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);
111PyAPI_FUNC(void *) _PyObject_DebugMallocApi(char api, size_t nbytes);
112PyAPI_FUNC(void *) _PyObject_DebugReallocApi(char api, void *p, size_t nbytes);
113PyAPI_FUNC(void) _PyObject_DebugFreeApi(char api, void *p);
114PyAPI_FUNC(void) _PyObject_DebugCheckAddressApi(char api, const void *p);
115PyAPI_FUNC(void *) _PyMem_DebugMalloc(size_t nbytes);
116PyAPI_FUNC(void *) _PyMem_DebugRealloc(void *p, size_t nbytes);
117PyAPI_FUNC(void) _PyMem_DebugFree(void *p);
118#define PyObject_MALLOC         _PyObject_DebugMalloc
119#define PyObject_Malloc         _PyObject_DebugMalloc
120#define PyObject_REALLOC        _PyObject_DebugRealloc
121#define PyObject_Realloc        _PyObject_DebugRealloc
122#define PyObject_FREE           _PyObject_DebugFree
123#define PyObject_Free           _PyObject_DebugFree
124
125#else   /* WITH_PYMALLOC && ! PYMALLOC_DEBUG */
126#define PyObject_MALLOC         PyObject_Malloc
127#define PyObject_REALLOC        PyObject_Realloc
128#define PyObject_FREE           PyObject_Free
129#endif
130
131#else   /* ! WITH_PYMALLOC */
132#define PyObject_MALLOC         PyMem_MALLOC
133#define PyObject_REALLOC        PyMem_REALLOC
134#define PyObject_FREE           PyMem_FREE
135
136#endif  /* WITH_PYMALLOC */
137
138#define PyObject_Del            PyObject_Free
139#define PyObject_DEL            PyObject_FREE
140
141/* for source compatibility with 2.2 */
142#define _PyObject_Del           PyObject_Free
143
144/*
145 * Generic object allocator interface
146 * ==================================
147 */
148
149/* Functions */
150PyAPI_FUNC(PyObject *) PyObject_Init(PyObject *, PyTypeObject *);
151PyAPI_FUNC(PyVarObject *) PyObject_InitVar(PyVarObject *,
152                                                 PyTypeObject *, Py_ssize_t);
153PyAPI_FUNC(PyObject *) _PyObject_New(PyTypeObject *);
154PyAPI_FUNC(PyVarObject *) _PyObject_NewVar(PyTypeObject *, Py_ssize_t);
155
156#define PyObject_New(type, typeobj) \
157                ( (type *) _PyObject_New(typeobj) )
158#define PyObject_NewVar(type, typeobj, n) \
159                ( (type *) _PyObject_NewVar((typeobj), (n)) )
160
161/* Macros trading binary compatibility for speed. See also pymem.h.
162   Note that these macros expect non-NULL object pointers.*/
163#define PyObject_INIT(op, typeobj) \
164    ( Py_TYPE(op) = (typeobj), _Py_NewReference((PyObject *)(op)), (op) )
165#define PyObject_INIT_VAR(op, typeobj, size) \
166    ( Py_SIZE(op) = (size), PyObject_INIT((op), (typeobj)) )
167
168#define _PyObject_SIZE(typeobj) ( (typeobj)->tp_basicsize )
169
170/* _PyObject_VAR_SIZE returns the number of bytes (as size_t) allocated for a
171   vrbl-size object with nitems items, exclusive of gc overhead (if any).  The
172   value is rounded up to the closest multiple of sizeof(void *), in order to
173   ensure that pointer fields at the end of the object are correctly aligned
174   for the platform (this is of special importance for subclasses of, e.g.,
175   str or long, so that pointers can be stored after the embedded data).
176
177   Note that there's no memory wastage in doing this, as malloc has to
178   return (at worst) pointer-aligned memory anyway.
179*/
180#if ((SIZEOF_VOID_P - 1) & SIZEOF_VOID_P) != 0
181#   error "_PyObject_VAR_SIZE requires SIZEOF_VOID_P be a power of 2"
182#endif
183
184#define _PyObject_VAR_SIZE(typeobj, nitems)     \
185    (size_t)                                    \
186    ( ( (typeobj)->tp_basicsize +               \
187        (nitems)*(typeobj)->tp_itemsize +       \
188        (SIZEOF_VOID_P - 1)                     \
189      ) & ~(SIZEOF_VOID_P - 1)                  \
190    )
191
192#define PyObject_NEW(type, typeobj) \
193( (type *) PyObject_Init( \
194    (PyObject *) PyObject_MALLOC( _PyObject_SIZE(typeobj) ), (typeobj)) )
195
196#define PyObject_NEW_VAR(type, typeobj, n) \
197( (type *) PyObject_InitVar( \
198      (PyVarObject *) PyObject_MALLOC(_PyObject_VAR_SIZE((typeobj),(n)) ),\
199      (typeobj), (n)) )
200
201/* This example code implements an object constructor with a custom
202   allocator, where PyObject_New is inlined, and shows the important
203   distinction between two steps (at least):
204       1) the actual allocation of the object storage;
205       2) the initialization of the Python specific fields
206      in this storage with PyObject_{Init, InitVar}.
207
208   PyObject *
209   YourObject_New(...)
210   {
211       PyObject *op;
212
213       op = (PyObject *) Your_Allocator(_PyObject_SIZE(YourTypeStruct));
214       if (op == NULL)
215       return PyErr_NoMemory();
216
217       PyObject_Init(op, &YourTypeStruct);
218
219       op->ob_field = value;
220       ...
221       return op;
222   }
223
224   Note that in C++, the use of the new operator usually implies that
225   the 1st step is performed automatically for you, so in a C++ class
226   constructor you would start directly with PyObject_Init/InitVar
227*/
228
229/*
230 * Garbage Collection Support
231 * ==========================
232 */
233
234/* C equivalent of gc.collect(). */
235PyAPI_FUNC(Py_ssize_t) PyGC_Collect(void);
236
237/* Test if a type has a GC head */
238#define PyType_IS_GC(t) PyType_HasFeature((t), Py_TPFLAGS_HAVE_GC)
239
240/* Test if an object has a GC head */
241#define PyObject_IS_GC(o) (PyType_IS_GC(Py_TYPE(o)) && \
242    (Py_TYPE(o)->tp_is_gc == NULL || Py_TYPE(o)->tp_is_gc(o)))
243
244PyAPI_FUNC(PyVarObject *) _PyObject_GC_Resize(PyVarObject *, Py_ssize_t);
245#define PyObject_GC_Resize(type, op, n) \
246                ( (type *) _PyObject_GC_Resize((PyVarObject *)(op), (n)) )
247
248/* for source compatibility with 2.2 */
249#define _PyObject_GC_Del PyObject_GC_Del
250
251/* GC information is stored BEFORE the object structure. */
252typedef union _gc_head {
253    struct {
254        union _gc_head *gc_next;
255        union _gc_head *gc_prev;
256        Py_ssize_t gc_refs;
257    } gc;
258    long double dummy;  /* force worst-case alignment */
259} PyGC_Head;
260
261extern PyGC_Head *_PyGC_generation0;
262
263#define _Py_AS_GC(o) ((PyGC_Head *)(o)-1)
264
265#define _PyGC_REFS_UNTRACKED                    (-2)
266#define _PyGC_REFS_REACHABLE                    (-3)
267#define _PyGC_REFS_TENTATIVELY_UNREACHABLE      (-4)
268
269/* Tell the GC to track this object.  NB: While the object is tracked the
270 * collector it must be safe to call the ob_traverse method. */
271#define _PyObject_GC_TRACK(o) do { \
272    PyGC_Head *g = _Py_AS_GC(o); \
273    if (g->gc.gc_refs != _PyGC_REFS_UNTRACKED) \
274        Py_FatalError("GC object already tracked"); \
275    g->gc.gc_refs = _PyGC_REFS_REACHABLE; \
276    g->gc.gc_next = _PyGC_generation0; \
277    g->gc.gc_prev = _PyGC_generation0->gc.gc_prev; \
278    g->gc.gc_prev->gc.gc_next = g; \
279    _PyGC_generation0->gc.gc_prev = g; \
280    } while (0);
281
282/* Tell the GC to stop tracking this object.
283 * gc_next doesn't need to be set to NULL, but doing so is a good
284 * way to provoke memory errors if calling code is confused.
285 */
286#define _PyObject_GC_UNTRACK(o) do { \
287    PyGC_Head *g = _Py_AS_GC(o); \
288    assert(g->gc.gc_refs != _PyGC_REFS_UNTRACKED); \
289    g->gc.gc_refs = _PyGC_REFS_UNTRACKED; \
290    g->gc.gc_prev->gc.gc_next = g->gc.gc_next; \
291    g->gc.gc_next->gc.gc_prev = g->gc.gc_prev; \
292    g->gc.gc_next = NULL; \
293    } while (0);
294
295/* True if the object is currently tracked by the GC. */
296#define _PyObject_GC_IS_TRACKED(o) \
297    ((_Py_AS_GC(o))->gc.gc_refs != _PyGC_REFS_UNTRACKED)
298
299/* True if the object may be tracked by the GC in the future, or already is.
300   This can be useful to implement some optimizations. */
301#define _PyObject_GC_MAY_BE_TRACKED(obj) \
302    (PyObject_IS_GC(obj) && \
303        (!PyTuple_CheckExact(obj) || _PyObject_GC_IS_TRACKED(obj)))
304
305
306PyAPI_FUNC(PyObject *) _PyObject_GC_Malloc(size_t);
307PyAPI_FUNC(PyObject *) _PyObject_GC_New(PyTypeObject *);
308PyAPI_FUNC(PyVarObject *) _PyObject_GC_NewVar(PyTypeObject *, Py_ssize_t);
309PyAPI_FUNC(void) PyObject_GC_Track(void *);
310PyAPI_FUNC(void) PyObject_GC_UnTrack(void *);
311PyAPI_FUNC(void) PyObject_GC_Del(void *);
312
313#define PyObject_GC_New(type, typeobj) \
314                ( (type *) _PyObject_GC_New(typeobj) )
315#define PyObject_GC_NewVar(type, typeobj, n) \
316                ( (type *) _PyObject_GC_NewVar((typeobj), (n)) )
317
318
319/* Utility macro to help write tp_traverse functions.
320 * To use this macro, the tp_traverse function must name its arguments
321 * "visit" and "arg".  This is intended to keep tp_traverse functions
322 * looking as much alike as possible.
323 */
324#define Py_VISIT(op)                                                    \
325    do {                                                                \
326        if (op) {                                                       \
327            int vret = visit((PyObject *)(op), arg);                    \
328            if (vret)                                                   \
329                return vret;                                            \
330        }                                                               \
331    } while (0)
332
333/* This is here for the sake of backwards compatibility.  Extensions that
334 * use the old GC API will still compile but the objects will not be
335 * tracked by the GC. */
336#define PyGC_HEAD_SIZE 0
337#define PyObject_GC_Init(op)
338#define PyObject_GC_Fini(op)
339#define PyObject_AS_GC(op) (op)
340#define PyObject_FROM_GC(op) (op)
341
342
343/* Test if a type supports weak references */
344#define PyType_SUPPORTS_WEAKREFS(t) \
345    (PyType_HasFeature((t), Py_TPFLAGS_HAVE_WEAKREFS) \
346     && ((t)->tp_weaklistoffset > 0))
347
348#define PyObject_GET_WEAKREFS_LISTPTR(o) \
349    ((PyObject **) (((char *) (o)) + Py_TYPE(o)->tp_weaklistoffset))
350
351#ifdef __cplusplus
352}
353#endif
354#endif /* !Py_OBJIMPL_H */
355