70 lines
2.2 KiB
C
70 lines
2.2 KiB
C
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#ifndef Py_INTERNAL_GC_H
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#define Py_INTERNAL_GC_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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#ifndef Py_BUILD_CORE
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# error "this header requires Py_BUILD_CORE define"
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#endif
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/* GC information is stored BEFORE the object structure. */
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typedef struct {
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// Pointer to next object in the list.
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// 0 means the object is not tracked
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uintptr_t _gc_next;
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// Pointer to previous object in the list.
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// Lowest two bits are used for flags documented later.
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uintptr_t _gc_prev;
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} PyGC_Head;
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#define _Py_AS_GC(o) ((PyGC_Head *)(o)-1)
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/* True if the object is currently tracked by the GC. */
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#define _PyObject_GC_IS_TRACKED(o) (_Py_AS_GC(o)->_gc_next != 0)
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/* True if the object may be tracked by the GC in the future, or already is.
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This can be useful to implement some optimizations. */
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#define _PyObject_GC_MAY_BE_TRACKED(obj) \
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(PyObject_IS_GC(obj) && \
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(!PyTuple_CheckExact(obj) || _PyObject_GC_IS_TRACKED(obj)))
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/* Bit flags for _gc_prev */
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/* Bit 0 is set when tp_finalize is called */
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#define _PyGC_PREV_MASK_FINALIZED (1)
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/* Bit 1 is set when the object is in generation which is GCed currently. */
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#define _PyGC_PREV_MASK_COLLECTING (2)
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/* The (N-2) most significant bits contain the real address. */
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#define _PyGC_PREV_SHIFT (2)
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#define _PyGC_PREV_MASK (((uintptr_t) -1) << _PyGC_PREV_SHIFT)
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// Lowest bit of _gc_next is used for flags only in GC.
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// But it is always 0 for normal code.
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#define _PyGCHead_NEXT(g) ((PyGC_Head*)(g)->_gc_next)
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#define _PyGCHead_SET_NEXT(g, p) ((g)->_gc_next = (uintptr_t)(p))
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// Lowest two bits of _gc_prev is used for _PyGC_PREV_MASK_* flags.
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#define _PyGCHead_PREV(g) ((PyGC_Head*)((g)->_gc_prev & _PyGC_PREV_MASK))
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#define _PyGCHead_SET_PREV(g, p) do { \
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assert(((uintptr_t)p & ~_PyGC_PREV_MASK) == 0); \
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(g)->_gc_prev = ((g)->_gc_prev & ~_PyGC_PREV_MASK) \
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| ((uintptr_t)(p)); \
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} while (0)
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#define _PyGCHead_FINALIZED(g) \
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(((g)->_gc_prev & _PyGC_PREV_MASK_FINALIZED) != 0)
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#define _PyGCHead_SET_FINALIZED(g) \
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((g)->_gc_prev |= _PyGC_PREV_MASK_FINALIZED)
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#define _PyGC_FINALIZED(o) \
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_PyGCHead_FINALIZED(_Py_AS_GC(o))
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#define _PyGC_SET_FINALIZED(o) \
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_PyGCHead_SET_FINALIZED(_Py_AS_GC(o))
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#ifdef __cplusplus
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}
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#endif
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#endif /* !Py_INTERNAL_GC_H */
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