Moving pymalloc along.

As threatened, PyMem_{Free, FREE} also invoke the object deallocator now
when pymalloc is enabled (well, it does when pymalloc isn't enabled too,
but in that case "the object deallocator" is plain free()).

This is maximally backward-compatible, but it leaves a bitter aftertaste.

Also massive reworking of comments.

1 files changed, 42 insertions, 37 deletions

diff --git a/Include/pymem.h b/Include/pymem.h
index 2330366f48..183dc758eb 100644
--- a/Include/pymem.h
+++ b/Include/pymem.h
@@ -1,5 +1,6 @@
-
-/* Lowest-level memory allocation interface */
+/* The PyMem_ family:  low-level memory allocation interfaces.
+   See objimpl.h for the PyObject_ memory family.
+*/
 
 #ifndef Py_PYMEM_H
 #define Py_PYMEM_H
@@ -12,37 +13,39 @@ extern "C" {
 
 /* BEWARE:
 
-   Each interface exports both functions and macros. Extension modules
-   should normally use the functions for ensuring binary compatibility
-   of the user's code across Python versions. Subsequently, if the
-   Python runtime switches to its own malloc (different from standard
-   malloc), no recompilation is required for the extensions.
-
-   The macro versions are free to trade compatibility for speed, although
-   there's no guarantee they're ever faster.  Extensions shouldn't use the
-   macro versions, as they don't gurantee binary compatibility across
-   releases.
-
-   Do not mix calls to PyMem_xyz with calls to platform
-   malloc/realloc/calloc/free. */
+   Each interface exports both functions and macros.  Extension modules should
+   use the functions, to ensure binary compatibility across Python versions.
+   Because the Python implementation is free to change internal details, and
+   the macros may (or may not) expose details for speed, if you do use the
+   macros you must recompile your extensions with each Python release.
+
+   Never mix calls to PyMem_ with calls to the platform malloc/realloc/
+   calloc/free.  For example, on Windows different DLLs may end up using
+   different heaps, and if you use PyMem_Malloc you'll get the memory from the
+   heap used by the Python DLL; it could be a disaster if you free()'ed that
+   directly in your own extension.  Using PyMem_Free instead ensures Python
+   can return the memory to the proper heap.  As another example, in
+   PYMALLOC_DEBUG mode, Python wraps all calls to all PyMem_ and PyObject_
+   memory functions in special debugging wrappers that add additional
+   debugging info to dynamic memory blocks.  The system routines have no idea
+   what to do with that stuff, and the Python wrappers have no idea what to do
+   with raw blocks obtained directly by the system routines then.
+*/
 
 /*
  * Raw memory interface
  * ====================
  */
 
-/* Functions */
+/* Functions
 
-/* Functions supplying platform-independent semantics for malloc/realloc/
-   free; useful if you need to be sure you're using the same memory
-   allocator as Python (this can be especially important on Windows, if
-   you need to make sure you're using the same MS malloc/free, and out of
-   the same heap, as the main Python DLL uses).
-   These functions make sure that allocating 0 bytes returns a distinct
+   Functions supplying platform-independent semantics for malloc/realloc/
+   free.  These functions make sure that allocating 0 bytes returns a distinct
    non-NULL pointer (whenever possible -- if we're flat out of memory, NULL
    may be returned), even if the platform malloc and realloc don't.
    Returned pointers must be checked for NULL explicitly.  No action is
-   performed on failure (no exception is set, no warning is printed, etc).` */
+   performed on failure (no exception is set, no warning is printed, etc).
+*/
 
 extern DL_IMPORT(void *) PyMem_Malloc(size_t);
 extern DL_IMPORT(void *) PyMem_Realloc(void *, size_t);
@@ -56,7 +59,6 @@ extern DL_IMPORT(void) PyMem_Free(void *);
 /* Redirect all memory operations to Python's debugging allocator. */
 #define PyMem_MALLOC		PyObject_MALLOC
 #define PyMem_REALLOC		PyObject_REALLOC
-#define PyMem_FREE		PyObject_FREE
 
 #else	/* ! PYMALLOC_DEBUG */
 
@@ -65,41 +67,44 @@ extern DL_IMPORT(void) PyMem_Free(void *);
 #else
 #define PyMem_MALLOC		malloc
 #endif
+
 /* Caution:  whether MALLOC_ZERO_RETURNS_NULL is #defined has nothing to
    do with whether platform realloc(non-NULL, 0) normally frees the memory
    or returns NULL.  Rather than introduce yet another config variation,
    just make a realloc to 0 bytes act as if to 1 instead. */
 #define PyMem_REALLOC(p, n)     realloc((p), (n) ? (n) : 1)
 
-#define PyMem_FREE           	free
 #endif	/* PYMALLOC_DEBUG */
 
+/* In order to avoid breaking old code mixing PyObject_{New, NEW} with
+   PyMem_{Del, DEL} and PyMem_{Free, FREE}, the PyMem "release memory"
+   functions have to be redirected to the object deallocator. */
+#define PyMem_FREE           	PyObject_FREE
+
 /*
  * Type-oriented memory interface
  * ==============================
  *
  * These are carried along for historical reasons.  There's rarely a good
- * reason to use them anymore.
+ * reason to use them anymore (you can just as easily do the multiply and
+ * cast yourself).
  */
 
-/* Functions */
 #define PyMem_New(type, n) \
 	( (type *) PyMem_Malloc((n) * sizeof(type)) )
-#define PyMem_Resize(p, type, n) \
-	( (p) = (type *) PyMem_Realloc((p), (n) * sizeof(type)) )
-
-/* In order to avoid breaking old code mixing PyObject_{New, NEW} with
-   PyMem_{Del, DEL} (there was no choice about this in 1.5.2), the latter
-   have to be redirected to the object allocator. */
-#define PyMem_Del  PyObject_Free
-
-/* Macros */
 #define PyMem_NEW(type, n) \
 	( (type *) PyMem_MALLOC((n) * sizeof(type)) )
+
+#define PyMem_Resize(p, type, n) \
+	( (p) = (type *) PyMem_Realloc((p), (n) * sizeof(type)) )
 #define PyMem_RESIZE(p, type, n) \
 	( (p) = (type *) PyMem_REALLOC((p), (n) * sizeof(type)) )
 
-#define PyMem_DEL PyObject_FREE
+/* In order to avoid breaking old code mixing PyObject_{New, NEW} with
+   PyMem_{Del, DEL} and PyMem_{Free, FREE}, the PyMem "release memory"
+   functions have to be redirected to the object deallocator. */
+#define PyMem_Del		PyObject_Free
+#define PyMem_DEL		PyObject_FREE
 
 #ifdef __cplusplus
 }