/Modules/gcmodule.c
http://unladen-swallow.googlecode.com/ · C · 1486 lines · 935 code · 155 blank · 396 comment · 198 complexity · 09fbe349ede1540e20837273c6736752 MD5 · raw file
- /*
- Reference Cycle Garbage Collection
- ==================================
- Neil Schemenauer <nas@arctrix.com>
- Based on a post on the python-dev list. Ideas from Guido van Rossum,
- Eric Tiedemann, and various others.
- http://www.arctrix.com/nas/python/gc/
- http://www.python.org/pipermail/python-dev/2000-March/003869.html
- http://www.python.org/pipermail/python-dev/2000-March/004010.html
- http://www.python.org/pipermail/python-dev/2000-March/004022.html
- For a highlevel view of the collection process, read the collect
- function.
- */
- #include "Python.h"
- #include "frameobject.h" /* for PyFrame_ClearFreeList */
- /* Get an object's GC head */
- #define AS_GC(o) ((PyGC_Head *)(o)-1)
- /* Get the object given the GC head */
- #define FROM_GC(g) ((PyObject *)(((PyGC_Head *)g)+1))
- /*** Global GC state ***/
- struct gc_generation {
- PyGC_Head head;
- int threshold; /* collection threshold */
- int count; /* count of allocations or collections of younger
- generations */
- };
- #define NUM_GENERATIONS 3
- #define GEN_HEAD(n) (&generations[n].head)
- /* linked lists of container objects */
- static struct gc_generation generations[NUM_GENERATIONS] = {
- /* PyGC_Head, threshold, count */
- {{{GEN_HEAD(0), GEN_HEAD(0), 0}}, 700, 0},
- {{{GEN_HEAD(1), GEN_HEAD(1), 0}}, 10, 0},
- {{{GEN_HEAD(2), GEN_HEAD(2), 0}}, 10, 0},
- };
- PyGC_Head *_PyGC_generation0 = GEN_HEAD(0);
- static int enabled = 1; /* automatic collection enabled? */
- /* true if we are currently running the collector */
- static int collecting = 0;
- /* list of uncollectable objects */
- static PyObject *garbage = NULL;
- /* Python string to use if unhandled exception occurs */
- static PyObject *gc_str = NULL;
- /* Python string used to look for __del__ attribute. */
- static PyObject *delstr = NULL;
- /* This is the number of objects who survived the last full collection. It
- approximates the number of long lived objects tracked by the GC.
- (by "full collection", we mean a collection of the oldest generation).
- */
- static Py_ssize_t long_lived_total = 0;
- /* This is the number of objects who survived all "non-full" collections,
- and are awaiting to undergo a full collection for the first time.
- */
- static Py_ssize_t long_lived_pending = 0;
- /*
- NOTE: about the counting of long-lived objects.
- To limit the cost of garbage collection, there are two strategies;
- - make each collection faster, e.g. by scanning fewer objects
- - do less collections
- This heuristic is about the latter strategy.
- In addition to the various configurable thresholds, we only trigger a
- full collection if the ratio
- long_lived_pending / long_lived_total
- is above a given value (hardwired to 25%).
- The reason is that, while "non-full" collections (i.e., collections of
- the young and middle generations) will always examine roughly the same
- number of objects -- determined by the aforementioned thresholds --,
- the cost of a full collection is proportional to the total number of
- long-lived objects, which is virtually unbounded.
- Indeed, it has been remarked that doing a full collection every
- <constant number> of object creations entails a dramatic performance
- degradation in workloads which consist in creating and storing lots of
- long-lived objects (e.g. building a large list of GC-tracked objects would
- show quadratic performance, instead of linear as expected: see issue #4074).
- Using the above ratio, instead, yields amortized linear performance in
- the total number of objects (the effect of which can be summarized
- thusly: "each full garbage collection is more and more costly as the
- number of objects grows, but we do fewer and fewer of them").
- This heuristic was suggested by Martin von Lรถwis on python-dev in
- June 2008. His original analysis and proposal can be found at:
- http://mail.python.org/pipermail/python-dev/2008-June/080579.html
- */
- /* set for debugging information */
- #define DEBUG_STATS (1<<0) /* print collection statistics */
- #define DEBUG_COLLECTABLE (1<<1) /* print collectable objects */
- #define DEBUG_UNCOLLECTABLE (1<<2) /* print uncollectable objects */
- #define DEBUG_INSTANCES (1<<3) /* print instances */
- #define DEBUG_OBJECTS (1<<4) /* print other objects */
- #define DEBUG_SAVEALL (1<<5) /* save all garbage in gc.garbage */
- #define DEBUG_LEAK DEBUG_COLLECTABLE | \
- DEBUG_UNCOLLECTABLE | \
- DEBUG_INSTANCES | \
- DEBUG_OBJECTS | \
- DEBUG_SAVEALL
- static int debug;
- static PyObject *tmod = NULL;
- /*--------------------------------------------------------------------------
- gc_refs values.
- Between collections, every gc'ed object has one of two gc_refs values:
- GC_UNTRACKED
- The initial state; objects returned by PyObject_GC_Malloc are in this
- state. The object doesn't live in any generation list, and its
- tp_traverse slot must not be called.
- GC_REACHABLE
- The object lives in some generation list, and its tp_traverse is safe to
- call. An object transitions to GC_REACHABLE when PyObject_GC_Track
- is called.
- During a collection, gc_refs can temporarily take on other states:
- >= 0
- At the start of a collection, update_refs() copies the true refcount
- to gc_refs, for each object in the generation being collected.
- subtract_refs() then adjusts gc_refs so that it equals the number of
- times an object is referenced directly from outside the generation
- being collected.
- gc_refs remains >= 0 throughout these steps.
- GC_TENTATIVELY_UNREACHABLE
- move_unreachable() then moves objects not reachable (whether directly or
- indirectly) from outside the generation into an "unreachable" set.
- Objects that are found to be reachable have gc_refs set to GC_REACHABLE
- again. Objects that are found to be unreachable have gc_refs set to
- GC_TENTATIVELY_UNREACHABLE. It's "tentatively" because the pass doing
- this can't be sure until it ends, and GC_TENTATIVELY_UNREACHABLE may
- transition back to GC_REACHABLE.
- Only objects with GC_TENTATIVELY_UNREACHABLE still set are candidates
- for collection. If it's decided not to collect such an object (e.g.,
- it has a __del__ method), its gc_refs is restored to GC_REACHABLE again.
- ----------------------------------------------------------------------------
- */
- #define GC_UNTRACKED _PyGC_REFS_UNTRACKED
- #define GC_REACHABLE _PyGC_REFS_REACHABLE
- #define GC_TENTATIVELY_UNREACHABLE _PyGC_REFS_TENTATIVELY_UNREACHABLE
- #define IS_TRACKED(o) ((AS_GC(o))->gc.gc_refs != GC_UNTRACKED)
- #define IS_REACHABLE(o) ((AS_GC(o))->gc.gc_refs == GC_REACHABLE)
- #define IS_TENTATIVELY_UNREACHABLE(o) ( \
- (AS_GC(o))->gc.gc_refs == GC_TENTATIVELY_UNREACHABLE)
- /*** list functions ***/
- static void
- gc_list_init(PyGC_Head *list)
- {
- list->gc.gc_prev = list;
- list->gc.gc_next = list;
- }
- static int
- gc_list_is_empty(PyGC_Head *list)
- {
- return (list->gc.gc_next == list);
- }
- #if 0
- /* This became unused after gc_list_move() was introduced. */
- /* Append `node` to `list`. */
- static void
- gc_list_append(PyGC_Head *node, PyGC_Head *list)
- {
- node->gc.gc_next = list;
- node->gc.gc_prev = list->gc.gc_prev;
- node->gc.gc_prev->gc.gc_next = node;
- list->gc.gc_prev = node;
- }
- #endif
- /* Remove `node` from the gc list it's currently in. */
- static void
- gc_list_remove(PyGC_Head *node)
- {
- node->gc.gc_prev->gc.gc_next = node->gc.gc_next;
- node->gc.gc_next->gc.gc_prev = node->gc.gc_prev;
- node->gc.gc_next = NULL; /* object is not currently tracked */
- }
- /* Move `node` from the gc list it's currently in (which is not explicitly
- * named here) to the end of `list`. This is semantically the same as
- * gc_list_remove(node) followed by gc_list_append(node, list).
- */
- static void
- gc_list_move(PyGC_Head *node, PyGC_Head *list)
- {
- PyGC_Head *new_prev;
- PyGC_Head *current_prev = node->gc.gc_prev;
- PyGC_Head *current_next = node->gc.gc_next;
- /* Unlink from current list. */
- current_prev->gc.gc_next = current_next;
- current_next->gc.gc_prev = current_prev;
- /* Relink at end of new list. */
- new_prev = node->gc.gc_prev = list->gc.gc_prev;
- new_prev->gc.gc_next = list->gc.gc_prev = node;
- node->gc.gc_next = list;
- }
- /* append list `from` onto list `to`; `from` becomes an empty list */
- static void
- gc_list_merge(PyGC_Head *from, PyGC_Head *to)
- {
- PyGC_Head *tail;
- assert(from != to);
- if (!gc_list_is_empty(from)) {
- tail = to->gc.gc_prev;
- tail->gc.gc_next = from->gc.gc_next;
- tail->gc.gc_next->gc.gc_prev = tail;
- to->gc.gc_prev = from->gc.gc_prev;
- to->gc.gc_prev->gc.gc_next = to;
- }
- gc_list_init(from);
- }
- static Py_ssize_t
- gc_list_size(PyGC_Head *list)
- {
- PyGC_Head *gc;
- Py_ssize_t n = 0;
- for (gc = list->gc.gc_next; gc != list; gc = gc->gc.gc_next) {
- n++;
- }
- return n;
- }
- /* Append objects in a GC list to a Python list.
- * Return 0 if all OK, < 0 if error (out of memory for list).
- */
- static int
- append_objects(PyObject *py_list, PyGC_Head *gc_list)
- {
- PyGC_Head *gc;
- for (gc = gc_list->gc.gc_next; gc != gc_list; gc = gc->gc.gc_next) {
- PyObject *op = FROM_GC(gc);
- if (op != py_list) {
- if (PyList_Append(py_list, op)) {
- return -1; /* exception */
- }
- }
- }
- return 0;
- }
- /*** end of list stuff ***/
- /* Set all gc_refs = ob_refcnt. After this, gc_refs is > 0 for all objects
- * in containers, and is GC_REACHABLE for all tracked gc objects not in
- * containers.
- */
- static void
- update_refs(PyGC_Head *containers)
- {
- PyGC_Head *gc = containers->gc.gc_next;
- for (; gc != containers; gc = gc->gc.gc_next) {
- assert(gc->gc.gc_refs == GC_REACHABLE);
- gc->gc.gc_refs = Py_REFCNT(FROM_GC(gc));
- /* Python's cyclic gc should never see an incoming refcount
- * of 0: if something decref'ed to 0, it should have been
- * deallocated immediately at that time.
- * Possible cause (if the assert triggers): a tp_dealloc
- * routine left a gc-aware object tracked during its teardown
- * phase, and did something-- or allowed something to happen --
- * that called back into Python. gc can trigger then, and may
- * see the still-tracked dying object. Before this assert
- * was added, such mistakes went on to allow gc to try to
- * delete the object again. In a debug build, that caused
- * a mysterious segfault, when _Py_ForgetReference tried
- * to remove the object from the doubly-linked list of all
- * objects a second time. In a release build, an actual
- * double deallocation occurred, which leads to corruption
- * of the allocator's internal bookkeeping pointers. That's
- * so serious that maybe this should be a release-build
- * check instead of an assert?
- */
- assert(gc->gc.gc_refs != 0);
- }
- }
- /* A traversal callback for subtract_refs. */
- static int
- visit_decref(PyObject *op, void *data)
- {
- assert(op != NULL);
- if (PyObject_IS_GC(op)) {
- PyGC_Head *gc = AS_GC(op);
- /* We're only interested in gc_refs for objects in the
- * generation being collected, which can be recognized
- * because only they have positive gc_refs.
- */
- assert(gc->gc.gc_refs != 0); /* else refcount was too small */
- if (gc->gc.gc_refs > 0)
- gc->gc.gc_refs--;
- }
- return 0;
- }
- /* Subtract internal references from gc_refs. After this, gc_refs is >= 0
- * for all objects in containers, and is GC_REACHABLE for all tracked gc
- * objects not in containers. The ones with gc_refs > 0 are directly
- * reachable from outside containers, and so can't be collected.
- */
- static void
- subtract_refs(PyGC_Head *containers)
- {
- traverseproc traverse;
- PyGC_Head *gc = containers->gc.gc_next;
- for (; gc != containers; gc=gc->gc.gc_next) {
- traverse = Py_TYPE(FROM_GC(gc))->tp_traverse;
- (void) traverse(FROM_GC(gc),
- (visitproc)visit_decref,
- NULL);
- }
- }
- /* A traversal callback for move_unreachable. */
- static int
- visit_reachable(PyObject *op, PyGC_Head *reachable)
- {
- if (PyObject_IS_GC(op)) {
- PyGC_Head *gc = AS_GC(op);
- const Py_ssize_t gc_refs = gc->gc.gc_refs;
- if (gc_refs == 0) {
- /* This is in move_unreachable's 'young' list, but
- * the traversal hasn't yet gotten to it. All
- * we need to do is tell move_unreachable that it's
- * reachable.
- */
- gc->gc.gc_refs = 1;
- }
- else if (gc_refs == GC_TENTATIVELY_UNREACHABLE) {
- /* This had gc_refs = 0 when move_unreachable got
- * to it, but turns out it's reachable after all.
- * Move it back to move_unreachable's 'young' list,
- * and move_unreachable will eventually get to it
- * again.
- */
- gc_list_move(gc, reachable);
- gc->gc.gc_refs = 1;
- }
- /* Else there's nothing to do.
- * If gc_refs > 0, it must be in move_unreachable's 'young'
- * list, and move_unreachable will eventually get to it.
- * If gc_refs == GC_REACHABLE, it's either in some other
- * generation so we don't care about it, or move_unreachable
- * already dealt with it.
- * If gc_refs == GC_UNTRACKED, it must be ignored.
- */
- else {
- assert(gc_refs > 0
- || gc_refs == GC_REACHABLE
- || gc_refs == GC_UNTRACKED);
- }
- }
- return 0;
- }
- /* Move the unreachable objects from young to unreachable. After this,
- * all objects in young have gc_refs = GC_REACHABLE, and all objects in
- * unreachable have gc_refs = GC_TENTATIVELY_UNREACHABLE. All tracked
- * gc objects not in young or unreachable still have gc_refs = GC_REACHABLE.
- * All objects in young after this are directly or indirectly reachable
- * from outside the original young; and all objects in unreachable are
- * not.
- */
- static void
- move_unreachable(PyGC_Head *young, PyGC_Head *unreachable)
- {
- PyGC_Head *gc = young->gc.gc_next;
- /* Invariants: all objects "to the left" of us in young have gc_refs
- * = GC_REACHABLE, and are indeed reachable (directly or indirectly)
- * from outside the young list as it was at entry. All other objects
- * from the original young "to the left" of us are in unreachable now,
- * and have gc_refs = GC_TENTATIVELY_UNREACHABLE. All objects to the
- * left of us in 'young' now have been scanned, and no objects here
- * or to the right have been scanned yet.
- */
- while (gc != young) {
- PyGC_Head *next;
- if (gc->gc.gc_refs) {
- /* gc is definitely reachable from outside the
- * original 'young'. Mark it as such, and traverse
- * its pointers to find any other objects that may
- * be directly reachable from it. Note that the
- * call to tp_traverse may append objects to young,
- * so we have to wait until it returns to determine
- * the next object to visit.
- */
- PyObject *op = FROM_GC(gc);
- traverseproc traverse = Py_TYPE(op)->tp_traverse;
- assert(gc->gc.gc_refs > 0);
- gc->gc.gc_refs = GC_REACHABLE;
- (void) traverse(op,
- (visitproc)visit_reachable,
- (void *)young);
- next = gc->gc.gc_next;
- }
- else {
- /* This *may* be unreachable. To make progress,
- * assume it is. gc isn't directly reachable from
- * any object we've already traversed, but may be
- * reachable from an object we haven't gotten to yet.
- * visit_reachable will eventually move gc back into
- * young if that's so, and we'll see it again.
- */
- next = gc->gc.gc_next;
- gc_list_move(gc, unreachable);
- gc->gc.gc_refs = GC_TENTATIVELY_UNREACHABLE;
- }
- gc = next;
- }
- }
- /* Return true if object has a finalization method.
- * CAUTION: An instance of an old-style class has to be checked for a
- *__del__ method, and earlier versions of this used to call PyObject_HasAttr,
- * which in turn could call the class's __getattr__ hook (if any). That
- * could invoke arbitrary Python code, mutating the object graph in arbitrary
- * ways, and that was the source of some excruciatingly subtle bugs.
- */
- static int
- has_finalizer(PyObject *op)
- {
- if (PyInstance_Check(op)) {
- assert(delstr != NULL);
- return _PyInstance_Lookup(op, delstr) != NULL;
- }
- else if (PyType_HasFeature(op->ob_type, Py_TPFLAGS_HEAPTYPE))
- return op->ob_type->tp_del != NULL;
- else if (PyGen_CheckExact(op))
- return PyGen_NeedsFinalizing((PyGenObject *)op);
- else
- return 0;
- }
- /* Move the objects in unreachable with __del__ methods into `finalizers`.
- * Objects moved into `finalizers` have gc_refs set to GC_REACHABLE; the
- * objects remaining in unreachable are left at GC_TENTATIVELY_UNREACHABLE.
- */
- static void
- move_finalizers(PyGC_Head *unreachable, PyGC_Head *finalizers)
- {
- PyGC_Head *gc;
- PyGC_Head *next;
- /* March over unreachable. Move objects with finalizers into
- * `finalizers`.
- */
- for (gc = unreachable->gc.gc_next; gc != unreachable; gc = next) {
- PyObject *op = FROM_GC(gc);
- assert(IS_TENTATIVELY_UNREACHABLE(op));
- next = gc->gc.gc_next;
- if (has_finalizer(op)) {
- gc_list_move(gc, finalizers);
- gc->gc.gc_refs = GC_REACHABLE;
- }
- }
- }
- /* A traversal callback for move_finalizer_reachable. */
- static int
- visit_move(PyObject *op, PyGC_Head *tolist)
- {
- if (PyObject_IS_GC(op)) {
- if (IS_TENTATIVELY_UNREACHABLE(op)) {
- PyGC_Head *gc = AS_GC(op);
- gc_list_move(gc, tolist);
- gc->gc.gc_refs = GC_REACHABLE;
- }
- }
- return 0;
- }
- /* Move objects that are reachable from finalizers, from the unreachable set
- * into finalizers set.
- */
- static void
- move_finalizer_reachable(PyGC_Head *finalizers)
- {
- traverseproc traverse;
- PyGC_Head *gc = finalizers->gc.gc_next;
- for (; gc != finalizers; gc = gc->gc.gc_next) {
- /* Note that the finalizers list may grow during this. */
- traverse = Py_TYPE(FROM_GC(gc))->tp_traverse;
- (void) traverse(FROM_GC(gc),
- (visitproc)visit_move,
- (void *)finalizers);
- }
- }
- /* Clear all weakrefs to unreachable objects, and if such a weakref has a
- * callback, invoke it if necessary. Note that it's possible for such
- * weakrefs to be outside the unreachable set -- indeed, those are precisely
- * the weakrefs whose callbacks must be invoked. See gc_weakref.txt for
- * overview & some details. Some weakrefs with callbacks may be reclaimed
- * directly by this routine; the number reclaimed is the return value. Other
- * weakrefs with callbacks may be moved into the `old` generation. Objects
- * moved into `old` have gc_refs set to GC_REACHABLE; the objects remaining in
- * unreachable are left at GC_TENTATIVELY_UNREACHABLE. When this returns,
- * no object in `unreachable` is weakly referenced anymore.
- */
- static int
- handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old)
- {
- PyGC_Head *gc;
- PyObject *op; /* generally FROM_GC(gc) */
- PyWeakReference *wr; /* generally a cast of op */
- PyGC_Head wrcb_to_call; /* weakrefs with callbacks to call */
- PyGC_Head *next;
- int num_freed = 0;
- gc_list_init(&wrcb_to_call);
- /* Clear all weakrefs to the objects in unreachable. If such a weakref
- * also has a callback, move it into `wrcb_to_call` if the callback
- * needs to be invoked. Note that we cannot invoke any callbacks until
- * all weakrefs to unreachable objects are cleared, lest the callback
- * resurrect an unreachable object via a still-active weakref. We
- * make another pass over wrcb_to_call, invoking callbacks, after this
- * pass completes.
- */
- for (gc = unreachable->gc.gc_next; gc != unreachable; gc = next) {
- PyWeakReference **wrlist;
- op = FROM_GC(gc);
- assert(IS_TENTATIVELY_UNREACHABLE(op));
- next = gc->gc.gc_next;
- if (! PyType_SUPPORTS_WEAKREFS(Py_TYPE(op)))
- continue;
- /* It supports weakrefs. Does it have any? */
- wrlist = (PyWeakReference **)
- PyObject_GET_WEAKREFS_LISTPTR(op);
- /* `op` may have some weakrefs. March over the list, clear
- * all the weakrefs, and move the weakrefs with callbacks
- * that must be called into wrcb_to_call.
- */
- for (wr = *wrlist; wr != NULL; wr = *wrlist) {
- PyGC_Head *wrasgc; /* AS_GC(wr) */
- /* _PyWeakref_ClearRef clears the weakref but leaves
- * the callback pointer intact. Obscure: it also
- * changes *wrlist.
- */
- assert(wr->wr_object == op);
- _PyWeakref_ClearRef(wr);
- assert(wr->wr_object == Py_None);
- if (wr->wr_callback == NULL)
- continue; /* no callback */
- /* Headache time. `op` is going away, and is weakly referenced by
- * `wr`, which has a callback. Should the callback be invoked? If wr
- * is also trash, no:
- *
- * 1. There's no need to call it. The object and the weakref are
- * both going away, so it's legitimate to pretend the weakref is
- * going away first. The user has to ensure a weakref outlives its
- * referent if they want a guarantee that the wr callback will get
- * invoked.
- *
- * 2. It may be catastrophic to call it. If the callback is also in
- * cyclic trash (CT), then although the CT is unreachable from
- * outside the current generation, CT may be reachable from the
- * callback. Then the callback could resurrect insane objects.
- *
- * Since the callback is never needed and may be unsafe in this case,
- * wr is simply left in the unreachable set. Note that because we
- * already called _PyWeakref_ClearRef(wr), its callback will never
- * trigger.
- *
- * OTOH, if wr isn't part of CT, we should invoke the callback: the
- * weakref outlived the trash. Note that since wr isn't CT in this
- * case, its callback can't be CT either -- wr acted as an external
- * root to this generation, and therefore its callback did too. So
- * nothing in CT is reachable from the callback either, so it's hard
- * to imagine how calling it later could create a problem for us. wr
- * is moved to wrcb_to_call in this case.
- */
- if (IS_TENTATIVELY_UNREACHABLE(wr))
- continue;
- assert(IS_REACHABLE(wr));
- /* Create a new reference so that wr can't go away
- * before we can process it again.
- */
- Py_INCREF(wr);
- /* Move wr to wrcb_to_call, for the next pass. */
- wrasgc = AS_GC(wr);
- assert(wrasgc != next); /* wrasgc is reachable, but
- next isn't, so they can't
- be the same */
- gc_list_move(wrasgc, &wrcb_to_call);
- }
- }
- /* Invoke the callbacks we decided to honor. It's safe to invoke them
- * because they can't reference unreachable objects.
- */
- while (! gc_list_is_empty(&wrcb_to_call)) {
- PyObject *temp;
- PyObject *callback;
- gc = wrcb_to_call.gc.gc_next;
- op = FROM_GC(gc);
- assert(IS_REACHABLE(op));
- assert(PyWeakref_Check(op));
- wr = (PyWeakReference *)op;
- callback = wr->wr_callback;
- assert(callback != NULL);
- /* copy-paste of weakrefobject.c's handle_callback() */
- temp = PyObject_CallFunctionObjArgs(callback, wr, NULL);
- if (temp == NULL)
- PyErr_WriteUnraisable(callback);
- else
- Py_DECREF(temp);
- /* Give up the reference we created in the first pass. When
- * op's refcount hits 0 (which it may or may not do right now),
- * op's tp_dealloc will decref op->wr_callback too. Note
- * that the refcount probably will hit 0 now, and because this
- * weakref was reachable to begin with, gc didn't already
- * add it to its count of freed objects. Example: a reachable
- * weak value dict maps some key to this reachable weakref.
- * The callback removes this key->weakref mapping from the
- * dict, leaving no other references to the weakref (excepting
- * ours).
- */
- Py_DECREF(op);
- if (wrcb_to_call.gc.gc_next == gc) {
- /* object is still alive -- move it */
- gc_list_move(gc, old);
- }
- else
- ++num_freed;
- }
- return num_freed;
- }
- static void
- debug_instance(char *msg, PyInstanceObject *inst)
- {
- char *cname;
- /* simple version of instance_repr */
- PyObject *classname = inst->in_class->cl_name;
- if (classname != NULL && PyString_Check(classname))
- cname = PyString_AsString(classname);
- else
- cname = "?";
- PySys_WriteStderr("gc: %.100s <%.100s instance at %p>\n",
- msg, cname, inst);
- }
- static void
- debug_cycle(char *msg, PyObject *op)
- {
- if ((debug & DEBUG_INSTANCES) && PyInstance_Check(op)) {
- debug_instance(msg, (PyInstanceObject *)op);
- }
- else if (debug & DEBUG_OBJECTS) {
- PySys_WriteStderr("gc: %.100s <%.100s %p>\n",
- msg, Py_TYPE(op)->tp_name, op);
- }
- }
- /* Handle uncollectable garbage (cycles with finalizers, and stuff reachable
- * only from such cycles).
- * If DEBUG_SAVEALL, all objects in finalizers are appended to the module
- * garbage list (a Python list), else only the objects in finalizers with
- * __del__ methods are appended to garbage. All objects in finalizers are
- * merged into the old list regardless.
- * Returns 0 if all OK, <0 on error (out of memory to grow the garbage list).
- * The finalizers list is made empty on a successful return.
- */
- static int
- handle_finalizers(PyGC_Head *finalizers, PyGC_Head *old)
- {
- PyGC_Head *gc = finalizers->gc.gc_next;
- if (garbage == NULL) {
- garbage = PyList_New(0);
- if (garbage == NULL)
- Py_FatalError("gc couldn't create gc.garbage list");
- }
- for (; gc != finalizers; gc = gc->gc.gc_next) {
- PyObject *op = FROM_GC(gc);
- if ((debug & DEBUG_SAVEALL) || has_finalizer(op)) {
- if (PyList_Append(garbage, op) < 0)
- return -1;
- }
- }
- gc_list_merge(finalizers, old);
- return 0;
- }
- /* Break reference cycles by clearing the containers involved. This is
- * tricky business as the lists can be changing and we don't know which
- * objects may be freed. It is possible I screwed something up here.
- */
- static void
- delete_garbage(PyGC_Head *collectable, PyGC_Head *old)
- {
- inquiry clear;
- while (!gc_list_is_empty(collectable)) {
- PyGC_Head *gc = collectable->gc.gc_next;
- PyObject *op = FROM_GC(gc);
- assert(IS_TENTATIVELY_UNREACHABLE(op));
- if (debug & DEBUG_SAVEALL) {
- PyList_Append(garbage, op);
- }
- else {
- if ((clear = Py_TYPE(op)->tp_clear) != NULL) {
- Py_INCREF(op);
- clear(op);
- Py_DECREF(op);
- }
- }
- if (collectable->gc.gc_next == gc) {
- /* object is still alive, move it, it may die later */
- gc_list_move(gc, old);
- gc->gc.gc_refs = GC_REACHABLE;
- }
- }
- }
- /* Clear all free lists
- * All free lists are cleared during the collection of the highest generation.
- * Allocated items in the free list may keep a pymalloc arena occupied.
- * Clearing the free lists may give back memory to the OS earlier.
- */
- static void
- clear_freelists(void)
- {
- (void)PyMethod_ClearFreeList();
- (void)PyFrame_ClearFreeList();
- (void)PyCFunction_ClearFreeList();
- (void)PyTuple_ClearFreeList();
- (void)PyUnicode_ClearFreeList();
- (void)PyInt_ClearFreeList();
- (void)PyFloat_ClearFreeList();
- }
- static double
- get_time(void)
- {
- double result = 0;
- if (tmod != NULL) {
- PyObject *f = PyObject_CallMethod(tmod, "time", NULL);
- if (f == NULL) {
- PyErr_Clear();
- }
- else {
- if (PyFloat_Check(f))
- result = PyFloat_AsDouble(f);
- Py_DECREF(f);
- }
- }
- return result;
- }
- /* This is the main function. Read this to understand how the
- * collection process works. */
- static Py_ssize_t
- collect(int generation)
- {
- int i;
- Py_ssize_t m = 0; /* # objects collected */
- Py_ssize_t n = 0; /* # unreachable objects that couldn't be collected */
- PyGC_Head *young; /* the generation we are examining */
- PyGC_Head *old; /* next older generation */
- PyGC_Head unreachable; /* non-problematic unreachable trash */
- PyGC_Head finalizers; /* objects with, & reachable from, __del__ */
- PyGC_Head *gc;
- double t1 = 0.0;
- if (delstr == NULL) {
- delstr = PyString_InternFromString("__del__");
- if (delstr == NULL)
- Py_FatalError("gc couldn't allocate \"__del__\"");
- }
- if (debug & DEBUG_STATS) {
- t1 = get_time();
- PySys_WriteStderr("gc: collecting generation %d...\n",
- generation);
- PySys_WriteStderr("gc: objects in each generation:");
- for (i = 0; i < NUM_GENERATIONS; i++)
- PySys_WriteStderr(" %" PY_FORMAT_SIZE_T "d",
- gc_list_size(GEN_HEAD(i)));
- PySys_WriteStderr("\n");
- }
- /* update collection and allocation counters */
- if (generation+1 < NUM_GENERATIONS)
- generations[generation+1].count += 1;
- for (i = 0; i <= generation; i++)
- generations[i].count = 0;
- /* merge younger generations with one we are currently collecting */
- for (i = 0; i < generation; i++) {
- gc_list_merge(GEN_HEAD(i), GEN_HEAD(generation));
- }
- /* handy references */
- young = GEN_HEAD(generation);
- if (generation < NUM_GENERATIONS-1)
- old = GEN_HEAD(generation+1);
- else
- old = young;
- /* Using ob_refcnt and gc_refs, calculate which objects in the
- * container set are reachable from outside the set (i.e., have a
- * refcount greater than 0 when all the references within the
- * set are taken into account).
- */
- update_refs(young);
- subtract_refs(young);
- /* Leave everything reachable from outside young in young, and move
- * everything else (in young) to unreachable.
- * NOTE: This used to move the reachable objects into a reachable
- * set instead. But most things usually turn out to be reachable,
- * so it's more efficient to move the unreachable things.
- */
- gc_list_init(&unreachable);
- move_unreachable(young, &unreachable);
- /* Move reachable objects to next generation. */
- if (young != old) {
- if (generation == NUM_GENERATIONS - 2) {
- long_lived_pending += gc_list_size(young);
- }
- gc_list_merge(young, old);
- }
- else {
- long_lived_pending = 0;
- long_lived_total = gc_list_size(young);
- }
- /* All objects in unreachable are trash, but objects reachable from
- * finalizers can't safely be deleted. Python programmers should take
- * care not to create such things. For Python, finalizers means
- * instance objects with __del__ methods. Weakrefs with callbacks
- * can also call arbitrary Python code but they will be dealt with by
- * handle_weakrefs().
- */
- gc_list_init(&finalizers);
- move_finalizers(&unreachable, &finalizers);
- /* finalizers contains the unreachable objects with a finalizer;
- * unreachable objects reachable *from* those are also uncollectable,
- * and we move those into the finalizers list too.
- */
- move_finalizer_reachable(&finalizers);
- /* Collect statistics on collectable objects found and print
- * debugging information.
- */
- for (gc = unreachable.gc.gc_next; gc != &unreachable;
- gc = gc->gc.gc_next) {
- m++;
- if (debug & DEBUG_COLLECTABLE) {
- debug_cycle("collectable", FROM_GC(gc));
- }
- }
- /* Clear weakrefs and invoke callbacks as necessary. */
- m += handle_weakrefs(&unreachable, old);
- /* Call tp_clear on objects in the unreachable set. This will cause
- * the reference cycles to be broken. It may also cause some objects
- * in finalizers to be freed.
- */
- delete_garbage(&unreachable, old);
- /* Collect statistics on uncollectable objects found and print
- * debugging information. */
- for (gc = finalizers.gc.gc_next;
- gc != &finalizers;
- gc = gc->gc.gc_next) {
- n++;
- if (debug & DEBUG_UNCOLLECTABLE)
- debug_cycle("uncollectable", FROM_GC(gc));
- }
- if (debug & DEBUG_STATS) {
- double t2 = get_time();
- if (m == 0 && n == 0)
- PySys_WriteStderr("gc: done");
- else
- PySys_WriteStderr(
- "gc: done, "
- "%" PY_FORMAT_SIZE_T "d unreachable, "
- "%" PY_FORMAT_SIZE_T "d uncollectable",
- n+m, n);
- if (t1 && t2) {
- PySys_WriteStderr(", %.4fs elapsed", t2-t1);
- }
- PySys_WriteStderr(".\n");
- }
- /* Append instances in the uncollectable set to a Python
- * reachable list of garbage. The programmer has to deal with
- * this if they insist on creating this type of structure.
- */
- (void)handle_finalizers(&finalizers, old);
- /* Clear free list only during the collection of the higest
- * generation */
- if (generation == NUM_GENERATIONS-1) {
- clear_freelists();
- }
- if (PyErr_Occurred()) {
- if (gc_str == NULL)
- gc_str = PyString_FromString("garbage collection");
- PyErr_WriteUnraisable(gc_str);
- Py_FatalError("unexpected exception during garbage collection");
- }
- return n+m;
- }
- static Py_ssize_t
- collect_generations(void)
- {
- int i;
- Py_ssize_t n = 0;
- /* Find the oldest generation (higest numbered) where the count
- * exceeds the threshold. Objects in the that generation and
- * generations younger than it will be collected. */
- for (i = NUM_GENERATIONS-1; i >= 0; i--) {
- if (generations[i].count > generations[i].threshold) {
- /* Avoid quadratic performance degradation in number
- of tracked objects. See comments at the beginning
- of this file, and issue #4074.
- */
- if (i == NUM_GENERATIONS - 1
- && long_lived_pending < long_lived_total / 4)
- continue;
- n = collect(i);
- break;
- }
- }
- return n;
- }
- PyDoc_STRVAR(gc_enable__doc__,
- "enable() -> None\n"
- "\n"
- "Enable automatic garbage collection.\n");
- static PyObject *
- gc_enable(PyObject *self, PyObject *noargs)
- {
- enabled = 1;
- Py_INCREF(Py_None);
- return Py_None;
- }
- PyDoc_STRVAR(gc_disable__doc__,
- "disable() -> None\n"
- "\n"
- "Disable automatic garbage collection.\n");
- static PyObject *
- gc_disable(PyObject *self, PyObject *noargs)
- {
- enabled = 0;
- Py_INCREF(Py_None);
- return Py_None;
- }
- PyDoc_STRVAR(gc_isenabled__doc__,
- "isenabled() -> status\n"
- "\n"
- "Returns true if automatic garbage collection is enabled.\n");
- static PyObject *
- gc_isenabled(PyObject *self, PyObject *noargs)
- {
- return PyBool_FromLong((long)enabled);
- }
- PyDoc_STRVAR(gc_collect__doc__,
- "collect([generation]) -> n\n"
- "\n"
- "With no arguments, run a full collection. The optional argument\n"
- "may be an integer specifying which generation to collect. A ValueError\n"
- "is raised if the generation number is invalid.\n\n"
- "The number of unreachable objects is returned.\n");
- static PyObject *
- gc_collect(PyObject *self, PyObject *args, PyObject *kws)
- {
- static char *keywords[] = {"generation", NULL};
- int genarg = NUM_GENERATIONS - 1;
- Py_ssize_t n;
- if (!PyArg_ParseTupleAndKeywords(args, kws, "|i", keywords, &genarg))
- return NULL;
- else if (genarg < 0 || genarg >= NUM_GENERATIONS) {
- PyErr_SetString(PyExc_ValueError, "invalid generation");
- return NULL;
- }
- if (collecting)
- n = 0; /* already collecting, don't do anything */
- else {
- collecting = 1;
- n = collect(genarg);
- collecting = 0;
- }
- return PyInt_FromSsize_t(n);
- }
- PyDoc_STRVAR(gc_set_debug__doc__,
- "set_debug(flags) -> None\n"
- "\n"
- "Set the garbage collection debugging flags. Debugging information is\n"
- "written to sys.stderr.\n"
- "\n"
- "flags is an integer and can have the following bits turned on:\n"
- "\n"
- " DEBUG_STATS - Print statistics during collection.\n"
- " DEBUG_COLLECTABLE - Print collectable objects found.\n"
- " DEBUG_UNCOLLECTABLE - Print unreachable but uncollectable objects found.\n"
- " DEBUG_INSTANCES - Print instance objects.\n"
- " DEBUG_OBJECTS - Print objects other than instances.\n"
- " DEBUG_SAVEALL - Save objects to gc.garbage rather than freeing them.\n"
- " DEBUG_LEAK - Debug leaking programs (everything but STATS).\n");
- static PyObject *
- gc_set_debug(PyObject *self, PyObject *args)
- {
- if (!PyArg_ParseTuple(args, "i:set_debug", &debug))
- return NULL;
- Py_INCREF(Py_None);
- return Py_None;
- }
- PyDoc_STRVAR(gc_get_debug__doc__,
- "get_debug() -> flags\n"
- "\n"
- "Get the garbage collection debugging flags.\n");
- static PyObject *
- gc_get_debug(PyObject *self, PyObject *noargs)
- {
- return Py_BuildValue("i", debug);
- }
- PyDoc_STRVAR(gc_set_thresh__doc__,
- "set_threshold(threshold0, [threshold1, threshold2]) -> None\n"
- "\n"
- "Sets the collection thresholds. Setting threshold0 to zero disables\n"
- "collection.\n");
- static PyObject *
- gc_set_thresh(PyObject *self, PyObject *args)
- {
- int i;
- if (!PyArg_ParseTuple(args, "i|ii:set_threshold",
- &generations[0].threshold,
- &generations[1].threshold,
- &generations[2].threshold))
- return NULL;
- for (i = 2; i < NUM_GENERATIONS; i++) {
- /* generations higher than 2 get the same threshold */
- generations[i].threshold = generations[2].threshold;
- }
- Py_INCREF(Py_None);
- return Py_None;
- }
- PyDoc_STRVAR(gc_get_thresh__doc__,
- "get_threshold() -> (threshold0, threshold1, threshold2)\n"
- "\n"
- "Return the current collection thresholds\n");
- static PyObject *
- gc_get_thresh(PyObject *self, PyObject *noargs)
- {
- return Py_BuildValue("(iii)",
- generations[0].threshold,
- generations[1].threshold,
- generations[2].threshold);
- }
- PyDoc_STRVAR(gc_get_count__doc__,
- "get_count() -> (count0, count1, count2)\n"
- "\n"
- "Return the current collection counts\n");
- static PyObject *
- gc_get_count(PyObject *self, PyObject *noargs)
- {
- return Py_BuildValue("(iii)",
- generations[0].count,
- generations[1].count,
- generations[2].count);
- }
- static int
- referrersvisit(PyObject* obj, PyObject *objs)
- {
- Py_ssize_t i;
- for (i = 0; i < PyTuple_GET_SIZE(objs); i++)
- if (PyTuple_GET_ITEM(objs, i) == obj)
- return 1;
- return 0;
- }
- static int
- gc_referrers_for(PyObject *objs, PyGC_Head *list, PyObject *resultlist)
- {
- PyGC_Head *gc;
- PyObject *obj;
- traverseproc traverse;
- for (gc = list->gc.gc_next; gc != list; gc = gc->gc.gc_next) {
- obj = FROM_GC(gc);
- traverse = Py_TYPE(obj)->tp_traverse;
- if (obj == objs || obj == resultlist)
- continue;
- if (traverse(obj, (visitproc)referrersvisit, objs)) {
- if (PyList_Append(resultlist, obj) < 0)
- return 0; /* error */
- }
- }
- return 1; /* no error */
- }
- PyDoc_STRVAR(gc_get_referrers__doc__,
- "get_referrers(*objs) -> list\n\
- Return the list of objects that directly refer to any of objs.");
- static PyObject *
- gc_get_referrers(PyObject *self, PyObject *args)
- {
- int i;
- PyObject *result = PyList_New(0);
- if (!result) return NULL;
- for (i = 0; i < NUM_GENERATIONS; i++) {
- if (!(gc_referrers_for(args, GEN_HEAD(i), result))) {
- Py_DECREF(result);
- return NULL;
- }
- }
- return result;
- }
- /* Append obj to list; return true if error (out of memory), false if OK. */
- static int
- referentsvisit(PyObject *obj, PyObject *list)
- {
- return PyList_Append(list, obj) < 0;
- }
- PyDoc_STRVAR(gc_get_referents__doc__,
- "get_referents(*objs) -> list\n\
- Return the list of objects that are directly referred to by objs.");
- static PyObject *
- gc_get_referents(PyObject *self, PyObject *args)
- {
- Py_ssize_t i;
- PyObject *result = PyList_New(0);
- if (result == NULL)
- return NULL;
- for (i = 0; i < PyTuple_GET_SIZE(args); i++) {
- traverseproc traverse;
- PyObject *obj = PyTuple_GET_ITEM(args, i);
- if (! PyObject_IS_GC(obj))
- continue;
- traverse = Py_TYPE(obj)->tp_traverse;
- if (! traverse)
- continue;
- if (traverse(obj, (visitproc)referentsvisit, result)) {
- Py_DECREF(result);
- return NULL;
- }
- }
- return result;
- }
- PyDoc_STRVAR(gc_get_objects__doc__,
- "get_objects() -> [...]\n"
- "\n"
- "Return a list of objects tracked by the collector (excluding the list\n"
- "returned).\n");
- static PyObject *
- gc_get_objects(PyObject *self, PyObject *noargs)
- {
- int i;
- PyObject* result;
- result = PyList_New(0);
- if (result == NULL)
- return NULL;
- for (i = 0; i < NUM_GENERATIONS; i++) {
- if (append_objects(result, GEN_HEAD(i))) {
- Py_DECREF(result);
- return NULL;
- }
- }
- return result;
- }
- PyDoc_STRVAR(gc__doc__,
- "This module provides access to the garbage collector for reference cycles.\n"
- "\n"
- "enable() -- Enable automatic garbage collection.\n"
- "disable() -- Disable automatic garbage collection.\n"
- "isenabled() -- Returns true if automatic collection is enabled.\n"
- "collect() -- Do a full collection right now.\n"
- "get_count() -- Return the current collection counts.\n"
- "set_debug() -- Set debugging flags.\n"
- "get_debug() -- Get debugging flags.\n"
- "set_threshold() -- Set the collection thresholds.\n"
- "get_threshold() -- Return the current the collection thresholds.\n"
- "get_objects() -- Return a list of all objects tracked by the collector.\n"
- "get_referrers() -- Return the list of objects that refer to an object.\n"
- "get_referents() -- Return the list of objects that an object refers to.\n");
- static PyMethodDef GcMethods[] = {
- {"enable", gc_enable, METH_NOARGS, gc_enable__doc__},
- {"disable", gc_disable, METH_NOARGS, gc_disable__doc__},
- {"isenabled", gc_isenabled, METH_NOARGS, gc_isenabled__doc__},
- {"set_debug", gc_set_debug, METH_VARARGS, gc_set_debug__doc__},
- {"get_debug", gc_get_debug, METH_NOARGS, gc_get_debug__doc__},
- {"get_count", gc_get_count, METH_NOARGS, gc_get_count__doc__},
- {"set_threshold", gc_set_thresh, METH_VARARGS, gc_set_thresh__doc__},
- {"get_threshold", gc_get_thresh, METH_NOARGS, gc_get_thresh__doc__},
- {"collect", (PyCFunction)gc_collect,
- METH_VARARGS | METH_KEYWORDS, gc_collect__doc__},
- {"get_objects", gc_get_objects,METH_NOARGS, gc_get_objects__doc__},
- {"get_referrers", gc_get_referrers, METH_VARARGS,
- gc_get_referrers__doc__},
- {"get_referents", gc_get_referents, METH_VARARGS,
- gc_get_referents__doc__},
- {NULL, NULL} /* Sentinel */
- };
- PyMODINIT_FUNC
- initgc(void)
- {
- PyObject *m;
- m = Py_InitModule4("gc",
- GcMethods,
- gc__doc__,
- NULL,
- PYTHON_API_VERSION);
- if (m == NULL)
- return;
- if (garbage == NULL) {
- garbage = PyList_New(0);
- if (garbage == NULL)
- return;
- }
- Py_INCREF(garbage);
- if (PyModule_AddObject(m, "garbage", garbage) < 0)
- return;
- /* Importing can't be done in collect() because collect()
- * can be called via PyGC_Collect() in Py_Finalize().
- * This wouldn't be a problem, except that <initialized> is
- * reset to 0 before calling collect which trips up
- * the import and triggers an assertion.
- */
- if (tmod == NULL) {
- tmod = PyImport_ImportModuleNoBlock("time");
- if (tmod == NULL)
- PyErr_Clear();
- }
- #define ADD_INT(NAME) if (PyModule_AddIntConstant(m, #NAME, NAME) < 0) return
- ADD_INT(DEBUG_STATS);
- ADD_INT(DEBUG_COLLECTABLE);
- ADD_INT(DEBUG_UNCOLLECTABLE);
- ADD_INT(DEBUG_INSTANCES);
- ADD_INT(DEBUG_OBJECTS);
- ADD_INT(DEBUG_SAVEALL);
- ADD_INT(DEBUG_LEAK);
- #undef ADD_INT
- }
- /* API to invoke gc.collect() from C */
- Py_ssize_t
- PyGC_Collect(void)
- {
- Py_ssize_t n;
- if (collecting)
- n = 0; /* already collecting, don't do anything */
- else {
- collecting = 1;
- n = collect(NUM_GENERATIONS - 1);
- collecting = 0;
- }
- return n;
- }
- /* for debugging */
- void
- _PyGC_Dump(PyGC_Head *g)
- {
- _PyObject_Dump(FROM_GC(g));
- }
- /* extension modules might be compiled with GC support so these
- functions must always be available */
- #undef PyObject_GC_Track
- #undef PyObject_GC_UnTrack
- #undef PyObject_GC_Del
- #undef _PyObject_GC_Malloc
- void
- PyObject_GC_Track(void *op)
- {
- _PyObject_GC_TRACK(op);
- }
- /* for binary compatibility with 2.2 */
- void
- _PyObject_GC_Track(PyObject *op)
- {
- PyObject_GC_Track(op);
- }
- void
- PyObject_GC_UnTrack(void *op)
- {
- /* Obscure: the Py_TRASHCAN mechanism requires that we be able to
- * call PyObject_GC_UnTrack twice on an object.
- */
- if (IS_TRACKED(op))
- _PyObject_GC_UNTRACK(op);
- }
- /* for binary compatibility with 2.2 */
- void
- _PyObject_GC_UnTrack(PyObject *op)
- {
- PyObject_GC_UnTrack(op);
- }
- PyObject *
- _PyObject_GC_Malloc(size_t basicsize)
- {
- PyObject *op;
- PyGC_Head *g;
- if (basicsize > PY_SSIZE_T_MAX - sizeof(PyGC_Head))
- return PyErr_NoMemory();
- g = (PyGC_Head *)PyObject_MALLOC(
- sizeof(PyGC_Head) + basicsize);
- if (g == NULL)
- return PyErr_NoMemory();
- g->gc.gc_refs = GC_UNTRACKED;
- generations[0].count++; /* number of allocated GC objects */
- if (generations[0].count > generations[0].threshold &&
- enabled &&
- generations[0].threshold &&
- !collecting &&
- !PyErr_Occurred()) {
- collecting = 1;
- collect_generations();
- collecting = 0;
- }
- op = FROM_GC(g);
- return op;
- }
- PyObject *
- _PyObject_GC_New(PyTypeObject *tp)
- {
- PyObject *op = _PyObject_GC_Malloc(_PyObject_SIZE(tp));
- if (op != NULL)
- op = PyObject_INIT(op, tp);
- return op;
- }
- PyVarObject *
- _PyObject_GC_NewVar(PyTypeObject *tp, Py_ssize_t nitems)
- {
- const size_t size = _PyObject_VAR_SIZE(tp, nitems);
- PyVarObject *op = (PyVarObject *) _PyObject_GC_Malloc(size);
- if (op != NULL)
- op = PyObject_INIT_VAR(op, tp, nitems);
- return op;
- }
- PyVarObject *
- _PyObject_GC_Resize(PyVarObject *op, Py_ssize_t nitems)
- {
- const size_t basicsize = _PyObject_VAR_SIZE(Py_TYPE(op), nitems);
- PyGC_Head *g = AS_GC(op);
- if (basicsize > PY_SSIZE_T_MAX - sizeof(PyGC_Head))
- return (PyVarObject *)PyErr_NoMemory();
- g = (PyGC_Head *)PyObject_REALLOC(g, sizeof(PyGC_Head) + basicsize);
- if (g == NULL)
- return (PyVarObject *)PyErr_NoMemory();
- op = (PyVarObject *) FROM_GC(g);
- Py_SIZE(op) = nitems;
- return op;
- }
- void
- PyObject_GC_Del(void *op)
- {
- PyGC_Head *g = AS_GC(op);
- if (IS_TRACKED(op))
- gc_list_remove(g);
- if (generations[0].count > 0) {
- generations[0].count--;
- }
- PyObject_FREE(g);
- }
- /* for binary compatibility with 2.2 */
- #undef _PyObject_GC_Del
- void
- _PyObject_GC_Del(PyObject *op)
- {
- PyObject_GC_Del(op);
- }