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.)
  17
  18 An object has a 'reference count' that is increased or decreased when a
  19 pointer to the object is copied or deleted; when the reference count
  20 reaches zero there are no references to the object left and it can be
  21 removed from the heap.
  22
  23 An object has a 'type' that determines what it represents and what kind
  24 of data it contains.  An object's type is fixed when it is created.
  25 Types themselves are represented as objects; an object contains a
  26 pointer to the corresponding type object.  The type itself has a type
  27 pointer pointing to the object representing the type 'type', which
  28 contains a pointer to itself!).
  29
  30 Objects do not float around in memory; once allocated an object keeps
  31 the same size and address.  Objects that must hold variable-size data
  32 can contain pointers to variable-size parts of the object.  Not all
  33 objects of the same type have the same size; but the size cannot change
  34 after allocation.  (These restrictions are made so a reference to an
  35 object can be simply a pointer -- moving an object would require
  36 updating all the pointers, and changing an object's size would require
  37 moving it if there was another object right next to it.)
  38
  39 Objects are always accessed through pointers of the type 'PyObject *'.
  40 The type 'PyObject' is a structure that only contains the reference count
  41 and the type pointer.  The actual memory allocated for an object
  42 contains other data that can only be accessed after casting the pointer
  43 to a pointer to a longer structure type.  This longer type must start
  44 with the reference count and type fields; the macro PyObject_HEAD should be
  45 used for this (to accommodate for future changes).  The implementation
  46 of a particular object type can cast the object pointer to the proper
  47 type and back.
  48
  49 A standard interface exists for objects that contain an array of items
  50 whose size is determined when the object is allocated.
  51 */
  52
  53 #ifdef Py_DEBUG
  54
  55 /* Turn on heavy reference debugging */
  56 #define Py_TRACE_REFS
  57
  58 /* Turn on reference counting */
  59 #define Py_REF_DEBUG
  60
  61 #endif /* Py_DEBUG */
  62
  63 #ifdef Py_TRACE_REFS
  64 #define PyObject_HEAD \
  65         struct _object *_ob_next, *_ob_prev; \
  66         int ob_refcnt; \
  67         struct _typeobject *ob_type;
  68 #define PyObject_HEAD_INIT(type) 0, 0, 1, type,
  69 #else /* !Py_TRACE_REFS */
  70 #define PyObject_HEAD \
  71         int ob_refcnt; \
  72         struct _typeobject *ob_type;
  73 #define PyObject_HEAD_INIT(type) 1, type,
  74 #endif /* !Py_TRACE_REFS */
  75
  76 #define PyObject_VAR_HEAD \
  77         PyObject_HEAD \
  78         int ob_size; /* Number of items in variable part */
  79
  80 typedef struct _object {
  81         PyObject_HEAD
  82 } PyObject;
  83
  84 typedef struct {
  85         PyObject_VAR_HEAD
  86 } PyVarObject;
  87
  88
  89 /*
  90 Type objects contain a string containing the type name (to help somewhat
  91 in debugging), the allocation parameters (see newobj() and newvarobj()),
  92 and methods for accessing objects of the type.  Methods are optional,a
  93 nil pointer meaning that particular kind of access is not available for
  94 this type.  The Py_DECREF() macro uses the tp_dealloc method without
  95 checking for a nil pointer; it should always be implemented except if
  96 the implementation can guarantee that the reference count will never
  97 reach zero (e.g., for type objects).
  98
  99 NB: the methods for certain type groups are now contained in separate
 100 method blocks.
 101 */
 102
 103 typedef PyObject * (*unaryfunc)(PyObject *);
 104 typedef PyObject * (*binaryfunc)(PyObject *, PyObject *);
 105 typedef PyObject * (*ternaryfunc)(PyObject *, PyObject *, PyObject *);
 106 typedef int (*inquiry)(PyObject *);
 107 typedef int (*coercion)(PyObject **, PyObject **);
 108 typedef PyObject *(*intargfunc)(PyObject *, int);
 109 typedef PyObject *(*intintargfunc)(PyObject *, int, int);
 110 typedef int(*intobjargproc)(PyObject *, int, PyObject *);
 111 typedef int(*intintobjargproc)(PyObject *, int, int, PyObject *);
 112 typedef int(*objobjargproc)(PyObject *, PyObject *, PyObject *);
 113 typedef int (*getreadbufferproc)(PyObject *, int, void **);
 114 typedef int (*getwritebufferproc)(PyObject *, int, void **);
 115 typedef int (*getsegcountproc)(PyObject *, int *);
 116 typedef int (*getcharbufferproc)(PyObject *, int, const char **);
 117 typedef int (*objobjproc)(PyObject *, PyObject *);
 118 typedef int (*visitproc)(PyObject *, void *);
 119 typedef int (*traverseproc)(PyObject *, visitproc, void *);
 120
 121 typedef struct {
 122         /* For numbers without flag bit Py_TPFLAGS_CHECKTYPES set, all
 123            arguments are guaranteed to be of the object's type (modulo
 124            coercion hacks that is -- i.e. if the type's coercion function
 125            returns other types, then these are allowed as well).  Numbers that
 126            have the Py_TPFLAGS_CHECKTYPES flag bit set should check *both*
 127            arguments for proper type and implement the necessary conversions
 128            in the slot functions themselves. */
 129
 130         binaryfunc nb_add;
 131         binaryfunc nb_subtract;
 132         binaryfunc nb_multiply;
 133         binaryfunc nb_divide;
 134         binaryfunc nb_remainder;
 135         binaryfunc nb_divmod;
 136         ternaryfunc nb_power;
 137         unaryfunc nb_negative;
 138         unaryfunc nb_positive;
 139         unaryfunc nb_absolute;
 140         inquiry nb_nonzero;
 141         unaryfunc nb_invert;
 142         binaryfunc nb_lshift;
 143         binaryfunc nb_rshift;
 144         binaryfunc nb_and;
 145         binaryfunc nb_xor;
 146         binaryfunc nb_or;
 147         coercion nb_coerce;
 148         unaryfunc nb_int;
 149         unaryfunc nb_long;
 150         unaryfunc nb_float;
 151         unaryfunc nb_oct;
 152         unaryfunc nb_hex;
 153         binaryfunc nb_inplace_add;
 154         binaryfunc nb_inplace_subtract;
 155         binaryfunc nb_inplace_multiply;
 156         binaryfunc nb_inplace_divide;
 157         binaryfunc nb_inplace_remainder;
 158         ternaryfunc nb_inplace_power;
 159         binaryfunc nb_inplace_lshift;
 160         binaryfunc nb_inplace_rshift;
 161         binaryfunc nb_inplace_and;
 162         binaryfunc nb_inplace_xor;
 163         binaryfunc nb_inplace_or;
 164
 165         /* The following require the Py_TPFLAGS_HAVE_CLASS flag */
 166         binaryfunc nb_floor_divide;
 167         binaryfunc nb_true_divide;
 168         binaryfunc nb_inplace_floor_divide;
 169         binaryfunc nb_inplace_true_divide;
 170 } PyNumberMethods;
 171
 172 typedef struct {
 173         inquiry sq_length;
 174         binaryfunc sq_concat;
 175         intargfunc sq_repeat;
 176         intargfunc sq_item;
 177         intintargfunc sq_slice;
 178         intobjargproc sq_ass_item;
 179         intintobjargproc sq_ass_slice;
 180         objobjproc sq_contains;
 181         binaryfunc sq_inplace_concat;
 182         intargfunc sq_inplace_repeat;
 183 } PySequenceMethods;
 184
 185 typedef struct {
 186         inquiry mp_length;
 187         binaryfunc mp_subscript;
 188         objobjargproc mp_ass_subscript;
 189 } PyMappingMethods;
 190
 191 typedef struct {
 192         getreadbufferproc bf_getreadbuffer;
 193         getwritebufferproc bf_getwritebuffer;
 194         getsegcountproc bf_getsegcount;
 195         getcharbufferproc bf_getcharbuffer;
 196 } PyBufferProcs;
 197
 198
 199 typedef void (*destructor)(PyObject *);
 200 typedef int (*printfunc)(PyObject *, FILE *, int);
 201 typedef PyObject *(*getattrfunc)(PyObject *, char *);
 202 typedef PyObject *(*getattrofunc)(PyObject *, PyObject *);
 203 typedef int (*setattrfunc)(PyObject *, char *, PyObject *);
 204 typedef int (*setattrofunc)(PyObject *, PyObject *, PyObject *);
 205 typedef int (*cmpfunc)(PyObject *, PyObject *);
 206 typedef PyObject *(*reprfunc)(PyObject *);
 207 typedef long (*hashfunc)(PyObject *);
 208 typedef PyObject *(*richcmpfunc) (PyObject *, PyObject *, int);
 209 typedef PyObject *(*getiterfunc) (PyObject *);
 210 typedef PyObject *(*iternextfunc) (PyObject *);
 211 typedef PyObject *(*descrgetfunc) (PyObject *, PyObject *, PyObject *);
 212 typedef int (*descrsetfunc) (PyObject *, PyObject *, PyObject *);
 213 typedef int (*initproc)(PyObject *, PyObject *, PyObject *);
 214 typedef PyObject *(*newfunc)(struct _typeobject *, PyObject *, PyObject *);
 215 typedef PyObject *(*allocfunc)(struct _typeobject *, int);
 216
 217 typedef struct _typeobject {
 218         PyObject_VAR_HEAD
 219         char *tp_name; /* For printing */
 220         int tp_basicsize, tp_itemsize; /* For allocation */
 221
 222         /* Methods to implement standard operations */
 223
 224         destructor tp_dealloc;
 225         printfunc tp_print;
 226         getattrfunc tp_getattr;
 227         setattrfunc tp_setattr;
 228         cmpfunc tp_compare;
 229         reprfunc tp_repr;
 230
 231         /* Method suites for standard classes */
 232
 233         PyNumberMethods *tp_as_number;
 234         PySequenceMethods *tp_as_sequence;
 235         PyMappingMethods *tp_as_mapping;
 236
 237         /* More standard operations (here for binary compatibility) */
 238
 239         hashfunc tp_hash;
 240         ternaryfunc tp_call;
 241         reprfunc tp_str;
 242         getattrofunc tp_getattro;
 243         setattrofunc tp_setattro;
 244
 245         /* Functions to access object as input/output buffer */
 246         PyBufferProcs *tp_as_buffer;
 247
 248         /* Flags to define presence of optional/expanded features */
 249         long tp_flags;
 250
 251         char *tp_doc; /* Documentation string */
 252
 253         /* call function for all accessible objects */
 254         traverseproc tp_traverse;
 255
 256         /* delete references to contained objects */
 257         inquiry tp_clear;
 258
 259         /* rich comparisons */
 260         richcmpfunc tp_richcompare;
 261
 262         /* weak reference enabler */
 263         long tp_weaklistoffset;
 264
 265         /* Iterators */
 266         getiterfunc tp_iter;
 267         iternextfunc tp_iternext;
 268
 269         /* Attribute descriptor and subclassing stuff */
 270         struct PyMethodDef *tp_methods;
 271         struct memberlist *tp_members;
 272         struct getsetlist *tp_getset;
 273         struct _typeobject *tp_base;
 274         PyObject *tp_dict;
 275         descrgetfunc tp_descr_get;
 276         descrsetfunc tp_descr_set;
 277         long tp_dictoffset;
 278         initproc tp_init;
 279         allocfunc tp_alloc;
 280         newfunc tp_new;
 281         destructor tp_free; /* Low-level free-memory routine */
 282         PyObject *tp_bases;
 283         PyObject *tp_mro; /* method resolution order */
 284         PyObject *tp_defined;
 285
 286 #ifdef COUNT_ALLOCS
 287         /* these must be last and never explicitly initialized */
 288         int tp_allocs;
 289         int tp_frees;
 290         int tp_maxalloc;
 291         struct _typeobject *tp_next;
 292 #endif
 293 } PyTypeObject;
 294
 295
 296 /* Generic type check */
 297 extern DL_IMPORT(int) PyType_IsSubtype(PyTypeObject *, PyTypeObject *);
 298 #define PyObject_TypeCheck(ob, tp) \
 299         ((ob)->ob_type == (tp) || PyType_IsSubtype((ob)->ob_type, (tp)))
 300
 301 extern DL_IMPORT(PyTypeObject) PyType_Type; /* Metatype */
 302 extern DL_IMPORT(PyTypeObject) PyBaseObject_Type; /* Most base object type */
 303
 304 #define PyType_Check(op) PyObject_TypeCheck(op, &PyType_Type)
 305
 306 extern DL_IMPORT(int) PyType_Ready(PyTypeObject *);
 307 extern DL_IMPORT(PyObject *) PyType_GenericAlloc(PyTypeObject *, int);
 308 extern DL_IMPORT(PyObject *) PyType_GenericNew(PyTypeObject *,
 309                                                PyObject *, PyObject *);
 310 extern DL_IMPORT(PyObject *) _PyType_Lookup(PyTypeObject *, PyObject *);
 311
 312 /* Generic operations on objects */
 313 extern DL_IMPORT(int) PyObject_Print(PyObject *, FILE *, int);
 314 extern DL_IMPORT(void) _PyObject_Dump(PyObject *);
 315 extern DL_IMPORT(PyObject *) PyObject_Repr(PyObject *);
 316 extern DL_IMPORT(PyObject *) PyObject_Str(PyObject *);
 317 extern DL_IMPORT(PyObject *) PyObject_Unicode(PyObject *);
 318 extern DL_IMPORT(int) PyObject_Compare(PyObject *, PyObject *);
 319 extern DL_IMPORT(PyObject *) PyObject_RichCompare(PyObject *, PyObject *, int);
 320 extern DL_IMPORT(int) PyObject_RichCompareBool(PyObject *, PyObject *, int);
 321 extern DL_IMPORT(PyObject *) PyObject_GetAttrString(PyObject *, char *);
 322 extern DL_IMPORT(int) PyObject_SetAttrString(PyObject *, char *, PyObject *);
 323 extern DL_IMPORT(int) PyObject_HasAttrString(PyObject *, char *);
 324 extern DL_IMPORT(PyObject *) PyObject_GetAttr(PyObject *, PyObject *);
 325 extern DL_IMPORT(int) PyObject_SetAttr(PyObject *, PyObject *, PyObject *);
 326 extern DL_IMPORT(int) PyObject_HasAttr(PyObject *, PyObject *);
 327 extern DL_IMPORT(PyObject **) _PyObject_GetDictPtr(PyObject *);
 328 extern DL_IMPORT(PyObject *) PyObject_GenericGetAttr(PyObject *, PyObject *);
 329 extern DL_IMPORT(int) PyObject_GenericSetAttr(PyObject *,
 330                                               PyObject *, PyObject *);
 331 extern DL_IMPORT(long) PyObject_Hash(PyObject *);
 332 extern DL_IMPORT(int) PyObject_IsTrue(PyObject *);
 333 extern DL_IMPORT(int) PyObject_Not(PyObject *);
 334 extern DL_IMPORT(int) PyCallable_Check(PyObject *);
 335 extern DL_IMPORT(int) PyNumber_Coerce(PyObject **, PyObject **);
 336 extern DL_IMPORT(int) PyNumber_CoerceEx(PyObject **, PyObject **);
 337
 338 extern DL_IMPORT(void) (*PyObject_ClearWeakRefs)(PyObject *);
 339
 340 /* Helpers for printing recursive container types */
 341 extern DL_IMPORT(int) Py_ReprEnter(PyObject *);
 342 extern DL_IMPORT(void) Py_ReprLeave(PyObject *);
 343
 344 /* Helpers for hash functions */
 345 extern DL_IMPORT(long) _Py_HashDouble(double);
 346 extern DL_IMPORT(long) _Py_HashPointer(void*);
 347
 348 /* Helper for passing objects to printf and the like */
 349 #define PyObject_REPR(obj) PyString_AS_STRING(PyObject_Repr(obj))
 350
 351 /* Flag bits for printing: */
 352 #define Py_PRINT_RAW    1       /* No string quotes etc. */
 353
 354 /*
 355
 356 Type flags (tp_flags)
 357
 358 These flags are used to extend the type structure in a backwards-compatible
 359 fashion. Extensions can use the flags to indicate (and test) when a given
 360 type structure contains a new feature. The Python core will use these when
 361 introducing new functionality between major revisions (to avoid mid-version
 362 changes in the PYTHON_API_VERSION).
 363
 364 Arbitration of the flag bit positions will need to be coordinated among
 365 all extension writers who publically release their extensions (this will
 366 be fewer than you might expect!)..
 367
 368 Python 1.5.2 introduced the bf_getcharbuffer slot into PyBufferProcs.
 369
 370 Type definitions should use Py_TPFLAGS_DEFAULT for their tp_flags value.
 371
 372 Code can use PyType_HasFeature(type_ob, flag_value) to test whether the
 373 given type object has a specified feature.
 374
 375 */
 376
 377 /* PyBufferProcs contains bf_getcharbuffer */
 378 #define Py_TPFLAGS_HAVE_GETCHARBUFFER  (1L<<0)
 379
 380 /* PySequenceMethods contains sq_contains */
 381 #define Py_TPFLAGS_HAVE_SEQUENCE_IN (1L<<1)
 382
 383 /* Objects which participate in garbage collection (see objimp.h) */
 384 #ifdef WITH_CYCLE_GC
 385 #define Py_TPFLAGS_GC (1L<<2)
 386 #else
 387 #define Py_TPFLAGS_GC 0
 388 #endif
 389
 390 /* PySequenceMethods and PyNumberMethods contain in-place operators */
 391 #define Py_TPFLAGS_HAVE_INPLACEOPS (1L<<3)
 392
 393 /* PyNumberMethods do their own coercion */
 394 #define Py_TPFLAGS_CHECKTYPES (1L<<4)
 395
 396 /* tp_richcompare is defined */
 397 #define Py_TPFLAGS_HAVE_RICHCOMPARE (1L<<5)
 398
 399 /* Objects which are weakly referencable if their tp_weaklistoffset is >0 */
 400 #define Py_TPFLAGS_HAVE_WEAKREFS (1L<<6)
 401
 402 /* tp_iter is defined */
 403 #define Py_TPFLAGS_HAVE_ITER (1L<<7)
 404
 405 /* New members introduced by Python 2.2 exist */
 406 #define Py_TPFLAGS_HAVE_CLASS (1L<<8)
 407
 408 /* Set if the type object is dynamically allocated */
 409 #define Py_TPFLAGS_HEAPTYPE (1L<<9)
 410
 411 /* Set if the type allows subclassing */
 412 #define Py_TPFLAGS_BASETYPE (1L<<10)
 413
 414 /* Set if the type's __dict__ may change */
 415 #define Py_TPFLAGS_DYNAMICTYPE (1L<<11)
 416
 417 /* Set if the type is 'ready' -- fully initialized */
 418 #define Py_TPFLAGS_READY (1L<<12)
 419
 420 /* Set while the type is being 'readied', to prevent recursive ready calls */
 421 #define Py_TPFLAGS_READYING (1L<<13)
 422
 423 #define Py_TPFLAGS_DEFAULT  ( \
 424                              Py_TPFLAGS_HAVE_GETCHARBUFFER | \
 425                              Py_TPFLAGS_HAVE_SEQUENCE_IN | \
 426                              Py_TPFLAGS_HAVE_INPLACEOPS | \
 427                              Py_TPFLAGS_HAVE_RICHCOMPARE | \
 428                              Py_TPFLAGS_HAVE_WEAKREFS | \
 429                              Py_TPFLAGS_HAVE_ITER | \
 430                              Py_TPFLAGS_HAVE_CLASS | \
 431                             0)
 432
 433 #define PyType_HasFeature(t,f)  (((t)->tp_flags & (f)) != 0)
 434
 435
 436 /*
 437 The macros Py_INCREF(op) and Py_DECREF(op) are used to increment or decrement
 438 reference counts.  Py_DECREF calls the object's deallocator function; for
 439 objects that don't contain references to other objects or heap memory
 440 this can be the standard function free().  Both macros can be used
 441 wherever a void expression is allowed.  The argument shouldn't be a
 442 NIL pointer.  The macro _Py_NewReference(op) is used only to initialize
 443 reference counts to 1; it is defined here for convenience.
 444
 445 We assume that the reference count field can never overflow; this can
 446 be proven when the size of the field is the same as the pointer size
 447 but even with a 16-bit reference count field it is pretty unlikely so
 448 we ignore the possibility.  (If you are paranoid, make it a long.)
 449
 450 Type objects should never be deallocated; the type pointer in an object
 451 is not considered to be a reference to the type object, to save
 452 complications in the deallocation function.  (This is actually a
 453 decision that's up to the implementer of each new type so if you want,
 454 you can count such references to the type object.)
 455
 456 *** WARNING*** The Py_DECREF macro must have a side-effect-free argument
 457 since it may evaluate its argument multiple times.  (The alternative
 458 would be to mace it a proper function or assign it to a global temporary
 459 variable first, both of which are slower; and in a multi-threaded
 460 environment the global variable trick is not safe.)
 461 */
 462
 463 #ifdef Py_TRACE_REFS
 464 #ifndef Py_REF_DEBUG
 465 #define Py_REF_DEBUG
 466 #endif
 467 #endif
 468
 469 #ifdef Py_TRACE_REFS
 470 extern DL_IMPORT(void) _Py_Dealloc(PyObject *);
 471 extern DL_IMPORT(void) _Py_NewReference(PyObject *);
 472 extern DL_IMPORT(void) _Py_ForgetReference(PyObject *);
 473 extern DL_IMPORT(void) _Py_PrintReferences(FILE *);
 474 extern DL_IMPORT(void) _Py_ResetReferences(void);
 475 #endif
 476
 477 #ifndef Py_TRACE_REFS
 478 #ifdef COUNT_ALLOCS
 479 #define _Py_Dealloc(op) ((op)->ob_type->tp_frees++, (*(op)->ob_type->tp_dealloc)((PyObject *)(op)))
 480 #define _Py_ForgetReference(op) ((op)->ob_type->tp_frees++)
 481 #else /* !COUNT_ALLOCS */
 482 #define _Py_Dealloc(op) (*(op)->ob_type->tp_dealloc)((PyObject *)(op))
 483 #define _Py_ForgetReference(op) /*empty*/
 484 #endif /* !COUNT_ALLOCS */
 485 #endif /* !Py_TRACE_REFS */
 486
 487 #ifdef COUNT_ALLOCS
 488 extern DL_IMPORT(void) inc_count(PyTypeObject *);
 489 #endif
 490
 491 #ifdef Py_REF_DEBUG
 492
 493 extern DL_IMPORT(long) _Py_RefTotal;
 494
 495 #ifndef Py_TRACE_REFS
 496 #ifdef COUNT_ALLOCS
 497 #define _Py_NewReference(op) (inc_count((op)->ob_type), _Py_RefTotal++, (op)->ob_refcnt = 1)
 498 #else
 499 #define _Py_NewReference(op) (_Py_RefTotal++, (op)->ob_refcnt = 1)
 500 #endif
 501 #endif /* !Py_TRACE_REFS */
 502
 503 #define Py_INCREF(op) (_Py_RefTotal++, (op)->ob_refcnt++)
 504   /* under Py_REF_DEBUG: also log negative ref counts after Py_DECREF() !! */
 505 #define Py_DECREF(op)                                                   \
 506        if (--_Py_RefTotal, 0 < (--((op)->ob_refcnt))) ;                 \
 507        else if (0 == (op)->ob_refcnt) _Py_Dealloc( (PyObject*)(op));    \
 508        else (void)fprintf( stderr, "%s:%i negative ref count %i\n",     \
 509                            __FILE__, __LINE__, (op)->ob_refcnt)
 510 #else /* !Py_REF_DEBUG */
 511
 512 #ifdef COUNT_ALLOCS
 513 #define _Py_NewReference(op) (inc_count((op)->ob_type), (op)->ob_refcnt = 1)
 514 #else
 515 #define _Py_NewReference(op) ((op)->ob_refcnt = 1)
 516 #endif
 517
 518 #define Py_INCREF(op) ((op)->ob_refcnt++)
 519 #define Py_DECREF(op) \
 520         if (--(op)->ob_refcnt != 0) \
 521                 ; \
 522         else \
 523                 _Py_Dealloc((PyObject *)(op))
 524 #endif /* !Py_REF_DEBUG */
 525
 526 /* Macros to use in case the object pointer may be NULL: */
 527
 528 #define Py_XINCREF(op) if ((op) == NULL) ; else Py_INCREF(op)
 529 #define Py_XDECREF(op) if ((op) == NULL) ; else Py_DECREF(op)
 530
 531 /*
 532 _Py_NoneStruct is an object of undefined type which can be used in contexts
 533 where NULL (nil) is not suitable (since NULL often means 'error').
 534
 535 Don't forget to apply Py_INCREF() when returning this value!!!
 536 */
 537
 538 extern DL_IMPORT(PyObject) _Py_NoneStruct; /* Don't use this directly */
 539
 540 #define Py_None (&_Py_NoneStruct)
 541
 542 /*
 543 Py_NotImplemented is a singleton used to signal that an operation is
 544 not implemented for a given type combination.
 545 */
 546
 547 extern DL_IMPORT(PyObject) _Py_NotImplementedStruct; /* Don't use this directly */
 548
 549 #define Py_NotImplemented (&_Py_NotImplementedStruct)
 550
 551 /* Rich comparison opcodes */
 552 #define Py_LT 0
 553 #define Py_LE 1
 554 #define Py_EQ 2
 555 #define Py_NE 3
 556 #define Py_GT 4
 557 #define Py_GE 5
 558
 559 /*
 560 A common programming style in Python requires the forward declaration
 561 of static, initialized structures, e.g. for a type object that is used
 562 by the functions whose address must be used in the initializer.
 563 Some compilers (notably SCO ODT 3.0, I seem to remember early AIX as
 564 well) botch this if you use the static keyword for both declarations
 565 (they allocate two objects, and use the first, uninitialized one until
 566 the second declaration is encountered).  Therefore, the forward
 567 declaration should use the 'forwardstatic' keyword.  This expands to
 568 static on most systems, but to extern on a few.  The actual storage
 569 and name will still be static because the second declaration is
 570 static, so no linker visible symbols will be generated.  (Standard C
 571 compilers take offense to the extern forward declaration of a static
 572 object, so I can't just put extern in all cases. :-( )
 573 */
 574
 575 #ifdef BAD_STATIC_FORWARD
 576 #define staticforward extern
 577 #define statichere static
 578 #else /* !BAD_STATIC_FORWARD */
 579 #define staticforward static
 580 #define statichere static
 581 #endif /* !BAD_STATIC_FORWARD */
 582
 583
 584 /*
 585 More conventions
 586 ================
 587
 588 Argument Checking
 589 -----------------
 590
 591 Functions that take objects as arguments normally don't check for nil
 592 arguments, but they do check the type of the argument, and return an
 593 error if the function doesn't apply to the type.
 594
 595 Failure Modes
 596 -------------
 597
 598 Functions may fail for a variety of reasons, including running out of
 599 memory.  This is communicated to the caller in two ways: an error string
 600 is set (see errors.h), and the function result differs: functions that
 601 normally return a pointer return NULL for failure, functions returning
 602 an integer return -1 (which could be a legal return value too!), and
 603 other functions return 0 for success and -1 for failure.
 604 Callers should always check for errors before using the result.
 605
 606 Reference Counts
 607 ----------------
 608
 609 It takes a while to get used to the proper usage of reference counts.
 610
 611 Functions that create an object set the reference count to 1; such new
 612 objects must be stored somewhere or destroyed again with Py_DECREF().
 613 Functions that 'store' objects such as PyTuple_SetItem() and
 614 PyDict_SetItemString()
 615 don't increment the reference count of the object, since the most
 616 frequent use is to store a fresh object.  Functions that 'retrieve'
 617 objects such as PyTuple_GetItem() and PyDict_GetItemString() also
 618 don't increment
 619 the reference count, since most frequently the object is only looked at
 620 quickly.  Thus, to retrieve an object and store it again, the caller
 621 must call Py_INCREF() explicitly.
 622
 623 NOTE: functions that 'consume' a reference count like
 624 PyList_SetItemString() even consume the reference if the object wasn't
 625 stored, to simplify error handling.
 626
 627 It seems attractive to make other functions that take an object as
 628 argument consume a reference count; however this may quickly get
 629 confusing (even the current practice is already confusing).  Consider
 630 it carefully, it may save lots of calls to Py_INCREF() and Py_DECREF() at
 631 times.
 632 */
 633
 634 /*
 635   trashcan
 636   CT 2k0130
 637   non-recursively destroy nested objects
 638
 639   CT 2k0223
 640   redefinition for better locality and less overhead.
 641
 642   Objects that want to be recursion safe need to use
 643   the macro's
 644                 Py_TRASHCAN_SAFE_BEGIN(name)
 645   and
 646                 Py_TRASHCAN_SAFE_END(name)
 647   surrounding their actual deallocation code.
 648
 649   It would be nice to do this using the thread state.
 650   Also, we could do an exact stack measure then.
 651   Unfortunately, deallocations also take place when
 652   the thread state is undefined.
 653
 654   CT 2k0422 complete rewrite.
 655   There is no need to allocate new objects.
 656   Everything is done vialob_refcnt and ob_type now.
 657   Adding support for free-threading should be easy, too.
 658 */
 659
 660 #define PyTrash_UNWIND_LEVEL 50
 661
 662 #define Py_TRASHCAN_SAFE_BEGIN(op) \
 663         { \
 664                 ++_PyTrash_delete_nesting; \
 665                 if (_PyTrash_delete_nesting < PyTrash_UNWIND_LEVEL) { \
 666
 667 #define Py_TRASHCAN_SAFE_END(op) \
 668                 ;} \
 669                 else \
 670                         _PyTrash_deposit_object((PyObject*)op);\
 671                 --_PyTrash_delete_nesting; \
 672                 if (_PyTrash_delete_later && _PyTrash_delete_nesting <= 0) \
 673                         _PyTrash_destroy_chain(); \
 674         } \
 675
 676 extern DL_IMPORT(void) _PyTrash_deposit_object(PyObject*);
 677 extern DL_IMPORT(void) _PyTrash_destroy_chain(void);
 678
 679 extern DL_IMPORT(int) _PyTrash_delete_nesting;
 680 extern DL_IMPORT(PyObject *) _PyTrash_delete_later;
 681
 682 /* swap the "xx" to check the speed loss */
 683
 684 #define xxPy_TRASHCAN_SAFE_BEGIN(op)
 685 #define xxPy_TRASHCAN_SAFE_END(op) ;
 686
 687 #ifdef __cplusplus
 688 }
 689 #endif
 690 #endif /* !Py_OBJECT_H */