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                   PyObject ob_base;
  79
  80 #define PyObject_HEAD_INIT(type)        \
  81         { _PyObject_EXTRA_INIT          \
  82         1, type },
  83
  84 #define PyVarObject_HEAD_INIT(type, size)       \
  85         { PyObject_HEAD_INIT(type) size },
  86
  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.
  92  */
  93 #define PyObject_VAR_HEAD      PyVarObject ob_base;
  94 #define Py_INVALID_SIZE (Py_ssize_t)-1
  95
  96 /* Nothing is actually declared to be a PyObject, but every pointer to
  97  * a Python object can be cast to a PyObject*.  This is inheritance built
  98  * by hand.  Similarly every pointer to a variable-size Python object can,
  99  * in addition, be cast to PyVarObject*.
 100  */
 101 typedef struct _object {
 102         _PyObject_HEAD_EXTRA
 103         Py_ssize_t ob_refcnt;
 104         struct _typeobject *ob_type;
 105 } PyObject;
 106
 107 typedef struct {
 108         PyObject ob_base;
 109         Py_ssize_t ob_size; /* Number of items in variable part */
 110 } PyVarObject;
 111
 112 #define Py_REFCNT(ob)           (((PyObject*)(ob))->ob_refcnt)
 113 #define Py_TYPE(ob)             (((PyObject*)(ob))->ob_type)
 114 #define Py_SIZE(ob)             (((PyVarObject*)(ob))->ob_size)
 115
 116 /*
 117 Type objects contain a string containing the type name (to help somewhat
 118 in debugging), the allocation parameters (see PyObject_New() and
 119 PyObject_NewVar()),
 120 and methods for accessing objects of the type.  Methods are optional, a
 121 nil pointer meaning that particular kind of access is not available for
 122 this type.  The Py_DECREF() macro uses the tp_dealloc method without
 123 checking for a nil pointer; it should always be implemented except if
 124 the implementation can guarantee that the reference count will never
 125 reach zero (e.g., for statically allocated type objects).
 126
 127 NB: the methods for certain type groups are now contained in separate
 128 method blocks.
 129 */
 130
 131 typedef PyObject * (*unaryfunc)(PyObject *);
 132 typedef PyObject * (*binaryfunc)(PyObject *, PyObject *);
 133 typedef PyObject * (*ternaryfunc)(PyObject *, PyObject *, PyObject *);
 134 typedef int (*inquiry)(PyObject *);
 135 typedef Py_ssize_t (*lenfunc)(PyObject *);
 136 typedef PyObject *(*ssizeargfunc)(PyObject *, Py_ssize_t);
 137 typedef PyObject *(*ssizessizeargfunc)(PyObject *, Py_ssize_t, Py_ssize_t);
 138 typedef int(*ssizeobjargproc)(PyObject *, Py_ssize_t, PyObject *);
 139 typedef int(*ssizessizeobjargproc)(PyObject *, Py_ssize_t, Py_ssize_t, PyObject *);
 140 typedef int(*objobjargproc)(PyObject *, PyObject *, PyObject *);
 141
 142
 143 /* buffer interface */
 144 typedef struct bufferinfo {
 145         void *buf;
 146         PyObject *obj;        /* owned reference */
 147         Py_ssize_t len;
 148         Py_ssize_t itemsize;  /* This is Py_ssize_t so it can be
 149                                  pointed to by strides in simple case.*/
 150         int readonly;
 151         int ndim;
 152         char *format;
 153         Py_ssize_t *shape;
 154         Py_ssize_t *strides;
 155         Py_ssize_t *suboffsets;
 156         Py_ssize_t smalltable[2];  /* static store for shape and strides of
 157                                       mono-dimensional buffers. */
 158         void *internal;
 159 } Py_buffer;
 160
 161 typedef int (*getbufferproc)(PyObject *, Py_buffer *, int);
 162 typedef void (*releasebufferproc)(PyObject *, Py_buffer *);
 163
 164         /* Flags for getting buffers */
 165 #define PyBUF_SIMPLE 0
 166 #define PyBUF_WRITABLE 0x0001
 167 /*  we used to include an E, backwards compatible alias  */
 168 #define PyBUF_WRITEABLE PyBUF_WRITABLE
 169 #define PyBUF_FORMAT 0x0004
 170 #define PyBUF_ND 0x0008
 171 #define PyBUF_STRIDES (0x0010 | PyBUF_ND)
 172 #define PyBUF_C_CONTIGUOUS (0x0020 | PyBUF_STRIDES)
 173 #define PyBUF_F_CONTIGUOUS (0x0040 | PyBUF_STRIDES)
 174 #define PyBUF_ANY_CONTIGUOUS (0x0080 | PyBUF_STRIDES)
 175 #define PyBUF_INDIRECT (0x0100 | PyBUF_STRIDES)
 176
 177 #define PyBUF_CONTIG (PyBUF_ND | PyBUF_WRITABLE)
 178 #define PyBUF_CONTIG_RO (PyBUF_ND)
 179
 180 #define PyBUF_STRIDED (PyBUF_STRIDES | PyBUF_WRITABLE)
 181 #define PyBUF_STRIDED_RO (PyBUF_STRIDES)
 182
 183 #define PyBUF_RECORDS (PyBUF_STRIDES | PyBUF_WRITABLE | PyBUF_FORMAT)
 184 #define PyBUF_RECORDS_RO (PyBUF_STRIDES | PyBUF_FORMAT)
 185
 186 #define PyBUF_FULL (PyBUF_INDIRECT | PyBUF_WRITABLE | PyBUF_FORMAT)
 187 #define PyBUF_FULL_RO (PyBUF_INDIRECT | PyBUF_FORMAT)
 188
 189
 190 #define PyBUF_READ  0x100
 191 #define PyBUF_WRITE 0x200
 192 #define PyBUF_SHADOW 0x400
 193
 194 /* End buffer interface */
 195
 196 typedef int (*objobjproc)(PyObject *, PyObject *);
 197 typedef int (*visitproc)(PyObject *, void *);
 198 typedef int (*traverseproc)(PyObject *, visitproc, void *);
 199
 200 typedef struct {
 201         /* Number implementations must check *both*
 202            arguments for proper type and implement the necessary conversions
 203            in the slot functions themselves. */
 204
 205         binaryfunc nb_add;
 206         binaryfunc nb_subtract;
 207         binaryfunc nb_multiply;
 208         binaryfunc nb_remainder;
 209         binaryfunc nb_divmod;
 210         ternaryfunc nb_power;
 211         unaryfunc nb_negative;
 212         unaryfunc nb_positive;
 213         unaryfunc nb_absolute;
 214         inquiry nb_bool;
 215         unaryfunc nb_invert;
 216         binaryfunc nb_lshift;
 217         binaryfunc nb_rshift;
 218         binaryfunc nb_and;
 219         binaryfunc nb_xor;
 220         binaryfunc nb_or;
 221         unaryfunc nb_int;
 222         void *nb_reserved;  /* the slot formerly known as nb_long */
 223         unaryfunc nb_float;
 224
 225         binaryfunc nb_inplace_add;
 226         binaryfunc nb_inplace_subtract;
 227         binaryfunc nb_inplace_multiply;
 228         binaryfunc nb_inplace_remainder;
 229         ternaryfunc nb_inplace_power;
 230         binaryfunc nb_inplace_lshift;
 231         binaryfunc nb_inplace_rshift;
 232         binaryfunc nb_inplace_and;
 233         binaryfunc nb_inplace_xor;
 234         binaryfunc nb_inplace_or;
 235
 236         binaryfunc nb_floor_divide;
 237         binaryfunc nb_true_divide;
 238         binaryfunc nb_inplace_floor_divide;
 239         binaryfunc nb_inplace_true_divide;
 240
 241         unaryfunc nb_index;
 242 } PyNumberMethods;
 243
 244 typedef struct {
 245         lenfunc sq_length;
 246         binaryfunc sq_concat;
 247         ssizeargfunc sq_repeat;
 248         ssizeargfunc sq_item;
 249         void *was_sq_slice;
 250         ssizeobjargproc sq_ass_item;
 251         void *was_sq_ass_slice;
 252         objobjproc sq_contains;
 253
 254         binaryfunc sq_inplace_concat;
 255         ssizeargfunc sq_inplace_repeat;
 256 } PySequenceMethods;
 257
 258 typedef struct {
 259         lenfunc mp_length;
 260         binaryfunc mp_subscript;
 261         objobjargproc mp_ass_subscript;
 262 } PyMappingMethods;
 263
 264
 265 typedef struct {
 266      getbufferproc bf_getbuffer;
 267      releasebufferproc bf_releasebuffer;
 268 } PyBufferProcs;
 269
 270 typedef void (*freefunc)(void *);
 271 typedef void (*destructor)(PyObject *);
 272 typedef int (*printfunc)(PyObject *, FILE *, int);
 273 typedef PyObject *(*getattrfunc)(PyObject *, char *);
 274 typedef PyObject *(*getattrofunc)(PyObject *, PyObject *);
 275 typedef int (*setattrfunc)(PyObject *, char *, PyObject *);
 276 typedef int (*setattrofunc)(PyObject *, PyObject *, PyObject *);
 277 typedef PyObject *(*reprfunc)(PyObject *);
 278 typedef long (*hashfunc)(PyObject *);
 279 typedef PyObject *(*richcmpfunc) (PyObject *, PyObject *, int);
 280 typedef PyObject *(*getiterfunc) (PyObject *);
 281 typedef PyObject *(*iternextfunc) (PyObject *);
 282 typedef PyObject *(*descrgetfunc) (PyObject *, PyObject *, PyObject *);
 283 typedef int (*descrsetfunc) (PyObject *, PyObject *, PyObject *);
 284 typedef int (*initproc)(PyObject *, PyObject *, PyObject *);
 285 typedef PyObject *(*newfunc)(struct _typeobject *, PyObject *, PyObject *);
 286 typedef PyObject *(*allocfunc)(struct _typeobject *, Py_ssize_t);
 287
 288 typedef struct _typeobject {
 289         PyObject_VAR_HEAD
 290         const char *tp_name; /* For printing, in format "<module>.<name>" */
 291         Py_ssize_t tp_basicsize, tp_itemsize; /* For allocation */
 292
 293         /* Methods to implement standard operations */
 294
 295         destructor tp_dealloc;
 296         printfunc tp_print;
 297         getattrfunc tp_getattr;
 298         setattrfunc tp_setattr;
 299         void *tp_reserved; /* formerly known as tp_compare */
 300         reprfunc tp_repr;
 301
 302         /* Method suites for standard classes */
 303
 304         PyNumberMethods *tp_as_number;
 305         PySequenceMethods *tp_as_sequence;
 306         PyMappingMethods *tp_as_mapping;
 307
 308         /* More standard operations (here for binary compatibility) */
 309
 310         hashfunc tp_hash;
 311         ternaryfunc tp_call;
 312         reprfunc tp_str;
 313         getattrofunc tp_getattro;
 314         setattrofunc tp_setattro;
 315
 316         /* Functions to access object as input/output buffer */
 317         PyBufferProcs *tp_as_buffer;
 318
 319         /* Flags to define presence of optional/expanded features */
 320         long tp_flags;
 321
 322         const char *tp_doc; /* Documentation string */
 323
 324         /* Assigned meaning in release 2.0 */
 325         /* call function for all accessible objects */
 326         traverseproc tp_traverse;
 327
 328         /* delete references to contained objects */
 329         inquiry tp_clear;
 330
 331         /* Assigned meaning in release 2.1 */
 332         /* rich comparisons */
 333         richcmpfunc tp_richcompare;
 334
 335         /* weak reference enabler */
 336         Py_ssize_t tp_weaklistoffset;
 337
 338         /* Iterators */
 339         getiterfunc tp_iter;
 340         iternextfunc tp_iternext;
 341
 342         /* Attribute descriptor and subclassing stuff */
 343         struct PyMethodDef *tp_methods;
 344         struct PyMemberDef *tp_members;
 345         struct PyGetSetDef *tp_getset;
 346         struct _typeobject *tp_base;
 347         PyObject *tp_dict;
 348         descrgetfunc tp_descr_get;
 349         descrsetfunc tp_descr_set;
 350         Py_ssize_t tp_dictoffset;
 351         initproc tp_init;
 352         allocfunc tp_alloc;
 353         newfunc tp_new;
 354         freefunc tp_free; /* Low-level free-memory routine */
 355         inquiry tp_is_gc; /* For PyObject_IS_GC */
 356         PyObject *tp_bases;
 357         PyObject *tp_mro; /* method resolution order */
 358         PyObject *tp_cache;
 359         PyObject *tp_subclasses;
 360         PyObject *tp_weaklist;
 361         destructor tp_del;
 362
 363         /* Type attribute cache version tag. Added in version 2.6 */
 364         unsigned int tp_version_tag;
 365
 366 #ifdef COUNT_ALLOCS
 367         /* these must be last and never explicitly initialized */
 368         Py_ssize_t tp_allocs;
 369         Py_ssize_t tp_frees;
 370         Py_ssize_t tp_maxalloc;
 371         struct _typeobject *tp_prev;
 372         struct _typeobject *tp_next;
 373 #endif
 374 } PyTypeObject;
 375
 376
 377 /* The *real* layout of a type object when allocated on the heap */
 378 typedef struct _heaptypeobject {
 379         /* Note: there's a dependency on the order of these members
 380            in slotptr() in typeobject.c . */
 381         PyTypeObject ht_type;
 382         PyNumberMethods as_number;
 383         PyMappingMethods as_mapping;
 384         PySequenceMethods as_sequence; /* as_sequence comes after as_mapping,
 385                                           so that the mapping wins when both
 386                                           the mapping and the sequence define
 387                                           a given operator (e.g. __getitem__).
 388                                           see add_operators() in typeobject.c . */
 389         PyBufferProcs as_buffer;
 390         PyObject *ht_name, *ht_slots;
 391         /* here are optional user slots, followed by the members. */
 392 } PyHeapTypeObject;
 393
 394 /* access macro to the members which are floating "behind" the object */
 395 #define PyHeapType_GET_MEMBERS(etype) \
 396     ((PyMemberDef *)(((char *)etype) + Py_TYPE(etype)->tp_basicsize))
 397
 398
 399 /* Generic type check */
 400 PyAPI_FUNC(int) PyType_IsSubtype(PyTypeObject *, PyTypeObject *);
 401 #define PyObject_TypeCheck(ob, tp) \
 402         (Py_TYPE(ob) == (tp) || PyType_IsSubtype(Py_TYPE(ob), (tp)))
 403
 404 PyAPI_DATA(PyTypeObject) PyType_Type; /* built-in 'type' */
 405 PyAPI_DATA(PyTypeObject) PyBaseObject_Type; /* built-in 'object' */
 406 PyAPI_DATA(PyTypeObject) PySuper_Type; /* built-in 'super' */
 407
 408 #define PyType_Check(op) \
 409         PyType_FastSubclass(Py_TYPE(op), Py_TPFLAGS_TYPE_SUBCLASS)
 410 #define PyType_CheckExact(op) (Py_TYPE(op) == &PyType_Type)
 411
 412 PyAPI_FUNC(int) PyType_Ready(PyTypeObject *);
 413 PyAPI_FUNC(PyObject *) PyType_GenericAlloc(PyTypeObject *, Py_ssize_t);
 414 PyAPI_FUNC(PyObject *) PyType_GenericNew(PyTypeObject *,
 415                                                PyObject *, PyObject *);
 416 PyAPI_FUNC(PyObject *) _PyType_Lookup(PyTypeObject *, PyObject *);
 417 PyAPI_FUNC(PyObject *) _PyObject_LookupSpecial(PyObject *, char *, PyObject **);
 418 PyAPI_FUNC(unsigned int) PyType_ClearCache(void);
 419 PyAPI_FUNC(void) PyType_Modified(PyTypeObject *);
 420
 421 /* Generic operations on objects */
 422 PyAPI_FUNC(int) PyObject_Print(PyObject *, FILE *, int);
 423 PyAPI_FUNC(void) _Py_BreakPoint(void);
 424 PyAPI_FUNC(void) _PyObject_Dump(PyObject *);
 425 PyAPI_FUNC(PyObject *) PyObject_Repr(PyObject *);
 426 PyAPI_FUNC(PyObject *) PyObject_Str(PyObject *);
 427 PyAPI_FUNC(PyObject *) PyObject_ASCII(PyObject *);
 428 PyAPI_FUNC(PyObject *) PyObject_Bytes(PyObject *);
 429 PyAPI_FUNC(PyObject *) PyObject_RichCompare(PyObject *, PyObject *, int);
 430 PyAPI_FUNC(int) PyObject_RichCompareBool(PyObject *, PyObject *, int);
 431 PyAPI_FUNC(PyObject *) PyObject_GetAttrString(PyObject *, const char *);
 432 PyAPI_FUNC(int) PyObject_SetAttrString(PyObject *, const char *, PyObject *);
 433 PyAPI_FUNC(int) PyObject_HasAttrString(PyObject *, const char *);
 434 PyAPI_FUNC(PyObject *) PyObject_GetAttr(PyObject *, PyObject *);
 435 PyAPI_FUNC(int) PyObject_SetAttr(PyObject *, PyObject *, PyObject *);
 436 PyAPI_FUNC(int) PyObject_HasAttr(PyObject *, PyObject *);
 437 PyAPI_FUNC(PyObject **) _PyObject_GetDictPtr(PyObject *);
 438 PyAPI_FUNC(PyObject *) PyObject_SelfIter(PyObject *);
 439 PyAPI_FUNC(PyObject *) _PyObject_NextNotImplemented(PyObject *);
 440 PyAPI_FUNC(PyObject *) PyObject_GenericGetAttr(PyObject *, PyObject *);
 441 PyAPI_FUNC(int) PyObject_GenericSetAttr(PyObject *,
 442                                               PyObject *, PyObject *);
 443 PyAPI_FUNC(long) PyObject_Hash(PyObject *);
 444 PyAPI_FUNC(long) PyObject_HashNotImplemented(PyObject *);
 445 PyAPI_FUNC(int) PyObject_IsTrue(PyObject *);
 446 PyAPI_FUNC(int) PyObject_Not(PyObject *);
 447 PyAPI_FUNC(int) PyCallable_Check(PyObject *);
 448
 449 PyAPI_FUNC(void) PyObject_ClearWeakRefs(PyObject *);
 450
 451
 452 /* PyObject_Dir(obj) acts like Python builtins.dir(obj), returning a
 453    list of strings.  PyObject_Dir(NULL) is like builtins.dir(),
 454    returning the names of the current locals.  In this case, if there are
 455    no current locals, NULL is returned, and PyErr_Occurred() is false.
 456 */
 457 PyAPI_FUNC(PyObject *) PyObject_Dir(PyObject *);
 458
 459
 460 /* Helpers for printing recursive container types */
 461 PyAPI_FUNC(int) Py_ReprEnter(PyObject *);
 462 PyAPI_FUNC(void) Py_ReprLeave(PyObject *);
 463
 464 /* Helpers for hash functions */
 465 PyAPI_FUNC(long) _Py_HashDouble(double);
 466 PyAPI_FUNC(long) _Py_HashPointer(void*);
 467
 468 /* Helper for passing objects to printf and the like */
 469 #define PyObject_REPR(obj) _PyUnicode_AsString(PyObject_Repr(obj))
 470
 471 /* Flag bits for printing: */
 472 #define Py_PRINT_RAW    1       /* No string quotes etc. */
 473
 474 /*
 475 `Type flags (tp_flags)
 476
 477 These flags are used to extend the type structure in a backwards-compatible
 478 fashion. Extensions can use the flags to indicate (and test) when a given
 479 type structure contains a new feature. The Python core will use these when
 480 introducing new functionality between major revisions (to avoid mid-version
 481 changes in the PYTHON_API_VERSION).
 482
 483 Arbitration of the flag bit positions will need to be coordinated among
 484 all extension writers who publically release their extensions (this will
 485 be fewer than you might expect!)..
 486
 487 Most flags were removed as of Python 3.0 to make room for new flags.  (Some
 488 flags are not for backwards compatibility but to indicate the presence of an
 489 optional feature; these flags remain of course.)
 490
 491 Type definitions should use Py_TPFLAGS_DEFAULT for their tp_flags value.
 492
 493 Code can use PyType_HasFeature(type_ob, flag_value) to test whether the
 494 given type object has a specified feature.
 495 */
 496
 497 /* Set if the type object is dynamically allocated */
 498 #define Py_TPFLAGS_HEAPTYPE (1L<<9)
 499
 500 /* Set if the type allows subclassing */
 501 #define Py_TPFLAGS_BASETYPE (1L<<10)
 502
 503 /* Set if the type is 'ready' -- fully initialized */
 504 #define Py_TPFLAGS_READY (1L<<12)
 505
 506 /* Set while the type is being 'readied', to prevent recursive ready calls */
 507 #define Py_TPFLAGS_READYING (1L<<13)
 508
 509 /* Objects support garbage collection (see objimp.h) */
 510 #define Py_TPFLAGS_HAVE_GC (1L<<14)
 511
 512 /* These two bits are preserved for Stackless Python, next after this is 17 */
 513 #ifdef STACKLESS
 514 #define Py_TPFLAGS_HAVE_STACKLESS_EXTENSION (3L<<15)
 515 #else
 516 #define Py_TPFLAGS_HAVE_STACKLESS_EXTENSION 0
 517 #endif
 518
 519 /* Objects support type attribute cache */
 520 #define Py_TPFLAGS_HAVE_VERSION_TAG   (1L<<18)
 521 #define Py_TPFLAGS_VALID_VERSION_TAG  (1L<<19)
 522
 523 /* Type is abstract and cannot be instantiated */
 524 #define Py_TPFLAGS_IS_ABSTRACT (1L<<20)
 525
 526 /* These flags are used to determine if a type is a subclass. */
 527 #define Py_TPFLAGS_INT_SUBCLASS         (1L<<23)
 528 #define Py_TPFLAGS_LONG_SUBCLASS        (1L<<24)
 529 #define Py_TPFLAGS_LIST_SUBCLASS        (1L<<25)
 530 #define Py_TPFLAGS_TUPLE_SUBCLASS       (1L<<26)
 531 #define Py_TPFLAGS_BYTES_SUBCLASS       (1L<<27)
 532 #define Py_TPFLAGS_UNICODE_SUBCLASS     (1L<<28)
 533 #define Py_TPFLAGS_DICT_SUBCLASS        (1L<<29)
 534 #define Py_TPFLAGS_BASE_EXC_SUBCLASS    (1L<<30)
 535 #define Py_TPFLAGS_TYPE_SUBCLASS        (1L<<31)
 536
 537 #define Py_TPFLAGS_DEFAULT  ( \
 538                              Py_TPFLAGS_HAVE_STACKLESS_EXTENSION | \
 539                              Py_TPFLAGS_HAVE_VERSION_TAG | \
 540                             0)
 541
 542 #define PyType_HasFeature(t,f)  (((t)->tp_flags & (f)) != 0)
 543 #define PyType_FastSubclass(t,f)  PyType_HasFeature(t,f)
 544
 545
 546 /*
 547 The macros Py_INCREF(op) and Py_DECREF(op) are used to increment or decrement
 548 reference counts.  Py_DECREF calls the object's deallocator function when
 549 the refcount falls to 0; for
 550 objects that don't contain references to other objects or heap memory
 551 this can be the standard function free().  Both macros can be used
 552 wherever a void expression is allowed.  The argument must not be a
 553 NULL pointer.  If it may be NULL, use Py_XINCREF/Py_XDECREF instead.
 554 The macro _Py_NewReference(op) initialize reference counts to 1, and
 555 in special builds (Py_REF_DEBUG, Py_TRACE_REFS) performs additional
 556 bookkeeping appropriate to the special build.
 557
 558 We assume that the reference count field can never overflow; this can
 559 be proven when the size of the field is the same as the pointer size, so
 560 we ignore the possibility.  Provided a C int is at least 32 bits (which
 561 is implicitly assumed in many parts of this code), that's enough for
 562 about 2**31 references to an object.
 563
 564 XXX The following became out of date in Python 2.2, but I'm not sure
 565 XXX what the full truth is now.  Certainly, heap-allocated type objects
 566 XXX can and should be deallocated.
 567 Type objects should never be deallocated; the type pointer in an object
 568 is not considered to be a reference to the type object, to save
 569 complications in the deallocation function.  (This is actually a
 570 decision that's up to the implementer of each new type so if you want,
 571 you can count such references to the type object.)
 572
 573 *** WARNING*** The Py_DECREF macro must have a side-effect-free argument
 574 since it may evaluate its argument multiple times.  (The alternative
 575 would be to mace it a proper function or assign it to a global temporary
 576 variable first, both of which are slower; and in a multi-threaded
 577 environment the global variable trick is not safe.)
 578 */
 579
 580 /* First define a pile of simple helper macros, one set per special
 581  * build symbol.  These either expand to the obvious things, or to
 582  * nothing at all when the special mode isn't in effect.  The main
 583  * macros can later be defined just once then, yet expand to different
 584  * things depending on which special build options are and aren't in effect.
 585  * Trust me <wink>:  while painful, this is 20x easier to understand than,
 586  * e.g, defining _Py_NewReference five different times in a maze of nested
 587  * #ifdefs (we used to do that -- it was impenetrable).
 588  */
 589 #ifdef Py_REF_DEBUG
 590 PyAPI_DATA(Py_ssize_t) _Py_RefTotal;
 591 PyAPI_FUNC(void) _Py_NegativeRefcount(const char *fname,
 592                                             int lineno, PyObject *op);
 593 PyAPI_FUNC(PyObject *) _PyDict_Dummy(void);
 594 PyAPI_FUNC(PyObject *) _PySet_Dummy(void);
 595 PyAPI_FUNC(Py_ssize_t) _Py_GetRefTotal(void);
 596 #define _Py_INC_REFTOTAL        _Py_RefTotal++
 597 #define _Py_DEC_REFTOTAL        _Py_RefTotal--
 598 #define _Py_REF_DEBUG_COMMA     ,
 599 #define _Py_CHECK_REFCNT(OP)                                    \
 600 {       if (((PyObject*)OP)->ob_refcnt < 0)                             \
 601                 _Py_NegativeRefcount(__FILE__, __LINE__,        \
 602                                      (PyObject *)(OP));         \
 603 }
 604 #else
 605 #define _Py_INC_REFTOTAL
 606 #define _Py_DEC_REFTOTAL
 607 #define _Py_REF_DEBUG_COMMA
 608 #define _Py_CHECK_REFCNT(OP)    /* a semicolon */;
 609 #endif /* Py_REF_DEBUG */
 610
 611 #ifdef COUNT_ALLOCS
 612 PyAPI_FUNC(void) inc_count(PyTypeObject *);
 613 PyAPI_FUNC(void) dec_count(PyTypeObject *);
 614 #define _Py_INC_TPALLOCS(OP)    inc_count(Py_TYPE(OP))
 615 #define _Py_INC_TPFREES(OP)     dec_count(Py_TYPE(OP))
 616 #define _Py_DEC_TPFREES(OP)     Py_TYPE(OP)->tp_frees--
 617 #define _Py_COUNT_ALLOCS_COMMA  ,
 618 #else
 619 #define _Py_INC_TPALLOCS(OP)
 620 #define _Py_INC_TPFREES(OP)
 621 #define _Py_DEC_TPFREES(OP)
 622 #define _Py_COUNT_ALLOCS_COMMA
 623 #endif /* COUNT_ALLOCS */
 624
 625 #ifdef Py_TRACE_REFS
 626 /* Py_TRACE_REFS is such major surgery that we call external routines. */
 627 PyAPI_FUNC(void) _Py_NewReference(PyObject *);
 628 PyAPI_FUNC(void) _Py_ForgetReference(PyObject *);
 629 PyAPI_FUNC(void) _Py_Dealloc(PyObject *);
 630 PyAPI_FUNC(void) _Py_PrintReferences(FILE *);
 631 PyAPI_FUNC(void) _Py_PrintReferenceAddresses(FILE *);
 632 PyAPI_FUNC(void) _Py_AddToAllObjects(PyObject *, int force);
 633
 634 #else
 635 /* Without Py_TRACE_REFS, there's little enough to do that we expand code
 636  * inline.
 637  */
 638 #define _Py_NewReference(op) (                          \
 639         _Py_INC_TPALLOCS(op) _Py_COUNT_ALLOCS_COMMA     \
 640         _Py_INC_REFTOTAL  _Py_REF_DEBUG_COMMA           \
 641         Py_REFCNT(op) = 1)
 642
 643 #define _Py_ForgetReference(op) _Py_INC_TPFREES(op)
 644
 645 #define _Py_Dealloc(op) (                               \
 646         _Py_INC_TPFREES(op) _Py_COUNT_ALLOCS_COMMA      \
 647         (*Py_TYPE(op)->tp_dealloc)((PyObject *)(op)))
 648 #endif /* !Py_TRACE_REFS */
 649
 650 #define Py_INCREF(op) (                         \
 651         _Py_INC_REFTOTAL  _Py_REF_DEBUG_COMMA   \
 652         ((PyObject*)(op))->ob_refcnt++)
 653
 654 #define Py_DECREF(op)                                   \
 655         do {                                            \
 656             if (_Py_DEC_REFTOTAL  _Py_REF_DEBUG_COMMA   \
 657                 --((PyObject*)(op))->ob_refcnt != 0)    \
 658                     _Py_CHECK_REFCNT(op)                \
 659             else                                        \
 660                 _Py_Dealloc((PyObject *)(op));          \
 661         } while (0)
 662
 663 /* Safely decref `op` and set `op` to NULL, especially useful in tp_clear
 664  * and tp_dealloc implementatons.
 665  *
 666  * Note that "the obvious" code can be deadly:
 667  *
 668  *     Py_XDECREF(op);
 669  *     op = NULL;
 670  *
 671  * Typically, `op` is something like self->containee, and `self` is done
 672  * using its `containee` member.  In the code sequence above, suppose
 673  * `containee` is non-NULL with a refcount of 1.  Its refcount falls to
 674  * 0 on the first line, which can trigger an arbitrary amount of code,
 675  * possibly including finalizers (like __del__ methods or weakref callbacks)
 676  * coded in Python, which in turn can release the GIL and allow other threads
 677  * to run, etc.  Such code may even invoke methods of `self` again, or cause
 678  * cyclic gc to trigger, but-- oops! --self->containee still points to the
 679  * object being torn down, and it may be in an insane state while being torn
 680  * down.  This has in fact been a rich historic source of miserable (rare &
 681  * hard-to-diagnose) segfaulting (and other) bugs.
 682  *
 683  * The safe way is:
 684  *
 685  *      Py_CLEAR(op);
 686  *
 687  * That arranges to set `op` to NULL _before_ decref'ing, so that any code
 688  * triggered as a side-effect of `op` getting torn down no longer believes
 689  * `op` points to a valid object.
 690  *
 691  * There are cases where it's safe to use the naive code, but they're brittle.
 692  * For example, if `op` points to a Python integer, you know that destroying
 693  * one of those can't cause problems -- but in part that relies on that
 694  * Python integers aren't currently weakly referencable.  Best practice is
 695  * to use Py_CLEAR() even if you can't think of a reason for why you need to.
 696  */
 697 #define Py_CLEAR(op)                            \
 698         do {                                    \
 699                 if (op) {                       \
 700                         PyObject *_py_tmp = (PyObject *)(op);   \
 701                         (op) = NULL;            \
 702                         Py_DECREF(_py_tmp);     \
 703                 }                               \
 704         } while (0)
 705
 706 /* Macros to use in case the object pointer may be NULL: */
 707 #define Py_XINCREF(op) do { if ((op) == NULL) ; else Py_INCREF(op); } while (0)
 708 #define Py_XDECREF(op) do { if ((op) == NULL) ; else Py_DECREF(op); } while (0)
 709
 710 /*
 711 These are provided as conveniences to Python runtime embedders, so that
 712 they can have object code that is not dependent on Python compilation flags.
 713 */
 714 PyAPI_FUNC(void) Py_IncRef(PyObject *);
 715 PyAPI_FUNC(void) Py_DecRef(PyObject *);
 716
 717 /*
 718 _Py_NoneStruct is an object of undefined type which can be used in contexts
 719 where NULL (nil) is not suitable (since NULL often means 'error').
 720
 721 Don't forget to apply Py_INCREF() when returning this value!!!
 722 */
 723 PyAPI_DATA(PyObject) _Py_NoneStruct; /* Don't use this directly */
 724 #define Py_None (&_Py_NoneStruct)
 725
 726 /* Macro for returning Py_None from a function */
 727 #define Py_RETURN_NONE return Py_INCREF(Py_None), Py_None
 728
 729 /*
 730 Py_NotImplemented is a singleton used to signal that an operation is
 731 not implemented for a given type combination.
 732 */
 733 PyAPI_DATA(PyObject) _Py_NotImplementedStruct; /* Don't use this directly */
 734 #define Py_NotImplemented (&_Py_NotImplementedStruct)
 735
 736 /* Rich comparison opcodes */
 737 #define Py_LT 0
 738 #define Py_LE 1
 739 #define Py_EQ 2
 740 #define Py_NE 3
 741 #define Py_GT 4
 742 #define Py_GE 5
 743
 744 /* Maps Py_LT to Py_GT, ..., Py_GE to Py_LE.
 745  * Defined in object.c.
 746  */
 747 PyAPI_DATA(int) _Py_SwappedOp[];
 748
 749
 750 /*
 751 More conventions
 752 ================
 753
 754 Argument Checking
 755 -----------------
 756
 757 Functions that take objects as arguments normally don't check for nil
 758 arguments, but they do check the type of the argument, and return an
 759 error if the function doesn't apply to the type.
 760
 761 Failure Modes
 762 -------------
 763
 764 Functions may fail for a variety of reasons, including running out of
 765 memory.  This is communicated to the caller in two ways: an error string
 766 is set (see errors.h), and the function result differs: functions that
 767 normally return a pointer return NULL for failure, functions returning
 768 an integer return -1 (which could be a legal return value too!), and
 769 other functions return 0 for success and -1 for failure.
 770 Callers should always check for errors before using the result.  If
 771 an error was set, the caller must either explicitly clear it, or pass
 772 the error on to its caller.
 773
 774 Reference Counts
 775 ----------------
 776
 777 It takes a while to get used to the proper usage of reference counts.
 778
 779 Functions that create an object set the reference count to 1; such new
 780 objects must be stored somewhere or destroyed again with Py_DECREF().
 781 Some functions that 'store' objects, such as PyTuple_SetItem() and
 782 PyList_SetItem(),
 783 don't increment the reference count of the object, since the most
 784 frequent use is to store a fresh object.  Functions that 'retrieve'
 785 objects, such as PyTuple_GetItem() and PyDict_GetItemString(), also
 786 don't increment
 787 the reference count, since most frequently the object is only looked at
 788 quickly.  Thus, to retrieve an object and store it again, the caller
 789 must call Py_INCREF() explicitly.
 790
 791 NOTE: functions that 'consume' a reference count, like
 792 PyList_SetItem(), consume the reference even if the object wasn't
 793 successfully stored, to simplify error handling.
 794
 795 It seems attractive to make other functions that take an object as
 796 argument consume a reference count; however, this may quickly get
 797 confusing (even the current practice is already confusing).  Consider
 798 it carefully, it may save lots of calls to Py_INCREF() and Py_DECREF() at
 799 times.
 800 */
 801
 802
 803 /* Trashcan mechanism, thanks to Christian Tismer.
 804
 805 When deallocating a container object, it's possible to trigger an unbounded
 806 chain of deallocations, as each Py_DECREF in turn drops the refcount on "the
 807 next" object in the chain to 0.  This can easily lead to stack faults, and
 808 especially in threads (which typically have less stack space to work with).
 809
 810 A container object that participates in cyclic gc can avoid this by
 811 bracketing the body of its tp_dealloc function with a pair of macros:
 812
 813 static void
 814 mytype_dealloc(mytype *p)
 815 {
 816         ... declarations go here ...
 817
 818         PyObject_GC_UnTrack(p);    // must untrack first
 819         Py_TRASHCAN_SAFE_BEGIN(p)
 820         ... The body of the deallocator goes here, including all calls ...
 821         ... to Py_DECREF on contained objects.                         ...
 822         Py_TRASHCAN_SAFE_END(p)
 823 }
 824
 825 CAUTION:  Never return from the middle of the body!  If the body needs to
 826 "get out early", put a label immediately before the Py_TRASHCAN_SAFE_END
 827 call, and goto it.  Else the call-depth counter (see below) will stay
 828 above 0 forever, and the trashcan will never get emptied.
 829
 830 How it works:  The BEGIN macro increments a call-depth counter.  So long
 831 as this counter is small, the body of the deallocator is run directly without
 832 further ado.  But if the counter gets large, it instead adds p to a list of
 833 objects to be deallocated later, skips the body of the deallocator, and
 834 resumes execution after the END macro.  The tp_dealloc routine then returns
 835 without deallocating anything (and so unbounded call-stack depth is avoided).
 836
 837 When the call stack finishes unwinding again, code generated by the END macro
 838 notices this, and calls another routine to deallocate all the objects that
 839 may have been added to the list of deferred deallocations.  In effect, a
 840 chain of N deallocations is broken into N / PyTrash_UNWIND_LEVEL pieces,
 841 with the call stack never exceeding a depth of PyTrash_UNWIND_LEVEL.
 842 */
 843
 844 PyAPI_FUNC(void) _PyTrash_deposit_object(PyObject*);
 845 PyAPI_FUNC(void) _PyTrash_destroy_chain(void);
 846 PyAPI_DATA(int) _PyTrash_delete_nesting;
 847 PyAPI_DATA(PyObject *) _PyTrash_delete_later;
 848
 849 #define PyTrash_UNWIND_LEVEL 50
 850
 851 #define Py_TRASHCAN_SAFE_BEGIN(op) \
 852         if (_PyTrash_delete_nesting < PyTrash_UNWIND_LEVEL) { \
 853                 ++_PyTrash_delete_nesting;
 854                 /* The body of the deallocator is here. */
 855 #define Py_TRASHCAN_SAFE_END(op) \
 856                 --_PyTrash_delete_nesting; \
 857                 if (_PyTrash_delete_later && _PyTrash_delete_nesting <= 0) \
 858                         _PyTrash_destroy_chain(); \
 859         } \
 860         else \
 861                 _PyTrash_deposit_object((PyObject*)op);
 862
 863 #ifdef __cplusplus
 864 }
 865 #endif
 866 #endif /* !Py_OBJECT_H */