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 \
81 struct _typeobject *ob_type;
83 #define PyObject_HEAD_INIT(type) \
84 _PyObject_EXTRA_INIT \
87 /* PyObject_VAR_HEAD defines the initial segment of all variable-size
88 * container objects. These end with a declaration of an array with 1
89 * element, but enough space is malloc'ed so that the array actually
90 * has room for ob_size elements. Note that ob_size is an element count,
91 * not necessarily a byte count.
93 #define PyObject_VAR_HEAD \
95 int ob_size; /* Number of items in variable part */
97 /* Nothing is actually declared to be a PyObject, but every pointer to
98 * a Python object can be cast to a PyObject*. This is inheritance built
99 * by hand. Similarly every pointer to a variable-size Python object can,
100 * in addition, be cast to PyVarObject*.
102 typedef struct _object
{
112 Type objects contain a string containing the type name (to help somewhat
113 in debugging), the allocation parameters (see PyObject_New() and
115 and methods for accessing objects of the type. Methods are optional, a
116 nil pointer meaning that particular kind of access is not available for
117 this type. The Py_DECREF() macro uses the tp_dealloc method without
118 checking for a nil pointer; it should always be implemented except if
119 the implementation can guarantee that the reference count will never
120 reach zero (e.g., for statically allocated type objects).
122 NB: the methods for certain type groups are now contained in separate
126 typedef PyObject
* (*unaryfunc
)(PyObject
*);
127 typedef PyObject
* (*binaryfunc
)(PyObject
*, PyObject
*);
128 typedef PyObject
* (*ternaryfunc
)(PyObject
*, PyObject
*, PyObject
*);
129 typedef int (*inquiry
)(PyObject
*);
130 typedef int (*coercion
)(PyObject
**, PyObject
**);
131 typedef PyObject
*(*intargfunc
)(PyObject
*, int);
132 typedef PyObject
*(*intintargfunc
)(PyObject
*, int, int);
133 typedef int(*intobjargproc
)(PyObject
*, int, PyObject
*);
134 typedef int(*intintobjargproc
)(PyObject
*, int, int, PyObject
*);
135 typedef int(*objobjargproc
)(PyObject
*, PyObject
*, PyObject
*);
136 typedef int (*getreadbufferproc
)(PyObject
*, int, void **);
137 typedef int (*getwritebufferproc
)(PyObject
*, int, void **);
138 typedef int (*getsegcountproc
)(PyObject
*, int *);
139 typedef int (*getcharbufferproc
)(PyObject
*, int, const char **);
140 typedef int (*objobjproc
)(PyObject
*, PyObject
*);
141 typedef int (*visitproc
)(PyObject
*, void *);
142 typedef int (*traverseproc
)(PyObject
*, visitproc
, void *);
145 /* For numbers without flag bit Py_TPFLAGS_CHECKTYPES set, all
146 arguments are guaranteed to be of the object's type (modulo
147 coercion hacks -- i.e. if the type's coercion function
148 returns other types, then these are allowed as well). Numbers that
149 have the Py_TPFLAGS_CHECKTYPES flag bit set should check *both*
150 arguments for proper type and implement the necessary conversions
151 in the slot functions themselves. */
154 binaryfunc nb_subtract
;
155 binaryfunc nb_multiply
;
156 binaryfunc nb_divide
;
157 binaryfunc nb_remainder
;
158 binaryfunc nb_divmod
;
159 ternaryfunc nb_power
;
160 unaryfunc nb_negative
;
161 unaryfunc nb_positive
;
162 unaryfunc nb_absolute
;
165 binaryfunc nb_lshift
;
166 binaryfunc nb_rshift
;
176 /* Added in release 2.0 */
177 binaryfunc nb_inplace_add
;
178 binaryfunc nb_inplace_subtract
;
179 binaryfunc nb_inplace_multiply
;
180 binaryfunc nb_inplace_divide
;
181 binaryfunc nb_inplace_remainder
;
182 ternaryfunc nb_inplace_power
;
183 binaryfunc nb_inplace_lshift
;
184 binaryfunc nb_inplace_rshift
;
185 binaryfunc nb_inplace_and
;
186 binaryfunc nb_inplace_xor
;
187 binaryfunc nb_inplace_or
;
189 /* Added in release 2.2 */
190 /* The following require the Py_TPFLAGS_HAVE_CLASS flag */
191 binaryfunc nb_floor_divide
;
192 binaryfunc nb_true_divide
;
193 binaryfunc nb_inplace_floor_divide
;
194 binaryfunc nb_inplace_true_divide
;
199 binaryfunc sq_concat
;
200 intargfunc sq_repeat
;
202 intintargfunc sq_slice
;
203 intobjargproc sq_ass_item
;
204 intintobjargproc sq_ass_slice
;
205 objobjproc sq_contains
;
206 /* Added in release 2.0 */
207 binaryfunc sq_inplace_concat
;
208 intargfunc sq_inplace_repeat
;
213 binaryfunc mp_subscript
;
214 objobjargproc mp_ass_subscript
;
218 getreadbufferproc bf_getreadbuffer
;
219 getwritebufferproc bf_getwritebuffer
;
220 getsegcountproc bf_getsegcount
;
221 getcharbufferproc bf_getcharbuffer
;
225 typedef void (*freefunc
)(void *);
226 typedef void (*destructor
)(PyObject
*);
227 typedef int (*printfunc
)(PyObject
*, FILE *, int);
228 typedef PyObject
*(*getattrfunc
)(PyObject
*, char *);
229 typedef PyObject
*(*getattrofunc
)(PyObject
*, PyObject
*);
230 typedef int (*setattrfunc
)(PyObject
*, char *, PyObject
*);
231 typedef int (*setattrofunc
)(PyObject
*, PyObject
*, PyObject
*);
232 typedef int (*cmpfunc
)(PyObject
*, PyObject
*);
233 typedef PyObject
*(*reprfunc
)(PyObject
*);
234 typedef long (*hashfunc
)(PyObject
*);
235 typedef PyObject
*(*richcmpfunc
) (PyObject
*, PyObject
*, int);
236 typedef PyObject
*(*getiterfunc
) (PyObject
*);
237 typedef PyObject
*(*iternextfunc
) (PyObject
*);
238 typedef PyObject
*(*descrgetfunc
) (PyObject
*, PyObject
*, PyObject
*);
239 typedef int (*descrsetfunc
) (PyObject
*, PyObject
*, PyObject
*);
240 typedef int (*initproc
)(PyObject
*, PyObject
*, PyObject
*);
241 typedef PyObject
*(*newfunc
)(struct _typeobject
*, PyObject
*, PyObject
*);
242 typedef PyObject
*(*allocfunc
)(struct _typeobject
*, int);
244 typedef struct _typeobject
{
246 char *tp_name
; /* For printing, in format "<module>.<name>" */
247 int tp_basicsize
, tp_itemsize
; /* For allocation */
249 /* Methods to implement standard operations */
251 destructor tp_dealloc
;
253 getattrfunc tp_getattr
;
254 setattrfunc tp_setattr
;
258 /* Method suites for standard classes */
260 PyNumberMethods
*tp_as_number
;
261 PySequenceMethods
*tp_as_sequence
;
262 PyMappingMethods
*tp_as_mapping
;
264 /* More standard operations (here for binary compatibility) */
269 getattrofunc tp_getattro
;
270 setattrofunc tp_setattro
;
272 /* Functions to access object as input/output buffer */
273 PyBufferProcs
*tp_as_buffer
;
275 /* Flags to define presence of optional/expanded features */
278 char *tp_doc
; /* Documentation string */
280 /* Assigned meaning in release 2.0 */
281 /* call function for all accessible objects */
282 traverseproc tp_traverse
;
284 /* delete references to contained objects */
287 /* Assigned meaning in release 2.1 */
288 /* rich comparisons */
289 richcmpfunc tp_richcompare
;
291 /* weak reference enabler */
292 long tp_weaklistoffset
;
294 /* Added in release 2.2 */
297 iternextfunc tp_iternext
;
299 /* Attribute descriptor and subclassing stuff */
300 struct PyMethodDef
*tp_methods
;
301 struct PyMemberDef
*tp_members
;
302 struct PyGetSetDef
*tp_getset
;
303 struct _typeobject
*tp_base
;
305 descrgetfunc tp_descr_get
;
306 descrsetfunc tp_descr_set
;
311 freefunc tp_free
; /* Low-level free-memory routine */
312 inquiry tp_is_gc
; /* For PyObject_IS_GC */
314 PyObject
*tp_mro
; /* method resolution order */
316 PyObject
*tp_subclasses
;
317 PyObject
*tp_weaklist
;
321 /* these must be last and never explicitly initialized */
325 struct _typeobject
*tp_next
;
330 /* The *real* layout of a type object when allocated on the heap */
331 typedef struct _heaptypeobject
{
332 /* Note: there's a dependency on the order of these members
333 in slotptr() in typeobject.c . */
335 PyNumberMethods as_number
;
336 PyMappingMethods as_mapping
;
337 PySequenceMethods as_sequence
; /* as_sequence comes after as_mapping,
338 so that the mapping wins when both
339 the mapping and the sequence define
340 a given operator (e.g. __getitem__).
341 see add_operators() in typeobject.c . */
342 PyBufferProcs as_buffer
;
343 PyObject
*name
, *slots
;
344 /* here are optional user slots, followed by the members. */
347 /* access macro to the members which are floating "behind" the object */
348 #define PyHeapType_GET_MEMBERS(etype) \
349 ((PyMemberDef *)(((char *)etype) + (etype)->type.ob_type->tp_basicsize))
352 /* Generic type check */
353 PyAPI_FUNC(int) PyType_IsSubtype(PyTypeObject
*, PyTypeObject
*);
354 #define PyObject_TypeCheck(ob, tp) \
355 ((ob)->ob_type == (tp) || PyType_IsSubtype((ob)->ob_type, (tp)))
357 PyAPI_DATA(PyTypeObject
) PyType_Type
; /* built-in 'type' */
358 PyAPI_DATA(PyTypeObject
) PyBaseObject_Type
; /* built-in 'object' */
359 PyAPI_DATA(PyTypeObject
) PySuper_Type
; /* built-in 'super' */
361 #define PyType_Check(op) PyObject_TypeCheck(op, &PyType_Type)
362 #define PyType_CheckExact(op) ((op)->ob_type == &PyType_Type)
364 PyAPI_FUNC(int) PyType_Ready(PyTypeObject
*);
365 PyAPI_FUNC(PyObject
*) PyType_GenericAlloc(PyTypeObject
*, int);
366 PyAPI_FUNC(PyObject
*) PyType_GenericNew(PyTypeObject
*,
367 PyObject
*, PyObject
*);
368 PyAPI_FUNC(PyObject
*) _PyType_Lookup(PyTypeObject
*, PyObject
*);
370 /* Generic operations on objects */
371 PyAPI_FUNC(int) PyObject_Print(PyObject
*, FILE *, int);
372 PyAPI_FUNC(void) _PyObject_Dump(PyObject
*);
373 PyAPI_FUNC(PyObject
*) PyObject_Repr(PyObject
*);
374 PyAPI_FUNC(PyObject
*) _PyObject_Str(PyObject
*);
375 PyAPI_FUNC(PyObject
*) PyObject_Str(PyObject
*);
376 #ifdef Py_USING_UNICODE
377 PyAPI_FUNC(PyObject
*) PyObject_Unicode(PyObject
*);
379 PyAPI_FUNC(int) PyObject_Compare(PyObject
*, PyObject
*);
380 PyAPI_FUNC(PyObject
*) PyObject_RichCompare(PyObject
*, PyObject
*, int);
381 PyAPI_FUNC(int) PyObject_RichCompareBool(PyObject
*, PyObject
*, int);
382 PyAPI_FUNC(PyObject
*) PyObject_GetAttrString(PyObject
*, char *);
383 PyAPI_FUNC(int) PyObject_SetAttrString(PyObject
*, char *, PyObject
*);
384 PyAPI_FUNC(int) PyObject_HasAttrString(PyObject
*, char *);
385 PyAPI_FUNC(PyObject
*) PyObject_GetAttr(PyObject
*, PyObject
*);
386 PyAPI_FUNC(int) PyObject_SetAttr(PyObject
*, PyObject
*, PyObject
*);
387 PyAPI_FUNC(int) PyObject_HasAttr(PyObject
*, PyObject
*);
388 PyAPI_FUNC(PyObject
**) _PyObject_GetDictPtr(PyObject
*);
389 PyAPI_FUNC(PyObject
*) PyObject_SelfIter(PyObject
*);
390 PyAPI_FUNC(PyObject
*) PyObject_GenericGetAttr(PyObject
*, PyObject
*);
391 PyAPI_FUNC(int) PyObject_GenericSetAttr(PyObject
*,
392 PyObject
*, PyObject
*);
393 PyAPI_FUNC(long) PyObject_Hash(PyObject
*);
394 PyAPI_FUNC(int) PyObject_IsTrue(PyObject
*);
395 PyAPI_FUNC(int) PyObject_Not(PyObject
*);
396 PyAPI_FUNC(int) PyCallable_Check(PyObject
*);
397 PyAPI_FUNC(int) PyNumber_Coerce(PyObject
**, PyObject
**);
398 PyAPI_FUNC(int) PyNumber_CoerceEx(PyObject
**, PyObject
**);
400 PyAPI_FUNC(void) PyObject_ClearWeakRefs(PyObject
*);
402 /* A slot function whose address we need to compare */
403 extern int _PyObject_SlotCompare(PyObject
*, PyObject
*);
406 /* PyObject_Dir(obj) acts like Python __builtin__.dir(obj), returning a
407 list of strings. PyObject_Dir(NULL) is like __builtin__.dir(),
408 returning the names of the current locals. In this case, if there are
409 no current locals, NULL is returned, and PyErr_Occurred() is false.
411 PyAPI_FUNC(PyObject
*) PyObject_Dir(PyObject
*);
414 /* Helpers for printing recursive container types */
415 PyAPI_FUNC(int) Py_ReprEnter(PyObject
*);
416 PyAPI_FUNC(void) Py_ReprLeave(PyObject
*);
418 /* Helpers for hash functions */
419 PyAPI_FUNC(long) _Py_HashDouble(double);
420 PyAPI_FUNC(long) _Py_HashPointer(void*);
422 /* Helper for passing objects to printf and the like */
423 #define PyObject_REPR(obj) PyString_AS_STRING(PyObject_Repr(obj))
425 /* Flag bits for printing: */
426 #define Py_PRINT_RAW 1 /* No string quotes etc. */
429 `Type flags (tp_flags)
431 These flags are used to extend the type structure in a backwards-compatible
432 fashion. Extensions can use the flags to indicate (and test) when a given
433 type structure contains a new feature. The Python core will use these when
434 introducing new functionality between major revisions (to avoid mid-version
435 changes in the PYTHON_API_VERSION).
437 Arbitration of the flag bit positions will need to be coordinated among
438 all extension writers who publically release their extensions (this will
439 be fewer than you might expect!)..
441 Python 1.5.2 introduced the bf_getcharbuffer slot into PyBufferProcs.
443 Type definitions should use Py_TPFLAGS_DEFAULT for their tp_flags value.
445 Code can use PyType_HasFeature(type_ob, flag_value) to test whether the
446 given type object has a specified feature.
449 /* PyBufferProcs contains bf_getcharbuffer */
450 #define Py_TPFLAGS_HAVE_GETCHARBUFFER (1L<<0)
452 /* PySequenceMethods contains sq_contains */
453 #define Py_TPFLAGS_HAVE_SEQUENCE_IN (1L<<1)
455 /* This is here for backwards compatibility. Extensions that use the old GC
456 * API will still compile but the objects will not be tracked by the GC. */
457 #define Py_TPFLAGS_GC 0 /* used to be (1L<<2) */
459 /* PySequenceMethods and PyNumberMethods contain in-place operators */
460 #define Py_TPFLAGS_HAVE_INPLACEOPS (1L<<3)
462 /* PyNumberMethods do their own coercion */
463 #define Py_TPFLAGS_CHECKTYPES (1L<<4)
465 /* tp_richcompare is defined */
466 #define Py_TPFLAGS_HAVE_RICHCOMPARE (1L<<5)
468 /* Objects which are weakly referencable if their tp_weaklistoffset is >0 */
469 #define Py_TPFLAGS_HAVE_WEAKREFS (1L<<6)
471 /* tp_iter is defined */
472 #define Py_TPFLAGS_HAVE_ITER (1L<<7)
474 /* New members introduced by Python 2.2 exist */
475 #define Py_TPFLAGS_HAVE_CLASS (1L<<8)
477 /* Set if the type object is dynamically allocated */
478 #define Py_TPFLAGS_HEAPTYPE (1L<<9)
480 /* Set if the type allows subclassing */
481 #define Py_TPFLAGS_BASETYPE (1L<<10)
483 /* Set if the type is 'ready' -- fully initialized */
484 #define Py_TPFLAGS_READY (1L<<12)
486 /* Set while the type is being 'readied', to prevent recursive ready calls */
487 #define Py_TPFLAGS_READYING (1L<<13)
489 /* Objects support garbage collection (see objimp.h) */
490 #define Py_TPFLAGS_HAVE_GC (1L<<14)
492 /* These two bits are preserved for Stackless Python, next after this is 16 */
494 #define Py_TPFLAGS_HAVE_STACKLESS_EXTENSION (3L<<15)
496 #define Py_TPFLAGS_HAVE_STACKLESS_EXTENSION 0
499 #define Py_TPFLAGS_DEFAULT ( \
500 Py_TPFLAGS_HAVE_GETCHARBUFFER | \
501 Py_TPFLAGS_HAVE_SEQUENCE_IN | \
502 Py_TPFLAGS_HAVE_INPLACEOPS | \
503 Py_TPFLAGS_HAVE_RICHCOMPARE | \
504 Py_TPFLAGS_HAVE_WEAKREFS | \
505 Py_TPFLAGS_HAVE_ITER | \
506 Py_TPFLAGS_HAVE_CLASS | \
507 Py_TPFLAGS_HAVE_STACKLESS_EXTENSION | \
510 #define PyType_HasFeature(t,f) (((t)->tp_flags & (f)) != 0)
514 The macros Py_INCREF(op) and Py_DECREF(op) are used to increment or decrement
515 reference counts. Py_DECREF calls the object's deallocator function when
516 the refcount falls to 0; for
517 objects that don't contain references to other objects or heap memory
518 this can be the standard function free(). Both macros can be used
519 wherever a void expression is allowed. The argument must not be a
520 NIL pointer. If it may be NIL, use Py_XINCREF/Py_XDECREF instead.
521 The macro _Py_NewReference(op) initialize reference counts to 1, and
522 in special builds (Py_REF_DEBUG, Py_TRACE_REFS) performs additional
523 bookkeeping appropriate to the special build.
525 We assume that the reference count field can never overflow; this can
526 be proven when the size of the field is the same as the pointer size, so
527 we ignore the possibility. Provided a C int is at least 32 bits (which
528 is implicitly assumed in many parts of this code), that's enough for
529 about 2**31 references to an object.
531 XXX The following became out of date in Python 2.2, but I'm not sure
532 XXX what the full truth is now. Certainly, heap-allocated type objects
533 XXX can and should be deallocated.
534 Type objects should never be deallocated; the type pointer in an object
535 is not considered to be a reference to the type object, to save
536 complications in the deallocation function. (This is actually a
537 decision that's up to the implementer of each new type so if you want,
538 you can count such references to the type object.)
540 *** WARNING*** The Py_DECREF macro must have a side-effect-free argument
541 since it may evaluate its argument multiple times. (The alternative
542 would be to mace it a proper function or assign it to a global temporary
543 variable first, both of which are slower; and in a multi-threaded
544 environment the global variable trick is not safe.)
547 /* First define a pile of simple helper macros, one set per special
548 * build symbol. These either expand to the obvious things, or to
549 * nothing at all when the special mode isn't in effect. The main
550 * macros can later be defined just once then, yet expand to different
551 * things depending on which special build options are and aren't in effect.
552 * Trust me <wink>: while painful, this is 20x easier to understand than,
553 * e.g, defining _Py_NewReference five different times in a maze of nested
554 * #ifdefs (we used to do that -- it was impenetrable).
557 PyAPI_DATA(long) _Py_RefTotal
;
558 PyAPI_FUNC(void) _Py_NegativeRefcount(const char *fname
,
559 int lineno
, PyObject
*op
);
560 #define _Py_INC_REFTOTAL _Py_RefTotal++
561 #define _Py_DEC_REFTOTAL _Py_RefTotal--
562 #define _Py_REF_DEBUG_COMMA ,
563 #define _Py_CHECK_REFCNT(OP) \
564 { if ((OP)->ob_refcnt < 0) \
565 _Py_NegativeRefcount(__FILE__, __LINE__, \
569 #define _Py_INC_REFTOTAL
570 #define _Py_DEC_REFTOTAL
571 #define _Py_REF_DEBUG_COMMA
572 #define _Py_CHECK_REFCNT(OP) /* a semicolon */;
573 #endif /* Py_REF_DEBUG */
576 PyAPI_FUNC(void) inc_count(PyTypeObject
*);
577 #define _Py_INC_TPALLOCS(OP) inc_count((OP)->ob_type)
578 #define _Py_INC_TPFREES(OP) (OP)->ob_type->tp_frees++
579 #define _Py_DEC_TPFREES(OP) (OP)->ob_type->tp_frees--
580 #define _Py_COUNT_ALLOCS_COMMA ,
582 #define _Py_INC_TPALLOCS(OP)
583 #define _Py_INC_TPFREES(OP)
584 #define _Py_DEC_TPFREES(OP)
585 #define _Py_COUNT_ALLOCS_COMMA
586 #endif /* COUNT_ALLOCS */
589 /* Py_TRACE_REFS is such major surgery that we call external routines. */
590 PyAPI_FUNC(void) _Py_NewReference(PyObject
*);
591 PyAPI_FUNC(void) _Py_ForgetReference(PyObject
*);
592 PyAPI_FUNC(void) _Py_Dealloc(PyObject
*);
593 PyAPI_FUNC(void) _Py_PrintReferences(FILE *);
594 PyAPI_FUNC(void) _Py_PrintReferenceAddresses(FILE *);
595 PyAPI_FUNC(void) _Py_AddToAllObjects(PyObject
*, int force
);
598 /* Without Py_TRACE_REFS, there's little enough to do that we expand code
601 #define _Py_NewReference(op) ( \
602 _Py_INC_TPALLOCS(op) _Py_COUNT_ALLOCS_COMMA \
603 _Py_INC_REFTOTAL _Py_REF_DEBUG_COMMA \
606 #define _Py_ForgetReference(op) _Py_INC_TPFREES(op)
608 #define _Py_Dealloc(op) ( \
609 _Py_INC_TPFREES(op) _Py_COUNT_ALLOCS_COMMA \
610 (*(op)->ob_type->tp_dealloc)((PyObject *)(op)))
611 #endif /* !Py_TRACE_REFS */
613 #define Py_INCREF(op) ( \
614 _Py_INC_REFTOTAL _Py_REF_DEBUG_COMMA \
617 #define Py_DECREF(op) \
618 if (_Py_DEC_REFTOTAL _Py_REF_DEBUG_COMMA \
619 --(op)->ob_refcnt != 0) \
620 _Py_CHECK_REFCNT(op) \
622 _Py_Dealloc((PyObject *)(op))
624 #define Py_CLEAR(op) \
627 PyObject *tmp = (PyObject *)(op); \
633 /* Macros to use in case the object pointer may be NULL: */
634 #define Py_XINCREF(op) if ((op) == NULL) ; else Py_INCREF(op)
635 #define Py_XDECREF(op) if ((op) == NULL) ; else Py_DECREF(op)
638 These are provided as conveniences to Python runtime embedders, so that
639 they can have object code that is not dependent on Python compilation flags.
641 PyAPI_FUNC(void) Py_IncRef(PyObject
*);
642 PyAPI_FUNC(void) Py_DecRef(PyObject
*);
645 _Py_NoneStruct is an object of undefined type which can be used in contexts
646 where NULL (nil) is not suitable (since NULL often means 'error').
648 Don't forget to apply Py_INCREF() when returning this value!!!
650 PyAPI_DATA(PyObject
) _Py_NoneStruct
; /* Don't use this directly */
651 #define Py_None (&_Py_NoneStruct)
653 /* Macro for returning Py_None from a function */
654 #define Py_RETURN_NONE return Py_INCREF(Py_None), Py_None
657 Py_NotImplemented is a singleton used to signal that an operation is
658 not implemented for a given type combination.
660 PyAPI_DATA(PyObject
) _Py_NotImplementedStruct
; /* Don't use this directly */
661 #define Py_NotImplemented (&_Py_NotImplementedStruct)
663 /* Rich comparison opcodes */
671 /* Maps Py_LT to Py_GT, ..., Py_GE to Py_LE.
672 * Defined in object.c.
674 PyAPI_DATA(int) _Py_SwappedOp
[];
677 Define staticforward and statichere for source compatibility with old
680 The staticforward define was needed to support certain broken C
681 compilers (notably SCO ODT 3.0, perhaps early AIX as well) botched the
682 static keyword when it was used with a forward declaration of a static
683 initialized structure. Standard C allows the forward declaration with
684 static, and we've decided to stop catering to broken C compilers.
685 (In fact, we expect that the compilers are all fixed eight years later.)
688 #define staticforward static
689 #define statichere static
699 Functions that take objects as arguments normally don't check for nil
700 arguments, but they do check the type of the argument, and return an
701 error if the function doesn't apply to the type.
706 Functions may fail for a variety of reasons, including running out of
707 memory. This is communicated to the caller in two ways: an error string
708 is set (see errors.h), and the function result differs: functions that
709 normally return a pointer return NULL for failure, functions returning
710 an integer return -1 (which could be a legal return value too!), and
711 other functions return 0 for success and -1 for failure.
712 Callers should always check for errors before using the result. If
713 an error was set, the caller must either explicitly clear it, or pass
714 the error on to its caller.
719 It takes a while to get used to the proper usage of reference counts.
721 Functions that create an object set the reference count to 1; such new
722 objects must be stored somewhere or destroyed again with Py_DECREF().
723 Some functions that 'store' objects, such as PyTuple_SetItem() and
725 don't increment the reference count of the object, since the most
726 frequent use is to store a fresh object. Functions that 'retrieve'
727 objects, such as PyTuple_GetItem() and PyDict_GetItemString(), also
729 the reference count, since most frequently the object is only looked at
730 quickly. Thus, to retrieve an object and store it again, the caller
731 must call Py_INCREF() explicitly.
733 NOTE: functions that 'consume' a reference count, like
734 PyList_SetItem(), consume the reference even if the object wasn't
735 successfully stored, to simplify error handling.
737 It seems attractive to make other functions that take an object as
738 argument consume a reference count; however, this may quickly get
739 confusing (even the current practice is already confusing). Consider
740 it carefully, it may save lots of calls to Py_INCREF() and Py_DECREF() at
745 /* Trashcan mechanism, thanks to Christian Tismer.
747 When deallocating a container object, it's possible to trigger an unbounded
748 chain of deallocations, as each Py_DECREF in turn drops the refcount on "the
749 next" object in the chain to 0. This can easily lead to stack faults, and
750 especially in threads (which typically have less stack space to work with).
752 A container object that participates in cyclic gc can avoid this by
753 bracketing the body of its tp_dealloc function with a pair of macros:
756 mytype_dealloc(mytype *p)
758 ... declarations go here ...
760 PyObject_GC_UnTrack(p); // must untrack first
761 Py_TRASHCAN_SAFE_BEGIN(p)
762 ... The body of the deallocator goes here, including all calls ...
763 ... to Py_DECREF on contained objects. ...
764 Py_TRASHCAN_SAFE_END(p)
767 CAUTION: Never return from the middle of the body! If the body needs to
768 "get out early", put a label immediately before the Py_TRASHCAN_SAFE_END
769 call, and goto it. Else the call-depth counter (see below) will stay
770 above 0 forever, and the trashcan will never get emptied.
772 How it works: The BEGIN macro increments a call-depth counter. So long
773 as this counter is small, the body of the deallocator is run directly without
774 further ado. But if the counter gets large, it instead adds p to a list of
775 objects to be deallocated later, skips the body of the deallocator, and
776 resumes execution after the END macro. The tp_dealloc routine then returns
777 without deallocating anything (and so unbounded call-stack depth is avoided).
779 When the call stack finishes unwinding again, code generated by the END macro
780 notices this, and calls another routine to deallocate all the objects that
781 may have been added to the list of deferred deallocations. In effect, a
782 chain of N deallocations is broken into N / PyTrash_UNWIND_LEVEL pieces,
783 with the call stack never exceeding a depth of PyTrash_UNWIND_LEVEL.
786 PyAPI_FUNC(void) _PyTrash_deposit_object(PyObject
*);
787 PyAPI_FUNC(void) _PyTrash_destroy_chain(void);
788 PyAPI_DATA(int) _PyTrash_delete_nesting
;
789 PyAPI_DATA(PyObject
*) _PyTrash_delete_later
;
791 #define PyTrash_UNWIND_LEVEL 50
793 #define Py_TRASHCAN_SAFE_BEGIN(op) \
794 if (_PyTrash_delete_nesting < PyTrash_UNWIND_LEVEL) { \
795 ++_PyTrash_delete_nesting;
796 /* The body of the deallocator is here. */
797 #define Py_TRASHCAN_SAFE_END(op) \
798 --_PyTrash_delete_nesting; \
799 if (_PyTrash_delete_later && _PyTrash_delete_nesting <= 0) \
800 _PyTrash_destroy_chain(); \
803 _PyTrash_deposit_object((PyObject*)op);
808 #endif /* !Py_OBJECT_H */