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 } PyNumberMethods;
 165
 166 typedef struct {
 167         inquiry sq_length;
 168         binaryfunc sq_concat;
 169         intargfunc sq_repeat;
 170         intargfunc sq_item;
 171         intintargfunc sq_slice;
 172         intobjargproc sq_ass_item;
 173         intintobjargproc sq_ass_slice;
 174         objobjproc sq_contains;
 175         binaryfunc sq_inplace_concat;
 176         intargfunc sq_inplace_repeat;
 177 } PySequenceMethods;
 178
 179 typedef struct {
 180         inquiry mp_length;
 181         binaryfunc mp_subscript;
 182         objobjargproc mp_ass_subscript;
 183 } PyMappingMethods;
 184
 185 typedef struct {
 186         getreadbufferproc bf_getreadbuffer;
 187         getwritebufferproc bf_getwritebuffer;
 188         getsegcountproc bf_getsegcount;
 189         getcharbufferproc bf_getcharbuffer;
 190 } PyBufferProcs;
 191
 192
 193 typedef void (*destructor)(PyObject *);
 194 typedef int (*printfunc)(PyObject *, FILE *, int);
 195 typedef PyObject *(*getattrfunc)(PyObject *, char *);
 196 typedef PyObject *(*getattrofunc)(PyObject *, PyObject *);
 197 typedef int (*setattrfunc)(PyObject *, char *, PyObject *);
 198 typedef int (*setattrofunc)(PyObject *, PyObject *, PyObject *);
 199 typedef int (*cmpfunc)(PyObject *, PyObject *);
 200 typedef PyObject *(*reprfunc)(PyObject *);
 201 typedef long (*hashfunc)(PyObject *);
 202 typedef PyObject *(*richcmpfunc) (PyObject *, PyObject *, int);
 203
 204 typedef struct _typeobject {
 205         PyObject_VAR_HEAD
 206         char *tp_name; /* For printing */
 207         int tp_basicsize, tp_itemsize; /* For allocation */
 208
 209         /* Methods to implement standard operations */
 210
 211         destructor tp_dealloc;
 212         printfunc tp_print;
 213         getattrfunc tp_getattr;
 214         setattrfunc tp_setattr;
 215         cmpfunc tp_compare;
 216         reprfunc tp_repr;
 217
 218         /* Method suites for standard classes */
 219
 220         PyNumberMethods *tp_as_number;
 221         PySequenceMethods *tp_as_sequence;
 222         PyMappingMethods *tp_as_mapping;
 223
 224         /* More standard operations (here for binary compatibility) */
 225
 226         hashfunc tp_hash;
 227         ternaryfunc tp_call;
 228         reprfunc tp_str;
 229         getattrofunc tp_getattro;
 230         setattrofunc tp_setattro;
 231
 232         /* Functions to access object as input/output buffer */
 233         PyBufferProcs *tp_as_buffer;
 234
 235         /* Flags to define presence of optional/expanded features */
 236         long tp_flags;
 237
 238         char *tp_doc; /* Documentation string */
 239
 240         /* call function for all accessible objects */
 241         traverseproc tp_traverse;
 242
 243         /* delete references to contained objects */
 244         inquiry tp_clear;
 245
 246         /* rich comparisons */
 247         richcmpfunc tp_richcompare;
 248
 249         /* weak reference enabler */
 250         long tp_weaklistoffset;
 251
 252 #ifdef COUNT_ALLOCS
 253         /* these must be last */
 254         int tp_alloc;
 255         int tp_free;
 256         int tp_maxalloc;
 257         struct _typeobject *tp_next;
 258 #endif
 259 } PyTypeObject;
 260
 261 extern DL_IMPORT(PyTypeObject) PyType_Type; /* The type of type objects */
 262
 263 #define PyType_Check(op) ((op)->ob_type == &PyType_Type)
 264
 265 /* Generic operations on objects */
 266 extern DL_IMPORT(int) PyObject_Print(PyObject *, FILE *, int);
 267 extern DL_IMPORT(void) _PyObject_Dump(PyObject *);
 268 extern DL_IMPORT(PyObject *) PyObject_Repr(PyObject *);
 269 extern DL_IMPORT(PyObject *) PyObject_Str(PyObject *);
 270 extern DL_IMPORT(PyObject *) PyObject_Unicode(PyObject *);
 271 extern DL_IMPORT(int) PyObject_Compare(PyObject *, PyObject *);
 272 extern DL_IMPORT(PyObject *) PyObject_RichCompare(PyObject *, PyObject *, int);
 273 extern DL_IMPORT(int) PyObject_RichCompareBool(PyObject *, PyObject *, int);
 274 extern DL_IMPORT(PyObject *) PyObject_GetAttrString(PyObject *, char *);
 275 extern DL_IMPORT(int) PyObject_SetAttrString(PyObject *, char *, PyObject *);
 276 extern DL_IMPORT(int) PyObject_HasAttrString(PyObject *, char *);
 277 extern DL_IMPORT(PyObject *) PyObject_GetAttr(PyObject *, PyObject *);
 278 extern DL_IMPORT(int) PyObject_SetAttr(PyObject *, PyObject *, PyObject *);
 279 extern DL_IMPORT(int) PyObject_HasAttr(PyObject *, PyObject *);
 280 extern DL_IMPORT(long) PyObject_Hash(PyObject *);
 281 extern DL_IMPORT(int) PyObject_IsTrue(PyObject *);
 282 extern DL_IMPORT(int) PyObject_Not(PyObject *);
 283 extern DL_IMPORT(int) PyCallable_Check(PyObject *);
 284 extern DL_IMPORT(int) PyNumber_Coerce(PyObject **, PyObject **);
 285 extern DL_IMPORT(int) PyNumber_CoerceEx(PyObject **, PyObject **);
 286
 287 extern DL_IMPORT(void) (*PyObject_ClearWeakRefs)(PyObject *);
 288
 289 /* Helpers for printing recursive container types */
 290 extern DL_IMPORT(int) Py_ReprEnter(PyObject *);
 291 extern DL_IMPORT(void) Py_ReprLeave(PyObject *);
 292
 293 /* Helpers for hash functions */
 294 extern DL_IMPORT(long) _Py_HashDouble(double);
 295 extern DL_IMPORT(long) _Py_HashPointer(void*);
 296
 297 /* Helper for passing objects to printf and the like */
 298 #define PyObject_REPR(obj) PyString_AS_STRING(PyObject_Repr(obj))
 299
 300 /* Flag bits for printing: */
 301 #define Py_PRINT_RAW    1       /* No string quotes etc. */
 302
 303 /*
 304
 305 Type flags (tp_flags)
 306
 307 These flags are used to extend the type structure in a backwards-compatible
 308 fashion. Extensions can use the flags to indicate (and test) when a given
 309 type structure contains a new feature. The Python core will use these when
 310 introducing new functionality between major revisions (to avoid mid-version
 311 changes in the PYTHON_API_VERSION).
 312
 313 Arbitration of the flag bit positions will need to be coordinated among
 314 all extension writers who publically release their extensions (this will
 315 be fewer than you might expect!)..
 316
 317 Python 1.5.2 introduced the bf_getcharbuffer slot into PyBufferProcs.
 318
 319 Type definitions should use Py_TPFLAGS_DEFAULT for their tp_flags value.
 320
 321 Code can use PyType_HasFeature(type_ob, flag_value) to test whether the
 322 given type object has a specified feature.
 323
 324 */
 325
 326 /* PyBufferProcs contains bf_getcharbuffer */
 327 #define Py_TPFLAGS_HAVE_GETCHARBUFFER  (1L<<0)
 328
 329 /* PySequenceMethods contains sq_contains */
 330 #define Py_TPFLAGS_HAVE_SEQUENCE_IN (1L<<1)
 331
 332 /* Objects which participate in garbage collection (see objimp.h) */
 333 #ifdef WITH_CYCLE_GC
 334 #define Py_TPFLAGS_GC (1L<<2)
 335 #else
 336 #define Py_TPFLAGS_GC 0
 337 #endif
 338
 339 /* PySequenceMethods and PyNumberMethods contain in-place operators */
 340 #define Py_TPFLAGS_HAVE_INPLACEOPS (1L<<3)
 341
 342 /* PyNumberMethods do their own coercion */
 343 #define Py_TPFLAGS_CHECKTYPES (1L<<4)
 344
 345 #define Py_TPFLAGS_HAVE_RICHCOMPARE (1L<<5)
 346
 347 /* Objects which are weakly referencable if their tp_weaklistoffset is >0 */
 348 /* XXX Should this have the same value as Py_TPFLAGS_HAVE_RICHCOMPARE?
 349  * These both indicate a feature that appeared in the same alpha release.
 350  */
 351 #define Py_TPFLAGS_HAVE_WEAKREFS (1L<<6)
 352
 353 #define Py_TPFLAGS_DEFAULT  ( \
 354                              Py_TPFLAGS_HAVE_GETCHARBUFFER | \
 355                              Py_TPFLAGS_HAVE_SEQUENCE_IN | \
 356                              Py_TPFLAGS_HAVE_INPLACEOPS | \
 357                              Py_TPFLAGS_HAVE_RICHCOMPARE | \
 358                              Py_TPFLAGS_HAVE_WEAKREFS | \
 359                             0)
 360
 361 #define PyType_HasFeature(t,f)  (((t)->tp_flags & (f)) != 0)
 362
 363
 364 /*
 365 The macros Py_INCREF(op) and Py_DECREF(op) are used to increment or decrement
 366 reference counts.  Py_DECREF calls the object's deallocator function; for
 367 objects that don't contain references to other objects or heap memory
 368 this can be the standard function free().  Both macros can be used
 369 wherever a void expression is allowed.  The argument shouldn't be a
 370 NIL pointer.  The macro _Py_NewReference(op) is used only to initialize
 371 reference counts to 1; it is defined here for convenience.
 372
 373 We assume that the reference count field can never overflow; this can
 374 be proven when the size of the field is the same as the pointer size
 375 but even with a 16-bit reference count field it is pretty unlikely so
 376 we ignore the possibility.  (If you are paranoid, make it a long.)
 377
 378 Type objects should never be deallocated; the type pointer in an object
 379 is not considered to be a reference to the type object, to save
 380 complications in the deallocation function.  (This is actually a
 381 decision that's up to the implementer of each new type so if you want,
 382 you can count such references to the type object.)
 383
 384 *** WARNING*** The Py_DECREF macro must have a side-effect-free argument
 385 since it may evaluate its argument multiple times.  (The alternative
 386 would be to mace it a proper function or assign it to a global temporary
 387 variable first, both of which are slower; and in a multi-threaded
 388 environment the global variable trick is not safe.)
 389 */
 390
 391 #ifdef Py_TRACE_REFS
 392 #ifndef Py_REF_DEBUG
 393 #define Py_REF_DEBUG
 394 #endif
 395 #endif
 396
 397 #ifdef Py_TRACE_REFS
 398 extern DL_IMPORT(void) _Py_Dealloc(PyObject *);
 399 extern DL_IMPORT(void) _Py_NewReference(PyObject *);
 400 extern DL_IMPORT(void) _Py_ForgetReference(PyObject *);
 401 extern DL_IMPORT(void) _Py_PrintReferences(FILE *);
 402 extern DL_IMPORT(void) _Py_ResetReferences(void);
 403 #endif
 404
 405 #ifndef Py_TRACE_REFS
 406 #ifdef COUNT_ALLOCS
 407 #define _Py_Dealloc(op) ((op)->ob_type->tp_free++, (*(op)->ob_type->tp_dealloc)((PyObject *)(op)))
 408 #define _Py_ForgetReference(op) ((op)->ob_type->tp_free++)
 409 #else /* !COUNT_ALLOCS */
 410 #define _Py_Dealloc(op) (*(op)->ob_type->tp_dealloc)((PyObject *)(op))
 411 #define _Py_ForgetReference(op) /*empty*/
 412 #endif /* !COUNT_ALLOCS */
 413 #endif /* !Py_TRACE_REFS */
 414
 415 #ifdef COUNT_ALLOCS
 416 extern DL_IMPORT(void) inc_count(PyTypeObject *);
 417 #endif
 418
 419 #ifdef Py_REF_DEBUG
 420
 421 extern DL_IMPORT(long) _Py_RefTotal;
 422
 423 #ifndef Py_TRACE_REFS
 424 #ifdef COUNT_ALLOCS
 425 #define _Py_NewReference(op) (inc_count((op)->ob_type), _Py_RefTotal++, (op)->ob_refcnt = 1)
 426 #else
 427 #define _Py_NewReference(op) (_Py_RefTotal++, (op)->ob_refcnt = 1)
 428 #endif
 429 #endif /* !Py_TRACE_REFS */
 430
 431 #define Py_INCREF(op) (_Py_RefTotal++, (op)->ob_refcnt++)
 432 #define Py_DECREF(op) \
 433         if (--_Py_RefTotal, (--((op)->ob_refcnt) != 0)) \
 434                 ; \
 435         else \
 436                 _Py_Dealloc((PyObject *)(op))
 437 #else /* !Py_REF_DEBUG */
 438
 439 #ifdef COUNT_ALLOCS
 440 #define _Py_NewReference(op) (inc_count((op)->ob_type), (op)->ob_refcnt = 1)
 441 #else
 442 #define _Py_NewReference(op) ((op)->ob_refcnt = 1)
 443 #endif
 444
 445 #define Py_INCREF(op) ((op)->ob_refcnt++)
 446 #define Py_DECREF(op) \
 447         if (--(op)->ob_refcnt != 0) \
 448                 ; \
 449         else \
 450                 _Py_Dealloc((PyObject *)(op))
 451 #endif /* !Py_REF_DEBUG */
 452
 453 /* Macros to use in case the object pointer may be NULL: */
 454
 455 #define Py_XINCREF(op) if ((op) == NULL) ; else Py_INCREF(op)
 456 #define Py_XDECREF(op) if ((op) == NULL) ; else Py_DECREF(op)
 457
 458 /*
 459 _Py_NoneStruct is an object of undefined type which can be used in contexts
 460 where NULL (nil) is not suitable (since NULL often means 'error').
 461
 462 Don't forget to apply Py_INCREF() when returning this value!!!
 463 */
 464
 465 extern DL_IMPORT(PyObject) _Py_NoneStruct; /* Don't use this directly */
 466
 467 #define Py_None (&_Py_NoneStruct)
 468
 469 /*
 470 Py_NotImplemented is a singleton used to signal that an operation is
 471 not implemented for a given type combination.
 472 */
 473
 474 extern DL_IMPORT(PyObject) _Py_NotImplementedStruct; /* Don't use this directly */
 475
 476 #define Py_NotImplemented (&_Py_NotImplementedStruct)
 477
 478 /* Rich comparison opcodes */
 479 #define Py_LT 0
 480 #define Py_LE 1
 481 #define Py_EQ 2
 482 #define Py_NE 3
 483 #define Py_GT 4
 484 #define Py_GE 5
 485
 486 /*
 487 A common programming style in Python requires the forward declaration
 488 of static, initialized structures, e.g. for a type object that is used
 489 by the functions whose address must be used in the initializer.
 490 Some compilers (notably SCO ODT 3.0, I seem to remember early AIX as
 491 well) botch this if you use the static keyword for both declarations
 492 (they allocate two objects, and use the first, uninitialized one until
 493 the second declaration is encountered).  Therefore, the forward
 494 declaration should use the 'forwardstatic' keyword.  This expands to
 495 static on most systems, but to extern on a few.  The actual storage
 496 and name will still be static because the second declaration is
 497 static, so no linker visible symbols will be generated.  (Standard C
 498 compilers take offense to the extern forward declaration of a static
 499 object, so I can't just put extern in all cases. :-( )
 500 */
 501
 502 #ifdef BAD_STATIC_FORWARD
 503 #define staticforward extern
 504 #define statichere static
 505 #else /* !BAD_STATIC_FORWARD */
 506 #define staticforward static
 507 #define statichere static
 508 #endif /* !BAD_STATIC_FORWARD */
 509
 510
 511 /*
 512 More conventions
 513 ================
 514
 515 Argument Checking
 516 -----------------
 517
 518 Functions that take objects as arguments normally don't check for nil
 519 arguments, but they do check the type of the argument, and return an
 520 error if the function doesn't apply to the type.
 521
 522 Failure Modes
 523 -------------
 524
 525 Functions may fail for a variety of reasons, including running out of
 526 memory.  This is communicated to the caller in two ways: an error string
 527 is set (see errors.h), and the function result differs: functions that
 528 normally return a pointer return NULL for failure, functions returning
 529 an integer return -1 (which could be a legal return value too!), and
 530 other functions return 0 for success and -1 for failure.
 531 Callers should always check for errors before using the result.
 532
 533 Reference Counts
 534 ----------------
 535
 536 It takes a while to get used to the proper usage of reference counts.
 537
 538 Functions that create an object set the reference count to 1; such new
 539 objects must be stored somewhere or destroyed again with Py_DECREF().
 540 Functions that 'store' objects such as PyTuple_SetItem() and
 541 PyDict_SetItemString()
 542 don't increment the reference count of the object, since the most
 543 frequent use is to store a fresh object.  Functions that 'retrieve'
 544 objects such as PyTuple_GetItem() and PyDict_GetItemString() also
 545 don't increment
 546 the reference count, since most frequently the object is only looked at
 547 quickly.  Thus, to retrieve an object and store it again, the caller
 548 must call Py_INCREF() explicitly.
 549
 550 NOTE: functions that 'consume' a reference count like
 551 PyList_SetItemString() even consume the reference if the object wasn't
 552 stored, to simplify error handling.
 553
 554 It seems attractive to make other functions that take an object as
 555 argument consume a reference count; however this may quickly get
 556 confusing (even the current practice is already confusing).  Consider
 557 it carefully, it may save lots of calls to Py_INCREF() and Py_DECREF() at
 558 times.
 559 */
 560
 561 /*
 562   trashcan
 563   CT 2k0130
 564   non-recursively destroy nested objects
 565
 566   CT 2k0223
 567   redefinition for better locality and less overhead.
 568
 569   Objects that want to be recursion safe need to use
 570   the macro's
 571                 Py_TRASHCAN_SAFE_BEGIN(name)
 572   and
 573                 Py_TRASHCAN_SAFE_END(name)
 574   surrounding their actual deallocation code.
 575
 576   It would be nice to do this using the thread state.
 577   Also, we could do an exact stack measure then.
 578   Unfortunately, deallocations also take place when
 579   the thread state is undefined.
 580
 581   CT 2k0422 complete rewrite.
 582   There is no need to allocate new objects.
 583   Everything is done vialob_refcnt and ob_type now.
 584   Adding support for free-threading should be easy, too.
 585 */
 586
 587 #define PyTrash_UNWIND_LEVEL 50
 588
 589 #define Py_TRASHCAN_SAFE_BEGIN(op) \
 590         { \
 591                 ++_PyTrash_delete_nesting; \
 592                 if (_PyTrash_delete_nesting < PyTrash_UNWIND_LEVEL) { \
 593
 594 #define Py_TRASHCAN_SAFE_END(op) \
 595                 ;} \
 596                 else \
 597                         _PyTrash_deposit_object((PyObject*)op);\
 598                 --_PyTrash_delete_nesting; \
 599                 if (_PyTrash_delete_later && _PyTrash_delete_nesting <= 0) \
 600                         _PyTrash_destroy_chain(); \
 601         } \
 602
 603 extern DL_IMPORT(void) _PyTrash_deposit_object(PyObject*);
 604 extern DL_IMPORT(void) _PyTrash_destroy_chain(void);
 605
 606 extern DL_IMPORT(int) _PyTrash_delete_nesting;
 607 extern DL_IMPORT(PyObject *) _PyTrash_delete_later;
 608
 609 /* swap the "xx" to check the speed loss */
 610
 611 #define xxPy_TRASHCAN_SAFE_BEGIN(op)
 612 #define xxPy_TRASHCAN_SAFE_END(op) ;
 613
 614 #ifdef __cplusplus
 615 }
 616 #endif
 617 #endif /* !Py_OBJECT_H */