source: python/vendor/Python-2.6.5/Include/objimpl.h

Last change on this file was 2, checked in by Yuri Dario, 15 years ago

Initial import for vendor code.
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1/* The PyObject_ memory family: high-level object memory interfaces.
2 See pymem.h for the low-level PyMem_ family.
3*/
4
5#ifndef Py_OBJIMPL_H
6#define Py_OBJIMPL_H
7
8#include "pymem.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 PyObject_ memory functions with calls to the platform
23 malloc/realloc/ calloc/free, or with calls to PyMem_.
24*/
25
26/*
27Functions and macros for modules that implement new object types.
28
29 - PyObject_New(type, typeobj) allocates memory for a new object of the given
30 type, and initializes part of it. 'type' must be the C structure type used
31 to represent the object, and 'typeobj' the address of the corresponding
32 type object. Reference count and type pointer are filled in; the rest of
33 the bytes of the object are *undefined*! The resulting expression type is
34 'type *'. The size of the object is determined by the tp_basicsize field
35 of the type object.
36
37 - PyObject_NewVar(type, typeobj, n) is similar but allocates a variable-size
38 object with room for n items. In addition to the refcount and type pointer
39 fields, this also fills in the ob_size field.
40
41 - PyObject_Del(op) releases the memory allocated for an object. It does not
42 run a destructor -- it only frees the memory. PyObject_Free is identical.
43
44 - PyObject_Init(op, typeobj) and PyObject_InitVar(op, typeobj, n) don't
45 allocate memory. Instead of a 'type' parameter, they take a pointer to a
46 new object (allocated by an arbitrary allocator), and initialize its object
47 header fields.
48
49Note that objects created with PyObject_{New, NewVar} are allocated using the
50specialized Python allocator (implemented in obmalloc.c), if WITH_PYMALLOC is
51enabled. In addition, a special debugging allocator is used if PYMALLOC_DEBUG
52is also #defined.
53
54In case a specific form of memory management is needed (for example, if you
55must use the platform malloc heap(s), or shared memory, or C++ local storage or
56operator new), you must first allocate the object with your custom allocator,
57then pass its pointer to PyObject_{Init, InitVar} for filling in its Python-
58specific fields: reference count, type pointer, possibly others. You should
59be aware that Python no control over these objects because they don't
60cooperate with the Python memory manager. Such objects may not be eligible
61for automatic garbage collection and you have to make sure that they are
62released accordingly whenever their destructor gets called (cf. the specific
63form of memory management you're using).
64
65Unless you have specific memory management requirements, use
66PyObject_{New, NewVar, Del}.
67*/
68
69/*
70 * Raw object memory interface
71 * ===========================
72 */
73
74/* Functions to call the same malloc/realloc/free as used by Python's
75 object allocator. If WITH_PYMALLOC is enabled, these may differ from
76 the platform malloc/realloc/free. The Python object allocator is
77 designed for fast, cache-conscious allocation of many "small" objects,
78 and with low hidden memory overhead.
79
80 PyObject_Malloc(0) returns a unique non-NULL pointer if possible.
81
82 PyObject_Realloc(NULL, n) acts like PyObject_Malloc(n).
83 PyObject_Realloc(p != NULL, 0) does not return NULL, or free the memory
84 at p.
85
86 Returned pointers must be checked for NULL explicitly; no action is
87 performed on failure other than to return NULL (no warning it printed, no
88 exception is set, etc).
89
90 For allocating objects, use PyObject_{New, NewVar} instead whenever
91 possible. The PyObject_{Malloc, Realloc, Free} family is exposed
92 so that you can exploit Python's small-block allocator for non-object
93 uses. If you must use these routines to allocate object memory, make sure
94 the object gets initialized via PyObject_{Init, InitVar} after obtaining
95 the raw memory.
96*/
97PyAPI_FUNC(void *) PyObject_Malloc(size_t);
98PyAPI_FUNC(void *) PyObject_Realloc(void *, size_t);
99PyAPI_FUNC(void) PyObject_Free(void *);
100
101
102/* Macros */
103#ifdef WITH_PYMALLOC
104#ifdef PYMALLOC_DEBUG /* WITH_PYMALLOC && PYMALLOC_DEBUG */
105PyAPI_FUNC(void *) _PyObject_DebugMalloc(size_t nbytes);
106PyAPI_FUNC(void *) _PyObject_DebugRealloc(void *p, size_t nbytes);
107PyAPI_FUNC(void) _PyObject_DebugFree(void *p);
108PyAPI_FUNC(void) _PyObject_DebugDumpAddress(const void *p);
109PyAPI_FUNC(void) _PyObject_DebugCheckAddress(const void *p);
110PyAPI_FUNC(void) _PyObject_DebugMallocStats(void);
111#define PyObject_MALLOC _PyObject_DebugMalloc
112#define PyObject_Malloc _PyObject_DebugMalloc
113#define PyObject_REALLOC _PyObject_DebugRealloc
114#define PyObject_Realloc _PyObject_DebugRealloc
115#define PyObject_FREE _PyObject_DebugFree
116#define PyObject_Free _PyObject_DebugFree
117
118#else /* WITH_PYMALLOC && ! PYMALLOC_DEBUG */
119#define PyObject_MALLOC PyObject_Malloc
120#define PyObject_REALLOC PyObject_Realloc
121#define PyObject_FREE PyObject_Free
122#endif
123
124#else /* ! WITH_PYMALLOC */
125#define PyObject_MALLOC PyMem_MALLOC
126#define PyObject_REALLOC PyMem_REALLOC
127#define PyObject_FREE PyMem_FREE
128
129#endif /* WITH_PYMALLOC */
130
131#define PyObject_Del PyObject_Free
132#define PyObject_DEL PyObject_FREE
133
134/* for source compatibility with 2.2 */
135#define _PyObject_Del PyObject_Free
136
137/*
138 * Generic object allocator interface
139 * ==================================
140 */
141
142/* Functions */
143PyAPI_FUNC(PyObject *) PyObject_Init(PyObject *, PyTypeObject *);
144PyAPI_FUNC(PyVarObject *) PyObject_InitVar(PyVarObject *,
145 PyTypeObject *, Py_ssize_t);
146PyAPI_FUNC(PyObject *) _PyObject_New(PyTypeObject *);
147PyAPI_FUNC(PyVarObject *) _PyObject_NewVar(PyTypeObject *, Py_ssize_t);
148
149#define PyObject_New(type, typeobj) \
150 ( (type *) _PyObject_New(typeobj) )
151#define PyObject_NewVar(type, typeobj, n) \
152 ( (type *) _PyObject_NewVar((typeobj), (n)) )
153
154/* Macros trading binary compatibility for speed. See also pymem.h.
155 Note that these macros expect non-NULL object pointers.*/
156#define PyObject_INIT(op, typeobj) \
157 ( Py_TYPE(op) = (typeobj), _Py_NewReference((PyObject *)(op)), (op) )
158#define PyObject_INIT_VAR(op, typeobj, size) \
159 ( Py_SIZE(op) = (size), PyObject_INIT((op), (typeobj)) )
160
161#define _PyObject_SIZE(typeobj) ( (typeobj)->tp_basicsize )
162
163/* _PyObject_VAR_SIZE returns the number of bytes (as size_t) allocated for a
164 vrbl-size object with nitems items, exclusive of gc overhead (if any). The
165 value is rounded up to the closest multiple of sizeof(void *), in order to
166 ensure that pointer fields at the end of the object are correctly aligned
167 for the platform (this is of special importance for subclasses of, e.g.,
168 str or long, so that pointers can be stored after the embedded data).
169
170 Note that there's no memory wastage in doing this, as malloc has to
171 return (at worst) pointer-aligned memory anyway.
172*/
173#if ((SIZEOF_VOID_P - 1) & SIZEOF_VOID_P) != 0
174# error "_PyObject_VAR_SIZE requires SIZEOF_VOID_P be a power of 2"
175#endif
176
177#define _PyObject_VAR_SIZE(typeobj, nitems) \
178 (size_t) \
179 ( ( (typeobj)->tp_basicsize + \
180 (nitems)*(typeobj)->tp_itemsize + \
181 (SIZEOF_VOID_P - 1) \
182 ) & ~(SIZEOF_VOID_P - 1) \
183 )
184
185#define PyObject_NEW(type, typeobj) \
186( (type *) PyObject_Init( \
187 (PyObject *) PyObject_MALLOC( _PyObject_SIZE(typeobj) ), (typeobj)) )
188
189#define PyObject_NEW_VAR(type, typeobj, n) \
190( (type *) PyObject_InitVar( \
191 (PyVarObject *) PyObject_MALLOC(_PyObject_VAR_SIZE((typeobj),(n)) ),\
192 (typeobj), (n)) )
193
194/* This example code implements an object constructor with a custom
195 allocator, where PyObject_New is inlined, and shows the important
196 distinction between two steps (at least):
197 1) the actual allocation of the object storage;
198 2) the initialization of the Python specific fields
199 in this storage with PyObject_{Init, InitVar}.
200
201 PyObject *
202 YourObject_New(...)
203 {
204 PyObject *op;
205
206 op = (PyObject *) Your_Allocator(_PyObject_SIZE(YourTypeStruct));
207 if (op == NULL)
208 return PyErr_NoMemory();
209
210 PyObject_Init(op, &YourTypeStruct);
211
212 op->ob_field = value;
213 ...
214 return op;
215 }
216
217 Note that in C++, the use of the new operator usually implies that
218 the 1st step is performed automatically for you, so in a C++ class
219 constructor you would start directly with PyObject_Init/InitVar
220*/
221
222/*
223 * Garbage Collection Support
224 * ==========================
225 */
226
227/* C equivalent of gc.collect(). */
228PyAPI_FUNC(Py_ssize_t) PyGC_Collect(void);
229
230/* Test if a type has a GC head */
231#define PyType_IS_GC(t) PyType_HasFeature((t), Py_TPFLAGS_HAVE_GC)
232
233/* Test if an object has a GC head */
234#define PyObject_IS_GC(o) (PyType_IS_GC(Py_TYPE(o)) && \
235 (Py_TYPE(o)->tp_is_gc == NULL || Py_TYPE(o)->tp_is_gc(o)))
236
237PyAPI_FUNC(PyVarObject *) _PyObject_GC_Resize(PyVarObject *, Py_ssize_t);
238#define PyObject_GC_Resize(type, op, n) \
239 ( (type *) _PyObject_GC_Resize((PyVarObject *)(op), (n)) )
240
241/* for source compatibility with 2.2 */
242#define _PyObject_GC_Del PyObject_GC_Del
243
244/* GC information is stored BEFORE the object structure. */
245typedef union _gc_head {
246 struct {
247 union _gc_head *gc_next;
248 union _gc_head *gc_prev;
249 Py_ssize_t gc_refs;
250 } gc;
251 long double dummy; /* force worst-case alignment */
252} PyGC_Head;
253
254extern PyGC_Head *_PyGC_generation0;
255
256#define _Py_AS_GC(o) ((PyGC_Head *)(o)-1)
257
258#define _PyGC_REFS_UNTRACKED (-2)
259#define _PyGC_REFS_REACHABLE (-3)
260#define _PyGC_REFS_TENTATIVELY_UNREACHABLE (-4)
261
262/* Tell the GC to track this object. NB: While the object is tracked the
263 * collector it must be safe to call the ob_traverse method. */
264#define _PyObject_GC_TRACK(o) do { \
265 PyGC_Head *g = _Py_AS_GC(o); \
266 if (g->gc.gc_refs != _PyGC_REFS_UNTRACKED) \
267 Py_FatalError("GC object already tracked"); \
268 g->gc.gc_refs = _PyGC_REFS_REACHABLE; \
269 g->gc.gc_next = _PyGC_generation0; \
270 g->gc.gc_prev = _PyGC_generation0->gc.gc_prev; \
271 g->gc.gc_prev->gc.gc_next = g; \
272 _PyGC_generation0->gc.gc_prev = g; \
273 } while (0);
274
275/* Tell the GC to stop tracking this object.
276 * gc_next doesn't need to be set to NULL, but doing so is a good
277 * way to provoke memory errors if calling code is confused.
278 */
279#define _PyObject_GC_UNTRACK(o) do { \
280 PyGC_Head *g = _Py_AS_GC(o); \
281 assert(g->gc.gc_refs != _PyGC_REFS_UNTRACKED); \
282 g->gc.gc_refs = _PyGC_REFS_UNTRACKED; \
283 g->gc.gc_prev->gc.gc_next = g->gc.gc_next; \
284 g->gc.gc_next->gc.gc_prev = g->gc.gc_prev; \
285 g->gc.gc_next = NULL; \
286 } while (0);
287
288PyAPI_FUNC(PyObject *) _PyObject_GC_Malloc(size_t);
289PyAPI_FUNC(PyObject *) _PyObject_GC_New(PyTypeObject *);
290PyAPI_FUNC(PyVarObject *) _PyObject_GC_NewVar(PyTypeObject *, Py_ssize_t);
291PyAPI_FUNC(void) PyObject_GC_Track(void *);
292PyAPI_FUNC(void) PyObject_GC_UnTrack(void *);
293PyAPI_FUNC(void) PyObject_GC_Del(void *);
294
295#define PyObject_GC_New(type, typeobj) \
296 ( (type *) _PyObject_GC_New(typeobj) )
297#define PyObject_GC_NewVar(type, typeobj, n) \
298 ( (type *) _PyObject_GC_NewVar((typeobj), (n)) )
299
300
301/* Utility macro to help write tp_traverse functions.
302 * To use this macro, the tp_traverse function must name its arguments
303 * "visit" and "arg". This is intended to keep tp_traverse functions
304 * looking as much alike as possible.
305 */
306#define Py_VISIT(op) \
307 do { \
308 if (op) { \
309 int vret = visit((PyObject *)(op), arg); \
310 if (vret) \
311 return vret; \
312 } \
313 } while (0)
314
315/* This is here for the sake of backwards compatibility. Extensions that
316 * use the old GC API will still compile but the objects will not be
317 * tracked by the GC. */
318#define PyGC_HEAD_SIZE 0
319#define PyObject_GC_Init(op)
320#define PyObject_GC_Fini(op)
321#define PyObject_AS_GC(op) (op)
322#define PyObject_FROM_GC(op) (op)
323
324
325/* Test if a type supports weak references */
326#define PyType_SUPPORTS_WEAKREFS(t) \
327 (PyType_HasFeature((t), Py_TPFLAGS_HAVE_WEAKREFS) \
328 && ((t)->tp_weaklistoffset > 0))
329
330#define PyObject_GET_WEAKREFS_LISTPTR(o) \
331 ((PyObject **) (((char *) (o)) + Py_TYPE(o)->tp_weaklistoffset))
332
333#ifdef __cplusplus
334}
335#endif
336#endif /* !Py_OBJIMPL_H */
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