Tweak the description of pymalloc. Mention pymemcompat.h.

1 files changed, 34 insertions, 24 deletions

diff --git a/Doc/whatsnew/whatsnew23.tex b/Doc/whatsnew/whatsnew23.tex
index f79b882..5652797 100644
--- a/Doc/whatsnew/whatsnew23.tex
+++ b/Doc/whatsnew/whatsnew23.tex
@@ -357,9 +357,10 @@ or warnings.filterwarnings().
 An experimental feature added to Python 2.1 was a specialized object
 allocator called pymalloc, written by Vladimir Marangozov.  Pymalloc
 was intended to be faster than the system \function{malloc()} and have
-less memory overhead.  The allocator uses C's \function{malloc()}
-function to get large pools of memory, and then fulfills smaller
-memory requests from these pools.  
+less memory overhead for typical allocation patterns of Python
+programs.  The allocator uses C's \function{malloc()} function to get
+large pools of memory, and then fulfills smaller memory requests from
+these pools.
 
 In 2.1 and 2.2, pymalloc was an experimental feature and wasn't
 enabled by default; you had to explicitly turn it on by providing the
@@ -378,32 +379,34 @@ 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.
+wrong function to free memory may get you a core dump.  For example,
+if memory was allocated using \function{PyObject_Malloc()}, it has to
+be freed using \function{PyObject_Free()}, 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.
 
 As part of this change, the confusing multiple interfaces for
-allocating memory have been consolidated down into two APIs.  
-Memory allocated with one API must not be freed with the other API.
+allocating memory have been consolidated down into two API families.
+Memory allocated with one family must not be manipulated with
+functions from the other family.
+
+There is another family of functions specifically for allocating
+Python \emph{objects} (as opposed to memory).
 
 \begin{itemize}
-  \item To allocate and free an undistinguished chunk of memory using 
-  Python's allocator, use
-  \cfunction{PyMem_Malloc()}, \cfunction{PyMem_Realloc()}, and
-  \cfunction{PyMem_Free()}.
-
-  \item In rare cases you may want to avoid using Python's allocator 
-  in order to allocate a chunk of memory; 
-  use \cfunction{PyObject_Malloc}, \cfunction{PyObject_Realloc}, 
-  and \cfunction{PyObject_Free}.
-
-  \item To allocate and free Python objects,  
-  use \cfunction{PyObject_New()}, \cfunction{PyObject_NewVar()}, and 
-  \cfunction{PyObject_Del()}.
+  \item To allocate and free an undistinguished chunk of memory use
+  the ``raw memory'' family: \cfunction{PyMem_Malloc()},
+  \cfunction{PyMem_Realloc()}, and \cfunction{PyMem_Free()}.
+
+  \item The ``object memory'' family is the interface to the pymalloc
+  facility described above and is biased towards a large number of
+  ``small'' allocations: \cfunction{PyObject_Malloc},
+  \cfunction{PyObject_Realloc}, and \cfunction{PyObject_Free}.
 
+  \item To allocate and free Python objects, use the ``object'' family
+  \cfunction{PyObject_New()}, \cfunction{PyObject_NewVar()}, and
+  \cfunction{PyObject_Del()}.
 \end{itemize}
 
 Thanks to lots of work by Tim Peters, pymalloc in 2.3 also provides
@@ -412,6 +415,13 @@ both extension modules and in the interpreter itself.  To enable this
 support, turn on the Python interpreter's debugging code by running
 \program{configure} with \longprogramopt{with-pydebug}.  
 
+To aid extension writers, a header file \file{Misc/pymemcompat.h} is
+distributed with the source to Python 2.3 that allows Python
+extensions to use the 2.3 interfaces to memory allocation and compile
+against any version of Python since 1.5.2.  (The idea is that you take
+the file from Python's source distribution and bundle it with the
+source of you extension).
+
 \begin{seealso}
 
 \seeurl{http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/python/python/dist/src/Objects/obmalloc.c}