Mass Deface tp_basicsize ) /* _PyObject_VAR_SIZE returns the number of bytes (as size_t) allocated for a vrbl-size object with nitems items, exclusive of gc overhead (if any). The value is rounded up to the closest multiple of sizeof(void *), in order to ensure that pointer fields at the end of the object are correctly aligned for the platform (this is of special importance for subclasses of, e.g., str or long, so that pointers can be stored after the embedded data). Note that there's no memory wastage in doing this, as malloc has to return (at worst) pointer-aligned memory anyway. */ #if ((SIZEOF_VOID_P - 1) & SIZEOF_VOID_P) != 0 # error "_PyObject_VAR_SIZE requires SIZEOF_VOID_P be a power of 2" #endif #define _PyObject_VAR_SIZE(typeobj, nitems) \ (size_t) \ ( ( (typeobj)->tp_basicsize + \ (nitems)*(typeobj)->tp_itemsize + \ (SIZEOF_VOID_P - 1) \ ) & ~(SIZEOF_VOID_P - 1) \ ) #define PyObject_NEW(type, typeobj) \ ( (type *) PyObject_Init( \ (PyObject *) PyObject_MALLOC( _PyObject_SIZE(typeobj) ), (typeobj)) ) #define PyObject_NEW_VAR(type, typeobj, n) \ ( (type *) PyObject_InitVar( \ (PyVarObject *) PyObject_MALLOC(_PyObject_VAR_SIZE((typeobj),(n)) ),\ (typeobj), (n)) ) /* This example code implements an object constructor with a custom allocator, where PyObject_New is inlined, and shows the important distinction between two steps (at least): 1) the actual allocation of the object storage; 2) the initialization of the Python specific fields in this storage with PyObject_{Init, InitVar}. PyObject * YourObject_New(...) { PyObject *op; op = (PyObject *) Your_Allocator(_PyObject_SIZE(YourTypeStruct)); if (op == NULL) return PyErr_NoMemory(); PyObject_Init(op, &YourTypeStruct); op->ob_field = value; ... return op; } Note that in C++, the use of the new operator usually implies that the 1st step is performed automatically for you, so in a C++ class constructor you would start directly with PyObject_Init/InitVar */ /* * Garbage Collection Support * ========================== */ /* C equivalent of gc.collect(). */ PyAPI_FUNC(Py_ssize_t) PyGC_Collect(void); /* Test if a type has a GC head */ #define PyType_IS_GC(t) PyType_HasFeature((t), Py_TPFLAGS_HAVE_GC) /* Test if an object has a GC head */ #define PyObject_IS_GC(o) (PyType_IS_GC(Py_TYPE(o)) && \ (Py_TYPE(o)->tp_is_gc == NULL || Py_TYPE(o)->tp_is_gc(o))) PyAPI_FUNC(PyVarObject *) _PyObject_GC_Resize(PyVarObject *, Py_ssize_t); #define PyObject_GC_Resize(type, op, n) \ ( (type *) _PyObject_GC_Resize((PyVarObject *)(op), (n)) ) /* for source compatibility with 2.2 */ #define _PyObject_GC_Del PyObject_GC_Del /* GC information is stored BEFORE the object structure. */ typedef union _gc_head { struct { union _gc_head *gc_next; union _gc_head *gc_prev; Py_ssize_t gc_refs; } gc; long double dummy; /* force worst-case alignment */ } PyGC_Head; extern PyGC_Head *_PyGC_generation0; #define _Py_AS_GC(o) ((PyGC_Head *)(o)-1) #define _PyGC_REFS_UNTRACKED (-2) #define _PyGC_REFS_REACHABLE (-3) #define _PyGC_REFS_TENTATIVELY_UNREACHABLE (-4) /* Tell the GC to track this object. NB: While the object is tracked the * collector it must be safe to call the ob_traverse method. */ #define _PyObject_GC_TRACK(o) do { \ PyGC_Head *g = _Py_AS_GC(o); \ if (g->gc.gc_refs != _PyGC_REFS_UNTRACKED) \ Py_FatalError("GC object already tracked"); \ g->gc.gc_refs = _PyGC_REFS_REACHABLE; \ g->gc.gc_next = _PyGC_generation0; \ g->gc.gc_prev = _PyGC_generation0->gc.gc_prev; \ g->gc.gc_prev->gc.gc_next = g; \ _PyGC_generation0->gc.gc_prev = g; \ } while (0); /* Tell the GC to stop tracking this object. * gc_next doesn't need to be set to NULL, but doing so is a good * way to provoke memory errors if calling code is confused. */ #define _PyObject_GC_UNTRACK(o) do { \ PyGC_Head *g = _Py_AS_GC(o); \ assert(g->gc.gc_refs != _PyGC_REFS_UNTRACKED); \ g->gc.gc_refs = _PyGC_REFS_UNTRACKED; \ g->gc.gc_prev->gc.gc_next = g->gc.gc_next; \ g->gc.gc_next->gc.gc_prev = g->gc.gc_prev; \ g->gc.gc_next = NULL; \ } while (0); /* True if the object is currently tracked by the GC. */ #define _PyObject_GC_IS_TRACKED(o) \ ((_Py_AS_GC(o))->gc.gc_refs != _PyGC_REFS_UNTRACKED) /* True if the object may be tracked by the GC in the future, or already is. This can be useful to implement some optimizations. */ #define _PyObject_GC_MAY_BE_TRACKED(obj) \ (PyObject_IS_GC(obj) && \ (!PyTuple_CheckExact(obj) || _PyObject_GC_IS_TRACKED(obj))) PyAPI_FUNC(PyObject *) _PyObject_GC_Malloc(size_t); PyAPI_FUNC(PyObject *) _PyObject_GC_New(PyTypeObject *); PyAPI_FUNC(PyVarObject *) _PyObject_GC_NewVar(PyTypeObject *, Py_ssize_t); PyAPI_FUNC(void) PyObject_GC_Track(void *); PyAPI_FUNC(void) PyObject_GC_UnTrack(void *); PyAPI_FUNC(void) PyObject_GC_Del(void *); #define PyObject_GC_New(type, typeobj) \ ( (type *) _PyObject_GC_New(typeobj) ) #define PyObject_GC_NewVar(type, typeobj, n) \ ( (type *) _PyObject_GC_NewVar((typeobj), (n)) ) /* Utility macro to help write tp_traverse functions. * To use this macro, the tp_traverse function must name its arguments * "visit" and "arg". This is intended to keep tp_traverse functions * looking as much alike as possible. */ #define Py_VISIT(op) \ do { \ if (op) { \ int vret = visit((PyObject *)(op), arg); \ if (vret) \ return vret; \ } \ } while (0) /* This is here for the sake of backwards compatibility. Extensions that * use the old GC API will still compile but the objects will not be * tracked by the GC. */ #define PyGC_HEAD_SIZE 0 #define PyObject_GC_Init(op) #define PyObject_GC_Fini(op) #define PyObject_AS_GC(op) (op) #define PyObject_FROM_GC(op) (op) /* Test if a type supports weak references */ #define PyType_SUPPORTS_WEAKREFS(t) \ (PyType_HasFeature((t), Py_TPFLAGS_HAVE_WEAKREFS) \ && ((t)->tp_weaklistoffset > 0)) #define PyObject_GET_WEAKREFS_LISTPTR(o) \ ((PyObject **) (((char *) (o)) + Py_TYPE(o)->tp_weaklistoffset)) #ifdef __cplusplus } #endif #endif /* !Py_OBJIMPL_H */