/*

 * Python interface to the garbage collector.

 *

 * See Python/gc.c for the implementation of the garbage collector.

 */

#include "Python.h"

#include "pycore_gc.h"

#include "pycore_object.h"      // _PyObject_IS_GC()

#include "pycore_pystate.h"     // _PyInterpreterState_GET()

#include "pycore_tuple.h"       // _PyTuple_FromArray()

typedef struct _gc_runtime_state GCState;

static GCState *

get_gc_state(void)

{

    PyInterpreterState *interp = _PyInterpreterState_GET();

    return &interp->gc;

}

/*[clinic input]

module gc

[clinic start generated code]*/

/*[clinic end generated code: output=da39a3ee5e6b4b0d input=b5c9690ecc842d79]*/

#include "clinic/gcmodule.c.h"

/*[clinic input]

gc.enable

Enable automatic garbage collection.

[clinic start generated code]*/

static PyObject *

gc_enable_impl(PyObject *module)

/*[clinic end generated code: output=45a427e9dce9155c input=81ac4940ca579707]*/

{

    PyGC_Enable();

    Py_RETURN_NONE;

}

/*[clinic input]

gc.disable

Disable automatic garbage collection.

[clinic start generated code]*/

static PyObject *

gc_disable_impl(PyObject *module)

/*[clinic end generated code: output=97d1030f7aa9d279 input=8c2e5a14e800d83b]*/

{

    PyGC_Disable();

    Py_RETURN_NONE;

}

/*[clinic input]

gc.isenabled -> bool

Returns true if automatic garbage collection is enabled.

[clinic start generated code]*/

static int

gc_isenabled_impl(PyObject *module)

/*[clinic end generated code: output=1874298331c49130 input=30005e0422373b31]*/

{

    return PyGC_IsEnabled();

}

/*[clinic input]

gc.collect -> Py_ssize_t

    generation: int(c_default="NUM_GENERATIONS - 1") = 2

Run the garbage collector.

With no arguments, run a full collection.  The optional argument

may be an integer specifying which generation to collect.  A ValueError

is raised if the generation number is invalid.

The number of unreachable objects is returned.

[clinic start generated code]*/

static Py_ssize_t

gc_collect_impl(PyObject *module, int generation)

/*[clinic end generated code: output=b697e633043233c7 input=40720128b682d879]*/

{

    PyThreadState *tstate = _PyThreadState_GET();

    if (generation < 0 || generation >= NUM_GENERATIONS) {

        _PyErr_SetString(tstate, PyExc_ValueError, "invalid generation");

        return -1;

    }

    return _PyGC_Collect(tstate, generation, _Py_GC_REASON_MANUAL);

}

/*[clinic input]

gc.set_debug

    flags: int

        An integer that can have the following bits turned on:

          DEBUG_STATS - Print statistics during collection.

          DEBUG_COLLECTABLE - Print collectable objects found.

          DEBUG_UNCOLLECTABLE - Print unreachable but uncollectable objects

            found.

          DEBUG_SAVEALL - Save objects to gc.garbage rather than freeing them.

          DEBUG_LEAK - Debug leaking programs (everything but STATS).

    /

Set the garbage collection debugging flags.

Debugging information is written to sys.stderr.

[clinic start generated code]*/

static PyObject *

gc_set_debug_impl(PyObject *module, int flags)

/*[clinic end generated code: output=7c8366575486b228 input=5e5ce15e84fbed15]*/

{

    GCState *gcstate = get_gc_state();

    gcstate->debug = flags;

    Py_RETURN_NONE;

}

/*[clinic input]

gc.get_debug -> int

Get the garbage collection debugging flags.

[clinic start generated code]*/

static int

gc_get_debug_impl(PyObject *module)

/*[clinic end generated code: output=91242f3506cd1e50 input=91a101e1c3b98366]*/

{

    GCState *gcstate = get_gc_state();

    return gcstate->debug;

}

/*[clinic input]

gc.set_threshold

    threshold0: int

    [

    threshold1: int

    [

    threshold2: int

    ]

    ]

    /

Set the collection thresholds (the collection frequency).

Setting 'threshold0' to zero disables collection.

[clinic start generated code]*/

static PyObject *

gc_set_threshold_impl(PyObject *module, int threshold0, int group_right_1,

                      int threshold1, int group_right_2, int threshold2)

/*[clinic end generated code: output=2e3c7c7dd59060f3 input=0d9612db50984eec]*/

{

    GCState *gcstate = get_gc_state();

    gcstate->young.threshold = threshold0;

    if (group_right_1) {

        gcstate->old[0].threshold = threshold1;

    }

    if (group_right_2) {

        gcstate->old[1].threshold = threshold2;

    }

    Py_RETURN_NONE;

}

/*[clinic input]

gc.get_threshold

Return the current collection thresholds.

[clinic start generated code]*/

static PyObject *

gc_get_threshold_impl(PyObject *module)

/*[clinic end generated code: output=7902bc9f41ecbbd8 input=286d79918034d6e6]*/

{

    GCState *gcstate = get_gc_state();

    return Py_BuildValue("(iii)",

                         gcstate->young.threshold,

                         gcstate->old[0].threshold,

                         0);

}

/*[clinic input]

gc.get_count

Return a three-tuple of the current collection counts.

[clinic start generated code]*/

static PyObject *

gc_get_count_impl(PyObject *module)

/*[clinic end generated code: output=354012e67b16398f input=a392794a08251751]*/

{

    GCState *gcstate = get_gc_state();

#ifdef Py_GIL_DISABLED

    _PyThreadStateImpl *tstate = (_PyThreadStateImpl *)_PyThreadState_GET();

    struct _gc_thread_state *gc = &tstate->gc;

    // Flush the local allocation count to the global count

    _Py_atomic_add_int(&gcstate->young.count, (int)gc->alloc_count);

    gc->alloc_count = 0;

#endif

    return Py_BuildValue("(iii)",

                         gcstate->young.count,

                         gcstate->old[gcstate->visited_space].count,

                         gcstate->old[gcstate->visited_space^1].count);

}

/*[clinic input]

gc.get_referrers

    *objs: tuple

Return the list of objects that directly refer to any of 'objs'.

[clinic start generated code]*/

static PyObject *

gc_get_referrers_impl(PyObject *module, PyObject *objs)

/*[clinic end generated code: output=929d6dff26f609b9 input=9102be7ebee69ee3]*/

{

    if (PySys_Audit("gc.get_referrers", "(O)", objs) < 0) {

        return NULL;

    }

    PyInterpreterState *interp = _PyInterpreterState_GET();

    return _PyGC_GetReferrers(interp, objs);

}

/* Append obj to list; return true if error (out of memory), false if OK. */

static int

referentsvisit(PyObject *obj, void *arg)

{

    PyObject *list = arg;

    return PyList_Append(list, obj) < 0;

}

static int

append_referrents(PyObject *result, PyObject *args)

{

    for (Py_ssize_t i = 0; i < PyTuple_GET_SIZE(args); i++) {

        PyObject *obj = PyTuple_GET_ITEM(args, i);

        if (!_PyObject_IS_GC(obj)) {

            continue;

        }

        traverseproc traverse = Py_TYPE(obj)->tp_traverse;

        if (!traverse) {

            continue;

        }

        if (traverse(obj, referentsvisit, result)) {

            return -1;

        }

    }

    return 0;

}

/*[clinic input]

gc.get_referents

    *objs: tuple

Return the list of objects that are directly referred to by 'objs'.

[clinic start generated code]*/

static PyObject *

gc_get_referents_impl(PyObject *module, PyObject *objs)

/*[clinic end generated code: output=6dfde40cd1588e1d input=55c078a6d0248fe0]*/

{

    if (PySys_Audit("gc.get_referents", "(O)", objs) < 0) {

        return NULL;

    }

    PyInterpreterState *interp = _PyInterpreterState_GET();

    PyObject *result = PyList_New(0);

    if (result == NULL) {

        return NULL;

    }

    // NOTE: stop the world is a no-op in default build

    _PyEval_StopTheWorld(interp);

    int err = append_referrents(result, objs);

    _PyEval_StartTheWorld(interp);

    if (err < 0) {

        Py_CLEAR(result);

    }

    return result;

}

/*[clinic input]

gc.get_objects

    generation: Py_ssize_t(accept={int, NoneType}, c_default="-1") = None

        Generation to extract the objects from.

Return a list of objects tracked by the collector (excluding the list returned).

If generation is not None, return only the objects tracked by the collector

that are in that generation.

[clinic start generated code]*/

static PyObject *

gc_get_objects_impl(PyObject *module, Py_ssize_t generation)

/*[clinic end generated code: output=48b35fea4ba6cb0e input=ef7da9df9806754c]*/

{

    if (PySys_Audit("gc.get_objects", "n", generation) < 0) {

        return NULL;

    }

    if (generation >= NUM_GENERATIONS) {

        return PyErr_Format(PyExc_ValueError,

                            "generation parameter must be less than the number of "

                            "available generations (%i)",

                            NUM_GENERATIONS);

    }

    if (generation < -1) {

        PyErr_SetString(PyExc_ValueError,

                        "generation parameter cannot be negative");

        return NULL;

    }

    PyInterpreterState *interp = _PyInterpreterState_GET();

    return _PyGC_GetObjects(interp, (int)generation);

}

/*[clinic input]

gc.get_stats

Return a list of dictionaries containing per-generation statistics.

[clinic start generated code]*/

static PyObject *

gc_get_stats_impl(PyObject *module)

/*[clinic end generated code: output=a8ab1d8a5d26f3ab input=1ef4ed9d17b1a470]*/

{

    int i;

    struct gc_generation_stats stats[NUM_GENERATIONS], *st;

    /* To get consistent values despite allocations while constructing

       the result list, we use a snapshot of the running stats. */

    GCState *gcstate = get_gc_state();

    for (i = 0; i < NUM_GENERATIONS; i++) {

        stats[i] = gcstate->generation_stats[i];

    }

    PyObject *result = PyList_New(0);

    if (result == NULL)

        return NULL;

    for (i = 0; i < NUM_GENERATIONS; i++) {

        PyObject *dict;

        st = &stats[i];

        dict = Py_BuildValue("{snsnsn}",

                             "collections", st->collections,

                             "collected", st->collected,

                             "uncollectable", st->uncollectable

                            );

        if (dict == NULL)

            goto error;

        if (PyList_Append(result, dict)) {

            Py_DECREF(dict);

            goto error;

        }

        Py_DECREF(dict);

    }

    return result;

error:

    Py_XDECREF(result);

    return NULL;

}

/*[clinic input]

gc.is_tracked -> bool

    obj: object

    /

Returns true if the object is tracked by the garbage collector.

Simple atomic objects will return false.

[clinic start generated code]*/

static int

gc_is_tracked_impl(PyObject *module, PyObject *obj)

/*[clinic end generated code: output=91c8d086b7f47a33 input=423b98ec680c3126]*/

{

    return PyObject_GC_IsTracked(obj);

}

/*[clinic input]

gc.is_finalized -> bool

    obj: object

    /

Returns true if the object has been already finalized by the GC.

[clinic start generated code]*/

static int

gc_is_finalized_impl(PyObject *module, PyObject *obj)

/*[clinic end generated code: output=401ff5d6fc660429 input=ca4d111c8f8c4e3a]*/

{

    return PyObject_GC_IsFinalized(obj);

}

/*[clinic input]

gc.freeze

Freeze all current tracked objects and ignore them for future collections.

This can be used before a POSIX fork() call to make the gc copy-on-write friendly.

Note: collection before a POSIX fork() call may free pages for future allocation

which can cause copy-on-write.

[clinic start generated code]*/

static PyObject *

gc_freeze_impl(PyObject *module)

/*[clinic end generated code: output=502159d9cdc4c139 input=b602b16ac5febbe5]*/

{

    PyInterpreterState *interp = _PyInterpreterState_GET();

    _PyGC_Freeze(interp);

    Py_RETURN_NONE;

}

/*[clinic input]

gc.unfreeze

Unfreeze all objects in the permanent generation.

Put all objects in the permanent generation back into oldest generation.

[clinic start generated code]*/

static PyObject *

gc_unfreeze_impl(PyObject *module)

/*[clinic end generated code: output=1c15f2043b25e169 input=2dd52b170f4cef6c]*/

{

    PyInterpreterState *interp = _PyInterpreterState_GET();

    _PyGC_Unfreeze(interp);

    Py_RETURN_NONE;

}

/*[clinic input]

gc.get_freeze_count -> Py_ssize_t

Return the number of objects in the permanent generation.

[clinic start generated code]*/

static Py_ssize_t

gc_get_freeze_count_impl(PyObject *module)

/*[clinic end generated code: output=61cbd9f43aa032e1 input=45ffbc65cfe2a6ed]*/

{

    PyInterpreterState *interp = _PyInterpreterState_GET();

    return _PyGC_GetFreezeCount(interp);

}

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"

"get_stats() -- Return list of dictionaries containing per-generation stats.\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"

"is_finalized() -- Returns true if a given object has been already finalized.\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"

"freeze() -- Freeze all tracked objects and ignore them for future collections.\n"

"unfreeze() -- Unfreeze all objects in the permanent generation.\n"

"get_freeze_count() -- Return the number of objects in the permanent generation.\n");

static PyMethodDef GcMethods[] = {

    GC_ENABLE_METHODDEF

    GC_DISABLE_METHODDEF

    GC_ISENABLED_METHODDEF

    GC_SET_DEBUG_METHODDEF

    GC_GET_DEBUG_METHODDEF

    GC_GET_COUNT_METHODDEF

    GC_SET_THRESHOLD_METHODDEF

    GC_GET_THRESHOLD_METHODDEF

    GC_COLLECT_METHODDEF

    GC_GET_OBJECTS_METHODDEF

    GC_GET_STATS_METHODDEF

    GC_IS_TRACKED_METHODDEF

    GC_IS_FINALIZED_METHODDEF

    GC_GET_REFERRERS_METHODDEF

    GC_GET_REFERENTS_METHODDEF

    GC_FREEZE_METHODDEF

    GC_UNFREEZE_METHODDEF

    GC_GET_FREEZE_COUNT_METHODDEF

    {NULL,      NULL}           /* Sentinel */

};

static int

gcmodule_exec(PyObject *module)

{

    GCState *gcstate = get_gc_state();

    /* garbage and callbacks are initialized by _PyGC_Init() early in

     * interpreter lifecycle. */

    assert(gcstate->garbage != NULL);

    if (PyModule_AddObjectRef(module, "garbage", gcstate->garbage) < 0) {

        return -1;

    }

    assert(gcstate->callbacks != NULL);

    if (PyModule_AddObjectRef(module, "callbacks", gcstate->callbacks) < 0) {

        return -1;

    }

#define ADD_INT(NAME) if (PyModule_AddIntConstant(module, #NAME, _PyGC_ ## NAME) < 0) { return -1; }

    ADD_INT(DEBUG_STATS);

    ADD_INT(DEBUG_COLLECTABLE);

    ADD_INT(DEBUG_UNCOLLECTABLE);

    ADD_INT(DEBUG_SAVEALL);

    ADD_INT(DEBUG_LEAK);

#undef ADD_INT

    return 0;

}

static PyModuleDef_Slot gcmodule_slots[] = {

    {Py_mod_exec, gcmodule_exec},

    {Py_mod_multiple_interpreters, Py_MOD_PER_INTERPRETER_GIL_SUPPORTED},

    {Py_mod_gil, Py_MOD_GIL_NOT_USED},

    {0, NULL}

};

static struct PyModuleDef gcmodule = {

    PyModuleDef_HEAD_INIT,

    .m_name = "gc",

    .m_doc = gc__doc__,

    .m_size = 0,  // per interpreter state, see: get_gc_state()

    .m_methods = GcMethods,

    .m_slots = gcmodule_slots

};

PyMODINIT_FUNC

PyInit_gc(void)

{

    return PyModuleDef_Init(&gcmodule);

}