python (3.12.0)
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
11 extern "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 /*
27 Functions 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_Free(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
49 Note that objects created with PyObject_{New, NewVar} are allocated using the
50 specialized Python allocator (implemented in obmalloc.c), if WITH_PYMALLOC is
51 enabled. In addition, a special debugging allocator is used if Py_DEBUG
52 macro is also defined.
53
54 In case a specific form of memory management is needed (for example, if you
55 must use the platform malloc heap(s), or shared memory, or C++ local storage or
56 operator new), you must first allocate the object with your custom allocator,
57 then pass its pointer to PyObject_{Init, InitVar} for filling in its Python-
58 specific fields: reference count, type pointer, possibly others. You should
59 be aware that Python has no control over these objects because they don't
60 cooperate with the Python memory manager. Such objects may not be eligible
61 for automatic garbage collection and you have to make sure that they are
62 released accordingly whenever their destructor gets called (cf. the specific
63 form of memory management you're using).
64
65 Unless you have specific memory management requirements, use
66 PyObject_{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 */
97 PyAPI_FUNC(void *) PyObject_Malloc(size_t size);
98 #if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03050000
99 PyAPI_FUNC(void *) PyObject_Calloc(size_t nelem, size_t elsize);
100 #endif
101 PyAPI_FUNC(void *) PyObject_Realloc(void *ptr, size_t new_size);
102 PyAPI_FUNC(void) PyObject_Free(void *ptr);
103
104
105 // Deprecated aliases only kept for backward compatibility.
106 // PyObject_Del and PyObject_DEL are defined with no parameter to be able to
107 // use them as function pointers (ex: tp_free = PyObject_Del).
108 #define PyObject_MALLOC PyObject_Malloc
109 #define PyObject_REALLOC PyObject_Realloc
110 #define PyObject_FREE PyObject_Free
111 #define PyObject_Del PyObject_Free
112 #define PyObject_DEL PyObject_Free
113
114
115 /*
116 * Generic object allocator interface
117 * ==================================
118 */
119
120 /* Functions */
121 PyAPI_FUNC(PyObject *) PyObject_Init(PyObject *, PyTypeObject *);
122 PyAPI_FUNC(PyVarObject *) PyObject_InitVar(PyVarObject *,
123 PyTypeObject *, Py_ssize_t);
124
125 #define PyObject_INIT(op, typeobj) \
126 PyObject_Init(_PyObject_CAST(op), (typeobj))
127 #define PyObject_INIT_VAR(op, typeobj, size) \
128 PyObject_InitVar(_PyVarObject_CAST(op), (typeobj), (size))
129
130
131 PyAPI_FUNC(PyObject *) _PyObject_New(PyTypeObject *);
132 PyAPI_FUNC(PyVarObject *) _PyObject_NewVar(PyTypeObject *, Py_ssize_t);
133
134 #define PyObject_New(type, typeobj) ((type *)_PyObject_New(typeobj))
135
136 // Alias to PyObject_New(). In Python 3.8, PyObject_NEW() called directly
137 // PyObject_MALLOC() with _PyObject_SIZE().
138 #define PyObject_NEW(type, typeobj) PyObject_New(type, (typeobj))
139
140 #define PyObject_NewVar(type, typeobj, n) \
141 ( (type *) _PyObject_NewVar((typeobj), (n)) )
142
143 // Alias to PyObject_NewVar(). In Python 3.8, PyObject_NEW_VAR() called
144 // directly PyObject_MALLOC() with _PyObject_VAR_SIZE().
145 #define PyObject_NEW_VAR(type, typeobj, n) PyObject_NewVar(type, (typeobj), (n))
146
147
148 /*
149 * Garbage Collection Support
150 * ==========================
151 */
152
153 /* C equivalent of gc.collect(). */
154 PyAPI_FUNC(Py_ssize_t) PyGC_Collect(void);
155 /* C API for controlling the state of the garbage collector */
156 PyAPI_FUNC(int) PyGC_Enable(void);
157 PyAPI_FUNC(int) PyGC_Disable(void);
158 PyAPI_FUNC(int) PyGC_IsEnabled(void);
159
160
161 #if !defined(Py_LIMITED_API)
162 /* Visit all live GC-capable objects, similar to gc.get_objects(None). The
163 * supplied callback is called on every such object with the void* arg set
164 * to the supplied arg. Returning 0 from the callback ends iteration, returning
165 * 1 allows iteration to continue. Returning any other value may result in
166 * undefined behaviour.
167 *
168 * If new objects are (de)allocated by the callback it is undefined if they
169 * will be visited.
170
171 * Garbage collection is disabled during operation. Explicitly running a
172 * collection in the callback may lead to undefined behaviour e.g. visiting the
173 * same objects multiple times or not at all.
174 */
175 typedef int (*gcvisitobjects_t)(PyObject*, void*);
176 PyAPI_FUNC(void) PyUnstable_GC_VisitObjects(gcvisitobjects_t callback, void* arg);
177 #endif
178
179 /* Test if a type has a GC head */
180 #define PyType_IS_GC(t) PyType_HasFeature((t), Py_TPFLAGS_HAVE_GC)
181
182 PyAPI_FUNC(PyVarObject *) _PyObject_GC_Resize(PyVarObject *, Py_ssize_t);
183 #define PyObject_GC_Resize(type, op, n) \
184 ( (type *) _PyObject_GC_Resize(_PyVarObject_CAST(op), (n)) )
185
186
187
188 PyAPI_FUNC(PyObject *) _PyObject_GC_New(PyTypeObject *);
189 PyAPI_FUNC(PyVarObject *) _PyObject_GC_NewVar(PyTypeObject *, Py_ssize_t);
190
191 /* Tell the GC to track this object.
192 *
193 * See also private _PyObject_GC_TRACK() macro. */
194 PyAPI_FUNC(void) PyObject_GC_Track(void *);
195
196 /* Tell the GC to stop tracking this object.
197 *
198 * See also private _PyObject_GC_UNTRACK() macro. */
199 PyAPI_FUNC(void) PyObject_GC_UnTrack(void *);
200
201 PyAPI_FUNC(void) PyObject_GC_Del(void *);
202
203 #define PyObject_GC_New(type, typeobj) \
204 _Py_CAST(type*, _PyObject_GC_New(typeobj))
205 #define PyObject_GC_NewVar(type, typeobj, n) \
206 _Py_CAST(type*, _PyObject_GC_NewVar((typeobj), (n)))
207
208 PyAPI_FUNC(int) PyObject_GC_IsTracked(PyObject *);
209 PyAPI_FUNC(int) PyObject_GC_IsFinalized(PyObject *);
210
211 /* Utility macro to help write tp_traverse functions.
212 * To use this macro, the tp_traverse function must name its arguments
213 * "visit" and "arg". This is intended to keep tp_traverse functions
214 * looking as much alike as possible.
215 */
216 #define Py_VISIT(op) \
217 do { \
218 if (op) { \
219 int vret = visit(_PyObject_CAST(op), arg); \
220 if (vret) \
221 return vret; \
222 } \
223 } while (0)
224
225 #ifndef Py_LIMITED_API
226 # define Py_CPYTHON_OBJIMPL_H
227 # include "cpython/objimpl.h"
228 # undef Py_CPYTHON_OBJIMPL_H
229 #endif
230
231 #ifdef __cplusplus
232 }
233 #endif
234 #endif /* !Py_OBJIMPL_H */
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