8 /* Object and type object interface */
11 Objects are structures allocated on the heap. Special rules apply to
12 the use of objects to ensure they are properly garbage-collected.
13 Objects are never allocated statically or on the stack; they must be
14 accessed through special macros and functions only. (Type objects are
15 exceptions to the first rule; the standard types are represented by
16 statically initialized type objects, although work on type/class unification
17 for Python 2.2 made it possible to have heap-allocated type objects too).
19 An object has a 'reference count' that is increased or decreased when a
20 pointer to the object is copied or deleted; when the reference count
21 reaches zero there are no references to the object left and it can be
22 removed from the heap.
24 An object has a 'type' that determines what it represents and what kind
25 of data it contains. An object's type is fixed when it is created.
26 Types themselves are represented as objects; an object contains a
27 pointer to the corresponding type object. The type itself has a type
28 pointer pointing to the object representing the type 'type', which
29 contains a pointer to itself!).
31 Objects do not float around in memory; once allocated an object keeps
32 the same size and address. Objects that must hold variable-size data
33 can contain pointers to variable-size parts of the object. Not all
34 objects of the same type have the same size; but the size cannot change
35 after allocation. (These restrictions are made so a reference to an
36 object can be simply a pointer -- moving an object would require
37 updating all the pointers, and changing an object's size would require
38 moving it if there was another object right next to it.)
40 Objects are always accessed through pointers of the type 'PyObject *'.
41 The type 'PyObject' is a structure that only contains the reference count
42 and the type pointer. The actual memory allocated for an object
43 contains other data that can only be accessed after casting the pointer
44 to a pointer to a longer structure type. This longer type must start
45 with the reference count and type fields; the macro PyObject_HEAD should be
46 used for this (to accommodate for future changes). The implementation
47 of a particular object type can cast the object pointer to the proper
50 A standard interface exists for objects that contain an array of items
51 whose size is determined when the object is allocated.
54 /* Py_DEBUG implies Py_TRACE_REFS. */
55 #if defined(Py_DEBUG) && !defined(Py_TRACE_REFS)
59 /* Py_TRACE_REFS implies Py_REF_DEBUG. */
60 #if defined(Py_TRACE_REFS) && !defined(Py_REF_DEBUG)
65 /* Define pointers to support a doubly-linked list of all live heap objects. */
66 #define _PyObject_HEAD_EXTRA \
67 struct _object *_ob_next; \
68 struct _object *_ob_prev;
70 #define _PyObject_EXTRA_INIT 0, 0,
73 #define _PyObject_HEAD_EXTRA
74 #define _PyObject_EXTRA_INIT
77 /* PyObject_HEAD defines the initial segment of every PyObject. */
78 #define PyObject_HEAD \
79 _PyObject_HEAD_EXTRA \
80 Py_ssize_t ob_refcnt; \
81 struct _typeobject *ob_type;
83 #define PyObject_HEAD_INIT(type) \
84 _PyObject_EXTRA_INIT \
87 #define PyVarObject_HEAD_INIT(type, size) \
88 PyObject_HEAD_INIT(type) size,
90 /* PyObject_VAR_HEAD defines the initial segment of all variable-size
91 * container objects. These end with a declaration of an array with 1
92 * element, but enough space is malloc'ed so that the array actually
93 * has room for ob_size elements. Note that ob_size is an element count,
94 * not necessarily a byte count.
96 #define PyObject_VAR_HEAD \
98 Py_ssize_t ob_size; /* Number of items in variable part */
99 #define Py_INVALID_SIZE (Py_ssize_t)-1
101 /* Nothing is actually declared to be a PyObject, but every pointer to
102 * a Python object can be cast to a PyObject*. This is inheritance built
103 * by hand. Similarly every pointer to a variable-size Python object can,
104 * in addition, be cast to PyVarObject*.
106 typedef struct _object
{
114 #define Py_REFCNT(ob) (((PyObject*)(ob))->ob_refcnt)
115 #define Py_TYPE(ob) (((PyObject*)(ob))->ob_type)
116 #define Py_SIZE(ob) (((PyVarObject*)(ob))->ob_size)
119 Type objects contain a string containing the type name (to help somewhat
120 in debugging), the allocation parameters (see PyObject_New() and
122 and methods for accessing objects of the type. Methods are optional, a
123 nil pointer meaning that particular kind of access is not available for
124 this type. The Py_DECREF() macro uses the tp_dealloc method without
125 checking for a nil pointer; it should always be implemented except if
126 the implementation can guarantee that the reference count will never
127 reach zero (e.g., for statically allocated type objects).
129 NB: the methods for certain type groups are now contained in separate
133 typedef PyObject
* (*unaryfunc
)(PyObject
*);
134 typedef PyObject
* (*binaryfunc
)(PyObject
*, PyObject
*);
135 typedef PyObject
* (*ternaryfunc
)(PyObject
*, PyObject
*, PyObject
*);
136 typedef int (*inquiry
)(PyObject
*);
137 typedef Py_ssize_t (*lenfunc
)(PyObject
*);
138 typedef int (*coercion
)(PyObject
**, PyObject
**);
139 typedef PyObject
*(*intargfunc
)(PyObject
*, int) Py_DEPRECATED(2.5);
140 typedef PyObject
*(*intintargfunc
)(PyObject
*, int, int) Py_DEPRECATED(2.5);
141 typedef PyObject
*(*ssizeargfunc
)(PyObject
*, Py_ssize_t
);
142 typedef PyObject
*(*ssizessizeargfunc
)(PyObject
*, Py_ssize_t
, Py_ssize_t
);
143 typedef int(*intobjargproc
)(PyObject
*, int, PyObject
*);
144 typedef int(*intintobjargproc
)(PyObject
*, int, int, PyObject
*);
145 typedef int(*ssizeobjargproc
)(PyObject
*, Py_ssize_t
, PyObject
*);
146 typedef int(*ssizessizeobjargproc
)(PyObject
*, Py_ssize_t
, Py_ssize_t
, PyObject
*);
147 typedef int(*objobjargproc
)(PyObject
*, PyObject
*, PyObject
*);
151 /* int-based buffer interface */
152 typedef int (*getreadbufferproc
)(PyObject
*, int, void **);
153 typedef int (*getwritebufferproc
)(PyObject
*, int, void **);
154 typedef int (*getsegcountproc
)(PyObject
*, int *);
155 typedef int (*getcharbufferproc
)(PyObject
*, int, char **);
156 /* ssize_t-based buffer interface */
157 typedef Py_ssize_t (*readbufferproc
)(PyObject
*, Py_ssize_t
, void **);
158 typedef Py_ssize_t (*writebufferproc
)(PyObject
*, Py_ssize_t
, void **);
159 typedef Py_ssize_t (*segcountproc
)(PyObject
*, Py_ssize_t
*);
160 typedef Py_ssize_t (*charbufferproc
)(PyObject
*, Py_ssize_t
, char **);
163 /* Py3k buffer interface */
164 typedef struct bufferinfo
{
166 PyObject
*obj
; /* owned reference */
168 Py_ssize_t itemsize
; /* This is Py_ssize_t so it can be
169 pointed to by strides in simple case.*/
175 Py_ssize_t
*suboffsets
;
176 Py_ssize_t smalltable
[2]; /* static store for shape and strides of
177 mono-dimensional buffers. */
181 typedef int (*getbufferproc
)(PyObject
*, Py_buffer
*, int);
182 typedef void (*releasebufferproc
)(PyObject
*, Py_buffer
*);
184 /* Flags for getting buffers */
185 #define PyBUF_SIMPLE 0
186 #define PyBUF_WRITABLE 0x0001
187 /* we used to include an E, backwards compatible alias */
188 #define PyBUF_WRITEABLE PyBUF_WRITABLE
189 #define PyBUF_FORMAT 0x0004
190 #define PyBUF_ND 0x0008
191 #define PyBUF_STRIDES (0x0010 | PyBUF_ND)
192 #define PyBUF_C_CONTIGUOUS (0x0020 | PyBUF_STRIDES)
193 #define PyBUF_F_CONTIGUOUS (0x0040 | PyBUF_STRIDES)
194 #define PyBUF_ANY_CONTIGUOUS (0x0080 | PyBUF_STRIDES)
195 #define PyBUF_INDIRECT (0x0100 | PyBUF_STRIDES)
197 #define PyBUF_CONTIG (PyBUF_ND | PyBUF_WRITABLE)
198 #define PyBUF_CONTIG_RO (PyBUF_ND)
200 #define PyBUF_STRIDED (PyBUF_STRIDES | PyBUF_WRITABLE)
201 #define PyBUF_STRIDED_RO (PyBUF_STRIDES)
203 #define PyBUF_RECORDS (PyBUF_STRIDES | PyBUF_WRITABLE | PyBUF_FORMAT)
204 #define PyBUF_RECORDS_RO (PyBUF_STRIDES | PyBUF_FORMAT)
206 #define PyBUF_FULL (PyBUF_INDIRECT | PyBUF_WRITABLE | PyBUF_FORMAT)
207 #define PyBUF_FULL_RO (PyBUF_INDIRECT | PyBUF_FORMAT)
210 #define PyBUF_READ 0x100
211 #define PyBUF_WRITE 0x200
212 #define PyBUF_SHADOW 0x400
213 /* end Py3k buffer interface */
215 typedef int (*objobjproc
)(PyObject
*, PyObject
*);
216 typedef int (*visitproc
)(PyObject
*, void *);
217 typedef int (*traverseproc
)(PyObject
*, visitproc
, void *);
220 /* For numbers without flag bit Py_TPFLAGS_CHECKTYPES set, all
221 arguments are guaranteed to be of the object's type (modulo
222 coercion hacks -- i.e. if the type's coercion function
223 returns other types, then these are allowed as well). Numbers that
224 have the Py_TPFLAGS_CHECKTYPES flag bit set should check *both*
225 arguments for proper type and implement the necessary conversions
226 in the slot functions themselves. */
229 binaryfunc nb_subtract
;
230 binaryfunc nb_multiply
;
231 binaryfunc nb_divide
;
232 binaryfunc nb_remainder
;
233 binaryfunc nb_divmod
;
234 ternaryfunc nb_power
;
235 unaryfunc nb_negative
;
236 unaryfunc nb_positive
;
237 unaryfunc nb_absolute
;
240 binaryfunc nb_lshift
;
241 binaryfunc nb_rshift
;
251 /* Added in release 2.0 */
252 binaryfunc nb_inplace_add
;
253 binaryfunc nb_inplace_subtract
;
254 binaryfunc nb_inplace_multiply
;
255 binaryfunc nb_inplace_divide
;
256 binaryfunc nb_inplace_remainder
;
257 ternaryfunc nb_inplace_power
;
258 binaryfunc nb_inplace_lshift
;
259 binaryfunc nb_inplace_rshift
;
260 binaryfunc nb_inplace_and
;
261 binaryfunc nb_inplace_xor
;
262 binaryfunc nb_inplace_or
;
264 /* Added in release 2.2 */
265 /* The following require the Py_TPFLAGS_HAVE_CLASS flag */
266 binaryfunc nb_floor_divide
;
267 binaryfunc nb_true_divide
;
268 binaryfunc nb_inplace_floor_divide
;
269 binaryfunc nb_inplace_true_divide
;
271 /* Added in release 2.5 */
277 binaryfunc sq_concat
;
278 ssizeargfunc sq_repeat
;
279 ssizeargfunc sq_item
;
280 ssizessizeargfunc sq_slice
;
281 ssizeobjargproc sq_ass_item
;
282 ssizessizeobjargproc sq_ass_slice
;
283 objobjproc sq_contains
;
284 /* Added in release 2.0 */
285 binaryfunc sq_inplace_concat
;
286 ssizeargfunc sq_inplace_repeat
;
291 binaryfunc mp_subscript
;
292 objobjargproc mp_ass_subscript
;
296 readbufferproc bf_getreadbuffer
;
297 writebufferproc bf_getwritebuffer
;
298 segcountproc bf_getsegcount
;
299 charbufferproc bf_getcharbuffer
;
300 getbufferproc bf_getbuffer
;
301 releasebufferproc bf_releasebuffer
;
305 typedef void (*freefunc
)(void *);
306 typedef void (*destructor
)(PyObject
*);
307 typedef int (*printfunc
)(PyObject
*, FILE *, int);
308 typedef PyObject
*(*getattrfunc
)(PyObject
*, char *);
309 typedef PyObject
*(*getattrofunc
)(PyObject
*, PyObject
*);
310 typedef int (*setattrfunc
)(PyObject
*, char *, PyObject
*);
311 typedef int (*setattrofunc
)(PyObject
*, PyObject
*, PyObject
*);
312 typedef int (*cmpfunc
)(PyObject
*, PyObject
*);
313 typedef PyObject
*(*reprfunc
)(PyObject
*);
314 typedef long (*hashfunc
)(PyObject
*);
315 typedef PyObject
*(*richcmpfunc
) (PyObject
*, PyObject
*, int);
316 typedef PyObject
*(*getiterfunc
) (PyObject
*);
317 typedef PyObject
*(*iternextfunc
) (PyObject
*);
318 typedef PyObject
*(*descrgetfunc
) (PyObject
*, PyObject
*, PyObject
*);
319 typedef int (*descrsetfunc
) (PyObject
*, PyObject
*, PyObject
*);
320 typedef int (*initproc
)(PyObject
*, PyObject
*, PyObject
*);
321 typedef PyObject
*(*newfunc
)(struct _typeobject
*, PyObject
*, PyObject
*);
322 typedef PyObject
*(*allocfunc
)(struct _typeobject
*, Py_ssize_t
);
324 typedef struct _typeobject
{
326 const char *tp_name
; /* For printing, in format "<module>.<name>" */
327 Py_ssize_t tp_basicsize
, tp_itemsize
; /* For allocation */
329 /* Methods to implement standard operations */
331 destructor tp_dealloc
;
333 getattrfunc tp_getattr
;
334 setattrfunc tp_setattr
;
338 /* Method suites for standard classes */
340 PyNumberMethods
*tp_as_number
;
341 PySequenceMethods
*tp_as_sequence
;
342 PyMappingMethods
*tp_as_mapping
;
344 /* More standard operations (here for binary compatibility) */
349 getattrofunc tp_getattro
;
350 setattrofunc tp_setattro
;
352 /* Functions to access object as input/output buffer */
353 PyBufferProcs
*tp_as_buffer
;
355 /* Flags to define presence of optional/expanded features */
358 const char *tp_doc
; /* Documentation string */
360 /* Assigned meaning in release 2.0 */
361 /* call function for all accessible objects */
362 traverseproc tp_traverse
;
364 /* delete references to contained objects */
367 /* Assigned meaning in release 2.1 */
368 /* rich comparisons */
369 richcmpfunc tp_richcompare
;
371 /* weak reference enabler */
372 Py_ssize_t tp_weaklistoffset
;
374 /* Added in release 2.2 */
377 iternextfunc tp_iternext
;
379 /* Attribute descriptor and subclassing stuff */
380 struct PyMethodDef
*tp_methods
;
381 struct PyMemberDef
*tp_members
;
382 struct PyGetSetDef
*tp_getset
;
383 struct _typeobject
*tp_base
;
385 descrgetfunc tp_descr_get
;
386 descrsetfunc tp_descr_set
;
387 Py_ssize_t tp_dictoffset
;
391 freefunc tp_free
; /* Low-level free-memory routine */
392 inquiry tp_is_gc
; /* For PyObject_IS_GC */
394 PyObject
*tp_mro
; /* method resolution order */
396 PyObject
*tp_subclasses
;
397 PyObject
*tp_weaklist
;
400 /* Type attribute cache version tag. Added in version 2.6 */
401 unsigned int tp_version_tag
;
404 /* these must be last and never explicitly initialized */
405 Py_ssize_t tp_allocs
;
407 Py_ssize_t tp_maxalloc
;
408 struct _typeobject
*tp_prev
;
409 struct _typeobject
*tp_next
;
414 /* The *real* layout of a type object when allocated on the heap */
415 typedef struct _heaptypeobject
{
416 /* Note: there's a dependency on the order of these members
417 in slotptr() in typeobject.c . */
418 PyTypeObject ht_type
;
419 PyNumberMethods as_number
;
420 PyMappingMethods as_mapping
;
421 PySequenceMethods as_sequence
; /* as_sequence comes after as_mapping,
422 so that the mapping wins when both
423 the mapping and the sequence define
424 a given operator (e.g. __getitem__).
425 see add_operators() in typeobject.c . */
426 PyBufferProcs as_buffer
;
427 PyObject
*ht_name
, *ht_slots
;
428 /* here are optional user slots, followed by the members. */
431 /* access macro to the members which are floating "behind" the object */
432 #define PyHeapType_GET_MEMBERS(etype) \
433 ((PyMemberDef *)(((char *)etype) + Py_TYPE(etype)->tp_basicsize))
436 /* Generic type check */
437 PyAPI_FUNC(int) PyType_IsSubtype(PyTypeObject
*, PyTypeObject
*);
438 #define PyObject_TypeCheck(ob, tp) \
439 (Py_TYPE(ob) == (tp) || PyType_IsSubtype(Py_TYPE(ob), (tp)))
441 PyAPI_DATA(PyTypeObject
) PyType_Type
; /* built-in 'type' */
442 PyAPI_DATA(PyTypeObject
) PyBaseObject_Type
; /* built-in 'object' */
443 PyAPI_DATA(PyTypeObject
) PySuper_Type
; /* built-in 'super' */
445 #define PyType_Check(op) \
446 PyType_FastSubclass(Py_TYPE(op), Py_TPFLAGS_TYPE_SUBCLASS)
447 #define PyType_CheckExact(op) (Py_TYPE(op) == &PyType_Type)
449 PyAPI_FUNC(int) PyType_Ready(PyTypeObject
*);
450 PyAPI_FUNC(PyObject
*) PyType_GenericAlloc(PyTypeObject
*, Py_ssize_t
);
451 PyAPI_FUNC(PyObject
*) PyType_GenericNew(PyTypeObject
*,
452 PyObject
*, PyObject
*);
453 PyAPI_FUNC(PyObject
*) _PyType_Lookup(PyTypeObject
*, PyObject
*);
454 PyAPI_FUNC(unsigned int) PyType_ClearCache(void);
455 PyAPI_FUNC(void) PyType_Modified(PyTypeObject
*);
457 /* Generic operations on objects */
458 PyAPI_FUNC(int) PyObject_Print(PyObject
*, FILE *, int);
459 PyAPI_FUNC(void) _PyObject_Dump(PyObject
*);
460 PyAPI_FUNC(PyObject
*) PyObject_Repr(PyObject
*);
461 PyAPI_FUNC(PyObject
*) _PyObject_Str(PyObject
*);
462 PyAPI_FUNC(PyObject
*) PyObject_Str(PyObject
*);
463 #define PyObject_Bytes PyObject_Str
464 #ifdef Py_USING_UNICODE
465 PyAPI_FUNC(PyObject
*) PyObject_Unicode(PyObject
*);
467 PyAPI_FUNC(int) PyObject_Compare(PyObject
*, PyObject
*);
468 PyAPI_FUNC(PyObject
*) PyObject_RichCompare(PyObject
*, PyObject
*, int);
469 PyAPI_FUNC(int) PyObject_RichCompareBool(PyObject
*, PyObject
*, int);
470 PyAPI_FUNC(PyObject
*) PyObject_GetAttrString(PyObject
*, const char *);
471 PyAPI_FUNC(int) PyObject_SetAttrString(PyObject
*, const char *, PyObject
*);
472 PyAPI_FUNC(int) PyObject_HasAttrString(PyObject
*, const char *);
473 PyAPI_FUNC(PyObject
*) PyObject_GetAttr(PyObject
*, PyObject
*);
474 PyAPI_FUNC(int) PyObject_SetAttr(PyObject
*, PyObject
*, PyObject
*);
475 PyAPI_FUNC(int) PyObject_HasAttr(PyObject
*, PyObject
*);
476 PyAPI_FUNC(PyObject
**) _PyObject_GetDictPtr(PyObject
*);
477 PyAPI_FUNC(PyObject
*) PyObject_SelfIter(PyObject
*);
478 PyAPI_FUNC(PyObject
*) _PyObject_NextNotImplemented(PyObject
*);
479 PyAPI_FUNC(PyObject
*) PyObject_GenericGetAttr(PyObject
*, PyObject
*);
480 PyAPI_FUNC(int) PyObject_GenericSetAttr(PyObject
*,
481 PyObject
*, PyObject
*);
482 PyAPI_FUNC(long) PyObject_Hash(PyObject
*);
483 PyAPI_FUNC(long) PyObject_HashNotImplemented(PyObject
*);
484 PyAPI_FUNC(int) PyObject_IsTrue(PyObject
*);
485 PyAPI_FUNC(int) PyObject_Not(PyObject
*);
486 PyAPI_FUNC(int) PyCallable_Check(PyObject
*);
487 PyAPI_FUNC(int) PyNumber_Coerce(PyObject
**, PyObject
**);
488 PyAPI_FUNC(int) PyNumber_CoerceEx(PyObject
**, PyObject
**);
490 PyAPI_FUNC(void) PyObject_ClearWeakRefs(PyObject
*);
492 /* A slot function whose address we need to compare */
493 extern int _PyObject_SlotCompare(PyObject
*, PyObject
*);
496 /* PyObject_Dir(obj) acts like Python __builtin__.dir(obj), returning a
497 list of strings. PyObject_Dir(NULL) is like __builtin__.dir(),
498 returning the names of the current locals. In this case, if there are
499 no current locals, NULL is returned, and PyErr_Occurred() is false.
501 PyAPI_FUNC(PyObject
*) PyObject_Dir(PyObject
*);
504 /* Helpers for printing recursive container types */
505 PyAPI_FUNC(int) Py_ReprEnter(PyObject
*);
506 PyAPI_FUNC(void) Py_ReprLeave(PyObject
*);
508 /* Helpers for hash functions */
509 PyAPI_FUNC(long) _Py_HashDouble(double);
510 PyAPI_FUNC(long) _Py_HashPointer(void*);
512 /* Helper for passing objects to printf and the like */
513 #define PyObject_REPR(obj) PyString_AS_STRING(PyObject_Repr(obj))
515 /* Flag bits for printing: */
516 #define Py_PRINT_RAW 1 /* No string quotes etc. */
519 `Type flags (tp_flags)
521 These flags are used to extend the type structure in a backwards-compatible
522 fashion. Extensions can use the flags to indicate (and test) when a given
523 type structure contains a new feature. The Python core will use these when
524 introducing new functionality between major revisions (to avoid mid-version
525 changes in the PYTHON_API_VERSION).
527 Arbitration of the flag bit positions will need to be coordinated among
528 all extension writers who publically release their extensions (this will
529 be fewer than you might expect!)..
531 Python 1.5.2 introduced the bf_getcharbuffer slot into PyBufferProcs.
533 Type definitions should use Py_TPFLAGS_DEFAULT for their tp_flags value.
535 Code can use PyType_HasFeature(type_ob, flag_value) to test whether the
536 given type object has a specified feature.
538 NOTE: when building the core, Py_TPFLAGS_DEFAULT includes
539 Py_TPFLAGS_HAVE_VERSION_TAG; outside the core, it doesn't. This is so
540 that extensions that modify tp_dict of their own types directly don't
541 break, since this was allowed in 2.5. In 3.0 they will have to
542 manually remove this flag though!
545 /* PyBufferProcs contains bf_getcharbuffer */
546 #define Py_TPFLAGS_HAVE_GETCHARBUFFER (1L<<0)
548 /* PySequenceMethods contains sq_contains */
549 #define Py_TPFLAGS_HAVE_SEQUENCE_IN (1L<<1)
551 /* This is here for backwards compatibility. Extensions that use the old GC
552 * API will still compile but the objects will not be tracked by the GC. */
553 #define Py_TPFLAGS_GC 0 /* used to be (1L<<2) */
555 /* PySequenceMethods and PyNumberMethods contain in-place operators */
556 #define Py_TPFLAGS_HAVE_INPLACEOPS (1L<<3)
558 /* PyNumberMethods do their own coercion */
559 #define Py_TPFLAGS_CHECKTYPES (1L<<4)
561 /* tp_richcompare is defined */
562 #define Py_TPFLAGS_HAVE_RICHCOMPARE (1L<<5)
564 /* Objects which are weakly referencable if their tp_weaklistoffset is >0 */
565 #define Py_TPFLAGS_HAVE_WEAKREFS (1L<<6)
567 /* tp_iter is defined */
568 #define Py_TPFLAGS_HAVE_ITER (1L<<7)
570 /* New members introduced by Python 2.2 exist */
571 #define Py_TPFLAGS_HAVE_CLASS (1L<<8)
573 /* Set if the type object is dynamically allocated */
574 #define Py_TPFLAGS_HEAPTYPE (1L<<9)
576 /* Set if the type allows subclassing */
577 #define Py_TPFLAGS_BASETYPE (1L<<10)
579 /* Set if the type is 'ready' -- fully initialized */
580 #define Py_TPFLAGS_READY (1L<<12)
582 /* Set while the type is being 'readied', to prevent recursive ready calls */
583 #define Py_TPFLAGS_READYING (1L<<13)
585 /* Objects support garbage collection (see objimp.h) */
586 #define Py_TPFLAGS_HAVE_GC (1L<<14)
588 /* These two bits are preserved for Stackless Python, next after this is 17 */
590 #define Py_TPFLAGS_HAVE_STACKLESS_EXTENSION (3L<<15)
592 #define Py_TPFLAGS_HAVE_STACKLESS_EXTENSION 0
595 /* Objects support nb_index in PyNumberMethods */
596 #define Py_TPFLAGS_HAVE_INDEX (1L<<17)
598 /* Objects support type attribute cache */
599 #define Py_TPFLAGS_HAVE_VERSION_TAG (1L<<18)
600 #define Py_TPFLAGS_VALID_VERSION_TAG (1L<<19)
602 /* Type is abstract and cannot be instantiated */
603 #define Py_TPFLAGS_IS_ABSTRACT (1L<<20)
605 /* Has the new buffer protocol */
606 #define Py_TPFLAGS_HAVE_NEWBUFFER (1L<<21)
608 /* These flags are used to determine if a type is a subclass. */
609 #define Py_TPFLAGS_INT_SUBCLASS (1L<<23)
610 #define Py_TPFLAGS_LONG_SUBCLASS (1L<<24)
611 #define Py_TPFLAGS_LIST_SUBCLASS (1L<<25)
612 #define Py_TPFLAGS_TUPLE_SUBCLASS (1L<<26)
613 #define Py_TPFLAGS_STRING_SUBCLASS (1L<<27)
614 #define Py_TPFLAGS_UNICODE_SUBCLASS (1L<<28)
615 #define Py_TPFLAGS_DICT_SUBCLASS (1L<<29)
616 #define Py_TPFLAGS_BASE_EXC_SUBCLASS (1L<<30)
617 #define Py_TPFLAGS_TYPE_SUBCLASS (1L<<31)
619 #define Py_TPFLAGS_DEFAULT_EXTERNAL ( \
620 Py_TPFLAGS_HAVE_GETCHARBUFFER | \
621 Py_TPFLAGS_HAVE_SEQUENCE_IN | \
622 Py_TPFLAGS_HAVE_INPLACEOPS | \
623 Py_TPFLAGS_HAVE_RICHCOMPARE | \
624 Py_TPFLAGS_HAVE_WEAKREFS | \
625 Py_TPFLAGS_HAVE_ITER | \
626 Py_TPFLAGS_HAVE_CLASS | \
627 Py_TPFLAGS_HAVE_STACKLESS_EXTENSION | \
628 Py_TPFLAGS_HAVE_INDEX | \
630 #define Py_TPFLAGS_DEFAULT_CORE (Py_TPFLAGS_DEFAULT_EXTERNAL | \
631 Py_TPFLAGS_HAVE_VERSION_TAG)
634 #define Py_TPFLAGS_DEFAULT Py_TPFLAGS_DEFAULT_CORE
636 #define Py_TPFLAGS_DEFAULT Py_TPFLAGS_DEFAULT_EXTERNAL
639 #define PyType_HasFeature(t,f) (((t)->tp_flags & (f)) != 0)
640 #define PyType_FastSubclass(t,f) PyType_HasFeature(t,f)
644 The macros Py_INCREF(op) and Py_DECREF(op) are used to increment or decrement
645 reference counts. Py_DECREF calls the object's deallocator function when
646 the refcount falls to 0; for
647 objects that don't contain references to other objects or heap memory
648 this can be the standard function free(). Both macros can be used
649 wherever a void expression is allowed. The argument must not be a
650 NULL pointer. If it may be NULL, use Py_XINCREF/Py_XDECREF instead.
651 The macro _Py_NewReference(op) initialize reference counts to 1, and
652 in special builds (Py_REF_DEBUG, Py_TRACE_REFS) performs additional
653 bookkeeping appropriate to the special build.
655 We assume that the reference count field can never overflow; this can
656 be proven when the size of the field is the same as the pointer size, so
657 we ignore the possibility. Provided a C int is at least 32 bits (which
658 is implicitly assumed in many parts of this code), that's enough for
659 about 2**31 references to an object.
661 XXX The following became out of date in Python 2.2, but I'm not sure
662 XXX what the full truth is now. Certainly, heap-allocated type objects
663 XXX can and should be deallocated.
664 Type objects should never be deallocated; the type pointer in an object
665 is not considered to be a reference to the type object, to save
666 complications in the deallocation function. (This is actually a
667 decision that's up to the implementer of each new type so if you want,
668 you can count such references to the type object.)
670 *** WARNING*** The Py_DECREF macro must have a side-effect-free argument
671 since it may evaluate its argument multiple times. (The alternative
672 would be to mace it a proper function or assign it to a global temporary
673 variable first, both of which are slower; and in a multi-threaded
674 environment the global variable trick is not safe.)
677 /* First define a pile of simple helper macros, one set per special
678 * build symbol. These either expand to the obvious things, or to
679 * nothing at all when the special mode isn't in effect. The main
680 * macros can later be defined just once then, yet expand to different
681 * things depending on which special build options are and aren't in effect.
682 * Trust me <wink>: while painful, this is 20x easier to understand than,
683 * e.g, defining _Py_NewReference five different times in a maze of nested
684 * #ifdefs (we used to do that -- it was impenetrable).
687 PyAPI_DATA(Py_ssize_t
) _Py_RefTotal
;
688 PyAPI_FUNC(void) _Py_NegativeRefcount(const char *fname
,
689 int lineno
, PyObject
*op
);
690 PyAPI_FUNC(PyObject
*) _PyDict_Dummy(void);
691 PyAPI_FUNC(PyObject
*) _PySet_Dummy(void);
692 PyAPI_FUNC(Py_ssize_t
) _Py_GetRefTotal(void);
693 #define _Py_INC_REFTOTAL _Py_RefTotal++
694 #define _Py_DEC_REFTOTAL _Py_RefTotal--
695 #define _Py_REF_DEBUG_COMMA ,
696 #define _Py_CHECK_REFCNT(OP) \
697 { if (((PyObject*)OP)->ob_refcnt < 0) \
698 _Py_NegativeRefcount(__FILE__, __LINE__, \
702 #define _Py_INC_REFTOTAL
703 #define _Py_DEC_REFTOTAL
704 #define _Py_REF_DEBUG_COMMA
705 #define _Py_CHECK_REFCNT(OP) /* a semicolon */;
706 #endif /* Py_REF_DEBUG */
709 PyAPI_FUNC(void) inc_count(PyTypeObject
*);
710 PyAPI_FUNC(void) dec_count(PyTypeObject
*);
711 #define _Py_INC_TPALLOCS(OP) inc_count(Py_TYPE(OP))
712 #define _Py_INC_TPFREES(OP) dec_count(Py_TYPE(OP))
713 #define _Py_DEC_TPFREES(OP) Py_TYPE(OP)->tp_frees--
714 #define _Py_COUNT_ALLOCS_COMMA ,
716 #define _Py_INC_TPALLOCS(OP)
717 #define _Py_INC_TPFREES(OP)
718 #define _Py_DEC_TPFREES(OP)
719 #define _Py_COUNT_ALLOCS_COMMA
720 #endif /* COUNT_ALLOCS */
723 /* Py_TRACE_REFS is such major surgery that we call external routines. */
724 PyAPI_FUNC(void) _Py_NewReference(PyObject
*);
725 PyAPI_FUNC(void) _Py_ForgetReference(PyObject
*);
726 PyAPI_FUNC(void) _Py_Dealloc(PyObject
*);
727 PyAPI_FUNC(void) _Py_PrintReferences(FILE *);
728 PyAPI_FUNC(void) _Py_PrintReferenceAddresses(FILE *);
729 PyAPI_FUNC(void) _Py_AddToAllObjects(PyObject
*, int force
);
732 /* Without Py_TRACE_REFS, there's little enough to do that we expand code
735 #define _Py_NewReference(op) ( \
736 _Py_INC_TPALLOCS(op) _Py_COUNT_ALLOCS_COMMA \
737 _Py_INC_REFTOTAL _Py_REF_DEBUG_COMMA \
740 #define _Py_ForgetReference(op) _Py_INC_TPFREES(op)
742 #define _Py_Dealloc(op) ( \
743 _Py_INC_TPFREES(op) _Py_COUNT_ALLOCS_COMMA \
744 (*Py_TYPE(op)->tp_dealloc)((PyObject *)(op)))
745 #endif /* !Py_TRACE_REFS */
747 #define Py_INCREF(op) ( \
748 _Py_INC_REFTOTAL _Py_REF_DEBUG_COMMA \
749 ((PyObject*)(op))->ob_refcnt++)
751 #define Py_DECREF(op) \
753 if (_Py_DEC_REFTOTAL _Py_REF_DEBUG_COMMA \
754 --((PyObject*)(op))->ob_refcnt != 0) \
755 _Py_CHECK_REFCNT(op) \
757 _Py_Dealloc((PyObject *)(op)); \
760 /* Safely decref `op` and set `op` to NULL, especially useful in tp_clear
761 * and tp_dealloc implementatons.
763 * Note that "the obvious" code can be deadly:
768 * Typically, `op` is something like self->containee, and `self` is done
769 * using its `containee` member. In the code sequence above, suppose
770 * `containee` is non-NULL with a refcount of 1. Its refcount falls to
771 * 0 on the first line, which can trigger an arbitrary amount of code,
772 * possibly including finalizers (like __del__ methods or weakref callbacks)
773 * coded in Python, which in turn can release the GIL and allow other threads
774 * to run, etc. Such code may even invoke methods of `self` again, or cause
775 * cyclic gc to trigger, but-- oops! --self->containee still points to the
776 * object being torn down, and it may be in an insane state while being torn
777 * down. This has in fact been a rich historic source of miserable (rare &
778 * hard-to-diagnose) segfaulting (and other) bugs.
784 * That arranges to set `op` to NULL _before_ decref'ing, so that any code
785 * triggered as a side-effect of `op` getting torn down no longer believes
786 * `op` points to a valid object.
788 * There are cases where it's safe to use the naive code, but they're brittle.
789 * For example, if `op` points to a Python integer, you know that destroying
790 * one of those can't cause problems -- but in part that relies on that
791 * Python integers aren't currently weakly referencable. Best practice is
792 * to use Py_CLEAR() even if you can't think of a reason for why you need to.
794 #define Py_CLEAR(op) \
797 PyObject *_py_tmp = (PyObject *)(op); \
799 Py_DECREF(_py_tmp); \
803 /* Macros to use in case the object pointer may be NULL: */
804 #define Py_XINCREF(op) do { if ((op) == NULL) ; else Py_INCREF(op); } while (0)
805 #define Py_XDECREF(op) do { if ((op) == NULL) ; else Py_DECREF(op); } while (0)
808 These are provided as conveniences to Python runtime embedders, so that
809 they can have object code that is not dependent on Python compilation flags.
811 PyAPI_FUNC(void) Py_IncRef(PyObject
*);
812 PyAPI_FUNC(void) Py_DecRef(PyObject
*);
815 _Py_NoneStruct is an object of undefined type which can be used in contexts
816 where NULL (nil) is not suitable (since NULL often means 'error').
818 Don't forget to apply Py_INCREF() when returning this value!!!
820 PyAPI_DATA(PyObject
) _Py_NoneStruct
; /* Don't use this directly */
821 #define Py_None (&_Py_NoneStruct)
823 /* Macro for returning Py_None from a function */
824 #define Py_RETURN_NONE return Py_INCREF(Py_None), Py_None
827 Py_NotImplemented is a singleton used to signal that an operation is
828 not implemented for a given type combination.
830 PyAPI_DATA(PyObject
) _Py_NotImplementedStruct
; /* Don't use this directly */
831 #define Py_NotImplemented (&_Py_NotImplementedStruct)
833 /* Rich comparison opcodes */
841 /* Maps Py_LT to Py_GT, ..., Py_GE to Py_LE.
842 * Defined in object.c.
844 PyAPI_DATA(int) _Py_SwappedOp
[];
847 Define staticforward and statichere for source compatibility with old
850 The staticforward define was needed to support certain broken C
851 compilers (notably SCO ODT 3.0, perhaps early AIX as well) botched the
852 static keyword when it was used with a forward declaration of a static
853 initialized structure. Standard C allows the forward declaration with
854 static, and we've decided to stop catering to broken C compilers.
855 (In fact, we expect that the compilers are all fixed eight years later.)
858 #define staticforward static
859 #define statichere static
869 Functions that take objects as arguments normally don't check for nil
870 arguments, but they do check the type of the argument, and return an
871 error if the function doesn't apply to the type.
876 Functions may fail for a variety of reasons, including running out of
877 memory. This is communicated to the caller in two ways: an error string
878 is set (see errors.h), and the function result differs: functions that
879 normally return a pointer return NULL for failure, functions returning
880 an integer return -1 (which could be a legal return value too!), and
881 other functions return 0 for success and -1 for failure.
882 Callers should always check for errors before using the result. If
883 an error was set, the caller must either explicitly clear it, or pass
884 the error on to its caller.
889 It takes a while to get used to the proper usage of reference counts.
891 Functions that create an object set the reference count to 1; such new
892 objects must be stored somewhere or destroyed again with Py_DECREF().
893 Some functions that 'store' objects, such as PyTuple_SetItem() and
895 don't increment the reference count of the object, since the most
896 frequent use is to store a fresh object. Functions that 'retrieve'
897 objects, such as PyTuple_GetItem() and PyDict_GetItemString(), also
899 the reference count, since most frequently the object is only looked at
900 quickly. Thus, to retrieve an object and store it again, the caller
901 must call Py_INCREF() explicitly.
903 NOTE: functions that 'consume' a reference count, like
904 PyList_SetItem(), consume the reference even if the object wasn't
905 successfully stored, to simplify error handling.
907 It seems attractive to make other functions that take an object as
908 argument consume a reference count; however, this may quickly get
909 confusing (even the current practice is already confusing). Consider
910 it carefully, it may save lots of calls to Py_INCREF() and Py_DECREF() at
915 /* Trashcan mechanism, thanks to Christian Tismer.
917 When deallocating a container object, it's possible to trigger an unbounded
918 chain of deallocations, as each Py_DECREF in turn drops the refcount on "the
919 next" object in the chain to 0. This can easily lead to stack faults, and
920 especially in threads (which typically have less stack space to work with).
922 A container object that participates in cyclic gc can avoid this by
923 bracketing the body of its tp_dealloc function with a pair of macros:
926 mytype_dealloc(mytype *p)
928 ... declarations go here ...
930 PyObject_GC_UnTrack(p); // must untrack first
931 Py_TRASHCAN_SAFE_BEGIN(p)
932 ... The body of the deallocator goes here, including all calls ...
933 ... to Py_DECREF on contained objects. ...
934 Py_TRASHCAN_SAFE_END(p)
937 CAUTION: Never return from the middle of the body! If the body needs to
938 "get out early", put a label immediately before the Py_TRASHCAN_SAFE_END
939 call, and goto it. Else the call-depth counter (see below) will stay
940 above 0 forever, and the trashcan will never get emptied.
942 How it works: The BEGIN macro increments a call-depth counter. So long
943 as this counter is small, the body of the deallocator is run directly without
944 further ado. But if the counter gets large, it instead adds p to a list of
945 objects to be deallocated later, skips the body of the deallocator, and
946 resumes execution after the END macro. The tp_dealloc routine then returns
947 without deallocating anything (and so unbounded call-stack depth is avoided).
949 When the call stack finishes unwinding again, code generated by the END macro
950 notices this, and calls another routine to deallocate all the objects that
951 may have been added to the list of deferred deallocations. In effect, a
952 chain of N deallocations is broken into N / PyTrash_UNWIND_LEVEL pieces,
953 with the call stack never exceeding a depth of PyTrash_UNWIND_LEVEL.
956 PyAPI_FUNC(void) _PyTrash_deposit_object(PyObject
*);
957 PyAPI_FUNC(void) _PyTrash_destroy_chain(void);
958 PyAPI_DATA(int) _PyTrash_delete_nesting
;
959 PyAPI_DATA(PyObject
*) _PyTrash_delete_later
;
961 #define PyTrash_UNWIND_LEVEL 50
963 #define Py_TRASHCAN_SAFE_BEGIN(op) \
964 if (_PyTrash_delete_nesting < PyTrash_UNWIND_LEVEL) { \
965 ++_PyTrash_delete_nesting;
966 /* The body of the deallocator is here. */
967 #define Py_TRASHCAN_SAFE_END(op) \
968 --_PyTrash_delete_nesting; \
969 if (_PyTrash_delete_later && _PyTrash_delete_nesting <= 0) \
970 _PyTrash_destroy_chain(); \
973 _PyTrash_deposit_object((PyObject*)op);
978 #endif /* !Py_OBJECT_H */