pymem.h revision 9c74b14fe9b6dddc9d41dd37f431f174350004d4 
1/* The PyMem_ family:  low-level memory allocation interfaces.
2   See objimpl.h for the PyObject_ memory family.
3*/
4
5#ifndef Py_PYMEM_H
6#define Py_PYMEM_H
7
8#include "pyport.h"
9
10#ifdef __cplusplus
11extern "C" {
12#endif
13
14/* BEWARE:
15
16   Each interface exports both functions and macros.  Extension modules should
17   use the functions, to ensure binary compatibility across Python versions.
18   Because the Python implementation is free to change internal details, and
19   the macros may (or may not) expose details for speed, if you do use the
20   macros you must recompile your extensions with each Python release.
21
22   Never mix calls to PyMem_ with calls to the platform malloc/realloc/
23   calloc/free.  For example, on Windows different DLLs may end up using
24   different heaps, and if you use PyMem_Malloc you'll get the memory from the
25   heap used by the Python DLL; it could be a disaster if you free()'ed that
26   directly in your own extension.  Using PyMem_Free instead ensures Python
27   can return the memory to the proper heap.  As another example, in
28   PYMALLOC_DEBUG mode, Python wraps all calls to all PyMem_ and PyObject_
29   memory functions in special debugging wrappers that add additional
30   debugging info to dynamic memory blocks.  The system routines have no idea
31   what to do with that stuff, and the Python wrappers have no idea what to do
32   with raw blocks obtained directly by the system routines then.
33
34   The GIL must be held when using these APIs.
35*/
36
37/*
38 * Raw memory interface
39 * ====================
40 */
41
42/* Functions
43
44   Functions supplying platform-independent semantics for malloc/realloc/
45   free.  These functions make sure that allocating 0 bytes returns a distinct
46   non-NULL pointer (whenever possible -- if we're flat out of memory, NULL
47   may be returned), even if the platform malloc and realloc don't.
48   Returned pointers must be checked for NULL explicitly.  No action is
49   performed on failure (no exception is set, no warning is printed, etc).
50*/
51
52PyAPI_FUNC(void *) PyMem_Malloc(size_t);
53PyAPI_FUNC(void *) PyMem_Realloc(void *, size_t);
54PyAPI_FUNC(void) PyMem_Free(void *);
55
56/* Starting from Python 1.6, the wrappers Py_{Malloc,Realloc,Free} are
57   no longer supported. They used to call PyErr_NoMemory() on failure. */
58
59/* Macros. */
60#ifdef PYMALLOC_DEBUG
61/* Redirect all memory operations to Python's debugging allocator. */
62#define PyMem_MALLOC		PyObject_MALLOC
63#define PyMem_REALLOC		PyObject_REALLOC
64#define PyMem_FREE		PyObject_FREE
65
66#else	/* ! PYMALLOC_DEBUG */
67
68/* PyMem_MALLOC(0) means malloc(1). Some systems would return NULL
69   for malloc(0), which would be treated as an error. Some platforms
70   would return a pointer with no memory behind it, which would break
71   pymalloc. To solve these problems, allocate an extra byte. */
72#define PyMem_MALLOC(n)         malloc((n) ? (n) : 1)
73#define PyMem_REALLOC(p, n)     realloc((p), (n) ? (n) : 1)
74#define PyMem_FREE		free
75
76#endif	/* PYMALLOC_DEBUG */
77
78/*
79 * Type-oriented memory interface
80 * ==============================
81 *
82 * These are carried along for historical reasons.  There's rarely a good
83 * reason to use them anymore (you can just as easily do the multiply and
84 * cast yourself).
85 */
86
87#define PyMem_New(type, n) \
88  ( assert((n) <= PY_SIZE_MAX / sizeof(type)) , \
89	( (type *) PyMem_Malloc((n) * sizeof(type)) ) )
90#define PyMem_NEW(type, n) \
91  ( assert((n) <= PY_SIZE_MAX / sizeof(type)) , \
92	( (type *) PyMem_MALLOC((n) * sizeof(type)) ) )
93
94#define PyMem_Resize(p, type, n) \
95  ( assert((n) <= PY_SIZE_MAX / sizeof(type)) , \
96	( (p) = (type *) PyMem_Realloc((p), (n) * sizeof(type)) ) )
97#define PyMem_RESIZE(p, type, n) \
98  ( assert((n) <= PY_SIZE_MAX / sizeof(type)) , \
99	( (p) = (type *) PyMem_REALLOC((p), (n) * sizeof(type)) ) )
100
101/* PyMem{Del,DEL} are left over from ancient days, and shouldn't be used
102 * anymore.  They're just confusing aliases for PyMem_{Free,FREE} now.
103 */
104#define PyMem_Del		PyMem_Free
105#define PyMem_DEL		PyMem_FREE
106
107#ifdef __cplusplus
108}
109#endif
110
111#endif /* !Py_PYMEM_H */
112