1#ifndef Py_CPYTHON_OBJIMPL_H
2# error "this header file must not be included directly"
3#endif
4
5static inline size_t _PyObject_SIZE(PyTypeObject *type) {
6 return _Py_STATIC_CAST(size_t, type->tp_basicsize);
7}
8
9/* _PyObject_VAR_SIZE returns the number of bytes (as size_t) allocated for a
10 vrbl-size object with nitems items, exclusive of gc overhead (if any). The
11 value is rounded up to the closest multiple of sizeof(void *), in order to
12 ensure that pointer fields at the end of the object are correctly aligned
13 for the platform (this is of special importance for subclasses of, e.g.,
14 str or int, so that pointers can be stored after the embedded data).
15
16 Note that there's no memory wastage in doing this, as malloc has to
17 return (at worst) pointer-aligned memory anyway.
18*/
19#if ((SIZEOF_VOID_P - 1) & SIZEOF_VOID_P) != 0
20# error "_PyObject_VAR_SIZE requires SIZEOF_VOID_P be a power of 2"
21#endif
22
23static inline size_t _PyObject_VAR_SIZE(PyTypeObject *type, Py_ssize_t nitems) {
24 size_t size = _Py_STATIC_CAST(size_t, type->tp_basicsize);
25 size += _Py_STATIC_CAST(size_t, nitems) * _Py_STATIC_CAST(size_t, type->tp_itemsize);
26 return _Py_SIZE_ROUND_UP(size, SIZEOF_VOID_P);
27}
28
29
30/* This example code implements an object constructor with a custom
31 allocator, where PyObject_New is inlined, and shows the important
32 distinction between two steps (at least):
33 1) the actual allocation of the object storage;
34 2) the initialization of the Python specific fields
35 in this storage with PyObject_{Init, InitVar}.
36
37 PyObject *
38 YourObject_New(...)
39 {
40 PyObject *op;
41
42 op = (PyObject *) Your_Allocator(_PyObject_SIZE(YourTypeStruct));
43 if (op == NULL) {
44 return PyErr_NoMemory();
45 }
46
47 PyObject_Init(op, &YourTypeStruct);
48
49 op->ob_field = value;
50 ...
51 return op;
52 }
53
54 Note that in C++, the use of the new operator usually implies that
55 the 1st step is performed automatically for you, so in a C++ class
56 constructor you would start directly with PyObject_Init/InitVar. */
57
58
59typedef struct {
60 /* user context passed as the first argument to the 2 functions */
61 void *ctx;
62
63 /* allocate an arena of size bytes */
64 void* (*alloc) (void *ctx, size_t size);
65
66 /* free an arena */
67 void (*free) (void *ctx, void *ptr, size_t size);
68} PyObjectArenaAllocator;
69
70/* Get the arena allocator. */
71PyAPI_FUNC(void) PyObject_GetArenaAllocator(PyObjectArenaAllocator *allocator);
72
73/* Set the arena allocator. */
74PyAPI_FUNC(void) PyObject_SetArenaAllocator(PyObjectArenaAllocator *allocator);
75
76
77/* Test if an object implements the garbage collector protocol */
78PyAPI_FUNC(int) PyObject_IS_GC(PyObject *obj);
79
80
81/* Code built with Py_BUILD_CORE must include pycore_gc.h instead which
82 defines a different _PyGC_FINALIZED() macro. */
83#ifndef Py_BUILD_CORE
84 // Kept for backward compatibility with Python 3.8
85# define _PyGC_FINALIZED(o) PyObject_GC_IsFinalized(o)
86#endif
87
88
89// Test if a type supports weak references
90PyAPI_FUNC(int) PyType_SUPPORTS_WEAKREFS(PyTypeObject *type);
91
92PyAPI_FUNC(PyObject **) PyObject_GET_WEAKREFS_LISTPTR(PyObject *op);
93
94PyAPI_FUNC(PyObject *) PyUnstable_Object_GC_NewWithExtraData(PyTypeObject *,
95 size_t);
96

source code of include/python3.12/cpython/objimpl.h