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planemo upload commit 2e9511a184a1ca667c7be0c6321a36dc4e3d116d
author jpayne
date Tue, 18 Mar 2025 17:55:14 -0400
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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
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_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
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 PYMALLOC_DEBUG
52 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 /* Macros */
106 #define PyObject_MALLOC PyObject_Malloc
107 #define PyObject_REALLOC PyObject_Realloc
108 #define PyObject_FREE PyObject_Free
109 #define PyObject_Del PyObject_Free
110 #define PyObject_DEL PyObject_Free
111
112
113 /*
114 * Generic object allocator interface
115 * ==================================
116 */
117
118 /* Functions */
119 PyAPI_FUNC(PyObject *) PyObject_Init(PyObject *, PyTypeObject *);
120 PyAPI_FUNC(PyVarObject *) PyObject_InitVar(PyVarObject *,
121 PyTypeObject *, Py_ssize_t);
122 PyAPI_FUNC(PyObject *) _PyObject_New(PyTypeObject *);
123 PyAPI_FUNC(PyVarObject *) _PyObject_NewVar(PyTypeObject *, Py_ssize_t);
124
125 #define PyObject_New(type, typeobj) \
126 ( (type *) _PyObject_New(typeobj) )
127 #define PyObject_NewVar(type, typeobj, n) \
128 ( (type *) _PyObject_NewVar((typeobj), (n)) )
129
130 /* Inline functions trading binary compatibility for speed:
131 PyObject_INIT() is the fast version of PyObject_Init(), and
132 PyObject_INIT_VAR() is the fast version of PyObject_InitVar.
133 See also pymem.h.
134
135 These inline functions expect non-NULL object pointers. */
136 static inline PyObject*
137 _PyObject_INIT(PyObject *op, PyTypeObject *typeobj)
138 {
139 assert(op != NULL);
140 Py_TYPE(op) = typeobj;
141 if (PyType_GetFlags(typeobj) & Py_TPFLAGS_HEAPTYPE) {
142 Py_INCREF(typeobj);
143 }
144 _Py_NewReference(op);
145 return op;
146 }
147
148 #define PyObject_INIT(op, typeobj) \
149 _PyObject_INIT(_PyObject_CAST(op), (typeobj))
150
151 static inline PyVarObject*
152 _PyObject_INIT_VAR(PyVarObject *op, PyTypeObject *typeobj, Py_ssize_t size)
153 {
154 assert(op != NULL);
155 Py_SIZE(op) = size;
156 PyObject_INIT((PyObject *)op, typeobj);
157 return op;
158 }
159
160 #define PyObject_INIT_VAR(op, typeobj, size) \
161 _PyObject_INIT_VAR(_PyVarObject_CAST(op), (typeobj), (size))
162
163 #define _PyObject_SIZE(typeobj) ( (typeobj)->tp_basicsize )
164
165 /* _PyObject_VAR_SIZE returns the number of bytes (as size_t) allocated for a
166 vrbl-size object with nitems items, exclusive of gc overhead (if any). The
167 value is rounded up to the closest multiple of sizeof(void *), in order to
168 ensure that pointer fields at the end of the object are correctly aligned
169 for the platform (this is of special importance for subclasses of, e.g.,
170 str or int, so that pointers can be stored after the embedded data).
171
172 Note that there's no memory wastage in doing this, as malloc has to
173 return (at worst) pointer-aligned memory anyway.
174 */
175 #if ((SIZEOF_VOID_P - 1) & SIZEOF_VOID_P) != 0
176 # error "_PyObject_VAR_SIZE requires SIZEOF_VOID_P be a power of 2"
177 #endif
178
179 #define _PyObject_VAR_SIZE(typeobj, nitems) \
180 _Py_SIZE_ROUND_UP((typeobj)->tp_basicsize + \
181 (nitems)*(typeobj)->tp_itemsize, \
182 SIZEOF_VOID_P)
183
184 #define PyObject_NEW(type, typeobj) \
185 ( (type *) PyObject_Init( \
186 (PyObject *) PyObject_MALLOC( _PyObject_SIZE(typeobj) ), (typeobj)) )
187
188 #define PyObject_NEW_VAR(type, typeobj, n) \
189 ( (type *) PyObject_InitVar( \
190 (PyVarObject *) PyObject_MALLOC(_PyObject_VAR_SIZE((typeobj),(n)) ),\
191 (typeobj), (n)) )
192
193 /* This example code implements an object constructor with a custom
194 allocator, where PyObject_New is inlined, and shows the important
195 distinction between two steps (at least):
196 1) the actual allocation of the object storage;
197 2) the initialization of the Python specific fields
198 in this storage with PyObject_{Init, InitVar}.
199
200 PyObject *
201 YourObject_New(...)
202 {
203 PyObject *op;
204
205 op = (PyObject *) Your_Allocator(_PyObject_SIZE(YourTypeStruct));
206 if (op == NULL)
207 return PyErr_NoMemory();
208
209 PyObject_Init(op, &YourTypeStruct);
210
211 op->ob_field = value;
212 ...
213 return op;
214 }
215
216 Note that in C++, the use of the new operator usually implies that
217 the 1st step is performed automatically for you, so in a C++ class
218 constructor you would start directly with PyObject_Init/InitVar
219 */
220
221
222
223 /*
224 * Garbage Collection Support
225 * ==========================
226 */
227
228 /* C equivalent of gc.collect() which ignores the state of gc.enabled. */
229 PyAPI_FUNC(Py_ssize_t) PyGC_Collect(void);
230
231 /* Test if a type has a GC head */
232 #define PyType_IS_GC(t) PyType_HasFeature((t), Py_TPFLAGS_HAVE_GC)
233
234 PyAPI_FUNC(PyVarObject *) _PyObject_GC_Resize(PyVarObject *, Py_ssize_t);
235 #define PyObject_GC_Resize(type, op, n) \
236 ( (type *) _PyObject_GC_Resize(_PyVarObject_CAST(op), (n)) )
237
238
239
240 PyAPI_FUNC(PyObject *) _PyObject_GC_New(PyTypeObject *);
241 PyAPI_FUNC(PyVarObject *) _PyObject_GC_NewVar(PyTypeObject *, Py_ssize_t);
242
243 /* Tell the GC to track this object.
244 *
245 * See also private _PyObject_GC_TRACK() macro. */
246 PyAPI_FUNC(void) PyObject_GC_Track(void *);
247
248 /* Tell the GC to stop tracking this object.
249 *
250 * See also private _PyObject_GC_UNTRACK() macro. */
251 PyAPI_FUNC(void) PyObject_GC_UnTrack(void *);
252
253 PyAPI_FUNC(void) PyObject_GC_Del(void *);
254
255 #define PyObject_GC_New(type, typeobj) \
256 ( (type *) _PyObject_GC_New(typeobj) )
257 #define PyObject_GC_NewVar(type, typeobj, n) \
258 ( (type *) _PyObject_GC_NewVar((typeobj), (n)) )
259
260
261 /* Utility macro to help write tp_traverse functions.
262 * To use this macro, the tp_traverse function must name its arguments
263 * "visit" and "arg". This is intended to keep tp_traverse functions
264 * looking as much alike as possible.
265 */
266 #define Py_VISIT(op) \
267 do { \
268 if (op) { \
269 int vret = visit(_PyObject_CAST(op), arg); \
270 if (vret) \
271 return vret; \
272 } \
273 } while (0)
274
275 #ifndef Py_LIMITED_API
276 # define Py_CPYTHON_OBJIMPL_H
277 # include "cpython/objimpl.h"
278 # undef Py_CPYTHON_OBJIMPL_H
279 #endif
280
281 #ifdef __cplusplus
282 }
283 #endif
284 #endif /* !Py_OBJIMPL_H */