Include/object.h

   1 #ifndef Py_OBJECT_H
   2 #define Py_OBJECT_H
   3 #ifdef __cplusplus
   4 extern "C" {
   5 #endif
   6
   7
   8 /* Object and type object interface */
   9
  10 /*
  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).
  18
  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.
  23
  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!).
  30
  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.)
  39
  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
  48 type and back.
  49
  50 A standard interface exists for objects that contain an array of items
  51 whose size is determined when the object is allocated.
  52 */
  53
  54 /* Py_DEBUG implies Py_TRACE_REFS. */
  55 #if defined(Py_DEBUG) && !defined(Py_TRACE_REFS)
  56 #define Py_TRACE_REFS
  57 #endif
  58
  59 /* Py_TRACE_REFS implies Py_REF_DEBUG. */
  60 #if defined(Py_TRACE_REFS) && !defined(Py_REF_DEBUG)
  61 #define Py_REF_DEBUG
  62 #endif
  63
  64 #ifdef Py_TRACE_REFS
  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;
  69
  70 #define _PyObject_EXTRA_INIT 0, 0,
  71
  72 #else
  73 #define _PyObject_HEAD_EXTRA
  74 #define _PyObject_EXTRA_INIT
  75 #endif
  76
  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;
  82
  83 #define PyObject_HEAD_INIT(type)        \
  84         _PyObject_EXTRA_INIT            \
  85         1, type,
  86
  87 #define PyVarObject_HEAD_INIT(type, size)       \
  88         PyObject_HEAD_INIT(type) size,
  89
  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.
  95  */
  96 #define PyObject_VAR_HEAD               \
  97         PyObject_HEAD                   \
  98         Py_ssize_t ob_size; /* Number of items in variable part */
  99 #define Py_INVALID_SIZE (Py_ssize_t)-1
 100
 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*.
 105  */
 106 typedef struct _object {
 107         PyObject_HEAD
 108 } PyObject;
 109
 110 typedef struct {
 111         PyObject_VAR_HEAD
 112 } PyVarObject;
 113
 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)
 117
 118 /* B/w compatibility */
 119 #define Py_Refcnt(ob)           Py_REFCNT(op)
 120 #define Py_Type(op)             Py_TYPE(op)
 121 #define Py_Size(op)             Py_SIZE(op)
 122
 123 /*
 124 Type objects contain a string containing the type name (to help somewhat
 125 in debugging), the allocation parameters (see PyObject_New() and
 126 PyObject_NewVar()),
 127 and methods for accessing objects of the type.  Methods are optional, a
 128 nil pointer meaning that particular kind of access is not available for
 129 this type.  The Py_DECREF() macro uses the tp_dealloc method without
 130 checking for a nil pointer; it should always be implemented except if
 131 the implementation can guarantee that the reference count will never
 132 reach zero (e.g., for statically allocated type objects).
 133
 134 NB: the methods for certain type groups are now contained in separate
 135 method blocks.
 136 */
 137
 138 typedef PyObject * (*unaryfunc)(PyObject *);
 139 typedef PyObject * (*binaryfunc)(PyObject *, PyObject *);
 140 typedef PyObject * (*ternaryfunc)(PyObject *, PyObject *, PyObject *);
 141 typedef int (*inquiry)(PyObject *);
 142 typedef Py_ssize_t (*lenfunc)(PyObject *);
 143 typedef int (*coercion)(PyObject **, PyObject **);
 144 typedef PyObject *(*intargfunc)(PyObject *, int) Py_DEPRECATED(2.5);
 145 typedef PyObject *(*intintargfunc)(PyObject *, int, int) Py_DEPRECATED(2.5);
 146 typedef PyObject *(*ssizeargfunc)(PyObject *, Py_ssize_t);
 147 typedef PyObject *(*ssizessizeargfunc)(PyObject *, Py_ssize_t, Py_ssize_t);
 148 typedef int(*intobjargproc)(PyObject *, int, PyObject *);
 149 typedef int(*intintobjargproc)(PyObject *, int, int, PyObject *);
 150 typedef int(*ssizeobjargproc)(PyObject *, Py_ssize_t, PyObject *);
 151 typedef int(*ssizessizeobjargproc)(PyObject *, Py_ssize_t, Py_ssize_t, PyObject *);
 152 typedef int(*objobjargproc)(PyObject *, PyObject *, PyObject *);
 153
 154 /* int-based buffer interface */
 155 typedef int (*getreadbufferproc)(PyObject *, int, void **);
 156 typedef int (*getwritebufferproc)(PyObject *, int, void **);
 157 typedef int (*getsegcountproc)(PyObject *, int *);
 158 typedef int (*getcharbufferproc)(PyObject *, int, char **);
 159 /* ssize_t-based buffer interface */
 160 typedef Py_ssize_t (*readbufferproc)(PyObject *, Py_ssize_t, void **);
 161 typedef Py_ssize_t (*writebufferproc)(PyObject *, Py_ssize_t, void **);
 162 typedef Py_ssize_t (*segcountproc)(PyObject *, Py_ssize_t *);
 163 typedef Py_ssize_t (*charbufferproc)(PyObject *, Py_ssize_t, char **);
 164
 165 typedef int (*objobjproc)(PyObject *, PyObject *);
 166 typedef int (*visitproc)(PyObject *, void *);
 167 typedef int (*traverseproc)(PyObject *, visitproc, void *);
 168
 169 typedef struct {
 170         /* For numbers without flag bit Py_TPFLAGS_CHECKTYPES set, all
 171            arguments are guaranteed to be of the object's type (modulo
 172            coercion hacks -- i.e. if the type's coercion function
 173            returns other types, then these are allowed as well).  Numbers that
 174            have the Py_TPFLAGS_CHECKTYPES flag bit set should check *both*
 175            arguments for proper type and implement the necessary conversions
 176            in the slot functions themselves. */
 177
 178         binaryfunc nb_add;
 179         binaryfunc nb_subtract;
 180         binaryfunc nb_multiply;
 181         binaryfunc nb_divide;
 182         binaryfunc nb_remainder;
 183         binaryfunc nb_divmod;
 184         ternaryfunc nb_power;
 185         unaryfunc nb_negative;
 186         unaryfunc nb_positive;
 187         unaryfunc nb_absolute;
 188         inquiry nb_nonzero;
 189         unaryfunc nb_invert;
 190         binaryfunc nb_lshift;
 191         binaryfunc nb_rshift;
 192         binaryfunc nb_and;
 193         binaryfunc nb_xor;
 194         binaryfunc nb_or;
 195         coercion nb_coerce;
 196         unaryfunc nb_int;
 197         unaryfunc nb_long;
 198         unaryfunc nb_float;
 199         unaryfunc nb_oct;
 200         unaryfunc nb_hex;
 201         /* Added in release 2.0 */
 202         binaryfunc nb_inplace_add;
 203         binaryfunc nb_inplace_subtract;
 204         binaryfunc nb_inplace_multiply;
 205         binaryfunc nb_inplace_divide;
 206         binaryfunc nb_inplace_remainder;
 207         ternaryfunc nb_inplace_power;
 208         binaryfunc nb_inplace_lshift;
 209         binaryfunc nb_inplace_rshift;
 210         binaryfunc nb_inplace_and;
 211         binaryfunc nb_inplace_xor;
 212         binaryfunc nb_inplace_or;
 213
 214         /* Added in release 2.2 */
 215         /* The following require the Py_TPFLAGS_HAVE_CLASS flag */
 216         binaryfunc nb_floor_divide;
 217         binaryfunc nb_true_divide;
 218         binaryfunc nb_inplace_floor_divide;
 219         binaryfunc nb_inplace_true_divide;
 220
 221         /* Added in release 2.5 */
 222         unaryfunc nb_index;
 223 } PyNumberMethods;
 224
 225 typedef struct {
 226         lenfunc sq_length;
 227         binaryfunc sq_concat;
 228         ssizeargfunc sq_repeat;
 229         ssizeargfunc sq_item;
 230         ssizessizeargfunc sq_slice;
 231         ssizeobjargproc sq_ass_item;
 232         ssizessizeobjargproc sq_ass_slice;
 233         objobjproc sq_contains;
 234         /* Added in release 2.0 */
 235         binaryfunc sq_inplace_concat;
 236         ssizeargfunc sq_inplace_repeat;
 237 } PySequenceMethods;
 238
 239 typedef struct {
 240         lenfunc mp_length;
 241         binaryfunc mp_subscript;
 242         objobjargproc mp_ass_subscript;
 243 } PyMappingMethods;
 244
 245 typedef struct {
 246         readbufferproc bf_getreadbuffer;
 247         writebufferproc bf_getwritebuffer;
 248         segcountproc bf_getsegcount;
 249         charbufferproc bf_getcharbuffer;
 250 } PyBufferProcs;
 251
 252
 253 typedef void (*freefunc)(void *);
 254 typedef void (*destructor)(PyObject *);
 255 typedef int (*printfunc)(PyObject *, FILE *, int);
 256 typedef PyObject *(*getattrfunc)(PyObject *, char *);
 257 typedef PyObject *(*getattrofunc)(PyObject *, PyObject *);
 258 typedef int (*setattrfunc)(PyObject *, char *, PyObject *);
 259 typedef int (*setattrofunc)(PyObject *, PyObject *, PyObject *);
 260 typedef int (*cmpfunc)(PyObject *, PyObject *);
 261 typedef PyObject *(*reprfunc)(PyObject *);
 262 typedef long (*hashfunc)(PyObject *);
 263 typedef PyObject *(*richcmpfunc) (PyObject *, PyObject *, int);
 264 typedef PyObject *(*getiterfunc) (PyObject *);
 265 typedef PyObject *(*iternextfunc) (PyObject *);
 266 typedef PyObject *(*descrgetfunc) (PyObject *, PyObject *, PyObject *);
 267 typedef int (*descrsetfunc) (PyObject *, PyObject *, PyObject *);
 268 typedef int (*initproc)(PyObject *, PyObject *, PyObject *);
 269 typedef PyObject *(*newfunc)(struct _typeobject *, PyObject *, PyObject *);
 270 typedef PyObject *(*allocfunc)(struct _typeobject *, Py_ssize_t);
 271
 272 typedef struct _typeobject {
 273         PyObject_VAR_HEAD
 274         const char *tp_name; /* For printing, in format "<module>.<name>" */
 275         Py_ssize_t tp_basicsize, tp_itemsize; /* For allocation */
 276
 277         /* Methods to implement standard operations */
 278
 279         destructor tp_dealloc;
 280         printfunc tp_print;
 281         getattrfunc tp_getattr;
 282         setattrfunc tp_setattr;
 283         cmpfunc tp_compare;
 284         reprfunc tp_repr;
 285
 286         /* Method suites for standard classes */
 287
 288         PyNumberMethods *tp_as_number;
 289         PySequenceMethods *tp_as_sequence;
 290         PyMappingMethods *tp_as_mapping;
 291
 292         /* More standard operations (here for binary compatibility) */
 293
 294         hashfunc tp_hash;
 295         ternaryfunc tp_call;
 296         reprfunc tp_str;
 297         getattrofunc tp_getattro;
 298         setattrofunc tp_setattro;
 299
 300         /* Functions to access object as input/output buffer */
 301         PyBufferProcs *tp_as_buffer;
 302
 303         /* Flags to define presence of optional/expanded features */
 304         long tp_flags;
 305
 306         const char *tp_doc; /* Documentation string */
 307
 308         /* Assigned meaning in release 2.0 */
 309         /* call function for all accessible objects */
 310         traverseproc tp_traverse;
 311
 312         /* delete references to contained objects */
 313         inquiry tp_clear;
 314
 315         /* Assigned meaning in release 2.1 */
 316         /* rich comparisons */
 317         richcmpfunc tp_richcompare;
 318
 319         /* weak reference enabler */
 320         Py_ssize_t tp_weaklistoffset;
 321
 322         /* Added in release 2.2 */
 323         /* Iterators */
 324         getiterfunc tp_iter;
 325         iternextfunc tp_iternext;
 326
 327         /* Attribute descriptor and subclassing stuff */
 328         struct PyMethodDef *tp_methods;
 329         struct PyMemberDef *tp_members;
 330         struct PyGetSetDef *tp_getset;
 331         struct _typeobject *tp_base;
 332         PyObject *tp_dict;
 333         descrgetfunc tp_descr_get;
 334         descrsetfunc tp_descr_set;
 335         Py_ssize_t tp_dictoffset;
 336         initproc tp_init;
 337         allocfunc tp_alloc;
 338         newfunc tp_new;
 339         freefunc tp_free; /* Low-level free-memory routine */
 340         inquiry tp_is_gc; /* For PyObject_IS_GC */
 341         PyObject *tp_bases;
 342         PyObject *tp_mro; /* method resolution order */
 343         PyObject *tp_cache;
 344         PyObject *tp_subclasses;
 345         PyObject *tp_weaklist;
 346         destructor tp_del;
 347
 348         /* Type attribute cache version tag. Added in version 2.6 */
 349         unsigned int tp_version_tag;
 350
 351 #ifdef COUNT_ALLOCS
 352         /* these must be last and never explicitly initialized */
 353         Py_ssize_t tp_allocs;
 354         Py_ssize_t tp_frees;
 355         Py_ssize_t tp_maxalloc;
 356         struct _typeobject *tp_prev;
 357         struct _typeobject *tp_next;
 358 #endif
 359 } PyTypeObject;
 360
 361
 362 /* The *real* layout of a type object when allocated on the heap */
 363 typedef struct _heaptypeobject {
 364         /* Note: there's a dependency on the order of these members
 365            in slotptr() in typeobject.c . */
 366         PyTypeObject ht_type;
 367         PyNumberMethods as_number;
 368         PyMappingMethods as_mapping;
 369         PySequenceMethods as_sequence; /* as_sequence comes after as_mapping,
 370                                           so that the mapping wins when both
 371                                           the mapping and the sequence define
 372                                           a given operator (e.g. __getitem__).
 373                                           see add_operators() in typeobject.c . */
 374         PyBufferProcs as_buffer;
 375         PyObject *ht_name, *ht_slots;
 376         /* here are optional user slots, followed by the members. */
 377 } PyHeapTypeObject;
 378
 379 /* access macro to the members which are floating "behind" the object */
 380 #define PyHeapType_GET_MEMBERS(etype) \
 381     ((PyMemberDef *)(((char *)etype) + Py_TYPE(etype)->tp_basicsize))
 382
 383
 384 /* Generic type check */
 385 PyAPI_FUNC(int) PyType_IsSubtype(PyTypeObject *, PyTypeObject *);
 386 #define PyObject_TypeCheck(ob, tp) \
 387         (Py_TYPE(ob) == (tp) || PyType_IsSubtype(Py_TYPE(ob), (tp)))
 388
 389 PyAPI_DATA(PyTypeObject) PyType_Type; /* built-in 'type' */
 390 PyAPI_DATA(PyTypeObject) PyBaseObject_Type; /* built-in 'object' */
 391 PyAPI_DATA(PyTypeObject) PySuper_Type; /* built-in 'super' */
 392
 393 #define PyType_Check(op) \
 394         PyType_FastSubclass(Py_TYPE(op), Py_TPFLAGS_TYPE_SUBCLASS)
 395 #define PyType_CheckExact(op) (Py_TYPE(op) == &PyType_Type)
 396
 397 PyAPI_FUNC(int) PyType_Ready(PyTypeObject *);
 398 PyAPI_FUNC(PyObject *) PyType_GenericAlloc(PyTypeObject *, Py_ssize_t);
 399 PyAPI_FUNC(PyObject *) PyType_GenericNew(PyTypeObject *,
 400                                                PyObject *, PyObject *);
 401 PyAPI_FUNC(PyObject *) _PyType_Lookup(PyTypeObject *, PyObject *);
 402 PyAPI_FUNC(unsigned int) PyType_ClearCache(void);
 403
 404 /* Generic operations on objects */
 405 PyAPI_FUNC(int) PyObject_Print(PyObject *, FILE *, int);
 406 PyAPI_FUNC(void) _PyObject_Dump(PyObject *);
 407 PyAPI_FUNC(PyObject *) PyObject_Repr(PyObject *);
 408 PyAPI_FUNC(PyObject *) _PyObject_Str(PyObject *);
 409 PyAPI_FUNC(PyObject *) PyObject_Str(PyObject *);
 410 #ifdef Py_USING_UNICODE
 411 PyAPI_FUNC(PyObject *) PyObject_Unicode(PyObject *);
 412 #endif
 413 PyAPI_FUNC(int) PyObject_Compare(PyObject *, PyObject *);
 414 PyAPI_FUNC(PyObject *) PyObject_RichCompare(PyObject *, PyObject *, int);
 415 PyAPI_FUNC(int) PyObject_RichCompareBool(PyObject *, PyObject *, int);
 416 PyAPI_FUNC(PyObject *) PyObject_GetAttrString(PyObject *, const char *);
 417 PyAPI_FUNC(int) PyObject_SetAttrString(PyObject *, const char *, PyObject *);
 418 PyAPI_FUNC(int) PyObject_HasAttrString(PyObject *, const char *);
 419 PyAPI_FUNC(PyObject *) PyObject_GetAttr(PyObject *, PyObject *);
 420 PyAPI_FUNC(int) PyObject_SetAttr(PyObject *, PyObject *, PyObject *);
 421 PyAPI_FUNC(int) PyObject_HasAttr(PyObject *, PyObject *);
 422 PyAPI_FUNC(PyObject **) _PyObject_GetDictPtr(PyObject *);
 423 PyAPI_FUNC(PyObject *) PyObject_SelfIter(PyObject *);
 424 PyAPI_FUNC(PyObject *) PyObject_GenericGetAttr(PyObject *, PyObject *);
 425 PyAPI_FUNC(int) PyObject_GenericSetAttr(PyObject *,
 426                                               PyObject *, PyObject *);
 427 PyAPI_FUNC(long) PyObject_Hash(PyObject *);
 428 PyAPI_FUNC(int) PyObject_IsTrue(PyObject *);
 429 PyAPI_FUNC(int) PyObject_Not(PyObject *);
 430 PyAPI_FUNC(int) PyCallable_Check(PyObject *);
 431 PyAPI_FUNC(int) PyNumber_Coerce(PyObject **, PyObject **);
 432 PyAPI_FUNC(int) PyNumber_CoerceEx(PyObject **, PyObject **);
 433
 434 PyAPI_FUNC(void) PyObject_ClearWeakRefs(PyObject *);
 435
 436 /* A slot function whose address we need to compare */
 437 extern int _PyObject_SlotCompare(PyObject *, PyObject *);
 438
 439
 440 /* PyObject_Dir(obj) acts like Python __builtin__.dir(obj), returning a
 441    list of strings.  PyObject_Dir(NULL) is like __builtin__.dir(),
 442    returning the names of the current locals.  In this case, if there are
 443    no current locals, NULL is returned, and PyErr_Occurred() is false.
 444 */
 445 PyAPI_FUNC(PyObject *) PyObject_Dir(PyObject *);
 446
 447
 448 /* Helpers for printing recursive container types */
 449 PyAPI_FUNC(int) Py_ReprEnter(PyObject *);
 450 PyAPI_FUNC(void) Py_ReprLeave(PyObject *);
 451
 452 /* Helpers for hash functions */
 453 PyAPI_FUNC(long) _Py_HashDouble(double);
 454 PyAPI_FUNC(long) _Py_HashPointer(void*);
 455
 456 /* Helper for passing objects to printf and the like */
 457 #define PyObject_REPR(obj) PyString_AS_STRING(PyObject_Repr(obj))
 458
 459 /* Flag bits for printing: */
 460 #define Py_PRINT_RAW    1       /* No string quotes etc. */
 461
 462 /*
 463 `Type flags (tp_flags)
 464
 465 These flags are used to extend the type structure in a backwards-compatible
 466 fashion. Extensions can use the flags to indicate (and test) when a given
 467 type structure contains a new feature. The Python core will use these when
 468 introducing new functionality between major revisions (to avoid mid-version
 469 changes in the PYTHON_API_VERSION).
 470
 471 Arbitration of the flag bit positions will need to be coordinated among
 472 all extension writers who publically release their extensions (this will
 473 be fewer than you might expect!)..
 474
 475 Python 1.5.2 introduced the bf_getcharbuffer slot into PyBufferProcs.
 476
 477 Type definitions should use Py_TPFLAGS_DEFAULT for their tp_flags value.
 478
 479 Code can use PyType_HasFeature(type_ob, flag_value) to test whether the
 480 given type object has a specified feature.
 481 */
 482
 483 /* PyBufferProcs contains bf_getcharbuffer */
 484 #define Py_TPFLAGS_HAVE_GETCHARBUFFER  (1L<<0)
 485
 486 /* PySequenceMethods contains sq_contains */
 487 #define Py_TPFLAGS_HAVE_SEQUENCE_IN (1L<<1)
 488
 489 /* This is here for backwards compatibility.  Extensions that use the old GC
 490  * API will still compile but the objects will not be tracked by the GC. */
 491 #define Py_TPFLAGS_GC 0 /* used to be (1L<<2) */
 492
 493 /* PySequenceMethods and PyNumberMethods contain in-place operators */
 494 #define Py_TPFLAGS_HAVE_INPLACEOPS (1L<<3)
 495
 496 /* PyNumberMethods do their own coercion */
 497 #define Py_TPFLAGS_CHECKTYPES (1L<<4)
 498
 499 /* tp_richcompare is defined */
 500 #define Py_TPFLAGS_HAVE_RICHCOMPARE (1L<<5)
 501
 502 /* Objects which are weakly referencable if their tp_weaklistoffset is >0 */
 503 #define Py_TPFLAGS_HAVE_WEAKREFS (1L<<6)
 504
 505 /* tp_iter is defined */
 506 #define Py_TPFLAGS_HAVE_ITER (1L<<7)
 507
 508 /* New members introduced by Python 2.2 exist */
 509 #define Py_TPFLAGS_HAVE_CLASS (1L<<8)
 510
 511 /* Set if the type object is dynamically allocated */
 512 #define Py_TPFLAGS_HEAPTYPE (1L<<9)
 513
 514 /* Set if the type allows subclassing */
 515 #define Py_TPFLAGS_BASETYPE (1L<<10)
 516
 517 /* Set if the type is 'ready' -- fully initialized */
 518 #define Py_TPFLAGS_READY (1L<<12)
 519
 520 /* Set while the type is being 'readied', to prevent recursive ready calls */
 521 #define Py_TPFLAGS_READYING (1L<<13)
 522
 523 /* Objects support garbage collection (see objimp.h) */
 524 #define Py_TPFLAGS_HAVE_GC (1L<<14)
 525
 526 /* These two bits are preserved for Stackless Python, next after this is 17 */
 527 #ifdef STACKLESS
 528 #define Py_TPFLAGS_HAVE_STACKLESS_EXTENSION (3L<<15)
 529 #else
 530 #define Py_TPFLAGS_HAVE_STACKLESS_EXTENSION 0
 531 #endif
 532
 533 /* Objects support nb_index in PyNumberMethods */
 534 #define Py_TPFLAGS_HAVE_INDEX (1L<<17)
 535
 536 /* Objects support type attribute cache */
 537 #define Py_TPFLAGS_HAVE_VERSION_TAG   (1L<<18)
 538 #define Py_TPFLAGS_VALID_VERSION_TAG  (1L<<19)
 539
 540 /* Type is abstract and cannot be instantiated */
 541 #define Py_TPFLAGS_IS_ABSTRACT (1L<<20)
 542
 543 /* These flags are used to determine if a type is a subclass. */
 544 #define Py_TPFLAGS_INT_SUBCLASS         (1L<<23)
 545 #define Py_TPFLAGS_LONG_SUBCLASS        (1L<<24)
 546 #define Py_TPFLAGS_LIST_SUBCLASS        (1L<<25)
 547 #define Py_TPFLAGS_TUPLE_SUBCLASS       (1L<<26)
 548 #define Py_TPFLAGS_STRING_SUBCLASS      (1L<<27)
 549 #define Py_TPFLAGS_UNICODE_SUBCLASS     (1L<<28)
 550 #define Py_TPFLAGS_DICT_SUBCLASS        (1L<<29)
 551 #define Py_TPFLAGS_BASE_EXC_SUBCLASS    (1L<<30)
 552 #define Py_TPFLAGS_TYPE_SUBCLASS        (1L<<31)
 553
 554 #define Py_TPFLAGS_DEFAULT  ( \
 555                              Py_TPFLAGS_HAVE_GETCHARBUFFER | \
 556                              Py_TPFLAGS_HAVE_SEQUENCE_IN | \
 557                              Py_TPFLAGS_HAVE_INPLACEOPS | \
 558                              Py_TPFLAGS_HAVE_RICHCOMPARE | \
 559                              Py_TPFLAGS_HAVE_WEAKREFS | \
 560                              Py_TPFLAGS_HAVE_ITER | \
 561                              Py_TPFLAGS_HAVE_CLASS | \
 562                              Py_TPFLAGS_HAVE_STACKLESS_EXTENSION | \
 563                              Py_TPFLAGS_HAVE_INDEX | \
 564                              Py_TPFLAGS_HAVE_VERSION_TAG | \
 565                             0)
 566
 567 #define PyType_HasFeature(t,f)  (((t)->tp_flags & (f)) != 0)
 568 #define PyType_FastSubclass(t,f)  PyType_HasFeature(t,f)
 569
 570
 571 /*
 572 The macros Py_INCREF(op) and Py_DECREF(op) are used to increment or decrement
 573 reference counts.  Py_DECREF calls the object's deallocator function when
 574 the refcount falls to 0; for
 575 objects that don't contain references to other objects or heap memory
 576 this can be the standard function free().  Both macros can be used
 577 wherever a void expression is allowed.  The argument must not be a
 578 NIL pointer.  If it may be NIL, use Py_XINCREF/Py_XDECREF instead.
 579 The macro _Py_NewReference(op) initialize reference counts to 1, and
 580 in special builds (Py_REF_DEBUG, Py_TRACE_REFS) performs additional
 581 bookkeeping appropriate to the special build.
 582
 583 We assume that the reference count field can never overflow; this can
 584 be proven when the size of the field is the same as the pointer size, so
 585 we ignore the possibility.  Provided a C int is at least 32 bits (which
 586 is implicitly assumed in many parts of this code), that's enough for
 587 about 2**31 references to an object.
 588
 589 XXX The following became out of date in Python 2.2, but I'm not sure
 590 XXX what the full truth is now.  Certainly, heap-allocated type objects
 591 XXX can and should be deallocated.
 592 Type objects should never be deallocated; the type pointer in an object
 593 is not considered to be a reference to the type object, to save
 594 complications in the deallocation function.  (This is actually a
 595 decision that's up to the implementer of each new type so if you want,
 596 you can count such references to the type object.)
 597
 598 *** WARNING*** The Py_DECREF macro must have a side-effect-free argument
 599 since it may evaluate its argument multiple times.  (The alternative
 600 would be to mace it a proper function or assign it to a global temporary
 601 variable first, both of which are slower; and in a multi-threaded
 602 environment the global variable trick is not safe.)
 603 */
 604
 605 /* First define a pile of simple helper macros, one set per special
 606  * build symbol.  These either expand to the obvious things, or to
 607  * nothing at all when the special mode isn't in effect.  The main
 608  * macros can later be defined just once then, yet expand to different
 609  * things depending on which special build options are and aren't in effect.
 610  * Trust me <wink>:  while painful, this is 20x easier to understand than,
 611  * e.g, defining _Py_NewReference five different times in a maze of nested
 612  * #ifdefs (we used to do that -- it was impenetrable).
 613  */
 614 #ifdef Py_REF_DEBUG
 615 PyAPI_DATA(Py_ssize_t) _Py_RefTotal;
 616 PyAPI_FUNC(void) _Py_NegativeRefcount(const char *fname,
 617                                             int lineno, PyObject *op);
 618 PyAPI_FUNC(PyObject *) _PyDict_Dummy(void);
 619 PyAPI_FUNC(PyObject *) _PySet_Dummy(void);
 620 PyAPI_FUNC(Py_ssize_t) _Py_GetRefTotal(void);
 621 #define _Py_INC_REFTOTAL        _Py_RefTotal++
 622 #define _Py_DEC_REFTOTAL        _Py_RefTotal--
 623 #define _Py_REF_DEBUG_COMMA     ,
 624 #define _Py_CHECK_REFCNT(OP)                                    \
 625 {       if (((PyObject*)OP)->ob_refcnt < 0)                             \
 626                 _Py_NegativeRefcount(__FILE__, __LINE__,        \
 627                                      (PyObject *)(OP));         \
 628 }
 629 #else
 630 #define _Py_INC_REFTOTAL
 631 #define _Py_DEC_REFTOTAL
 632 #define _Py_REF_DEBUG_COMMA
 633 #define _Py_CHECK_REFCNT(OP)    /* a semicolon */;
 634 #endif /* Py_REF_DEBUG */
 635
 636 #ifdef COUNT_ALLOCS
 637 PyAPI_FUNC(void) inc_count(PyTypeObject *);
 638 PyAPI_FUNC(void) dec_count(PyTypeObject *);
 639 #define _Py_INC_TPALLOCS(OP)    inc_count(Py_TYPE(OP))
 640 #define _Py_INC_TPFREES(OP)     dec_count(Py_TYPE(OP))
 641 #define _Py_DEC_TPFREES(OP)     Py_TYPE(OP)->tp_frees--
 642 #define _Py_COUNT_ALLOCS_COMMA  ,
 643 #else
 644 #define _Py_INC_TPALLOCS(OP)
 645 #define _Py_INC_TPFREES(OP)
 646 #define _Py_DEC_TPFREES(OP)
 647 #define _Py_COUNT_ALLOCS_COMMA
 648 #endif /* COUNT_ALLOCS */
 649
 650 #ifdef Py_TRACE_REFS
 651 /* Py_TRACE_REFS is such major surgery that we call external routines. */
 652 PyAPI_FUNC(void) _Py_NewReference(PyObject *);
 653 PyAPI_FUNC(void) _Py_ForgetReference(PyObject *);
 654 PyAPI_FUNC(void) _Py_Dealloc(PyObject *);
 655 PyAPI_FUNC(void) _Py_PrintReferences(FILE *);
 656 PyAPI_FUNC(void) _Py_PrintReferenceAddresses(FILE *);
 657 PyAPI_FUNC(void) _Py_AddToAllObjects(PyObject *, int force);
 658
 659 #else
 660 /* Without Py_TRACE_REFS, there's little enough to do that we expand code
 661  * inline.
 662  */
 663 #define _Py_NewReference(op) (                          \
 664         _Py_INC_TPALLOCS(op) _Py_COUNT_ALLOCS_COMMA     \
 665         _Py_INC_REFTOTAL  _Py_REF_DEBUG_COMMA           \
 666         Py_REFCNT(op) = 1)
 667
 668 #define _Py_ForgetReference(op) _Py_INC_TPFREES(op)
 669
 670 #define _Py_Dealloc(op) (                               \
 671         _Py_INC_TPFREES(op) _Py_COUNT_ALLOCS_COMMA      \
 672         (*Py_TYPE(op)->tp_dealloc)((PyObject *)(op)))
 673 #endif /* !Py_TRACE_REFS */
 674
 675 #define Py_INCREF(op) (                         \
 676         _Py_INC_REFTOTAL  _Py_REF_DEBUG_COMMA   \
 677         ((PyObject*)(op))->ob_refcnt++)
 678
 679 #define Py_DECREF(op)                                   \
 680         if (_Py_DEC_REFTOTAL  _Py_REF_DEBUG_COMMA       \
 681             --((PyObject*)(op))->ob_refcnt != 0)                \
 682                 _Py_CHECK_REFCNT(op)                    \
 683         else                                            \
 684                 _Py_Dealloc((PyObject *)(op))
 685
 686 /* Safely decref `op` and set `op` to NULL, especially useful in tp_clear
 687  * and tp_dealloc implementatons.
 688  *
 689  * Note that "the obvious" code can be deadly:
 690  *
 691  *     Py_XDECREF(op);
 692  *     op = NULL;
 693  *
 694  * Typically, `op` is something like self->containee, and `self` is done
 695  * using its `containee` member.  In the code sequence above, suppose
 696  * `containee` is non-NULL with a refcount of 1.  Its refcount falls to
 697  * 0 on the first line, which can trigger an arbitrary amount of code,
 698  * possibly including finalizers (like __del__ methods or weakref callbacks)
 699  * coded in Python, which in turn can release the GIL and allow other threads
 700  * to run, etc.  Such code may even invoke methods of `self` again, or cause
 701  * cyclic gc to trigger, but-- oops! --self->containee still points to the
 702  * object being torn down, and it may be in an insane state while being torn
 703  * down.  This has in fact been a rich historic source of miserable (rare &
 704  * hard-to-diagnose) segfaulting (and other) bugs.
 705  *
 706  * The safe way is:
 707  *
 708  *      Py_CLEAR(op);
 709  *
 710  * That arranges to set `op` to NULL _before_ decref'ing, so that any code
 711  * triggered as a side-effect of `op` getting torn down no longer believes
 712  * `op` points to a valid object.
 713  *
 714  * There are cases where it's safe to use the naive code, but they're brittle.
 715  * For example, if `op` points to a Python integer, you know that destroying
 716  * one of those can't cause problems -- but in part that relies on that
 717  * Python integers aren't currently weakly referencable.  Best practice is
 718  * to use Py_CLEAR() even if you can't think of a reason for why you need to.
 719  */
 720 #define Py_CLEAR(op)                            \
 721         do {                                    \
 722                 if (op) {                       \
 723                         PyObject *tmp = (PyObject *)(op);       \
 724                         (op) = NULL;            \
 725                         Py_DECREF(tmp);         \
 726                 }                               \
 727         } while (0)
 728
 729 /* Macros to use in case the object pointer may be NULL: */
 730 #define Py_XINCREF(op) if ((op) == NULL) ; else Py_INCREF(op)
 731 #define Py_XDECREF(op) if ((op) == NULL) ; else Py_DECREF(op)
 732
 733 /*
 734 These are provided as conveniences to Python runtime embedders, so that
 735 they can have object code that is not dependent on Python compilation flags.
 736 */
 737 PyAPI_FUNC(void) Py_IncRef(PyObject *);
 738 PyAPI_FUNC(void) Py_DecRef(PyObject *);
 739
 740 /*
 741 _Py_NoneStruct is an object of undefined type which can be used in contexts
 742 where NULL (nil) is not suitable (since NULL often means 'error').
 743
 744 Don't forget to apply Py_INCREF() when returning this value!!!
 745 */
 746 PyAPI_DATA(PyObject) _Py_NoneStruct; /* Don't use this directly */
 747 #define Py_None (&_Py_NoneStruct)
 748
 749 /* Macro for returning Py_None from a function */
 750 #define Py_RETURN_NONE return Py_INCREF(Py_None), Py_None
 751
 752 /*
 753 Py_NotImplemented is a singleton used to signal that an operation is
 754 not implemented for a given type combination.
 755 */
 756 PyAPI_DATA(PyObject) _Py_NotImplementedStruct; /* Don't use this directly */
 757 #define Py_NotImplemented (&_Py_NotImplementedStruct)
 758
 759 /* Rich comparison opcodes */
 760 #define Py_LT 0
 761 #define Py_LE 1
 762 #define Py_EQ 2
 763 #define Py_NE 3
 764 #define Py_GT 4
 765 #define Py_GE 5
 766
 767 /* Maps Py_LT to Py_GT, ..., Py_GE to Py_LE.
 768  * Defined in object.c.
 769  */
 770 PyAPI_DATA(int) _Py_SwappedOp[];
 771
 772 /*
 773 Define staticforward and statichere for source compatibility with old
 774 C extensions.
 775
 776 The staticforward define was needed to support certain broken C
 777 compilers (notably SCO ODT 3.0, perhaps early AIX as well) botched the
 778 static keyword when it was used with a forward declaration of a static
 779 initialized structure.  Standard C allows the forward declaration with
 780 static, and we've decided to stop catering to broken C compilers.
 781 (In fact, we expect that the compilers are all fixed eight years later.)
 782 */
 783
 784 #define staticforward static
 785 #define statichere static
 786
 787
 788 /*
 789 More conventions
 790 ================
 791
 792 Argument Checking
 793 -----------------
 794
 795 Functions that take objects as arguments normally don't check for nil
 796 arguments, but they do check the type of the argument, and return an
 797 error if the function doesn't apply to the type.
 798
 799 Failure Modes
 800 -------------
 801
 802 Functions may fail for a variety of reasons, including running out of
 803 memory.  This is communicated to the caller in two ways: an error string
 804 is set (see errors.h), and the function result differs: functions that
 805 normally return a pointer return NULL for failure, functions returning
 806 an integer return -1 (which could be a legal return value too!), and
 807 other functions return 0 for success and -1 for failure.
 808 Callers should always check for errors before using the result.  If
 809 an error was set, the caller must either explicitly clear it, or pass
 810 the error on to its caller.
 811
 812 Reference Counts
 813 ----------------
 814
 815 It takes a while to get used to the proper usage of reference counts.
 816
 817 Functions that create an object set the reference count to 1; such new
 818 objects must be stored somewhere or destroyed again with Py_DECREF().
 819 Some functions that 'store' objects, such as PyTuple_SetItem() and
 820 PyList_SetItem(),
 821 don't increment the reference count of the object, since the most
 822 frequent use is to store a fresh object.  Functions that 'retrieve'
 823 objects, such as PyTuple_GetItem() and PyDict_GetItemString(), also
 824 don't increment
 825 the reference count, since most frequently the object is only looked at
 826 quickly.  Thus, to retrieve an object and store it again, the caller
 827 must call Py_INCREF() explicitly.
 828
 829 NOTE: functions that 'consume' a reference count, like
 830 PyList_SetItem(), consume the reference even if the object wasn't
 831 successfully stored, to simplify error handling.
 832
 833 It seems attractive to make other functions that take an object as
 834 argument consume a reference count; however, this may quickly get
 835 confusing (even the current practice is already confusing).  Consider
 836 it carefully, it may save lots of calls to Py_INCREF() and Py_DECREF() at
 837 times.
 838 */
 839
 840
 841 /* Trashcan mechanism, thanks to Christian Tismer.
 842
 843 When deallocating a container object, it's possible to trigger an unbounded
 844 chain of deallocations, as each Py_DECREF in turn drops the refcount on "the
 845 next" object in the chain to 0.  This can easily lead to stack faults, and
 846 especially in threads (which typically have less stack space to work with).
 847
 848 A container object that participates in cyclic gc can avoid this by
 849 bracketing the body of its tp_dealloc function with a pair of macros:
 850
 851 static void
 852 mytype_dealloc(mytype *p)
 853 {
 854         ... declarations go here ...
 855
 856         PyObject_GC_UnTrack(p);    // must untrack first
 857         Py_TRASHCAN_SAFE_BEGIN(p)
 858         ... The body of the deallocator goes here, including all calls ...
 859         ... to Py_DECREF on contained objects.                         ...
 860         Py_TRASHCAN_SAFE_END(p)
 861 }
 862
 863 CAUTION:  Never return from the middle of the body!  If the body needs to
 864 "get out early", put a label immediately before the Py_TRASHCAN_SAFE_END
 865 call, and goto it.  Else the call-depth counter (see below) will stay
 866 above 0 forever, and the trashcan will never get emptied.
 867
 868 How it works:  The BEGIN macro increments a call-depth counter.  So long
 869 as this counter is small, the body of the deallocator is run directly without
 870 further ado.  But if the counter gets large, it instead adds p to a list of
 871 objects to be deallocated later, skips the body of the deallocator, and
 872 resumes execution after the END macro.  The tp_dealloc routine then returns
 873 without deallocating anything (and so unbounded call-stack depth is avoided).
 874
 875 When the call stack finishes unwinding again, code generated by the END macro
 876 notices this, and calls another routine to deallocate all the objects that
 877 may have been added to the list of deferred deallocations.  In effect, a
 878 chain of N deallocations is broken into N / PyTrash_UNWIND_LEVEL pieces,
 879 with the call stack never exceeding a depth of PyTrash_UNWIND_LEVEL.
 880 */
 881
 882 PyAPI_FUNC(void) _PyTrash_deposit_object(PyObject*);
 883 PyAPI_FUNC(void) _PyTrash_destroy_chain(void);
 884 PyAPI_DATA(int) _PyTrash_delete_nesting;
 885 PyAPI_DATA(PyObject *) _PyTrash_delete_later;
 886
 887 #define PyTrash_UNWIND_LEVEL 50
 888
 889 #define Py_TRASHCAN_SAFE_BEGIN(op) \
 890         if (_PyTrash_delete_nesting < PyTrash_UNWIND_LEVEL) { \
 891                 ++_PyTrash_delete_nesting;
 892                 /* The body of the deallocator is here. */
 893 #define Py_TRASHCAN_SAFE_END(op) \
 894                 --_PyTrash_delete_nesting; \
 895                 if (_PyTrash_delete_later && _PyTrash_delete_nesting <= 0) \
 896                         _PyTrash_destroy_chain(); \
 897         } \
 898         else \
 899                 _PyTrash_deposit_object((PyObject*)op);
 900
 901 #ifdef __cplusplus
 902 }
 903 #endif
 904 #endif /* !Py_OBJECT_H */