Add a paragraph about obmalloc turning up bugs in extension modules
Mention the new ports
diff --git a/Doc/whatsnew/whatsnew21.tex b/Doc/whatsnew/whatsnew21.tex
index beca069..d54dd5b 100644
--- a/Doc/whatsnew/whatsnew21.tex
+++ b/Doc/whatsnew/whatsnew21.tex
@@ -751,8 +751,24 @@
to get large pools of memory, and then fulfills smaller memory
requests from these pools. It can be enabled by providing the
\longprogramopt{with-pymalloc} option to the \program{configure} script; see
-\file{Objects/obmalloc.c} for the implementation details.
-Contributed by Vladimir Marangozov.
+\file{Objects/obmalloc.c} for the implementation details.
+
+Authors of C extension modules should test their code with the object
+allocator enabled, because some incorrect code may break, causing core
+dumps at runtime. There are a bunch of memory allocation functions in
+Python's C API that have previously been just aliases for the C
+library's \function{malloc()} and \function{free()}, meaning that if
+you accidentally called mismatched functions, the error wouldn't be
+noticeable. When the object allocator is enabled, these functions
+aren't aliases of \function{malloc()} and \function{free()} any more,
+and calling the wrong function to free memory will get you a core
+dump. For example, if memory was allocated using
+\function{PyMem_New()}, it has to be freed using
+\function{PyMem_Del()}, not \function{free()}. A few modules included
+with Python fell afoul of this and had to be fixed; doubtless there
+are more third-party modules that will have the same problem.
+
+The object allocator was contributed by Vladimir Marangozov.
\item The speed of line-oriented file I/O has been improved because
people often complain about its lack of speed, and because it's often
@@ -827,6 +843,9 @@
\item The size of the Unicode character database was shrunk by another
340K thanks to Fredrik Lundh.
+\item Some new ports were contributed: MacOS X (by Steven Majewski),
+Cygwin (by Jason Tishler); RISCOS (by Dietmar Schwertberger).
+
\end{itemize}
And there's the usual list of minor bugfixes, minor memory leaks,