File: /Users/paulross/dev/Python-3.6.2/Include/object.h

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       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: #if defined(Py_LIMITED_API) && defined(Py_REF_DEBUG)
      65: #error Py_LIMITED_API is incompatible with Py_DEBUG, Py_TRACE_REFS, and Py_REF_DEBUG
      66: #endif
      67: 
      68: 
      69: #ifdef Py_TRACE_REFS
      70: /* Define pointers to support a doubly-linked list of all live heap objects. */
      71: #define _PyObject_HEAD_EXTRA            \
      72:     struct _object *_ob_next;           \
      73:     struct _object *_ob_prev;
      74: 
      75: #define _PyObject_EXTRA_INIT 0, 0,
      76: 
      77: #else
      78: #define _PyObject_HEAD_EXTRA
      79: #define _PyObject_EXTRA_INIT
      80: #endif
      81: 
      82: /* PyObject_HEAD defines the initial segment of every PyObject. */
      83: #define PyObject_HEAD                   PyObject ob_base;
      84: 
      85: #define PyObject_HEAD_INIT(type)        \
      86:     { _PyObject_EXTRA_INIT              \
      87:     1, type },
      88: 
      89: #define PyVarObject_HEAD_INIT(type, size)       \
      90:     { PyObject_HEAD_INIT(type) size },
      91: 
      92: /* PyObject_VAR_HEAD defines the initial segment of all variable-size
      93:  * container objects.  These end with a declaration of an array with 1
      94:  * element, but enough space is malloc'ed so that the array actually
      95:  * has room for ob_size elements.  Note that ob_size is an element count,
      96:  * not necessarily a byte count.
      97:  */
      98: #define PyObject_VAR_HEAD      PyVarObject ob_base;
      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_EXTRA
     108:     Py_ssize_t ob_refcnt;
     109:     struct _typeobject *ob_type;
     110: } PyObject;
     111: 
     112: typedef struct {
     113:     PyObject ob_base;
     114:     Py_ssize_t ob_size; /* Number of items in variable part */
     115: } PyVarObject;
     116: 
     117: #define Py_REFCNT(ob)           (((PyObject*)(ob))->ob_refcnt)
     118: #define Py_TYPE(ob)             (((PyObject*)(ob))->ob_type)
     119: #define Py_SIZE(ob)             (((PyVarObject*)(ob))->ob_size)
     120: 
     121: #ifndef Py_LIMITED_API
     122: /********************* String Literals ****************************************/
     123: /* This structure helps managing static strings. The basic usage goes like this:
     124:    Instead of doing
     125: 
     126:        r = PyObject_CallMethod(o, "foo", "args", ...);
     127: 
     128:    do
     129: 
     130:        _Py_IDENTIFIER(foo);
     131:        ...
     132:        r = _PyObject_CallMethodId(o, &PyId_foo, "args", ...);
     133: 
     134:    PyId_foo is a static variable, either on block level or file level. On first
     135:    usage, the string "foo" is interned, and the structures are linked. On interpreter
     136:    shutdown, all strings are released (through _PyUnicode_ClearStaticStrings).
     137: 
     138:    Alternatively, _Py_static_string allows choosing the variable name.
     139:    _PyUnicode_FromId returns a borrowed reference to the interned string.
     140:    _PyObject_{Get,Set,Has}AttrId are __getattr__ versions using _Py_Identifier*.
     141: */
     142: typedef struct _Py_Identifier {
     143:     struct _Py_Identifier *next;
     144:     const char* string;
     145:     PyObject *object;
     146: } _Py_Identifier;
     147: 
     148: #define _Py_static_string_init(value) { .next = NULL, .string = value, .object = NULL }
     149: #define _Py_static_string(varname, value)  static _Py_Identifier varname = _Py_static_string_init(value)
     150: #define _Py_IDENTIFIER(varname) _Py_static_string(PyId_##varname, #varname)
     151: 
     152: #endif /* !Py_LIMITED_API */
     153: 
     154: /*
     155: Type objects contain a string containing the type name (to help somewhat
     156: in debugging), the allocation parameters (see PyObject_New() and
     157: PyObject_NewVar()),
     158: and methods for accessing objects of the type.  Methods are optional, a
     159: nil pointer meaning that particular kind of access is not available for
     160: this type.  The Py_DECREF() macro uses the tp_dealloc method without
     161: checking for a nil pointer; it should always be implemented except if
     162: the implementation can guarantee that the reference count will never
     163: reach zero (e.g., for statically allocated type objects).
     164: 
     165: NB: the methods for certain type groups are now contained in separate
     166: method blocks.
     167: */
     168: 
     169: typedef PyObject * (*unaryfunc)(PyObject *);
     170: typedef PyObject * (*binaryfunc)(PyObject *, PyObject *);
     171: typedef PyObject * (*ternaryfunc)(PyObject *, PyObject *, PyObject *);
     172: typedef int (*inquiry)(PyObject *);
     173: typedef Py_ssize_t (*lenfunc)(PyObject *);
     174: typedef PyObject *(*ssizeargfunc)(PyObject *, Py_ssize_t);
     175: typedef PyObject *(*ssizessizeargfunc)(PyObject *, Py_ssize_t, Py_ssize_t);
     176: typedef int(*ssizeobjargproc)(PyObject *, Py_ssize_t, PyObject *);
     177: typedef int(*ssizessizeobjargproc)(PyObject *, Py_ssize_t, Py_ssize_t, PyObject *);
     178: typedef int(*objobjargproc)(PyObject *, PyObject *, PyObject *);
     179: 
     180: #ifndef Py_LIMITED_API
     181: /* buffer interface */
     182: typedef struct bufferinfo {
     183:     void *buf;
     184:     PyObject *obj;        /* owned reference */
     185:     Py_ssize_t len;
     186:     Py_ssize_t itemsize;  /* This is Py_ssize_t so it can be
     187:                              pointed to by strides in simple case.*/
     188:     int readonly;
     189:     int ndim;
     190:     char *format;
     191:     Py_ssize_t *shape;
     192:     Py_ssize_t *strides;
     193:     Py_ssize_t *suboffsets;
     194:     void *internal;
     195: } Py_buffer;
     196: 
     197: typedef int (*getbufferproc)(PyObject *, Py_buffer *, int);
     198: typedef void (*releasebufferproc)(PyObject *, Py_buffer *);
     199: 
     200: /* Maximum number of dimensions */
     201: #define PyBUF_MAX_NDIM 64
     202: 
     203: /* Flags for getting buffers */
     204: #define PyBUF_SIMPLE 0
     205: #define PyBUF_WRITABLE 0x0001
     206: /*  we used to include an E, backwards compatible alias  */
     207: #define PyBUF_WRITEABLE PyBUF_WRITABLE
     208: #define PyBUF_FORMAT 0x0004
     209: #define PyBUF_ND 0x0008
     210: #define PyBUF_STRIDES (0x0010 | PyBUF_ND)
     211: #define PyBUF_C_CONTIGUOUS (0x0020 | PyBUF_STRIDES)
     212: #define PyBUF_F_CONTIGUOUS (0x0040 | PyBUF_STRIDES)
     213: #define PyBUF_ANY_CONTIGUOUS (0x0080 | PyBUF_STRIDES)
     214: #define PyBUF_INDIRECT (0x0100 | PyBUF_STRIDES)
     215: 
     216: #define PyBUF_CONTIG (PyBUF_ND | PyBUF_WRITABLE)
     217: #define PyBUF_CONTIG_RO (PyBUF_ND)
     218: 
     219: #define PyBUF_STRIDED (PyBUF_STRIDES | PyBUF_WRITABLE)
     220: #define PyBUF_STRIDED_RO (PyBUF_STRIDES)
     221: 
     222: #define PyBUF_RECORDS (PyBUF_STRIDES | PyBUF_WRITABLE | PyBUF_FORMAT)
     223: #define PyBUF_RECORDS_RO (PyBUF_STRIDES | PyBUF_FORMAT)
     224: 
     225: #define PyBUF_FULL (PyBUF_INDIRECT | PyBUF_WRITABLE | PyBUF_FORMAT)
     226: #define PyBUF_FULL_RO (PyBUF_INDIRECT | PyBUF_FORMAT)
     227: 
     228: 
     229: #define PyBUF_READ  0x100
     230: #define PyBUF_WRITE 0x200
     231: 
     232: /* End buffer interface */
     233: #endif /* Py_LIMITED_API */
     234: 
     235: typedef int (*objobjproc)(PyObject *, PyObject *);
     236: typedef int (*visitproc)(PyObject *, void *);
     237: typedef int (*traverseproc)(PyObject *, visitproc, void *);
     238: 
     239: #ifndef Py_LIMITED_API
     240: typedef struct {
     241:     /* Number implementations must check *both*
     242:        arguments for proper type and implement the necessary conversions
     243:        in the slot functions themselves. */
     244: 
     245:     binaryfunc nb_add;
     246:     binaryfunc nb_subtract;
     247:     binaryfunc nb_multiply;
     248:     binaryfunc nb_remainder;
     249:     binaryfunc nb_divmod;
     250:     ternaryfunc nb_power;
     251:     unaryfunc nb_negative;
     252:     unaryfunc nb_positive;
     253:     unaryfunc nb_absolute;
     254:     inquiry nb_bool;
     255:     unaryfunc nb_invert;
     256:     binaryfunc nb_lshift;
     257:     binaryfunc nb_rshift;
     258:     binaryfunc nb_and;
     259:     binaryfunc nb_xor;
     260:     binaryfunc nb_or;
     261:     unaryfunc nb_int;
     262:     void *nb_reserved;  /* the slot formerly known as nb_long */
     263:     unaryfunc nb_float;
     264: 
     265:     binaryfunc nb_inplace_add;
     266:     binaryfunc nb_inplace_subtract;
     267:     binaryfunc nb_inplace_multiply;
     268:     binaryfunc nb_inplace_remainder;
     269:     ternaryfunc nb_inplace_power;
     270:     binaryfunc nb_inplace_lshift;
     271:     binaryfunc nb_inplace_rshift;
     272:     binaryfunc nb_inplace_and;
     273:     binaryfunc nb_inplace_xor;
     274:     binaryfunc nb_inplace_or;
     275: 
     276:     binaryfunc nb_floor_divide;
     277:     binaryfunc nb_true_divide;
     278:     binaryfunc nb_inplace_floor_divide;
     279:     binaryfunc nb_inplace_true_divide;
     280: 
     281:     unaryfunc nb_index;
     282: 
     283:     binaryfunc nb_matrix_multiply;
     284:     binaryfunc nb_inplace_matrix_multiply;
     285: } PyNumberMethods;
     286: 
     287: typedef struct {
     288:     lenfunc sq_length;
     289:     binaryfunc sq_concat;
     290:     ssizeargfunc sq_repeat;
     291:     ssizeargfunc sq_item;
     292:     void *was_sq_slice;
     293:     ssizeobjargproc sq_ass_item;
     294:     void *was_sq_ass_slice;
     295:     objobjproc sq_contains;
     296: 
     297:     binaryfunc sq_inplace_concat;
     298:     ssizeargfunc sq_inplace_repeat;
     299: } PySequenceMethods;
     300: 
     301: typedef struct {
     302:     lenfunc mp_length;
     303:     binaryfunc mp_subscript;
     304:     objobjargproc mp_ass_subscript;
     305: } PyMappingMethods;
     306: 
     307: typedef struct {
     308:     unaryfunc am_await;
     309:     unaryfunc am_aiter;
     310:     unaryfunc am_anext;
     311: } PyAsyncMethods;
     312: 
     313: typedef struct {
     314:      getbufferproc bf_getbuffer;
     315:      releasebufferproc bf_releasebuffer;
     316: } PyBufferProcs;
     317: #endif /* Py_LIMITED_API */
     318: 
     319: typedef void (*freefunc)(void *);
     320: typedef void (*destructor)(PyObject *);
     321: #ifndef Py_LIMITED_API
     322: /* We can't provide a full compile-time check that limited-API
     323:    users won't implement tp_print. However, not defining printfunc
     324:    and making tp_print of a different function pointer type
     325:    should at least cause a warning in most cases. */
     326: typedef int (*printfunc)(PyObject *, FILE *, int);
     327: #endif
     328: typedef PyObject *(*getattrfunc)(PyObject *, char *);
     329: typedef PyObject *(*getattrofunc)(PyObject *, PyObject *);
     330: typedef int (*setattrfunc)(PyObject *, char *, PyObject *);
     331: typedef int (*setattrofunc)(PyObject *, PyObject *, PyObject *);
     332: typedef PyObject *(*reprfunc)(PyObject *);
     333: typedef Py_hash_t (*hashfunc)(PyObject *);
     334: typedef PyObject *(*richcmpfunc) (PyObject *, PyObject *, int);
     335: typedef PyObject *(*getiterfunc) (PyObject *);
     336: typedef PyObject *(*iternextfunc) (PyObject *);
     337: typedef PyObject *(*descrgetfunc) (PyObject *, PyObject *, PyObject *);
     338: typedef int (*descrsetfunc) (PyObject *, PyObject *, PyObject *);
     339: typedef int (*initproc)(PyObject *, PyObject *, PyObject *);
     340: typedef PyObject *(*newfunc)(struct _typeobject *, PyObject *, PyObject *);
     341: typedef PyObject *(*allocfunc)(struct _typeobject *, Py_ssize_t);
     342: 
     343: #ifdef Py_LIMITED_API
     344: typedef struct _typeobject PyTypeObject; /* opaque */
     345: #else
     346: typedef struct _typeobject {
     347:     PyObject_VAR_HEAD
     348:     const char *tp_name; /* For printing, in format "<module>.<name>" */
     349:     Py_ssize_t tp_basicsize, tp_itemsize; /* For allocation */
     350: 
     351:     /* Methods to implement standard operations */
     352: 
     353:     destructor tp_dealloc;
     354:     printfunc tp_print;
     355:     getattrfunc tp_getattr;
     356:     setattrfunc tp_setattr;
     357:     PyAsyncMethods *tp_as_async; /* formerly known as tp_compare (Python 2)
     358:                                     or tp_reserved (Python 3) */
     359:     reprfunc tp_repr;
     360: 
     361:     /* Method suites for standard classes */
     362: 
     363:     PyNumberMethods *tp_as_number;
     364:     PySequenceMethods *tp_as_sequence;
     365:     PyMappingMethods *tp_as_mapping;
     366: 
     367:     /* More standard operations (here for binary compatibility) */
     368: 
     369:     hashfunc tp_hash;
     370:     ternaryfunc tp_call;
     371:     reprfunc tp_str;
     372:     getattrofunc tp_getattro;
     373:     setattrofunc tp_setattro;
     374: 
     375:     /* Functions to access object as input/output buffer */
     376:     PyBufferProcs *tp_as_buffer;
     377: 
     378:     /* Flags to define presence of optional/expanded features */
     379:     unsigned long tp_flags;
     380: 
     381:     const char *tp_doc; /* Documentation string */
     382: 
     383:     /* Assigned meaning in release 2.0 */
     384:     /* call function for all accessible objects */
     385:     traverseproc tp_traverse;
     386: 
     387:     /* delete references to contained objects */
     388:     inquiry tp_clear;
     389: 
     390:     /* Assigned meaning in release 2.1 */
     391:     /* rich comparisons */
     392:     richcmpfunc tp_richcompare;
     393: 
     394:     /* weak reference enabler */
     395:     Py_ssize_t tp_weaklistoffset;
     396: 
     397:     /* Iterators */
     398:     getiterfunc tp_iter;
     399:     iternextfunc tp_iternext;
     400: 
     401:     /* Attribute descriptor and subclassing stuff */
     402:     struct PyMethodDef *tp_methods;
     403:     struct PyMemberDef *tp_members;
     404:     struct PyGetSetDef *tp_getset;
     405:     struct _typeobject *tp_base;
     406:     PyObject *tp_dict;
     407:     descrgetfunc tp_descr_get;
     408:     descrsetfunc tp_descr_set;
     409:     Py_ssize_t tp_dictoffset;
     410:     initproc tp_init;
     411:     allocfunc tp_alloc;
     412:     newfunc tp_new;
     413:     freefunc tp_free; /* Low-level free-memory routine */
     414:     inquiry tp_is_gc; /* For PyObject_IS_GC */
     415:     PyObject *tp_bases;
     416:     PyObject *tp_mro; /* method resolution order */
     417:     PyObject *tp_cache;
     418:     PyObject *tp_subclasses;
     419:     PyObject *tp_weaklist;
     420:     destructor tp_del;
     421: 
     422:     /* Type attribute cache version tag. Added in version 2.6 */
     423:     unsigned int tp_version_tag;
     424: 
     425:     destructor tp_finalize;
     426: 
     427: #ifdef COUNT_ALLOCS
     428:     /* these must be last and never explicitly initialized */
     429:     Py_ssize_t tp_allocs;
     430:     Py_ssize_t tp_frees;
     431:     Py_ssize_t tp_maxalloc;
     432:     struct _typeobject *tp_prev;
     433:     struct _typeobject *tp_next;
     434: #endif
     435: } PyTypeObject;
     436: #endif
     437: 
     438: typedef struct{
     439:     int slot;    /* slot id, see below */
     440:     void *pfunc; /* function pointer */
     441: } PyType_Slot;
     442: 
     443: typedef struct{
     444:     const char* name;
     445:     int basicsize;
     446:     int itemsize;
     447:     unsigned int flags;
     448:     PyType_Slot *slots; /* terminated by slot==0. */
     449: } PyType_Spec;
     450: 
     451: PyAPI_FUNC(PyObject*) PyType_FromSpec(PyType_Spec*);
     452: #if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03030000
     453: PyAPI_FUNC(PyObject*) PyType_FromSpecWithBases(PyType_Spec*, PyObject*);
     454: #endif
     455: #if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03040000
     456: PyAPI_FUNC(void*) PyType_GetSlot(PyTypeObject*, int);
     457: #endif
     458: 
     459: #ifndef Py_LIMITED_API
     460: /* The *real* layout of a type object when allocated on the heap */
     461: typedef struct _heaptypeobject {
     462:     /* Note: there's a dependency on the order of these members
     463:        in slotptr() in typeobject.c . */
     464:     PyTypeObject ht_type;
     465:     PyAsyncMethods as_async;
     466:     PyNumberMethods as_number;
     467:     PyMappingMethods as_mapping;
     468:     PySequenceMethods as_sequence; /* as_sequence comes after as_mapping,
     469:                                       so that the mapping wins when both
     470:                                       the mapping and the sequence define
     471:                                       a given operator (e.g. __getitem__).
     472:                                       see add_operators() in typeobject.c . */
     473:     PyBufferProcs as_buffer;
     474:     PyObject *ht_name, *ht_slots, *ht_qualname;
     475:     struct _dictkeysobject *ht_cached_keys;
     476:     /* here are optional user slots, followed by the members. */
     477: } PyHeapTypeObject;
     478: 
     479: /* access macro to the members which are floating "behind" the object */
     480: #define PyHeapType_GET_MEMBERS(etype) \
     481:     ((PyMemberDef *)(((char *)etype) + Py_TYPE(etype)->tp_basicsize))
     482: #endif
     483: 
     484: /* Generic type check */
     485: PyAPI_FUNC(int) PyType_IsSubtype(PyTypeObject *, PyTypeObject *);
     486: #define PyObject_TypeCheck(ob, tp) \
     487:     (Py_TYPE(ob) == (tp) || PyType_IsSubtype(Py_TYPE(ob), (tp)))
     488: 
     489: PyAPI_DATA(PyTypeObject) PyType_Type; /* built-in 'type' */
     490: PyAPI_DATA(PyTypeObject) PyBaseObject_Type; /* built-in 'object' */
     491: PyAPI_DATA(PyTypeObject) PySuper_Type; /* built-in 'super' */
     492: 
     493: PyAPI_FUNC(unsigned long) PyType_GetFlags(PyTypeObject*);
     494: 
     495: #define PyType_Check(op) \
     496:     PyType_FastSubclass(Py_TYPE(op), Py_TPFLAGS_TYPE_SUBCLASS)
     497: #define PyType_CheckExact(op) (Py_TYPE(op) == &PyType_Type)
     498: 
     499: PyAPI_FUNC(int) PyType_Ready(PyTypeObject *);
     500: PyAPI_FUNC(PyObject *) PyType_GenericAlloc(PyTypeObject *, Py_ssize_t);
     501: PyAPI_FUNC(PyObject *) PyType_GenericNew(PyTypeObject *,
     502:                                                PyObject *, PyObject *);
     503: #ifndef Py_LIMITED_API
     504: PyAPI_FUNC(PyObject *) _PyType_Lookup(PyTypeObject *, PyObject *);
     505: PyAPI_FUNC(PyObject *) _PyType_LookupId(PyTypeObject *, _Py_Identifier *);
     506: PyAPI_FUNC(PyObject *) _PyObject_LookupSpecial(PyObject *, _Py_Identifier *);
     507: PyAPI_FUNC(PyTypeObject *) _PyType_CalculateMetaclass(PyTypeObject *, PyObject *);
     508: #endif
     509: PyAPI_FUNC(unsigned int) PyType_ClearCache(void);
     510: PyAPI_FUNC(void) PyType_Modified(PyTypeObject *);
     511: 
     512: #ifndef Py_LIMITED_API
     513: PyAPI_FUNC(PyObject *) _PyType_GetDocFromInternalDoc(const char *, const char *);
     514: PyAPI_FUNC(PyObject *) _PyType_GetTextSignatureFromInternalDoc(const char *, const char *);
     515: #endif
     516: 
     517: /* Generic operations on objects */
     518: #ifndef Py_LIMITED_API
     519: struct _Py_Identifier;
     520: PyAPI_FUNC(int) PyObject_Print(PyObject *, FILE *, int);
     521: PyAPI_FUNC(void) _Py_BreakPoint(void);
     522: PyAPI_FUNC(void) _PyObject_Dump(PyObject *);
     523: #endif
     524: PyAPI_FUNC(PyObject *) PyObject_Repr(PyObject *);
     525: PyAPI_FUNC(PyObject *) PyObject_Str(PyObject *);
     526: PyAPI_FUNC(PyObject *) PyObject_ASCII(PyObject *);
     527: PyAPI_FUNC(PyObject *) PyObject_Bytes(PyObject *);
     528: PyAPI_FUNC(PyObject *) PyObject_RichCompare(PyObject *, PyObject *, int);
     529: PyAPI_FUNC(int) PyObject_RichCompareBool(PyObject *, PyObject *, int);
     530: PyAPI_FUNC(PyObject *) PyObject_GetAttrString(PyObject *, const char *);
     531: PyAPI_FUNC(int) PyObject_SetAttrString(PyObject *, const char *, PyObject *);
     532: PyAPI_FUNC(int) PyObject_HasAttrString(PyObject *, const char *);
     533: PyAPI_FUNC(PyObject *) PyObject_GetAttr(PyObject *, PyObject *);
     534: PyAPI_FUNC(int) PyObject_SetAttr(PyObject *, PyObject *, PyObject *);
     535: PyAPI_FUNC(int) PyObject_HasAttr(PyObject *, PyObject *);
     536: #ifndef Py_LIMITED_API
     537: PyAPI_FUNC(int) _PyObject_IsAbstract(PyObject *);
     538: PyAPI_FUNC(PyObject *) _PyObject_GetAttrId(PyObject *, struct _Py_Identifier *);
     539: PyAPI_FUNC(int) _PyObject_SetAttrId(PyObject *, struct _Py_Identifier *, PyObject *);
     540: PyAPI_FUNC(int) _PyObject_HasAttrId(PyObject *, struct _Py_Identifier *);
     541: PyAPI_FUNC(PyObject **) _PyObject_GetDictPtr(PyObject *);
     542: #endif
     543: PyAPI_FUNC(PyObject *) PyObject_SelfIter(PyObject *);
     544: #ifndef Py_LIMITED_API
     545: PyAPI_FUNC(PyObject *) _PyObject_NextNotImplemented(PyObject *);
     546: #endif
     547: PyAPI_FUNC(PyObject *) PyObject_GenericGetAttr(PyObject *, PyObject *);
     548: PyAPI_FUNC(int) PyObject_GenericSetAttr(PyObject *,
     549:                                               PyObject *, PyObject *);
     550: #if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03030000
     551: PyAPI_FUNC(int) PyObject_GenericSetDict(PyObject *, PyObject *, void *);
     552: #endif
     553: PyAPI_FUNC(Py_hash_t) PyObject_Hash(PyObject *);
     554: PyAPI_FUNC(Py_hash_t) PyObject_HashNotImplemented(PyObject *);
     555: PyAPI_FUNC(int) PyObject_IsTrue(PyObject *);
     556: PyAPI_FUNC(int) PyObject_Not(PyObject *);
     557: PyAPI_FUNC(int) PyCallable_Check(PyObject *);
     558: 
     559: PyAPI_FUNC(void) PyObject_ClearWeakRefs(PyObject *);
     560: #ifndef Py_LIMITED_API
     561: PyAPI_FUNC(void) PyObject_CallFinalizer(PyObject *);
     562: PyAPI_FUNC(int) PyObject_CallFinalizerFromDealloc(PyObject *);
     563: #endif
     564: 
     565: #ifndef Py_LIMITED_API
     566: /* Same as PyObject_Generic{Get,Set}Attr, but passing the attributes
     567:    dict as the last parameter. */
     568: PyAPI_FUNC(PyObject *)
     569: _PyObject_GenericGetAttrWithDict(PyObject *, PyObject *, PyObject *);
     570: PyAPI_FUNC(int)
     571: _PyObject_GenericSetAttrWithDict(PyObject *, PyObject *,
     572:                                  PyObject *, PyObject *);
     573: #endif /* !Py_LIMITED_API */
     574: 
     575: /* Helper to look up a builtin object */
     576: #ifndef Py_LIMITED_API
     577: PyAPI_FUNC(PyObject *)
     578: _PyObject_GetBuiltin(const char *name);
     579: #endif
     580: 
     581: /* PyObject_Dir(obj) acts like Python builtins.dir(obj), returning a
     582:    list of strings.  PyObject_Dir(NULL) is like builtins.dir(),
     583:    returning the names of the current locals.  In this case, if there are
     584:    no current locals, NULL is returned, and PyErr_Occurred() is false.
     585: */
     586: PyAPI_FUNC(PyObject *) PyObject_Dir(PyObject *);
     587: 
     588: 
     589: /* Helpers for printing recursive container types */
     590: PyAPI_FUNC(int) Py_ReprEnter(PyObject *);
     591: PyAPI_FUNC(void) Py_ReprLeave(PyObject *);
     592: 
     593: /* Flag bits for printing: */
     594: #define Py_PRINT_RAW    1       /* No string quotes etc. */
     595: 
     596: /*
     597: `Type flags (tp_flags)
     598: 
     599: These flags are used to extend the type structure in a backwards-compatible
     600: fashion. Extensions can use the flags to indicate (and test) when a given
     601: type structure contains a new feature. The Python core will use these when
     602: introducing new functionality between major revisions (to avoid mid-version
     603: changes in the PYTHON_API_VERSION).
     604: 
     605: Arbitration of the flag bit positions will need to be coordinated among
     606: all extension writers who publically release their extensions (this will
     607: be fewer than you might expect!)..
     608: 
     609: Most flags were removed as of Python 3.0 to make room for new flags.  (Some
     610: flags are not for backwards compatibility but to indicate the presence of an
     611: optional feature; these flags remain of course.)
     612: 
     613: Type definitions should use Py_TPFLAGS_DEFAULT for their tp_flags value.
     614: 
     615: Code can use PyType_HasFeature(type_ob, flag_value) to test whether the
     616: given type object has a specified feature.
     617: */
     618: 
     619: /* Set if the type object is dynamically allocated */
     620: #define Py_TPFLAGS_HEAPTYPE (1UL << 9)
     621: 
     622: /* Set if the type allows subclassing */
     623: #define Py_TPFLAGS_BASETYPE (1UL << 10)
     624: 
     625: /* Set if the type is 'ready' -- fully initialized */
     626: #define Py_TPFLAGS_READY (1UL << 12)
     627: 
     628: /* Set while the type is being 'readied', to prevent recursive ready calls */
     629: #define Py_TPFLAGS_READYING (1UL << 13)
     630: 
     631: /* Objects support garbage collection (see objimp.h) */
     632: #define Py_TPFLAGS_HAVE_GC (1UL << 14)
     633: 
     634: /* These two bits are preserved for Stackless Python, next after this is 17 */
     635: #ifdef STACKLESS
     636: #define Py_TPFLAGS_HAVE_STACKLESS_EXTENSION (3UL << 15)
     637: #else
     638: #define Py_TPFLAGS_HAVE_STACKLESS_EXTENSION 0
     639: #endif
     640: 
     641: /* Objects support type attribute cache */
     642: #define Py_TPFLAGS_HAVE_VERSION_TAG   (1UL << 18)
     643: #define Py_TPFLAGS_VALID_VERSION_TAG  (1UL << 19)
     644: 
     645: /* Type is abstract and cannot be instantiated */
     646: #define Py_TPFLAGS_IS_ABSTRACT (1UL << 20)
     647: 
     648: /* These flags are used to determine if a type is a subclass. */
     649: #define Py_TPFLAGS_LONG_SUBCLASS        (1UL << 24)
     650: #define Py_TPFLAGS_LIST_SUBCLASS        (1UL << 25)
     651: #define Py_TPFLAGS_TUPLE_SUBCLASS       (1UL << 26)
     652: #define Py_TPFLAGS_BYTES_SUBCLASS       (1UL << 27)
     653: #define Py_TPFLAGS_UNICODE_SUBCLASS     (1UL << 28)
     654: #define Py_TPFLAGS_DICT_SUBCLASS        (1UL << 29)
     655: #define Py_TPFLAGS_BASE_EXC_SUBCLASS    (1UL << 30)
     656: #define Py_TPFLAGS_TYPE_SUBCLASS        (1UL << 31)
     657: 
     658: #define Py_TPFLAGS_DEFAULT  ( \
     659:                  Py_TPFLAGS_HAVE_STACKLESS_EXTENSION | \
     660:                  Py_TPFLAGS_HAVE_VERSION_TAG | \
     661:                 0)
     662: 
     663: /* NOTE: The following flags reuse lower bits (removed as part of the
     664:  * Python 3.0 transition). */
     665: 
     666: /* Type structure has tp_finalize member (3.4) */
     667: #define Py_TPFLAGS_HAVE_FINALIZE (1UL << 0)
     668: 
     669: #ifdef Py_LIMITED_API
     670: #define PyType_HasFeature(t,f)  ((PyType_GetFlags(t) & (f)) != 0)
     671: #else
     672: #define PyType_HasFeature(t,f)  (((t)->tp_flags & (f)) != 0)
     673: #endif
     674: #define PyType_FastSubclass(t,f)  PyType_HasFeature(t,f)
     675: 
     676: 
     677: /*
     678: The macros Py_INCREF(op) and Py_DECREF(op) are used to increment or decrement
     679: reference counts.  Py_DECREF calls the object's deallocator function when
     680: the refcount falls to 0; for
     681: objects that don't contain references to other objects or heap memory
     682: this can be the standard function free().  Both macros can be used
     683: wherever a void expression is allowed.  The argument must not be a
     684: NULL pointer.  If it may be NULL, use Py_XINCREF/Py_XDECREF instead.
     685: The macro _Py_NewReference(op) initialize reference counts to 1, and
     686: in special builds (Py_REF_DEBUG, Py_TRACE_REFS) performs additional
     687: bookkeeping appropriate to the special build.
     688: 
     689: We assume that the reference count field can never overflow; this can
     690: be proven when the size of the field is the same as the pointer size, so
     691: we ignore the possibility.  Provided a C int is at least 32 bits (which
     692: is implicitly assumed in many parts of this code), that's enough for
     693: about 2**31 references to an object.
     694: 
     695: XXX The following became out of date in Python 2.2, but I'm not sure
     696: XXX what the full truth is now.  Certainly, heap-allocated type objects
     697: XXX can and should be deallocated.
     698: Type objects should never be deallocated; the type pointer in an object
     699: is not considered to be a reference to the type object, to save
     700: complications in the deallocation function.  (This is actually a
     701: decision that's up to the implementer of each new type so if you want,
     702: you can count such references to the type object.)
     703: */
     704: 
     705: /* First define a pile of simple helper macros, one set per special
     706:  * build symbol.  These either expand to the obvious things, or to
     707:  * nothing at all when the special mode isn't in effect.  The main
     708:  * macros can later be defined just once then, yet expand to different
     709:  * things depending on which special build options are and aren't in effect.
     710:  * Trust me <wink>:  while painful, this is 20x easier to understand than,
     711:  * e.g, defining _Py_NewReference five different times in a maze of nested
     712:  * #ifdefs (we used to do that -- it was impenetrable).
     713:  */
     714: #ifdef Py_REF_DEBUG
     715: PyAPI_DATA(Py_ssize_t) _Py_RefTotal;
     716: PyAPI_FUNC(void) _Py_NegativeRefcount(const char *fname,
     717:                                             int lineno, PyObject *op);
     718: PyAPI_FUNC(Py_ssize_t) _Py_GetRefTotal(void);
     719: #define _Py_INC_REFTOTAL        _Py_RefTotal++
     720: #define _Py_DEC_REFTOTAL        _Py_RefTotal--
     721: #define _Py_REF_DEBUG_COMMA     ,
     722: #define _Py_CHECK_REFCNT(OP)                                    \
     723: {       if (((PyObject*)OP)->ob_refcnt < 0)                             \
     724:                 _Py_NegativeRefcount(__FILE__, __LINE__,        \
     725:                                      (PyObject *)(OP));         \
     726: }
     727: /* Py_REF_DEBUG also controls the display of refcounts and memory block
     728:  * allocations at the interactive prompt and at interpreter shutdown
     729:  */
     730: PyAPI_FUNC(void) _PyDebug_PrintTotalRefs(void);
     731: #define _PY_DEBUG_PRINT_TOTAL_REFS() _PyDebug_PrintTotalRefs()
     732: #else
     733: #define _Py_INC_REFTOTAL
     734: #define _Py_DEC_REFTOTAL
     735: #define _Py_REF_DEBUG_COMMA
     736: #define _Py_CHECK_REFCNT(OP)    /* a semicolon */;
     737: #define _PY_DEBUG_PRINT_TOTAL_REFS()
     738: #endif /* Py_REF_DEBUG */
     739: 
     740: #ifdef COUNT_ALLOCS
     741: PyAPI_FUNC(void) inc_count(PyTypeObject *);
     742: PyAPI_FUNC(void) dec_count(PyTypeObject *);
     743: #define _Py_INC_TPALLOCS(OP)    inc_count(Py_TYPE(OP))
     744: #define _Py_INC_TPFREES(OP)     dec_count(Py_TYPE(OP))
     745: #define _Py_DEC_TPFREES(OP)     Py_TYPE(OP)->tp_frees--
     746: #define _Py_COUNT_ALLOCS_COMMA  ,
     747: #else
     748: #define _Py_INC_TPALLOCS(OP)
     749: #define _Py_INC_TPFREES(OP)
     750: #define _Py_DEC_TPFREES(OP)
     751: #define _Py_COUNT_ALLOCS_COMMA
     752: #endif /* COUNT_ALLOCS */
     753: 
     754: #ifdef Py_TRACE_REFS
     755: /* Py_TRACE_REFS is such major surgery that we call external routines. */
     756: PyAPI_FUNC(void) _Py_NewReference(PyObject *);
     757: PyAPI_FUNC(void) _Py_ForgetReference(PyObject *);
     758: PyAPI_FUNC(void) _Py_Dealloc(PyObject *);
     759: PyAPI_FUNC(void) _Py_PrintReferences(FILE *);
     760: PyAPI_FUNC(void) _Py_PrintReferenceAddresses(FILE *);
     761: PyAPI_FUNC(void) _Py_AddToAllObjects(PyObject *, int force);
     762: 
     763: #else
     764: /* Without Py_TRACE_REFS, there's little enough to do that we expand code
     765:  * inline.
     766:  */
     767: #define _Py_NewReference(op) (                          \
     768:     _Py_INC_TPALLOCS(op) _Py_COUNT_ALLOCS_COMMA         \
     769:     _Py_INC_REFTOTAL  _Py_REF_DEBUG_COMMA               \
     770:     Py_REFCNT(op) = 1)
     771: 
     772: #define _Py_ForgetReference(op) _Py_INC_TPFREES(op)
     773: 
     774: #ifdef Py_LIMITED_API
     775: PyAPI_FUNC(void) _Py_Dealloc(PyObject *);
     776: #else
     777: #define _Py_Dealloc(op) (                               \
     778:     _Py_INC_TPFREES(op) _Py_COUNT_ALLOCS_COMMA          \
     779:     (*Py_TYPE(op)->tp_dealloc)((PyObject *)(op)))
     780: #endif
     781: #endif /* !Py_TRACE_REFS */
     782: 
     783: #define Py_INCREF(op) (                         \
     784:     _Py_INC_REFTOTAL  _Py_REF_DEBUG_COMMA       \
     785:     ((PyObject *)(op))->ob_refcnt++)
     786: 
     787: #define Py_DECREF(op)                                   \
     788:     do {                                                \
     789:         PyObject *_py_decref_tmp = (PyObject *)(op);    \
     790:         if (_Py_DEC_REFTOTAL  _Py_REF_DEBUG_COMMA       \
     791:         --(_py_decref_tmp)->ob_refcnt != 0)             \
     792:             _Py_CHECK_REFCNT(_py_decref_tmp)            \
     793:         else                                            \
     794:             _Py_Dealloc(_py_decref_tmp);                \
     795:     } while (0)
     796: 
     797: /* Safely decref `op` and set `op` to NULL, especially useful in tp_clear
     798:  * and tp_dealloc implementations.
     799:  *
     800:  * Note that "the obvious" code can be deadly:
     801:  *
     802:  *     Py_XDECREF(op);
     803:  *     op = NULL;
     804:  *
     805:  * Typically, `op` is something like self->containee, and `self` is done
     806:  * using its `containee` member.  In the code sequence above, suppose
     807:  * `containee` is non-NULL with a refcount of 1.  Its refcount falls to
     808:  * 0 on the first line, which can trigger an arbitrary amount of code,
     809:  * possibly including finalizers (like __del__ methods or weakref callbacks)
     810:  * coded in Python, which in turn can release the GIL and allow other threads
     811:  * to run, etc.  Such code may even invoke methods of `self` again, or cause
     812:  * cyclic gc to trigger, but-- oops! --self->containee still points to the
     813:  * object being torn down, and it may be in an insane state while being torn
     814:  * down.  This has in fact been a rich historic source of miserable (rare &
     815:  * hard-to-diagnose) segfaulting (and other) bugs.
     816:  *
     817:  * The safe way is:
     818:  *
     819:  *      Py_CLEAR(op);
     820:  *
     821:  * That arranges to set `op` to NULL _before_ decref'ing, so that any code
     822:  * triggered as a side-effect of `op` getting torn down no longer believes
     823:  * `op` points to a valid object.
     824:  *
     825:  * There are cases where it's safe to use the naive code, but they're brittle.
     826:  * For example, if `op` points to a Python integer, you know that destroying
     827:  * one of those can't cause problems -- but in part that relies on that
     828:  * Python integers aren't currently weakly referencable.  Best practice is
     829:  * to use Py_CLEAR() even if you can't think of a reason for why you need to.
     830:  */
     831: #define Py_CLEAR(op)                            \
     832:     do {                                        \
     833:         PyObject *_py_tmp = (PyObject *)(op);   \
     834:         if (_py_tmp != NULL) {                  \
     835:             (op) = NULL;                        \
     836:             Py_DECREF(_py_tmp);                 \
     837:         }                                       \
     838:     } while (0)
     839: 
     840: /* Macros to use in case the object pointer may be NULL: */
     841: #define Py_XINCREF(op)                                \
     842:     do {                                              \
     843:         PyObject *_py_xincref_tmp = (PyObject *)(op); \
     844:         if (_py_xincref_tmp != NULL)                  \
     845:             Py_INCREF(_py_xincref_tmp);               \
     846:     } while (0)
     847: 
     848: #define Py_XDECREF(op)                                \
     849:     do {                                              \
     850:         PyObject *_py_xdecref_tmp = (PyObject *)(op); \
     851:         if (_py_xdecref_tmp != NULL)                  \
     852:             Py_DECREF(_py_xdecref_tmp);               \
     853:     } while (0)
     854: 
     855: #ifndef Py_LIMITED_API
     856: /* Safely decref `op` and set `op` to `op2`.
     857:  *
     858:  * As in case of Py_CLEAR "the obvious" code can be deadly:
     859:  *
     860:  *     Py_DECREF(op);
     861:  *     op = op2;
     862:  *
     863:  * The safe way is:
     864:  *
     865:  *      Py_SETREF(op, op2);
     866:  *
     867:  * That arranges to set `op` to `op2` _before_ decref'ing, so that any code
     868:  * triggered as a side-effect of `op` getting torn down no longer believes
     869:  * `op` points to a valid object.
     870:  *
     871:  * Py_XSETREF is a variant of Py_SETREF that uses Py_XDECREF instead of
     872:  * Py_DECREF.
     873:  */
     874: 
     875: #define Py_SETREF(op, op2)                      \
     876:     do {                                        \
     877:         PyObject *_py_tmp = (PyObject *)(op);   \
     878:         (op) = (op2);                           \
     879:         Py_DECREF(_py_tmp);                     \
     880:     } while (0)
     881: 
     882: #define Py_XSETREF(op, op2)                     \
     883:     do {                                        \
     884:         PyObject *_py_tmp = (PyObject *)(op);   \
     885:         (op) = (op2);                           \
     886:         Py_XDECREF(_py_tmp);                    \
     887:     } while (0)
     888: 
     889: #endif /* ifndef Py_LIMITED_API */
     890: 
     891: /*
     892: These are provided as conveniences to Python runtime embedders, so that
     893: they can have object code that is not dependent on Python compilation flags.
     894: */
     895: PyAPI_FUNC(void) Py_IncRef(PyObject *);
     896: PyAPI_FUNC(void) Py_DecRef(PyObject *);
     897: 
     898: #ifndef Py_LIMITED_API
     899: PyAPI_DATA(PyTypeObject) _PyNone_Type;
     900: PyAPI_DATA(PyTypeObject) _PyNotImplemented_Type;
     901: #endif /* !Py_LIMITED_API */
     902: 
     903: /*
     904: _Py_NoneStruct is an object of undefined type which can be used in contexts
     905: where NULL (nil) is not suitable (since NULL often means 'error').
     906: 
     907: Don't forget to apply Py_INCREF() when returning this value!!!
     908: */
     909: PyAPI_DATA(PyObject) _Py_NoneStruct; /* Don't use this directly */
     910: #define Py_None (&_Py_NoneStruct)
     911: 
     912: /* Macro for returning Py_None from a function */
     913: #define Py_RETURN_NONE return Py_INCREF(Py_None), Py_None
     914: 
     915: /*
     916: Py_NotImplemented is a singleton used to signal that an operation is
     917: not implemented for a given type combination.
     918: */
     919: PyAPI_DATA(PyObject) _Py_NotImplementedStruct; /* Don't use this directly */
     920: #define Py_NotImplemented (&_Py_NotImplementedStruct)
     921: 
     922: /* Macro for returning Py_NotImplemented from a function */
     923: #define Py_RETURN_NOTIMPLEMENTED \
     924:     return Py_INCREF(Py_NotImplemented), Py_NotImplemented
     925: 
     926: /* Rich comparison opcodes */
     927: #define Py_LT 0
     928: #define Py_LE 1
     929: #define Py_EQ 2
     930: #define Py_NE 3
     931: #define Py_GT 4
     932: #define Py_GE 5
     933: 
     934: #ifndef Py_LIMITED_API
     935: /* Maps Py_LT to Py_GT, ..., Py_GE to Py_LE.
     936:  * Defined in object.c.
     937:  */
     938: PyAPI_DATA(int) _Py_SwappedOp[];
     939: #endif /* !Py_LIMITED_API */
     940: 
     941: 
     942: /*
     943: More conventions
     944: ================
     945: 
     946: Argument Checking
     947: -----------------
     948: 
     949: Functions that take objects as arguments normally don't check for nil
     950: arguments, but they do check the type of the argument, and return an
     951: error if the function doesn't apply to the type.
     952: 
     953: Failure Modes
     954: -------------
     955: 
     956: Functions may fail for a variety of reasons, including running out of
     957: memory.  This is communicated to the caller in two ways: an error string
     958: is set (see errors.h), and the function result differs: functions that
     959: normally return a pointer return NULL for failure, functions returning
     960: an integer return -1 (which could be a legal return value too!), and
     961: other functions return 0 for success and -1 for failure.
     962: Callers should always check for errors before using the result.  If
     963: an error was set, the caller must either explicitly clear it, or pass
     964: the error on to its caller.
     965: 
     966: Reference Counts
     967: ----------------
     968: 
     969: It takes a while to get used to the proper usage of reference counts.
     970: 
     971: Functions that create an object set the reference count to 1; such new
     972: objects must be stored somewhere or destroyed again with Py_DECREF().
     973: Some functions that 'store' objects, such as PyTuple_SetItem() and
     974: PyList_SetItem(),
     975: don't increment the reference count of the object, since the most
     976: frequent use is to store a fresh object.  Functions that 'retrieve'
     977: objects, such as PyTuple_GetItem() and PyDict_GetItemString(), also
     978: don't increment
     979: the reference count, since most frequently the object is only looked at
     980: quickly.  Thus, to retrieve an object and store it again, the caller
     981: must call Py_INCREF() explicitly.
     982: 
     983: NOTE: functions that 'consume' a reference count, like
     984: PyList_SetItem(), consume the reference even if the object wasn't
     985: successfully stored, to simplify error handling.
     986: 
     987: It seems attractive to make other functions that take an object as
     988: argument consume a reference count; however, this may quickly get
     989: confusing (even the current practice is already confusing).  Consider
     990: it carefully, it may save lots of calls to Py_INCREF() and Py_DECREF() at
     991: times.
     992: */
     993: 
     994: 
     995: /* Trashcan mechanism, thanks to Christian Tismer.
     996: 
     997: When deallocating a container object, it's possible to trigger an unbounded
     998: chain of deallocations, as each Py_DECREF in turn drops the refcount on "the
     999: next" object in the chain to 0.  This can easily lead to stack faults, and
    1000: especially in threads (which typically have less stack space to work with).
    1001: 
    1002: A container object that participates in cyclic gc can avoid this by
    1003: bracketing the body of its tp_dealloc function with a pair of macros:
    1004: 
    1005: static void
    1006: mytype_dealloc(mytype *p)
    1007: {
    1008:     ... declarations go here ...
    1009: 
    1010:     PyObject_GC_UnTrack(p);        // must untrack first
    1011:     Py_TRASHCAN_SAFE_BEGIN(p)
    1012:     ... The body of the deallocator goes here, including all calls ...
    1013:     ... to Py_DECREF on contained objects.                         ...
    1014:     Py_TRASHCAN_SAFE_END(p)
    1015: }
    1016: 
    1017: CAUTION:  Never return from the middle of the body!  If the body needs to
    1018: "get out early", put a label immediately before the Py_TRASHCAN_SAFE_END
    1019: call, and goto it.  Else the call-depth counter (see below) will stay
    1020: above 0 forever, and the trashcan will never get emptied.
    1021: 
    1022: How it works:  The BEGIN macro increments a call-depth counter.  So long
    1023: as this counter is small, the body of the deallocator is run directly without
    1024: further ado.  But if the counter gets large, it instead adds p to a list of
    1025: objects to be deallocated later, skips the body of the deallocator, and
    1026: resumes execution after the END macro.  The tp_dealloc routine then returns
    1027: without deallocating anything (and so unbounded call-stack depth is avoided).
    1028: 
    1029: When the call stack finishes unwinding again, code generated by the END macro
    1030: notices this, and calls another routine to deallocate all the objects that
    1031: may have been added to the list of deferred deallocations.  In effect, a
    1032: chain of N deallocations is broken into N / PyTrash_UNWIND_LEVEL pieces,
    1033: with the call stack never exceeding a depth of PyTrash_UNWIND_LEVEL.
    1034: */
    1035: 
    1036: #ifndef Py_LIMITED_API
    1037: /* This is the old private API, invoked by the macros before 3.2.4.
    1038:    Kept for binary compatibility of extensions using the stable ABI. */
    1039: PyAPI_FUNC(void) _PyTrash_deposit_object(PyObject*);
    1040: PyAPI_FUNC(void) _PyTrash_destroy_chain(void);
    1041: PyAPI_DATA(int) _PyTrash_delete_nesting;
    1042: PyAPI_DATA(PyObject *) _PyTrash_delete_later;
    1043: #endif /* !Py_LIMITED_API */
    1044: 
    1045: /* The new thread-safe private API, invoked by the macros below. */
    1046: PyAPI_FUNC(void) _PyTrash_thread_deposit_object(PyObject*);
    1047: PyAPI_FUNC(void) _PyTrash_thread_destroy_chain(void);
    1048: 
    1049: #define PyTrash_UNWIND_LEVEL 50
    1050: 
    1051: #define Py_TRASHCAN_SAFE_BEGIN(op) \
    1052:     do { \
    1053:         PyThreadState *_tstate = PyThreadState_GET(); \
    1054:         if (_tstate->trash_delete_nesting < PyTrash_UNWIND_LEVEL) { \
    1055:             ++_tstate->trash_delete_nesting;
    1056:             /* The body of the deallocator is here. */
    1057: #define Py_TRASHCAN_SAFE_END(op) \
    1058:             --_tstate->trash_delete_nesting; \
    1059:             if (_tstate->trash_delete_later && _tstate->trash_delete_nesting <= 0) \
    1060:                 _PyTrash_thread_destroy_chain(); \
    1061:         } \
    1062:         else \
    1063:             _PyTrash_thread_deposit_object((PyObject*)op); \
    1064:     } while (0);
    1065: 
    1066: #ifndef Py_LIMITED_API
    1067: PyAPI_FUNC(void)
    1068: _PyDebugAllocatorStats(FILE *out, const char *block_name, int num_blocks,
    1069:                        size_t sizeof_block);
    1070: PyAPI_FUNC(void)
    1071: _PyObject_DebugTypeStats(FILE *out);
    1072: #endif /* ifndef Py_LIMITED_API */
    1073: 
    1074: #ifdef __cplusplus
    1075: }
    1076: #endif
    1077: #endif /* !Py_OBJECT_H */
    1078: