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 /*
 119 Type objects contain a string containing the type name (to help somewhat
 120 in debugging), the allocation parameters (see PyObject_New() and
 121 PyObject_NewVar()),
 122 and methods for accessing objects of the type.  Methods are optional, a
 123 nil pointer meaning that particular kind of access is not available for
 124 this type.  The Py_DECREF() macro uses the tp_dealloc method without
 125 checking for a nil pointer; it should always be implemented except if
 126 the implementation can guarantee that the reference count will never
 127 reach zero (e.g., for statically allocated type objects).
 128
 129 NB: the methods for certain type groups are now contained in separate
 130 method blocks.
 131 */
 132
 133 typedef PyObject * (*unaryfunc)(PyObject *);
 134 typedef PyObject * (*binaryfunc)(PyObject *, PyObject *);
 135 typedef PyObject * (*ternaryfunc)(PyObject *, PyObject *, PyObject *);
 136 typedef int (*inquiry)(PyObject *);
 137 typedef Py_ssize_t (*lenfunc)(PyObject *);
 138 typedef int (*coercion)(PyObject **, PyObject **);
 139 typedef PyObject *(*intargfunc)(PyObject *, int) Py_DEPRECATED(2.5);
 140 typedef PyObject *(*intintargfunc)(PyObject *, int, int) Py_DEPRECATED(2.5);
 141 typedef PyObject *(*ssizeargfunc)(PyObject *, Py_ssize_t);
 142 typedef PyObject *(*ssizessizeargfunc)(PyObject *, Py_ssize_t, Py_ssize_t);
 143 typedef int(*intobjargproc)(PyObject *, int, PyObject *);
 144 typedef int(*intintobjargproc)(PyObject *, int, int, PyObject *);
 145 typedef int(*ssizeobjargproc)(PyObject *, Py_ssize_t, PyObject *);
 146 typedef int(*ssizessizeobjargproc)(PyObject *, Py_ssize_t, Py_ssize_t, PyObject *);
 147 typedef int(*objobjargproc)(PyObject *, PyObject *, PyObject *);
 148
 149
 150
 151 /* int-based buffer interface */
 152 typedef int (*getreadbufferproc)(PyObject *, int, void **);
 153 typedef int (*getwritebufferproc)(PyObject *, int, void **);
 154 typedef int (*getsegcountproc)(PyObject *, int *);
 155 typedef int (*getcharbufferproc)(PyObject *, int, char **);
 156 /* ssize_t-based buffer interface */
 157 typedef Py_ssize_t (*readbufferproc)(PyObject *, Py_ssize_t, void **);
 158 typedef Py_ssize_t (*writebufferproc)(PyObject *, Py_ssize_t, void **);
 159 typedef Py_ssize_t (*segcountproc)(PyObject *, Py_ssize_t *);
 160 typedef Py_ssize_t (*charbufferproc)(PyObject *, Py_ssize_t, char **);
 161
 162
 163 /* Py3k buffer interface */
 164 typedef struct bufferinfo {
 165         void *buf;
 166         PyObject *obj;        /* owned reference */
 167         Py_ssize_t len;
 168         Py_ssize_t itemsize;  /* This is Py_ssize_t so it can be
 169                                  pointed to by strides in simple case.*/
 170         int readonly;
 171         int ndim;
 172         char *format;
 173         Py_ssize_t *shape;
 174         Py_ssize_t *strides;
 175         Py_ssize_t *suboffsets;
 176         Py_ssize_t smalltable[2];  /* static store for shape and strides of
 177                                       mono-dimensional buffers. */
 178         void *internal;
 179 } Py_buffer;
 180
 181 typedef int (*getbufferproc)(PyObject *, Py_buffer *, int);
 182 typedef void (*releasebufferproc)(PyObject *, Py_buffer *);
 183
 184         /* Flags for getting buffers */
 185 #define PyBUF_SIMPLE 0
 186 #define PyBUF_WRITABLE 0x0001
 187 /*  we used to include an E, backwards compatible alias  */
 188 #define PyBUF_WRITEABLE PyBUF_WRITABLE
 189 #define PyBUF_FORMAT 0x0004
 190 #define PyBUF_ND 0x0008
 191 #define PyBUF_STRIDES (0x0010 | PyBUF_ND)
 192 #define PyBUF_C_CONTIGUOUS (0x0020 | PyBUF_STRIDES)
 193 #define PyBUF_F_CONTIGUOUS (0x0040 | PyBUF_STRIDES)
 194 #define PyBUF_ANY_CONTIGUOUS (0x0080 | PyBUF_STRIDES)
 195 #define PyBUF_INDIRECT (0x0100 | PyBUF_STRIDES)
 196
 197 #define PyBUF_CONTIG (PyBUF_ND | PyBUF_WRITABLE)
 198 #define PyBUF_CONTIG_RO (PyBUF_ND)
 199
 200 #define PyBUF_STRIDED (PyBUF_STRIDES | PyBUF_WRITABLE)
 201 #define PyBUF_STRIDED_RO (PyBUF_STRIDES)
 202
 203 #define PyBUF_RECORDS (PyBUF_STRIDES | PyBUF_WRITABLE | PyBUF_FORMAT)
 204 #define PyBUF_RECORDS_RO (PyBUF_STRIDES | PyBUF_FORMAT)
 205
 206 #define PyBUF_FULL (PyBUF_INDIRECT | PyBUF_WRITABLE | PyBUF_FORMAT)
 207 #define PyBUF_FULL_RO (PyBUF_INDIRECT | PyBUF_FORMAT)
 208
 209
 210 #define PyBUF_READ  0x100
 211 #define PyBUF_WRITE 0x200
 212 #define PyBUF_SHADOW 0x400
 213 /* end Py3k buffer interface */
 214
 215 typedef int (*objobjproc)(PyObject *, PyObject *);
 216 typedef int (*visitproc)(PyObject *, void *);
 217 typedef int (*traverseproc)(PyObject *, visitproc, void *);
 218
 219 typedef struct {
 220         /* For numbers without flag bit Py_TPFLAGS_CHECKTYPES set, all
 221            arguments are guaranteed to be of the object's type (modulo
 222            coercion hacks -- i.e. if the type's coercion function
 223            returns other types, then these are allowed as well).  Numbers that
 224            have the Py_TPFLAGS_CHECKTYPES flag bit set should check *both*
 225            arguments for proper type and implement the necessary conversions
 226            in the slot functions themselves. */
 227
 228         binaryfunc nb_add;
 229         binaryfunc nb_subtract;
 230         binaryfunc nb_multiply;
 231         binaryfunc nb_divide;
 232         binaryfunc nb_remainder;
 233         binaryfunc nb_divmod;
 234         ternaryfunc nb_power;
 235         unaryfunc nb_negative;
 236         unaryfunc nb_positive;
 237         unaryfunc nb_absolute;
 238         inquiry nb_nonzero;
 239         unaryfunc nb_invert;
 240         binaryfunc nb_lshift;
 241         binaryfunc nb_rshift;
 242         binaryfunc nb_and;
 243         binaryfunc nb_xor;
 244         binaryfunc nb_or;
 245         coercion nb_coerce;
 246         unaryfunc nb_int;
 247         unaryfunc nb_long;
 248         unaryfunc nb_float;
 249         unaryfunc nb_oct;
 250         unaryfunc nb_hex;
 251         /* Added in release 2.0 */
 252         binaryfunc nb_inplace_add;
 253         binaryfunc nb_inplace_subtract;
 254         binaryfunc nb_inplace_multiply;
 255         binaryfunc nb_inplace_divide;
 256         binaryfunc nb_inplace_remainder;
 257         ternaryfunc nb_inplace_power;
 258         binaryfunc nb_inplace_lshift;
 259         binaryfunc nb_inplace_rshift;
 260         binaryfunc nb_inplace_and;
 261         binaryfunc nb_inplace_xor;
 262         binaryfunc nb_inplace_or;
 263
 264         /* Added in release 2.2 */
 265         /* The following require the Py_TPFLAGS_HAVE_CLASS flag */
 266         binaryfunc nb_floor_divide;
 267         binaryfunc nb_true_divide;
 268         binaryfunc nb_inplace_floor_divide;
 269         binaryfunc nb_inplace_true_divide;
 270
 271         /* Added in release 2.5 */
 272         unaryfunc nb_index;
 273 } PyNumberMethods;
 274
 275 typedef struct {
 276         lenfunc sq_length;
 277         binaryfunc sq_concat;
 278         ssizeargfunc sq_repeat;
 279         ssizeargfunc sq_item;
 280         ssizessizeargfunc sq_slice;
 281         ssizeobjargproc sq_ass_item;
 282         ssizessizeobjargproc sq_ass_slice;
 283         objobjproc sq_contains;
 284         /* Added in release 2.0 */
 285         binaryfunc sq_inplace_concat;
 286         ssizeargfunc sq_inplace_repeat;
 287 } PySequenceMethods;
 288
 289 typedef struct {
 290         lenfunc mp_length;
 291         binaryfunc mp_subscript;
 292         objobjargproc mp_ass_subscript;
 293 } PyMappingMethods;
 294
 295 typedef struct {
 296         readbufferproc bf_getreadbuffer;
 297         writebufferproc bf_getwritebuffer;
 298         segcountproc bf_getsegcount;
 299         charbufferproc bf_getcharbuffer;
 300         getbufferproc bf_getbuffer;
 301         releasebufferproc bf_releasebuffer;
 302 } PyBufferProcs;
 303
 304
 305 typedef void (*freefunc)(void *);
 306 typedef void (*destructor)(PyObject *);
 307 typedef int (*printfunc)(PyObject *, FILE *, int);
 308 typedef PyObject *(*getattrfunc)(PyObject *, char *);
 309 typedef PyObject *(*getattrofunc)(PyObject *, PyObject *);
 310 typedef int (*setattrfunc)(PyObject *, char *, PyObject *);
 311 typedef int (*setattrofunc)(PyObject *, PyObject *, PyObject *);
 312 typedef int (*cmpfunc)(PyObject *, PyObject *);
 313 typedef PyObject *(*reprfunc)(PyObject *);
 314 typedef long (*hashfunc)(PyObject *);
 315 typedef PyObject *(*richcmpfunc) (PyObject *, PyObject *, int);
 316 typedef PyObject *(*getiterfunc) (PyObject *);
 317 typedef PyObject *(*iternextfunc) (PyObject *);
 318 typedef PyObject *(*descrgetfunc) (PyObject *, PyObject *, PyObject *);
 319 typedef int (*descrsetfunc) (PyObject *, PyObject *, PyObject *);
 320 typedef int (*initproc)(PyObject *, PyObject *, PyObject *);
 321 typedef PyObject *(*newfunc)(struct _typeobject *, PyObject *, PyObject *);
 322 typedef PyObject *(*allocfunc)(struct _typeobject *, Py_ssize_t);
 323
 324 typedef struct _typeobject {
 325         PyObject_VAR_HEAD
 326         const char *tp_name; /* For printing, in format "<module>.<name>" */
 327         Py_ssize_t tp_basicsize, tp_itemsize; /* For allocation */
 328
 329         /* Methods to implement standard operations */
 330
 331         destructor tp_dealloc;
 332         printfunc tp_print;
 333         getattrfunc tp_getattr;
 334         setattrfunc tp_setattr;
 335         cmpfunc tp_compare;
 336         reprfunc tp_repr;
 337
 338         /* Method suites for standard classes */
 339
 340         PyNumberMethods *tp_as_number;
 341         PySequenceMethods *tp_as_sequence;
 342         PyMappingMethods *tp_as_mapping;
 343
 344         /* More standard operations (here for binary compatibility) */
 345
 346         hashfunc tp_hash;
 347         ternaryfunc tp_call;
 348         reprfunc tp_str;
 349         getattrofunc tp_getattro;
 350         setattrofunc tp_setattro;
 351
 352         /* Functions to access object as input/output buffer */
 353         PyBufferProcs *tp_as_buffer;
 354
 355         /* Flags to define presence of optional/expanded features */
 356         long tp_flags;
 357
 358         const char *tp_doc; /* Documentation string */
 359
 360         /* Assigned meaning in release 2.0 */
 361         /* call function for all accessible objects */
 362         traverseproc tp_traverse;
 363
 364         /* delete references to contained objects */
 365         inquiry tp_clear;
 366
 367         /* Assigned meaning in release 2.1 */
 368         /* rich comparisons */
 369         richcmpfunc tp_richcompare;
 370
 371         /* weak reference enabler */
 372         Py_ssize_t tp_weaklistoffset;
 373
 374         /* Added in release 2.2 */
 375         /* Iterators */
 376         getiterfunc tp_iter;
 377         iternextfunc tp_iternext;
 378
 379         /* Attribute descriptor and subclassing stuff */
 380         struct PyMethodDef *tp_methods;
 381         struct PyMemberDef *tp_members;
 382         struct PyGetSetDef *tp_getset;
 383         struct _typeobject *tp_base;
 384         PyObject *tp_dict;
 385         descrgetfunc tp_descr_get;
 386         descrsetfunc tp_descr_set;
 387         Py_ssize_t tp_dictoffset;
 388         initproc tp_init;
 389         allocfunc tp_alloc;
 390         newfunc tp_new;
 391         freefunc tp_free; /* Low-level free-memory routine */
 392         inquiry tp_is_gc; /* For PyObject_IS_GC */
 393         PyObject *tp_bases;
 394         PyObject *tp_mro; /* method resolution order */
 395         PyObject *tp_cache;
 396         PyObject *tp_subclasses;
 397         PyObject *tp_weaklist;
 398         destructor tp_del;
 399
 400         /* Type attribute cache version tag. Added in version 2.6 */
 401         unsigned int tp_version_tag;
 402
 403 #ifdef COUNT_ALLOCS
 404         /* these must be last and never explicitly initialized */
 405         Py_ssize_t tp_allocs;
 406         Py_ssize_t tp_frees;
 407         Py_ssize_t tp_maxalloc;
 408         struct _typeobject *tp_prev;
 409         struct _typeobject *tp_next;
 410 #endif
 411 } PyTypeObject;
 412
 413
 414 /* The *real* layout of a type object when allocated on the heap */
 415 typedef struct _heaptypeobject {
 416         /* Note: there's a dependency on the order of these members
 417            in slotptr() in typeobject.c . */
 418         PyTypeObject ht_type;
 419         PyNumberMethods as_number;
 420         PyMappingMethods as_mapping;
 421         PySequenceMethods as_sequence; /* as_sequence comes after as_mapping,
 422                                           so that the mapping wins when both
 423                                           the mapping and the sequence define
 424                                           a given operator (e.g. __getitem__).
 425                                           see add_operators() in typeobject.c . */
 426         PyBufferProcs as_buffer;
 427         PyObject *ht_name, *ht_slots;
 428         /* here are optional user slots, followed by the members. */
 429 } PyHeapTypeObject;
 430
 431 /* access macro to the members which are floating "behind" the object */
 432 #define PyHeapType_GET_MEMBERS(etype) \
 433     ((PyMemberDef *)(((char *)etype) + Py_TYPE(etype)->tp_basicsize))
 434
 435
 436 /* Generic type check */
 437 PyAPI_FUNC(int) PyType_IsSubtype(PyTypeObject *, PyTypeObject *);
 438 #define PyObject_TypeCheck(ob, tp) \
 439         (Py_TYPE(ob) == (tp) || PyType_IsSubtype(Py_TYPE(ob), (tp)))
 440
 441 PyAPI_DATA(PyTypeObject) PyType_Type; /* built-in 'type' */
 442 PyAPI_DATA(PyTypeObject) PyBaseObject_Type; /* built-in 'object' */
 443 PyAPI_DATA(PyTypeObject) PySuper_Type; /* built-in 'super' */
 444
 445 #define PyType_Check(op) \
 446         PyType_FastSubclass(Py_TYPE(op), Py_TPFLAGS_TYPE_SUBCLASS)
 447 #define PyType_CheckExact(op) (Py_TYPE(op) == &PyType_Type)
 448
 449 PyAPI_FUNC(int) PyType_Ready(PyTypeObject *);
 450 PyAPI_FUNC(PyObject *) PyType_GenericAlloc(PyTypeObject *, Py_ssize_t);
 451 PyAPI_FUNC(PyObject *) PyType_GenericNew(PyTypeObject *,
 452                                                PyObject *, PyObject *);
 453 PyAPI_FUNC(PyObject *) _PyType_Lookup(PyTypeObject *, PyObject *);
 454 PyAPI_FUNC(PyObject *) _PyObject_LookupSpecial(PyObject *, char *, PyObject **);
 455 PyAPI_FUNC(unsigned int) PyType_ClearCache(void);
 456 PyAPI_FUNC(void) PyType_Modified(PyTypeObject *);
 457
 458 /* Generic operations on objects */
 459 PyAPI_FUNC(int) PyObject_Print(PyObject *, FILE *, int);
 460 PyAPI_FUNC(void) _PyObject_Dump(PyObject *);
 461 PyAPI_FUNC(PyObject *) PyObject_Repr(PyObject *);
 462 PyAPI_FUNC(PyObject *) _PyObject_Str(PyObject *);
 463 PyAPI_FUNC(PyObject *) PyObject_Str(PyObject *);
 464 #define PyObject_Bytes PyObject_Str
 465 #ifdef Py_USING_UNICODE
 466 PyAPI_FUNC(PyObject *) PyObject_Unicode(PyObject *);
 467 #endif
 468 PyAPI_FUNC(int) PyObject_Compare(PyObject *, PyObject *);
 469 PyAPI_FUNC(PyObject *) PyObject_RichCompare(PyObject *, PyObject *, int);
 470 PyAPI_FUNC(int) PyObject_RichCompareBool(PyObject *, PyObject *, int);
 471 PyAPI_FUNC(PyObject *) PyObject_GetAttrString(PyObject *, const char *);
 472 PyAPI_FUNC(int) PyObject_SetAttrString(PyObject *, const char *, PyObject *);
 473 PyAPI_FUNC(int) PyObject_HasAttrString(PyObject *, const char *);
 474 PyAPI_FUNC(PyObject *) PyObject_GetAttr(PyObject *, PyObject *);
 475 PyAPI_FUNC(int) PyObject_SetAttr(PyObject *, PyObject *, PyObject *);
 476 PyAPI_FUNC(int) PyObject_HasAttr(PyObject *, PyObject *);
 477 PyAPI_FUNC(PyObject **) _PyObject_GetDictPtr(PyObject *);
 478 PyAPI_FUNC(PyObject *) PyObject_SelfIter(PyObject *);
 479 PyAPI_FUNC(PyObject *) _PyObject_NextNotImplemented(PyObject *);
 480 PyAPI_FUNC(PyObject *) PyObject_GenericGetAttr(PyObject *, PyObject *);
 481 PyAPI_FUNC(int) PyObject_GenericSetAttr(PyObject *,
 482                                               PyObject *, PyObject *);
 483 PyAPI_FUNC(long) PyObject_Hash(PyObject *);
 484 PyAPI_FUNC(long) PyObject_HashNotImplemented(PyObject *);
 485 PyAPI_FUNC(int) PyObject_IsTrue(PyObject *);
 486 PyAPI_FUNC(int) PyObject_Not(PyObject *);
 487 PyAPI_FUNC(int) PyCallable_Check(PyObject *);
 488 PyAPI_FUNC(int) PyNumber_Coerce(PyObject **, PyObject **);
 489 PyAPI_FUNC(int) PyNumber_CoerceEx(PyObject **, PyObject **);
 490
 491 PyAPI_FUNC(void) PyObject_ClearWeakRefs(PyObject *);
 492
 493 /* A slot function whose address we need to compare */
 494 extern int _PyObject_SlotCompare(PyObject *, PyObject *);
 495
 496
 497 /* PyObject_Dir(obj) acts like Python __builtin__.dir(obj), returning a
 498    list of strings.  PyObject_Dir(NULL) is like __builtin__.dir(),
 499    returning the names of the current locals.  In this case, if there are
 500    no current locals, NULL is returned, and PyErr_Occurred() is false.
 501 */
 502 PyAPI_FUNC(PyObject *) PyObject_Dir(PyObject *);
 503
 504
 505 /* Helpers for printing recursive container types */
 506 PyAPI_FUNC(int) Py_ReprEnter(PyObject *);
 507 PyAPI_FUNC(void) Py_ReprLeave(PyObject *);
 508
 509 /* Helpers for hash functions */
 510 PyAPI_FUNC(long) _Py_HashDouble(double);
 511 PyAPI_FUNC(long) _Py_HashPointer(void*);
 512
 513 /* Helper for passing objects to printf and the like */
 514 #define PyObject_REPR(obj) PyString_AS_STRING(PyObject_Repr(obj))
 515
 516 /* Flag bits for printing: */
 517 #define Py_PRINT_RAW    1       /* No string quotes etc. */
 518
 519 /*
 520 `Type flags (tp_flags)
 521
 522 These flags are used to extend the type structure in a backwards-compatible
 523 fashion. Extensions can use the flags to indicate (and test) when a given
 524 type structure contains a new feature. The Python core will use these when
 525 introducing new functionality between major revisions (to avoid mid-version
 526 changes in the PYTHON_API_VERSION).
 527
 528 Arbitration of the flag bit positions will need to be coordinated among
 529 all extension writers who publically release their extensions (this will
 530 be fewer than you might expect!)..
 531
 532 Python 1.5.2 introduced the bf_getcharbuffer slot into PyBufferProcs.
 533
 534 Type definitions should use Py_TPFLAGS_DEFAULT for their tp_flags value.
 535
 536 Code can use PyType_HasFeature(type_ob, flag_value) to test whether the
 537 given type object has a specified feature.
 538
 539 NOTE: when building the core, Py_TPFLAGS_DEFAULT includes
 540 Py_TPFLAGS_HAVE_VERSION_TAG; outside the core, it doesn't.  This is so
 541 that extensions that modify tp_dict of their own types directly don't
 542 break, since this was allowed in 2.5.  In 3.0 they will have to
 543 manually remove this flag though!
 544 */
 545
 546 /* PyBufferProcs contains bf_getcharbuffer */
 547 #define Py_TPFLAGS_HAVE_GETCHARBUFFER  (1L<<0)
 548
 549 /* PySequenceMethods contains sq_contains */
 550 #define Py_TPFLAGS_HAVE_SEQUENCE_IN (1L<<1)
 551
 552 /* This is here for backwards compatibility.  Extensions that use the old GC
 553  * API will still compile but the objects will not be tracked by the GC. */
 554 #define Py_TPFLAGS_GC 0 /* used to be (1L<<2) */
 555
 556 /* PySequenceMethods and PyNumberMethods contain in-place operators */
 557 #define Py_TPFLAGS_HAVE_INPLACEOPS (1L<<3)
 558
 559 /* PyNumberMethods do their own coercion */
 560 #define Py_TPFLAGS_CHECKTYPES (1L<<4)
 561
 562 /* tp_richcompare is defined */
 563 #define Py_TPFLAGS_HAVE_RICHCOMPARE (1L<<5)
 564
 565 /* Objects which are weakly referencable if their tp_weaklistoffset is >0 */
 566 #define Py_TPFLAGS_HAVE_WEAKREFS (1L<<6)
 567
 568 /* tp_iter is defined */
 569 #define Py_TPFLAGS_HAVE_ITER (1L<<7)
 570
 571 /* New members introduced by Python 2.2 exist */
 572 #define Py_TPFLAGS_HAVE_CLASS (1L<<8)
 573
 574 /* Set if the type object is dynamically allocated */
 575 #define Py_TPFLAGS_HEAPTYPE (1L<<9)
 576
 577 /* Set if the type allows subclassing */
 578 #define Py_TPFLAGS_BASETYPE (1L<<10)
 579
 580 /* Set if the type is 'ready' -- fully initialized */
 581 #define Py_TPFLAGS_READY (1L<<12)
 582
 583 /* Set while the type is being 'readied', to prevent recursive ready calls */
 584 #define Py_TPFLAGS_READYING (1L<<13)
 585
 586 /* Objects support garbage collection (see objimp.h) */
 587 #define Py_TPFLAGS_HAVE_GC (1L<<14)
 588
 589 /* These two bits are preserved for Stackless Python, next after this is 17 */
 590 #ifdef STACKLESS
 591 #define Py_TPFLAGS_HAVE_STACKLESS_EXTENSION (3L<<15)
 592 #else
 593 #define Py_TPFLAGS_HAVE_STACKLESS_EXTENSION 0
 594 #endif
 595
 596 /* Objects support nb_index in PyNumberMethods */
 597 #define Py_TPFLAGS_HAVE_INDEX (1L<<17)
 598
 599 /* Objects support type attribute cache */
 600 #define Py_TPFLAGS_HAVE_VERSION_TAG   (1L<<18)
 601 #define Py_TPFLAGS_VALID_VERSION_TAG  (1L<<19)
 602
 603 /* Type is abstract and cannot be instantiated */
 604 #define Py_TPFLAGS_IS_ABSTRACT (1L<<20)
 605
 606 /* Has the new buffer protocol */
 607 #define Py_TPFLAGS_HAVE_NEWBUFFER (1L<<21)
 608
 609 /* These flags are used to determine if a type is a subclass. */
 610 #define Py_TPFLAGS_INT_SUBCLASS         (1L<<23)
 611 #define Py_TPFLAGS_LONG_SUBCLASS        (1L<<24)
 612 #define Py_TPFLAGS_LIST_SUBCLASS        (1L<<25)
 613 #define Py_TPFLAGS_TUPLE_SUBCLASS       (1L<<26)
 614 #define Py_TPFLAGS_STRING_SUBCLASS      (1L<<27)
 615 #define Py_TPFLAGS_UNICODE_SUBCLASS     (1L<<28)
 616 #define Py_TPFLAGS_DICT_SUBCLASS        (1L<<29)
 617 #define Py_TPFLAGS_BASE_EXC_SUBCLASS    (1L<<30)
 618 #define Py_TPFLAGS_TYPE_SUBCLASS        (1L<<31)
 619
 620 #define Py_TPFLAGS_DEFAULT_EXTERNAL ( \
 621                              Py_TPFLAGS_HAVE_GETCHARBUFFER | \
 622                              Py_TPFLAGS_HAVE_SEQUENCE_IN | \
 623                              Py_TPFLAGS_HAVE_INPLACEOPS | \
 624                              Py_TPFLAGS_HAVE_RICHCOMPARE | \
 625                              Py_TPFLAGS_HAVE_WEAKREFS | \
 626                              Py_TPFLAGS_HAVE_ITER | \
 627                              Py_TPFLAGS_HAVE_CLASS | \
 628                              Py_TPFLAGS_HAVE_STACKLESS_EXTENSION | \
 629                              Py_TPFLAGS_HAVE_INDEX | \
 630                              0)
 631 #define Py_TPFLAGS_DEFAULT_CORE (Py_TPFLAGS_DEFAULT_EXTERNAL | \
 632                                  Py_TPFLAGS_HAVE_VERSION_TAG)
 633
 634 #ifdef Py_BUILD_CORE
 635 #define Py_TPFLAGS_DEFAULT Py_TPFLAGS_DEFAULT_CORE
 636 #else
 637 #define Py_TPFLAGS_DEFAULT Py_TPFLAGS_DEFAULT_EXTERNAL
 638 #endif
 639
 640 #define PyType_HasFeature(t,f)  (((t)->tp_flags & (f)) != 0)
 641 #define PyType_FastSubclass(t,f)  PyType_HasFeature(t,f)
 642
 643
 644 /*
 645 The macros Py_INCREF(op) and Py_DECREF(op) are used to increment or decrement
 646 reference counts.  Py_DECREF calls the object's deallocator function when
 647 the refcount falls to 0; for
 648 objects that don't contain references to other objects or heap memory
 649 this can be the standard function free().  Both macros can be used
 650 wherever a void expression is allowed.  The argument must not be a
 651 NULL pointer.  If it may be NULL, use Py_XINCREF/Py_XDECREF instead.
 652 The macro _Py_NewReference(op) initialize reference counts to 1, and
 653 in special builds (Py_REF_DEBUG, Py_TRACE_REFS) performs additional
 654 bookkeeping appropriate to the special build.
 655
 656 We assume that the reference count field can never overflow; this can
 657 be proven when the size of the field is the same as the pointer size, so
 658 we ignore the possibility.  Provided a C int is at least 32 bits (which
 659 is implicitly assumed in many parts of this code), that's enough for
 660 about 2**31 references to an object.
 661
 662 XXX The following became out of date in Python 2.2, but I'm not sure
 663 XXX what the full truth is now.  Certainly, heap-allocated type objects
 664 XXX can and should be deallocated.
 665 Type objects should never be deallocated; the type pointer in an object
 666 is not considered to be a reference to the type object, to save
 667 complications in the deallocation function.  (This is actually a
 668 decision that's up to the implementer of each new type so if you want,
 669 you can count such references to the type object.)
 670
 671 *** WARNING*** The Py_DECREF macro must have a side-effect-free argument
 672 since it may evaluate its argument multiple times.  (The alternative
 673 would be to mace it a proper function or assign it to a global temporary
 674 variable first, both of which are slower; and in a multi-threaded
 675 environment the global variable trick is not safe.)
 676 */
 677
 678 /* First define a pile of simple helper macros, one set per special
 679  * build symbol.  These either expand to the obvious things, or to
 680  * nothing at all when the special mode isn't in effect.  The main
 681  * macros can later be defined just once then, yet expand to different
 682  * things depending on which special build options are and aren't in effect.
 683  * Trust me <wink>:  while painful, this is 20x easier to understand than,
 684  * e.g, defining _Py_NewReference five different times in a maze of nested
 685  * #ifdefs (we used to do that -- it was impenetrable).
 686  */
 687 #ifdef Py_REF_DEBUG
 688 PyAPI_DATA(Py_ssize_t) _Py_RefTotal;
 689 PyAPI_FUNC(void) _Py_NegativeRefcount(const char *fname,
 690                                             int lineno, PyObject *op);
 691 PyAPI_FUNC(PyObject *) _PyDict_Dummy(void);
 692 PyAPI_FUNC(PyObject *) _PySet_Dummy(void);
 693 PyAPI_FUNC(Py_ssize_t) _Py_GetRefTotal(void);
 694 #define _Py_INC_REFTOTAL        _Py_RefTotal++
 695 #define _Py_DEC_REFTOTAL        _Py_RefTotal--
 696 #define _Py_REF_DEBUG_COMMA     ,
 697 #define _Py_CHECK_REFCNT(OP)                                    \
 698 {       if (((PyObject*)OP)->ob_refcnt < 0)                             \
 699                 _Py_NegativeRefcount(__FILE__, __LINE__,        \
 700                                      (PyObject *)(OP));         \
 701 }
 702 #else
 703 #define _Py_INC_REFTOTAL
 704 #define _Py_DEC_REFTOTAL
 705 #define _Py_REF_DEBUG_COMMA
 706 #define _Py_CHECK_REFCNT(OP)    /* a semicolon */;
 707 #endif /* Py_REF_DEBUG */
 708
 709 #ifdef COUNT_ALLOCS
 710 PyAPI_FUNC(void) inc_count(PyTypeObject *);
 711 PyAPI_FUNC(void) dec_count(PyTypeObject *);
 712 #define _Py_INC_TPALLOCS(OP)    inc_count(Py_TYPE(OP))
 713 #define _Py_INC_TPFREES(OP)     dec_count(Py_TYPE(OP))
 714 #define _Py_DEC_TPFREES(OP)     Py_TYPE(OP)->tp_frees--
 715 #define _Py_COUNT_ALLOCS_COMMA  ,
 716 #else
 717 #define _Py_INC_TPALLOCS(OP)
 718 #define _Py_INC_TPFREES(OP)
 719 #define _Py_DEC_TPFREES(OP)
 720 #define _Py_COUNT_ALLOCS_COMMA
 721 #endif /* COUNT_ALLOCS */
 722
 723 #ifdef Py_TRACE_REFS
 724 /* Py_TRACE_REFS is such major surgery that we call external routines. */
 725 PyAPI_FUNC(void) _Py_NewReference(PyObject *);
 726 PyAPI_FUNC(void) _Py_ForgetReference(PyObject *);
 727 PyAPI_FUNC(void) _Py_Dealloc(PyObject *);
 728 PyAPI_FUNC(void) _Py_PrintReferences(FILE *);
 729 PyAPI_FUNC(void) _Py_PrintReferenceAddresses(FILE *);
 730 PyAPI_FUNC(void) _Py_AddToAllObjects(PyObject *, int force);
 731
 732 #else
 733 /* Without Py_TRACE_REFS, there's little enough to do that we expand code
 734  * inline.
 735  */
 736 #define _Py_NewReference(op) (                          \
 737         _Py_INC_TPALLOCS(op) _Py_COUNT_ALLOCS_COMMA     \
 738         _Py_INC_REFTOTAL  _Py_REF_DEBUG_COMMA           \
 739         Py_REFCNT(op) = 1)
 740
 741 #define _Py_ForgetReference(op) _Py_INC_TPFREES(op)
 742
 743 #define _Py_Dealloc(op) (                               \
 744         _Py_INC_TPFREES(op) _Py_COUNT_ALLOCS_COMMA      \
 745         (*Py_TYPE(op)->tp_dealloc)((PyObject *)(op)))
 746 #endif /* !Py_TRACE_REFS */
 747
 748 #define Py_INCREF(op) (                         \
 749         _Py_INC_REFTOTAL  _Py_REF_DEBUG_COMMA   \
 750         ((PyObject*)(op))->ob_refcnt++)
 751
 752 #define Py_DECREF(op)                                   \
 753         do {                                            \
 754             if (_Py_DEC_REFTOTAL  _Py_REF_DEBUG_COMMA   \
 755                 --((PyObject*)(op))->ob_refcnt != 0)    \
 756                     _Py_CHECK_REFCNT(op)                \
 757             else                                        \
 758                 _Py_Dealloc((PyObject *)(op));          \
 759         } while (0)
 760
 761 /* Safely decref `op` and set `op` to NULL, especially useful in tp_clear
 762  * and tp_dealloc implementatons.
 763  *
 764  * Note that "the obvious" code can be deadly:
 765  *
 766  *     Py_XDECREF(op);
 767  *     op = NULL;
 768  *
 769  * Typically, `op` is something like self->containee, and `self` is done
 770  * using its `containee` member.  In the code sequence above, suppose
 771  * `containee` is non-NULL with a refcount of 1.  Its refcount falls to
 772  * 0 on the first line, which can trigger an arbitrary amount of code,
 773  * possibly including finalizers (like __del__ methods or weakref callbacks)
 774  * coded in Python, which in turn can release the GIL and allow other threads
 775  * to run, etc.  Such code may even invoke methods of `self` again, or cause
 776  * cyclic gc to trigger, but-- oops! --self->containee still points to the
 777  * object being torn down, and it may be in an insane state while being torn
 778  * down.  This has in fact been a rich historic source of miserable (rare &
 779  * hard-to-diagnose) segfaulting (and other) bugs.
 780  *
 781  * The safe way is:
 782  *
 783  *      Py_CLEAR(op);
 784  *
 785  * That arranges to set `op` to NULL _before_ decref'ing, so that any code
 786  * triggered as a side-effect of `op` getting torn down no longer believes
 787  * `op` points to a valid object.
 788  *
 789  * There are cases where it's safe to use the naive code, but they're brittle.
 790  * For example, if `op` points to a Python integer, you know that destroying
 791  * one of those can't cause problems -- but in part that relies on that
 792  * Python integers aren't currently weakly referencable.  Best practice is
 793  * to use Py_CLEAR() even if you can't think of a reason for why you need to.
 794  */
 795 #define Py_CLEAR(op)                            \
 796         do {                                    \
 797                 if (op) {                       \
 798                         PyObject *_py_tmp = (PyObject *)(op);   \
 799                         (op) = NULL;            \
 800                         Py_DECREF(_py_tmp);     \
 801                 }                               \
 802         } while (0)
 803
 804 /* Macros to use in case the object pointer may be NULL: */
 805 #define Py_XINCREF(op) do { if ((op) == NULL) ; else Py_INCREF(op); } while (0)
 806 #define Py_XDECREF(op) do { if ((op) == NULL) ; else Py_DECREF(op); } while (0)
 807
 808 /*
 809 These are provided as conveniences to Python runtime embedders, so that
 810 they can have object code that is not dependent on Python compilation flags.
 811 */
 812 PyAPI_FUNC(void) Py_IncRef(PyObject *);
 813 PyAPI_FUNC(void) Py_DecRef(PyObject *);
 814
 815 /*
 816 _Py_NoneStruct is an object of undefined type which can be used in contexts
 817 where NULL (nil) is not suitable (since NULL often means 'error').
 818
 819 Don't forget to apply Py_INCREF() when returning this value!!!
 820 */
 821 PyAPI_DATA(PyObject) _Py_NoneStruct; /* Don't use this directly */
 822 #define Py_None (&_Py_NoneStruct)
 823
 824 /* Macro for returning Py_None from a function */
 825 #define Py_RETURN_NONE return Py_INCREF(Py_None), Py_None
 826
 827 /*
 828 Py_NotImplemented is a singleton used to signal that an operation is
 829 not implemented for a given type combination.
 830 */
 831 PyAPI_DATA(PyObject) _Py_NotImplementedStruct; /* Don't use this directly */
 832 #define Py_NotImplemented (&_Py_NotImplementedStruct)
 833
 834 /* Rich comparison opcodes */
 835 #define Py_LT 0
 836 #define Py_LE 1
 837 #define Py_EQ 2
 838 #define Py_NE 3
 839 #define Py_GT 4
 840 #define Py_GE 5
 841
 842 /* Maps Py_LT to Py_GT, ..., Py_GE to Py_LE.
 843  * Defined in object.c.
 844  */
 845 PyAPI_DATA(int) _Py_SwappedOp[];
 846
 847 /*
 848 Define staticforward and statichere for source compatibility with old
 849 C extensions.
 850
 851 The staticforward define was needed to support certain broken C
 852 compilers (notably SCO ODT 3.0, perhaps early AIX as well) botched the
 853 static keyword when it was used with a forward declaration of a static
 854 initialized structure.  Standard C allows the forward declaration with
 855 static, and we've decided to stop catering to broken C compilers.
 856 (In fact, we expect that the compilers are all fixed eight years later.)
 857 */
 858
 859 #define staticforward static
 860 #define statichere static
 861
 862
 863 /*
 864 More conventions
 865 ================
 866
 867 Argument Checking
 868 -----------------
 869
 870 Functions that take objects as arguments normally don't check for nil
 871 arguments, but they do check the type of the argument, and return an
 872 error if the function doesn't apply to the type.
 873
 874 Failure Modes
 875 -------------
 876
 877 Functions may fail for a variety of reasons, including running out of
 878 memory.  This is communicated to the caller in two ways: an error string
 879 is set (see errors.h), and the function result differs: functions that
 880 normally return a pointer return NULL for failure, functions returning
 881 an integer return -1 (which could be a legal return value too!), and
 882 other functions return 0 for success and -1 for failure.
 883 Callers should always check for errors before using the result.  If
 884 an error was set, the caller must either explicitly clear it, or pass
 885 the error on to its caller.
 886
 887 Reference Counts
 888 ----------------
 889
 890 It takes a while to get used to the proper usage of reference counts.
 891
 892 Functions that create an object set the reference count to 1; such new
 893 objects must be stored somewhere or destroyed again with Py_DECREF().
 894 Some functions that 'store' objects, such as PyTuple_SetItem() and
 895 PyList_SetItem(),
 896 don't increment the reference count of the object, since the most
 897 frequent use is to store a fresh object.  Functions that 'retrieve'
 898 objects, such as PyTuple_GetItem() and PyDict_GetItemString(), also
 899 don't increment
 900 the reference count, since most frequently the object is only looked at
 901 quickly.  Thus, to retrieve an object and store it again, the caller
 902 must call Py_INCREF() explicitly.
 903
 904 NOTE: functions that 'consume' a reference count, like
 905 PyList_SetItem(), consume the reference even if the object wasn't
 906 successfully stored, to simplify error handling.
 907
 908 It seems attractive to make other functions that take an object as
 909 argument consume a reference count; however, this may quickly get
 910 confusing (even the current practice is already confusing).  Consider
 911 it carefully, it may save lots of calls to Py_INCREF() and Py_DECREF() at
 912 times.
 913 */
 914
 915
 916 /* Trashcan mechanism, thanks to Christian Tismer.
 917
 918 When deallocating a container object, it's possible to trigger an unbounded
 919 chain of deallocations, as each Py_DECREF in turn drops the refcount on "the
 920 next" object in the chain to 0.  This can easily lead to stack faults, and
 921 especially in threads (which typically have less stack space to work with).
 922
 923 A container object that participates in cyclic gc can avoid this by
 924 bracketing the body of its tp_dealloc function with a pair of macros:
 925
 926 static void
 927 mytype_dealloc(mytype *p)
 928 {
 929         ... declarations go here ...
 930
 931         PyObject_GC_UnTrack(p);    // must untrack first
 932         Py_TRASHCAN_SAFE_BEGIN(p)
 933         ... The body of the deallocator goes here, including all calls ...
 934         ... to Py_DECREF on contained objects.                         ...
 935         Py_TRASHCAN_SAFE_END(p)
 936 }
 937
 938 CAUTION:  Never return from the middle of the body!  If the body needs to
 939 "get out early", put a label immediately before the Py_TRASHCAN_SAFE_END
 940 call, and goto it.  Else the call-depth counter (see below) will stay
 941 above 0 forever, and the trashcan will never get emptied.
 942
 943 How it works:  The BEGIN macro increments a call-depth counter.  So long
 944 as this counter is small, the body of the deallocator is run directly without
 945 further ado.  But if the counter gets large, it instead adds p to a list of
 946 objects to be deallocated later, skips the body of the deallocator, and
 947 resumes execution after the END macro.  The tp_dealloc routine then returns
 948 without deallocating anything (and so unbounded call-stack depth is avoided).
 949
 950 When the call stack finishes unwinding again, code generated by the END macro
 951 notices this, and calls another routine to deallocate all the objects that
 952 may have been added to the list of deferred deallocations.  In effect, a
 953 chain of N deallocations is broken into N / PyTrash_UNWIND_LEVEL pieces,
 954 with the call stack never exceeding a depth of PyTrash_UNWIND_LEVEL.
 955 */
 956
 957 PyAPI_FUNC(void) _PyTrash_deposit_object(PyObject*);
 958 PyAPI_FUNC(void) _PyTrash_destroy_chain(void);
 959 PyAPI_DATA(int) _PyTrash_delete_nesting;
 960 PyAPI_DATA(PyObject *) _PyTrash_delete_later;
 961
 962 #define PyTrash_UNWIND_LEVEL 50
 963
 964 #define Py_TRASHCAN_SAFE_BEGIN(op) \
 965         if (_PyTrash_delete_nesting < PyTrash_UNWIND_LEVEL) { \
 966                 ++_PyTrash_delete_nesting;
 967                 /* The body of the deallocator is here. */
 968 #define Py_TRASHCAN_SAFE_END(op) \
 969                 --_PyTrash_delete_nesting; \
 970                 if (_PyTrash_delete_later && _PyTrash_delete_nesting <= 0) \
 971                         _PyTrash_destroy_chain(); \
 972         } \
 973         else \
 974                 _PyTrash_deposit_object((PyObject*)op);
 975
 976 #ifdef __cplusplus
 977 }
 978 #endif
 979 #endif /* !Py_OBJECT_H */