diff options
Diffstat (limited to 'AppPkg/Applications/Python/Python-2.7.10/Modules/gcmodule.c')
| -rw-r--r-- | AppPkg/Applications/Python/Python-2.7.10/Modules/gcmodule.c | 1570 |
1 files changed, 1570 insertions, 0 deletions
diff --git a/AppPkg/Applications/Python/Python-2.7.10/Modules/gcmodule.c b/AppPkg/Applications/Python/Python-2.7.10/Modules/gcmodule.c new file mode 100644 index 0000000000..1746887391 --- /dev/null +++ b/AppPkg/Applications/Python/Python-2.7.10/Modules/gcmodule.c @@ -0,0 +1,1570 @@ +/*
+
+ 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 Löwis 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
+*/
+
+/*
+ NOTE: about untracking of mutable objects.
+
+ Certain types of container cannot participate in a reference cycle, and
+ so do not need to be tracked by the garbage collector. Untracking these
+ objects reduces the cost of garbage collections. However, determining
+ which objects may be untracked is not free, and the costs must be
+ weighed against the benefits for garbage collection.
+
+ There are two possible strategies for when to untrack a container:
+
+ i) When the container is created.
+ ii) When the container is examined by the garbage collector.
+
+ Tuples containing only immutable objects (integers, strings etc, and
+ recursively, tuples of immutable objects) do not need to be tracked.
+ The interpreter creates a large number of tuples, many of which will
+ not survive until garbage collection. It is therefore not worthwhile
+ to untrack eligible tuples at creation time.
+
+ Instead, all tuples except the empty tuple are tracked when created.
+ During garbage collection it is determined whether any surviving tuples
+ can be untracked. A tuple can be untracked if all of its contents are
+ already not tracked. Tuples are examined for untracking in all garbage
+ collection cycles. It may take more than one cycle to untrack a tuple.
+
+ Dictionaries containing only immutable objects also do not need to be
+ tracked. Dictionaries are untracked when created. If a tracked item is
+ inserted into a dictionary (either as a key or value), the dictionary
+ becomes tracked. During a full garbage collection (all generations),
+ the collector will untrack any dictionaries whose contents are not
+ tracked.
+
+ The module provides the python function is_tracked(obj), which returns
+ the CURRENT tracking status of the object. Subsequent garbage
+ collections may change the tracking status of the object.
+
+ Untracking of certain containers was introduced in issue #4688, and
+ the algorithm was refined in response to issue #14775.
+*/
+
+/* 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;
+ if (PyTuple_CheckExact(op)) {
+ _PyTuple_MaybeUntrack(op);
+ }
+ }
+ 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;
+}
+
+/* Try to untrack all currently tracked dictionaries */
+static void
+untrack_dicts(PyGC_Head *head)
+{
+ PyGC_Head *next, *gc = head->gc.gc_next;
+ while (gc != head) {
+ PyObject *op = FROM_GC(gc);
+ next = gc->gc.gc_next;
+ if (PyDict_CheckExact(op))
+ _PyDict_MaybeUntrack(op);
+ gc = next;
+ }
+}
+
+/* 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();
+#ifdef Py_USING_UNICODE
+ (void)PyUnicode_ClearFreeList();
+#endif
+ (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) {
+ 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)));
+ t1 = get_time();
+ 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 {
+ /* We only untrack dicts in full collections, to avoid quadratic
+ dict build-up. See issue #14775. */
+ untrack_dicts(young);
+ 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 highest
+ * 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 (highest 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_is_tracked__doc__,
+"is_tracked(obj) -> bool\n"
+"\n"
+"Returns true if the object is tracked by the garbage collector.\n"
+"Simple atomic objects will return false.\n"
+);
+
+static PyObject *
+gc_is_tracked(PyObject *self, PyObject *obj)
+{
+ PyObject *result;
+
+ if (PyObject_IS_GC(obj) && IS_TRACKED(obj))
+ result = Py_True;
+ else
+ result = Py_False;
+ Py_INCREF(result);
+ 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"
+"is_tracked() -- Returns true if a given object is tracked.\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__},
+ {"is_tracked", gc_is_tracked, METH_O, gc_is_tracked__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);
+}
|