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08be72d0aa
except when configured --with-pydebug. Emit this warning from the GC shutdown procedure, rather than just printing to stderr.
1522 lines
48 KiB
C
1522 lines
48 KiB
C
/*
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Reference Cycle Garbage Collection
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==================================
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Neil Schemenauer <nas@arctrix.com>
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Based on a post on the python-dev list. Ideas from Guido van Rossum,
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Eric Tiedemann, and various others.
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http://www.arctrix.com/nas/python/gc/
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The following mailing list threads provide a historical perspective on
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the design of this module. Note that a fair amount of refinement has
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occurred since those discussions.
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http://mail.python.org/pipermail/python-dev/2000-March/002385.html
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http://mail.python.org/pipermail/python-dev/2000-March/002434.html
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http://mail.python.org/pipermail/python-dev/2000-March/002497.html
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For a highlevel view of the collection process, read the collect
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function.
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*/
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#include "Python.h"
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#include "frameobject.h" /* for PyFrame_ClearFreeList */
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/* Get an object's GC head */
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#define AS_GC(o) ((PyGC_Head *)(o)-1)
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/* Get the object given the GC head */
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#define FROM_GC(g) ((PyObject *)(((PyGC_Head *)g)+1))
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/*** Global GC state ***/
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struct gc_generation {
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PyGC_Head head;
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int threshold; /* collection threshold */
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int count; /* count of allocations or collections of younger
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generations */
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};
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#define NUM_GENERATIONS 3
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#define GEN_HEAD(n) (&generations[n].head)
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/* linked lists of container objects */
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static struct gc_generation generations[NUM_GENERATIONS] = {
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/* PyGC_Head, threshold, count */
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{{{GEN_HEAD(0), GEN_HEAD(0), 0}}, 700, 0},
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{{{GEN_HEAD(1), GEN_HEAD(1), 0}}, 10, 0},
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{{{GEN_HEAD(2), GEN_HEAD(2), 0}}, 10, 0},
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};
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PyGC_Head *_PyGC_generation0 = GEN_HEAD(0);
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static int enabled = 1; /* automatic collection enabled? */
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/* true if we are currently running the collector */
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static int collecting = 0;
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/* list of uncollectable objects */
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static PyObject *garbage = NULL;
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/* Python string to use if unhandled exception occurs */
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static PyObject *gc_str = NULL;
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/* Python string used to look for __del__ attribute. */
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static PyObject *delstr = NULL;
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/* This is the number of objects who survived the last full collection. It
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approximates the number of long lived objects tracked by the GC.
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(by "full collection", we mean a collection of the oldest generation).
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*/
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static Py_ssize_t long_lived_total = 0;
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/* This is the number of objects who survived all "non-full" collections,
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and are awaiting to undergo a full collection for the first time.
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*/
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static Py_ssize_t long_lived_pending = 0;
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/*
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NOTE: about the counting of long-lived objects.
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To limit the cost of garbage collection, there are two strategies;
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- make each collection faster, e.g. by scanning fewer objects
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- do less collections
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This heuristic is about the latter strategy.
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In addition to the various configurable thresholds, we only trigger a
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full collection if the ratio
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long_lived_pending / long_lived_total
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is above a given value (hardwired to 25%).
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The reason is that, while "non-full" collections (i.e., collections of
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the young and middle generations) will always examine roughly the same
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number of objects -- determined by the aforementioned thresholds --,
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the cost of a full collection is proportional to the total number of
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long-lived objects, which is virtually unbounded.
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Indeed, it has been remarked that doing a full collection every
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<constant number> of object creations entails a dramatic performance
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degradation in workloads which consist in creating and storing lots of
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long-lived objects (e.g. building a large list of GC-tracked objects would
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show quadratic performance, instead of linear as expected: see issue #4074).
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Using the above ratio, instead, yields amortized linear performance in
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the total number of objects (the effect of which can be summarized
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thusly: "each full garbage collection is more and more costly as the
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number of objects grows, but we do fewer and fewer of them").
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This heuristic was suggested by Martin von Löwis on python-dev in
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June 2008. His original analysis and proposal can be found at:
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http://mail.python.org/pipermail/python-dev/2008-June/080579.html
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*/
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/* set for debugging information */
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#define DEBUG_STATS (1<<0) /* print collection statistics */
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#define DEBUG_COLLECTABLE (1<<1) /* print collectable objects */
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#define DEBUG_UNCOLLECTABLE (1<<2) /* print uncollectable objects */
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#define DEBUG_SAVEALL (1<<5) /* save all garbage in gc.garbage */
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#define DEBUG_LEAK DEBUG_COLLECTABLE | \
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DEBUG_UNCOLLECTABLE | \
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DEBUG_SAVEALL
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static int debug;
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static PyObject *tmod = NULL;
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/*--------------------------------------------------------------------------
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gc_refs values.
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Between collections, every gc'ed object has one of two gc_refs values:
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GC_UNTRACKED
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The initial state; objects returned by PyObject_GC_Malloc are in this
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state. The object doesn't live in any generation list, and its
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tp_traverse slot must not be called.
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GC_REACHABLE
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The object lives in some generation list, and its tp_traverse is safe to
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call. An object transitions to GC_REACHABLE when PyObject_GC_Track
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is called.
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During a collection, gc_refs can temporarily take on other states:
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>= 0
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At the start of a collection, update_refs() copies the true refcount
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to gc_refs, for each object in the generation being collected.
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subtract_refs() then adjusts gc_refs so that it equals the number of
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times an object is referenced directly from outside the generation
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being collected.
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gc_refs remains >= 0 throughout these steps.
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GC_TENTATIVELY_UNREACHABLE
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move_unreachable() then moves objects not reachable (whether directly or
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indirectly) from outside the generation into an "unreachable" set.
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Objects that are found to be reachable have gc_refs set to GC_REACHABLE
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again. Objects that are found to be unreachable have gc_refs set to
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GC_TENTATIVELY_UNREACHABLE. It's "tentatively" because the pass doing
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this can't be sure until it ends, and GC_TENTATIVELY_UNREACHABLE may
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transition back to GC_REACHABLE.
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Only objects with GC_TENTATIVELY_UNREACHABLE still set are candidates
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for collection. If it's decided not to collect such an object (e.g.,
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it has a __del__ method), its gc_refs is restored to GC_REACHABLE again.
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----------------------------------------------------------------------------
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*/
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#define GC_UNTRACKED _PyGC_REFS_UNTRACKED
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#define GC_REACHABLE _PyGC_REFS_REACHABLE
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#define GC_TENTATIVELY_UNREACHABLE _PyGC_REFS_TENTATIVELY_UNREACHABLE
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#define IS_TRACKED(o) ((AS_GC(o))->gc.gc_refs != GC_UNTRACKED)
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#define IS_REACHABLE(o) ((AS_GC(o))->gc.gc_refs == GC_REACHABLE)
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#define IS_TENTATIVELY_UNREACHABLE(o) ( \
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(AS_GC(o))->gc.gc_refs == GC_TENTATIVELY_UNREACHABLE)
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/*** list functions ***/
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static void
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gc_list_init(PyGC_Head *list)
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{
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list->gc.gc_prev = list;
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list->gc.gc_next = list;
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}
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static int
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gc_list_is_empty(PyGC_Head *list)
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{
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return (list->gc.gc_next == list);
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}
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#if 0
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/* This became unused after gc_list_move() was introduced. */
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/* Append `node` to `list`. */
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static void
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gc_list_append(PyGC_Head *node, PyGC_Head *list)
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{
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node->gc.gc_next = list;
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node->gc.gc_prev = list->gc.gc_prev;
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node->gc.gc_prev->gc.gc_next = node;
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list->gc.gc_prev = node;
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}
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#endif
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/* Remove `node` from the gc list it's currently in. */
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static void
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gc_list_remove(PyGC_Head *node)
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{
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node->gc.gc_prev->gc.gc_next = node->gc.gc_next;
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node->gc.gc_next->gc.gc_prev = node->gc.gc_prev;
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node->gc.gc_next = NULL; /* object is not currently tracked */
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}
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/* Move `node` from the gc list it's currently in (which is not explicitly
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* named here) to the end of `list`. This is semantically the same as
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* gc_list_remove(node) followed by gc_list_append(node, list).
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*/
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static void
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gc_list_move(PyGC_Head *node, PyGC_Head *list)
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{
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PyGC_Head *new_prev;
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PyGC_Head *current_prev = node->gc.gc_prev;
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PyGC_Head *current_next = node->gc.gc_next;
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/* Unlink from current list. */
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current_prev->gc.gc_next = current_next;
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current_next->gc.gc_prev = current_prev;
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/* Relink at end of new list. */
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new_prev = node->gc.gc_prev = list->gc.gc_prev;
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new_prev->gc.gc_next = list->gc.gc_prev = node;
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node->gc.gc_next = list;
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}
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/* append list `from` onto list `to`; `from` becomes an empty list */
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static void
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gc_list_merge(PyGC_Head *from, PyGC_Head *to)
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{
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PyGC_Head *tail;
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assert(from != to);
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if (!gc_list_is_empty(from)) {
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tail = to->gc.gc_prev;
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tail->gc.gc_next = from->gc.gc_next;
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tail->gc.gc_next->gc.gc_prev = tail;
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to->gc.gc_prev = from->gc.gc_prev;
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to->gc.gc_prev->gc.gc_next = to;
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}
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gc_list_init(from);
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}
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static Py_ssize_t
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gc_list_size(PyGC_Head *list)
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{
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PyGC_Head *gc;
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Py_ssize_t n = 0;
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for (gc = list->gc.gc_next; gc != list; gc = gc->gc.gc_next) {
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n++;
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}
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return n;
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}
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/* Append objects in a GC list to a Python list.
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* Return 0 if all OK, < 0 if error (out of memory for list).
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*/
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static int
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append_objects(PyObject *py_list, PyGC_Head *gc_list)
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{
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PyGC_Head *gc;
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for (gc = gc_list->gc.gc_next; gc != gc_list; gc = gc->gc.gc_next) {
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PyObject *op = FROM_GC(gc);
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if (op != py_list) {
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if (PyList_Append(py_list, op)) {
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return -1; /* exception */
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}
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}
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}
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return 0;
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}
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/*** end of list stuff ***/
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/* Set all gc_refs = ob_refcnt. After this, gc_refs is > 0 for all objects
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* in containers, and is GC_REACHABLE for all tracked gc objects not in
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* containers.
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*/
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static void
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update_refs(PyGC_Head *containers)
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{
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PyGC_Head *gc = containers->gc.gc_next;
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for (; gc != containers; gc = gc->gc.gc_next) {
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assert(gc->gc.gc_refs == GC_REACHABLE);
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gc->gc.gc_refs = Py_REFCNT(FROM_GC(gc));
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/* Python's cyclic gc should never see an incoming refcount
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* of 0: if something decref'ed to 0, it should have been
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* deallocated immediately at that time.
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* Possible cause (if the assert triggers): a tp_dealloc
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* routine left a gc-aware object tracked during its teardown
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* phase, and did something-- or allowed something to happen --
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* that called back into Python. gc can trigger then, and may
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* see the still-tracked dying object. Before this assert
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* was added, such mistakes went on to allow gc to try to
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* delete the object again. In a debug build, that caused
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* a mysterious segfault, when _Py_ForgetReference tried
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* to remove the object from the doubly-linked list of all
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* objects a second time. In a release build, an actual
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* double deallocation occurred, which leads to corruption
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* of the allocator's internal bookkeeping pointers. That's
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* so serious that maybe this should be a release-build
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* check instead of an assert?
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*/
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assert(gc->gc.gc_refs != 0);
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}
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}
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/* A traversal callback for subtract_refs. */
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static int
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visit_decref(PyObject *op, void *data)
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{
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assert(op != NULL);
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if (PyObject_IS_GC(op)) {
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PyGC_Head *gc = AS_GC(op);
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/* We're only interested in gc_refs for objects in the
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* generation being collected, which can be recognized
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* because only they have positive gc_refs.
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*/
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assert(gc->gc.gc_refs != 0); /* else refcount was too small */
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if (gc->gc.gc_refs > 0)
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gc->gc.gc_refs--;
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}
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return 0;
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}
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/* Subtract internal references from gc_refs. After this, gc_refs is >= 0
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* for all objects in containers, and is GC_REACHABLE for all tracked gc
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* objects not in containers. The ones with gc_refs > 0 are directly
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* reachable from outside containers, and so can't be collected.
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*/
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static void
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subtract_refs(PyGC_Head *containers)
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{
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traverseproc traverse;
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PyGC_Head *gc = containers->gc.gc_next;
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for (; gc != containers; gc=gc->gc.gc_next) {
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traverse = Py_TYPE(FROM_GC(gc))->tp_traverse;
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(void) traverse(FROM_GC(gc),
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(visitproc)visit_decref,
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NULL);
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}
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}
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/* A traversal callback for move_unreachable. */
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static int
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visit_reachable(PyObject *op, PyGC_Head *reachable)
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{
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if (PyObject_IS_GC(op)) {
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PyGC_Head *gc = AS_GC(op);
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const Py_ssize_t gc_refs = gc->gc.gc_refs;
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if (gc_refs == 0) {
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/* This is in move_unreachable's 'young' list, but
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* the traversal hasn't yet gotten to it. All
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* we need to do is tell move_unreachable that it's
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* reachable.
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*/
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gc->gc.gc_refs = 1;
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}
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else if (gc_refs == GC_TENTATIVELY_UNREACHABLE) {
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/* This had gc_refs = 0 when move_unreachable got
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* to it, but turns out it's reachable after all.
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* Move it back to move_unreachable's 'young' list,
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* and move_unreachable will eventually get to it
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* again.
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*/
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gc_list_move(gc, reachable);
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gc->gc.gc_refs = 1;
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}
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/* Else there's nothing to do.
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* If gc_refs > 0, it must be in move_unreachable's 'young'
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* list, and move_unreachable will eventually get to it.
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* If gc_refs == GC_REACHABLE, it's either in some other
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* generation so we don't care about it, or move_unreachable
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* already dealt with it.
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* If gc_refs == GC_UNTRACKED, it must be ignored.
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*/
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else {
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assert(gc_refs > 0
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|| gc_refs == GC_REACHABLE
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|| gc_refs == GC_UNTRACKED);
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}
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}
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return 0;
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}
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/* Move the unreachable objects from young to unreachable. After this,
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* all objects in young have gc_refs = GC_REACHABLE, and all objects in
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* unreachable have gc_refs = GC_TENTATIVELY_UNREACHABLE. All tracked
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* gc objects not in young or unreachable still have gc_refs = GC_REACHABLE.
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* All objects in young after this are directly or indirectly reachable
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* from outside the original young; and all objects in unreachable are
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* not.
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*/
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static void
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move_unreachable(PyGC_Head *young, PyGC_Head *unreachable)
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{
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PyGC_Head *gc = young->gc.gc_next;
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/* Invariants: all objects "to the left" of us in young have gc_refs
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* = GC_REACHABLE, and are indeed reachable (directly or indirectly)
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* from outside the young list as it was at entry. All other objects
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* from the original young "to the left" of us are in unreachable now,
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* and have gc_refs = GC_TENTATIVELY_UNREACHABLE. All objects to the
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* left of us in 'young' now have been scanned, and no objects here
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* or to the right have been scanned yet.
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*/
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while (gc != young) {
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PyGC_Head *next;
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if (gc->gc.gc_refs) {
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/* gc is definitely reachable from outside the
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* original 'young'. Mark it as such, and traverse
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* its pointers to find any other objects that may
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* be directly reachable from it. Note that the
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* call to tp_traverse may append objects to young,
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* so we have to wait until it returns to determine
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* the next object to visit.
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*/
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PyObject *op = FROM_GC(gc);
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traverseproc traverse = Py_TYPE(op)->tp_traverse;
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assert(gc->gc.gc_refs > 0);
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gc->gc.gc_refs = GC_REACHABLE;
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(void) traverse(op,
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(visitproc)visit_reachable,
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(void *)young);
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next = gc->gc.gc_next;
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if (PyTuple_CheckExact(op)) {
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_PyTuple_MaybeUntrack(op);
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}
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else if (PyDict_CheckExact(op)) {
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_PyDict_MaybeUntrack(op);
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}
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}
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else {
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/* This *may* be unreachable. To make progress,
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* assume it is. gc isn't directly reachable from
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* any object we've already traversed, but may be
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* reachable from an object we haven't gotten to yet.
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* visit_reachable will eventually move gc back into
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* young if that's so, and we'll see it again.
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*/
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next = gc->gc.gc_next;
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gc_list_move(gc, unreachable);
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gc->gc.gc_refs = GC_TENTATIVELY_UNREACHABLE;
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}
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gc = next;
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}
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}
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/* Return true if object has a finalization method. */
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static int
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has_finalizer(PyObject *op)
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{
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if (PyGen_CheckExact(op))
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return PyGen_NeedsFinalizing((PyGenObject *)op);
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else
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return op->ob_type->tp_del != NULL;
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}
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/* Move the objects in unreachable with __del__ methods into `finalizers`.
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* Objects moved into `finalizers` have gc_refs set to GC_REACHABLE; the
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* objects remaining in unreachable are left at GC_TENTATIVELY_UNREACHABLE.
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*/
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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_cycle(char *msg, PyObject *op)
|
|
{
|
|
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)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 = PyUnicode_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 {
|
|
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 = PyUnicode_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 PyLong_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_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 */
|
|
};
|
|
|
|
static struct PyModuleDef gcmodule = {
|
|
PyModuleDef_HEAD_INIT,
|
|
"gc", /* m_name */
|
|
gc__doc__, /* m_doc */
|
|
-1, /* m_size */
|
|
GcMethods, /* m_methods */
|
|
NULL, /* m_reload */
|
|
NULL, /* m_traverse */
|
|
NULL, /* m_clear */
|
|
NULL /* m_free */
|
|
};
|
|
|
|
PyMODINIT_FUNC
|
|
PyInit_gc(void)
|
|
{
|
|
PyObject *m;
|
|
|
|
m = PyModule_Create(&gcmodule);
|
|
|
|
if (m == NULL)
|
|
return NULL;
|
|
|
|
if (garbage == NULL) {
|
|
garbage = PyList_New(0);
|
|
if (garbage == NULL)
|
|
return NULL;
|
|
}
|
|
Py_INCREF(garbage);
|
|
if (PyModule_AddObject(m, "garbage", garbage) < 0)
|
|
return NULL;
|
|
|
|
/* 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 NULL
|
|
ADD_INT(DEBUG_STATS);
|
|
ADD_INT(DEBUG_COLLECTABLE);
|
|
ADD_INT(DEBUG_UNCOLLECTABLE);
|
|
ADD_INT(DEBUG_SAVEALL);
|
|
ADD_INT(DEBUG_LEAK);
|
|
#undef ADD_INT
|
|
return m;
|
|
}
|
|
|
|
/* 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;
|
|
}
|
|
|
|
void
|
|
_PyGC_Fini(void)
|
|
{
|
|
if (!(debug & DEBUG_SAVEALL)
|
|
&& garbage != NULL && PyList_GET_SIZE(garbage) > 0) {
|
|
char *message;
|
|
if (debug & DEBUG_UNCOLLECTABLE)
|
|
message = "gc: %" PY_FORMAT_SIZE_T "d uncollectable objects at " \
|
|
"shutdown";
|
|
else
|
|
message = "gc: %" PY_FORMAT_SIZE_T "d uncollectable objects at " \
|
|
"shutdown; use gc.set_debug(gc.DEBUG_UNCOLLECTABLE) to list them";
|
|
if (PyErr_WarnFormat(PyExc_ResourceWarning, 0, message,
|
|
PyList_GET_SIZE(garbage)) < 0)
|
|
PyErr_WriteUnraisable(NULL);
|
|
if (debug & DEBUG_UNCOLLECTABLE) {
|
|
PyObject *repr = NULL, *bytes = NULL;
|
|
repr = PyObject_Repr(garbage);
|
|
if (!repr || !(bytes = PyUnicode_EncodeFSDefault(repr)))
|
|
PyErr_WriteUnraisable(garbage);
|
|
else {
|
|
PySys_WriteStderr(
|
|
" %s\n",
|
|
PyBytes_AS_STRING(bytes)
|
|
);
|
|
}
|
|
Py_XDECREF(repr);
|
|
Py_XDECREF(bytes);
|
|
}
|
|
}
|
|
}
|
|
|
|
/* 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);
|
|
}
|