*``, except that it doesn't accept mutable buffer-like objects such
+   as :class:`bytearray`. The :ctype:`char \*` variable is set to point to the
+   first byte of the buffer, and the :ctype:`int` is set to the length of the
+   buffer. Only single-segment buffer objects are accepted; :exc:`TypeError`
+   is raised for all others. The buffer may contain embedded null bytes.
 
 ``es`` (string, Unicode object or character buffer compatible object) [const char \*encoding, char \*\*buffer]
    This variant on ``s`` is used for encoding Unicode and objects convertible to
Index: Doc/whatsnew/3.2.rst
===================================================================
--- Doc/whatsnew/3.2.rst	(révision 81783)
+++ Doc/whatsnew/3.2.rst	(copie de travail)
@@ -173,4 +173,7 @@
 
 * bytearray objects cannot be used anymore as filenames: convert them to bytes
 
+* PyArg_ParseTuple(): remove "w" format because the caller doesn't know the
+  buffer size. Use "w*" or "w#" format instead.
+
 * Stub