cpython/Include/internal/pycore_object.h

#ifndef Py_INTERNAL_OBJECT_H
#define Py_INTERNAL_OBJECT_H
#ifdef __cplusplus
extern "C" {
#endif

#ifndef Py_BUILD_CORE
#  error "this header requires Py_BUILD_CORE define"
#endif

#include "pycore_gc.h"         // _PyObject_GC_IS_TRACKED()
#include "pycore_interp.h"     // PyInterpreterState.gc
#include "pycore_pystate.h"    // _PyThreadState_GET()

PyAPI_FUNC(int) _PyType_CheckConsistency(PyTypeObject *type);
PyAPI_FUNC(int) _PyDict_CheckConsistency(PyObject *mp, int check_content);

/* Update the Python traceback of an object. This function must be called
   when a memory block is reused from a free list.

   Internal function called by _Py_NewReference(). */
extern int _PyTraceMalloc_NewReference(PyObject *op);

// Fast inlined version of PyType_HasFeature()
static inline int
_PyType_HasFeature(PyTypeObject *type, unsigned long feature) {
    return ((type->tp_flags & feature) != 0);
}

/* Inline functions trading binary compatibility for speed:
   _PyObject_Init() is the fast version of PyObject_Init(), and
   _PyObject_InitVar() is the fast version of PyObject_InitVar().

   These inline functions must not be called with op=NULL. */
static inline void
_PyObject_Init(PyObject *op, PyTypeObject *typeobj)
{
    assert(op != NULL);
    Py_SET_TYPE(op, typeobj);
    if (_PyType_HasFeature(typeobj, Py_TPFLAGS_HEAPTYPE)) {
        Py_INCREF(typeobj);
    }
    _Py_NewReference(op);
}

static inline void
_PyObject_InitVar(PyVarObject *op, PyTypeObject *typeobj, Py_ssize_t size)
{
    assert(op != NULL);
    Py_SET_SIZE(op, size);
    _PyObject_Init((PyObject *)op, typeobj);
}


/* Tell the GC to track this object.
 *
 * The object must not be tracked by the GC.
 *
 * NB: While the object is tracked by the collector, it must be safe to call the
 * ob_traverse method.
 *
 * Internal note: interp->gc.generation0->_gc_prev doesn't have any bit flags
 * because it's not object header.  So we don't use _PyGCHead_PREV() and
 * _PyGCHead_SET_PREV() for it to avoid unnecessary bitwise operations.
 *
 * See also the public PyObject_GC_Track() function.
 */
static inline void _PyObject_GC_TRACK(
// The preprocessor removes _PyObject_ASSERT_FROM() calls if NDEBUG is defined
#ifndef NDEBUG
    const char *filename, int lineno,
#endif
    PyObject *op)
{
    _PyObject_ASSERT_FROM(op, !_PyObject_GC_IS_TRACKED(op),
                          "object already tracked by the garbage collector",
                          filename, lineno, __func__);

    PyGC_Head *gc = _Py_AS_GC(op);
    _PyObject_ASSERT_FROM(op,
                          (gc->_gc_prev & _PyGC_PREV_MASK_COLLECTING) == 0,
                          "object is in generation which is garbage collected",
                          filename, lineno, __func__);

    PyThreadState *tstate = _PyThreadState_GET();
    PyGC_Head *generation0 = tstate->interp->gc.generation0;
    PyGC_Head *last = (PyGC_Head*)(generation0->_gc_prev);
    _PyGCHead_SET_NEXT(last, gc);
    _PyGCHead_SET_PREV(gc, last);
    _PyGCHead_SET_NEXT(gc, generation0);
    generation0->_gc_prev = (uintptr_t)gc;
}

/* Tell the GC to stop tracking this object.
 *
 * Internal note: This may be called while GC. So _PyGC_PREV_MASK_COLLECTING
 * must be cleared. But _PyGC_PREV_MASK_FINALIZED bit is kept.
 *
 * The object must be tracked by the GC.
 *
 * See also the public PyObject_GC_UnTrack() which accept an object which is
 * not tracked.
 */
static inline void _PyObject_GC_UNTRACK(
// The preprocessor removes _PyObject_ASSERT_FROM() calls if NDEBUG is defined
#ifndef NDEBUG
    const char *filename, int lineno,
#endif
    PyObject *op)
{
    _PyObject_ASSERT_FROM(op, _PyObject_GC_IS_TRACKED(op),
                          "object not tracked by the garbage collector",
                          filename, lineno, __func__);

    PyGC_Head *gc = _Py_AS_GC(op);
    PyGC_Head *prev = _PyGCHead_PREV(gc);
    PyGC_Head *next = _PyGCHead_NEXT(gc);
    _PyGCHead_SET_NEXT(prev, next);
    _PyGCHead_SET_PREV(next, prev);
    gc->_gc_next = 0;
    gc->_gc_prev &= _PyGC_PREV_MASK_FINALIZED;
}

// Macros to accept any type for the parameter, and to automatically pass
// the filename and the filename (if NDEBUG is not defined) where the macro
// is called.
#ifdef NDEBUG
#  define _PyObject_GC_TRACK(op) \
        _PyObject_GC_TRACK(_PyObject_CAST(op))
#  define _PyObject_GC_UNTRACK(op) \
        _PyObject_GC_UNTRACK(_PyObject_CAST(op))
#else
#  define _PyObject_GC_TRACK(op) \
        _PyObject_GC_TRACK(__FILE__, __LINE__, _PyObject_CAST(op))
#  define _PyObject_GC_UNTRACK(op) \
        _PyObject_GC_UNTRACK(__FILE__, __LINE__, _PyObject_CAST(op))
#endif

#ifdef Py_REF_DEBUG
extern void _PyDebug_PrintTotalRefs(void);
#endif

#ifdef Py_TRACE_REFS
extern void _Py_AddToAllObjects(PyObject *op, int force);
extern void _Py_PrintReferences(FILE *);
extern void _Py_PrintReferenceAddresses(FILE *);
#endif

static inline PyObject **
_PyObject_GET_WEAKREFS_LISTPTR(PyObject *op)
{
    Py_ssize_t offset = Py_TYPE(op)->tp_weaklistoffset;
    return (PyObject **)((char *)op + offset);
}

// Fast inlined version of PyObject_IS_GC()
static inline int
_PyObject_IS_GC(PyObject *obj)
{
    return (PyType_IS_GC(Py_TYPE(obj))
            && (Py_TYPE(obj)->tp_is_gc == NULL
                || Py_TYPE(obj)->tp_is_gc(obj)));
}

// Fast inlined version of PyType_IS_GC()
#define _PyType_IS_GC(t) _PyType_HasFeature((t), Py_TPFLAGS_HAVE_GC)

#ifdef __cplusplus
}
#endif
#endif /* !Py_INTERNAL_OBJECT_H */