_asynciomodule.c

#ifndef Py_BUILD_CORE_BUILTIN
#  define Py_BUILD_CORE_MODULE 1
#endif

#include "Python.h"
#include "pycore_pyerrors.h"      // _PyErr_ClearExcState()
#include "pycore_pystate.h"       // _PyThreadState_GET()
#include "pycore_runtime_init.h"  // _Py_ID()
#include "pycore_moduleobject.h"  // _PyModule_GetState()
#include "structmember.h"         // PyMemberDef
#include <stddef.h>               // offsetof()


/*[clinic input]
module _asyncio
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=8fd17862aa989c69]*/


/* State of the _asyncio module */
typedef struct {
    PyTypeObject *FutureIterType;
    PyTypeObject *TaskStepMethWrapper_Type;
    PyTypeObject *FutureType;
    PyTypeObject *TaskType;
    PyTypeObject *PyRunningLoopHolder_Type;

    PyObject *asyncio_mod;
    PyObject *context_kwname;

    /* Dictionary containing tasks that are currently active in
       all running event loops.  {EventLoop: Task} */
    PyObject *current_tasks;

    /* WeakSet containing all alive tasks. */
    PyObject *all_tasks;

    /* An isinstance type cache for the 'is_coroutine()' function. */
    PyObject *iscoroutine_typecache;

    /* Imports from asyncio.events. */
    PyObject *asyncio_get_event_loop_policy;

    /* Imports from asyncio.base_futures. */
    PyObject *asyncio_future_repr_func;

    /* Imports from asyncio.exceptions. */
    PyObject *asyncio_CancelledError;
    PyObject *asyncio_InvalidStateError;

    /* Imports from asyncio.base_tasks. */
    PyObject *asyncio_task_get_stack_func;
    PyObject *asyncio_task_print_stack_func;
    PyObject *asyncio_task_repr_func;

    /* Imports from asyncio.coroutines. */
    PyObject *asyncio_iscoroutine_func;

    /* Imports from traceback. */
    PyObject *traceback_extract_stack;

    PyObject *cached_running_holder;  // Borrowed ref.
    volatile uint64_t cached_running_holder_tsid;

    /* Counter for autogenerated Task names */
    uint64_t task_name_counter;
} asyncio_state;

static inline asyncio_state *
get_asyncio_state(PyObject *mod)
{
    asyncio_state *state = _PyModule_GetState(mod);
    assert(state != NULL);
    return state;
}

static inline asyncio_state *
get_asyncio_state_by_cls(PyTypeObject *cls)
{
    asyncio_state *state = (asyncio_state *)PyType_GetModuleState(cls);
    assert(state != NULL);
    return state;
}

static struct PyModuleDef _asynciomodule;

static inline asyncio_state *
get_asyncio_state_by_def(PyObject *self)
{
    PyTypeObject *tp = Py_TYPE(self);
    PyObject *mod = PyType_GetModuleByDef(tp, &_asynciomodule);
    assert(mod != NULL);
    return get_asyncio_state(mod);
}

typedef enum {
    STATE_PENDING,
    STATE_CANCELLED,
    STATE_FINISHED
} fut_state;

#define FutureObj_HEAD(prefix)                                              \
    PyObject_HEAD                                                           \
    PyObject *prefix##_loop;                                                \
    PyObject *prefix##_callback0;                                           \
    PyObject *prefix##_context0;                                            \
    PyObject *prefix##_callbacks;                                           \
    PyObject *prefix##_exception;                                           \
    PyObject *prefix##_exception_tb;                                        \
    PyObject *prefix##_result;                                              \
    PyObject *prefix##_source_tb;                                           \
    PyObject *prefix##_cancel_msg;                                          \
    fut_state prefix##_state;                                               \
    int prefix##_log_tb;                                                    \
    int prefix##_blocking;                                                  \
    PyObject *dict;                                                         \
    PyObject *prefix##_weakreflist;                                         \
    PyObject *prefix##_cancelled_exc;

typedef struct {
    FutureObj_HEAD(fut)
} FutureObj;

typedef struct {
    FutureObj_HEAD(task)
    PyObject *task_fut_waiter;
    PyObject *task_coro;
    PyObject *task_name;
    PyObject *task_context;
    int task_must_cancel;
    int task_log_destroy_pending;
    int task_num_cancels_requested;
} TaskObj;

typedef struct {
    PyObject_HEAD
    TaskObj *sw_task;
    PyObject *sw_arg;
} TaskStepMethWrapper;

typedef struct {
    PyObject_HEAD
    PyObject *rl_loop;
#if defined(HAVE_GETPID) && !defined(MS_WINDOWS)
    pid_t rl_pid;
#endif
} PyRunningLoopHolder;


#define Future_CheckExact(state, obj) Py_IS_TYPE(obj, state->FutureType)
#define Task_CheckExact(state, obj) Py_IS_TYPE(obj, state->TaskType)

#define Future_Check(state, obj) PyObject_TypeCheck(obj, state->FutureType)
#define Task_Check(state, obj) PyObject_TypeCheck(obj, state->TaskType)

#include "clinic/_asynciomodule.c.h"


/*[clinic input]
class _asyncio.Future "FutureObj *" "&Future_Type"
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=00d3e4abca711e0f]*/


/* Get FutureIter from Future */
static PyObject * future_new_iter(PyObject *);

static PyRunningLoopHolder * new_running_loop_holder(asyncio_state *, PyObject *);


static int
_is_coroutine(asyncio_state *state, PyObject *coro)
{
    /* 'coro' is not a native coroutine, call asyncio.iscoroutine()
       to check if it's another coroutine flavour.

       Do this check after 'future_init()'; in case we need to raise
       an error, __del__ needs a properly initialized object.
    */
    PyObject *res = PyObject_CallOneArg(state->asyncio_iscoroutine_func, coro);
    if (res == NULL) {
        return -1;
    }

    int is_res_true = PyObject_IsTrue(res);
    Py_DECREF(res);
    if (is_res_true <= 0) {
        return is_res_true;
    }

    if (PySet_GET_SIZE(state->iscoroutine_typecache) < 100) {
        /* Just in case we don't want to cache more than 100
           positive types.  That shouldn't ever happen, unless
           someone stressing the system on purpose.
        */
        if (PySet_Add(state->iscoroutine_typecache, (PyObject*) Py_TYPE(coro))) {
            return -1;
        }
    }

    return 1;
}


static inline int
is_coroutine(asyncio_state *state, PyObject *coro)
{
    if (PyCoro_CheckExact(coro)) {
        return 1;
    }

    /* Check if `type(coro)` is in the cache.
       Caching makes is_coroutine() function almost as fast as
       PyCoro_CheckExact() for non-native coroutine-like objects
       (like coroutines compiled with Cython).

       asyncio.iscoroutine() has its own type caching mechanism.
       This cache allows us to avoid the cost of even calling
       a pure-Python function in 99.9% cases.
    */
    int has_it = PySet_Contains(
        state->iscoroutine_typecache, (PyObject*) Py_TYPE(coro));
    if (has_it == 0) {
        /* type(coro) is not in iscoroutine_typecache */
        return _is_coroutine(state, coro);
    }

    /* either an error has occurred or
       type(coro) is in iscoroutine_typecache
    */
    return has_it;
}


static PyObject *
get_future_loop(asyncio_state *state, PyObject *fut)
{
    /* Implementation of `asyncio.futures._get_loop` */

    PyObject *getloop;

    if (Future_CheckExact(state, fut) || Task_CheckExact(state, fut)) {
        PyObject *loop = ((FutureObj *)fut)->fut_loop;
        return Py_NewRef(loop);
    }

    if (_PyObject_LookupAttr(fut, &_Py_ID(get_loop), &getloop) < 0) {
        return NULL;
    }
    if (getloop != NULL) {
        PyObject *res = PyObject_CallNoArgs(getloop);
        Py_DECREF(getloop);
        return res;
    }

    return PyObject_GetAttr(fut, &_Py_ID(_loop));
}


static int
get_running_loop(asyncio_state *state, PyObject **loop)
{
    PyObject *rl;

    PyThreadState *ts = _PyThreadState_GET();
    uint64_t ts_id = PyThreadState_GetID(ts);
    if (state->cached_running_holder_tsid == ts_id &&
        state->cached_running_holder != NULL)
    {
        // Fast path, check the cache.
        rl = state->cached_running_holder;  // borrowed
    }
    else {
        PyObject *ts_dict = _PyThreadState_GetDict(ts);  // borrowed
        if (ts_dict == NULL) {
            goto not_found;
        }

        rl = PyDict_GetItemWithError(
            ts_dict, &_Py_ID(__asyncio_running_event_loop__));  // borrowed
        if (rl == NULL) {
            if (PyErr_Occurred()) {
                goto error;
            }
            else {
                goto not_found;
            }
        }

        state->cached_running_holder = rl;  // borrowed
        state->cached_running_holder_tsid = ts_id;
    }

    assert(Py_IS_TYPE(rl, state->PyRunningLoopHolder_Type));
    PyObject *running_loop = ((PyRunningLoopHolder *)rl)->rl_loop;

    if (running_loop == Py_None) {
        goto not_found;
    }

#if defined(HAVE_GETPID) && !defined(MS_WINDOWS)
    /* On Windows there is no getpid, but there is also no os.fork(),
       so there is no need for this check.
    */
    if (getpid() != ((PyRunningLoopHolder *)rl)->rl_pid) {
        goto not_found;
    }
#endif

    *loop = Py_NewRef(running_loop);
    return 0;

not_found:
    *loop = NULL;
    return 0;

error:
    *loop = NULL;
    return -1;
}


static int
set_running_loop(asyncio_state *state, PyObject *loop)
{
    PyObject *ts_dict = NULL;

    PyThreadState *tstate = _PyThreadState_GET();
    if (tstate != NULL) {
        ts_dict = _PyThreadState_GetDict(tstate);  // borrowed
    }

    if (ts_dict == NULL) {
        PyErr_SetString(
            PyExc_RuntimeError, "thread-local storage is not available");
        return -1;
    }

    PyRunningLoopHolder *rl = new_running_loop_holder(state, loop);
    if (rl == NULL) {
        return -1;
    }

    if (PyDict_SetItem(
            ts_dict, &_Py_ID(__asyncio_running_event_loop__), (PyObject *)rl) < 0)
    {
        Py_DECREF(rl);  // will cleanup loop & current_pid
        return -1;
    }
    Py_DECREF(rl);

    state->cached_running_holder = (PyObject *)rl;
    state->cached_running_holder_tsid = PyThreadState_GetID(tstate);

    return 0;
}


static PyObject *
get_event_loop(asyncio_state *state)
{
    PyObject *loop;
    PyObject *policy;

    if (get_running_loop(state, &loop)) {
        return NULL;
    }
    if (loop != NULL) {
        return loop;
    }

    policy = PyObject_CallNoArgs(state->asyncio_get_event_loop_policy);
    if (policy == NULL) {
        return NULL;
    }

    loop = PyObject_CallMethodNoArgs(policy, &_Py_ID(get_event_loop));
    Py_DECREF(policy);
    return loop;
}


static int
call_soon(asyncio_state *state, PyObject *loop, PyObject *func, PyObject *arg,
          PyObject *ctx)
{
    PyObject *handle;
    PyObject *stack[3];
    Py_ssize_t nargs;

    if (ctx == NULL) {
        handle = PyObject_CallMethodObjArgs(
            loop, &_Py_ID(call_soon), func, arg, NULL);
    }
    else {
        /* Use FASTCALL to pass a keyword-only argument to call_soon */

        PyObject *callable = PyObject_GetAttr(loop, &_Py_ID(call_soon));
        if (callable == NULL) {
            return -1;
        }

        /* All refs in 'stack' are borrowed. */
        nargs = 1;
        stack[0] = func;
        if (arg != NULL) {
            stack[1] = arg;
            nargs++;
        }
        stack[nargs] = (PyObject *)ctx;
        EVAL_CALL_STAT_INC_IF_FUNCTION(EVAL_CALL_API, callable);
        handle = PyObject_Vectorcall(callable, stack, nargs,
                                     state->context_kwname);
        Py_DECREF(callable);
    }

    if (handle == NULL) {
        return -1;
    }
    Py_DECREF(handle);
    return 0;
}


static inline int
future_is_alive(FutureObj *fut)
{
    return fut->fut_loop != NULL;
}


static inline int
future_ensure_alive(FutureObj *fut)
{
    if (!future_is_alive(fut)) {
        PyErr_SetString(PyExc_RuntimeError,
                        "Future object is not initialized.");
        return -1;
    }
    return 0;
}


#define ENSURE_FUTURE_ALIVE(state, fut)                             \
    do {                                                            \
        assert(Future_Check(state, fut) || Task_Check(state, fut)); \
        (void)state;                                                \
        if (future_ensure_alive((FutureObj*)fut)) {                 \
            return NULL;                                            \
        }                                                           \
    } while(0);


static int
future_schedule_callbacks(asyncio_state *state, FutureObj *fut)
{
    Py_ssize_t len;
    Py_ssize_t i;

    if (fut->fut_callback0 != NULL) {
        /* There's a 1st callback */

        int ret = call_soon(state,
            fut->fut_loop, fut->fut_callback0,
            (PyObject *)fut, fut->fut_context0);

        Py_CLEAR(fut->fut_callback0);
        Py_CLEAR(fut->fut_context0);
        if (ret) {
            /* If an error occurs in pure-Python implementation,
               all callbacks are cleared. */
            Py_CLEAR(fut->fut_callbacks);
            return ret;
        }

        /* we called the first callback, now try calling
           callbacks from the 'fut_callbacks' list. */
    }

    if (fut->fut_callbacks == NULL) {
        /* No more callbacks, return. */
        return 0;
    }

    len = PyList_GET_SIZE(fut->fut_callbacks);
    if (len == 0) {
        /* The list of callbacks was empty; clear it and return. */
        Py_CLEAR(fut->fut_callbacks);
        return 0;
    }

    for (i = 0; i < len; i++) {
        PyObject *cb_tup = PyList_GET_ITEM(fut->fut_callbacks, i);
        PyObject *cb = PyTuple_GET_ITEM(cb_tup, 0);
        PyObject *ctx = PyTuple_GET_ITEM(cb_tup, 1);

        if (call_soon(state, fut->fut_loop, cb, (PyObject *)fut, ctx)) {
            /* If an error occurs in pure-Python implementation,
               all callbacks are cleared. */
            Py_CLEAR(fut->fut_callbacks);
            return -1;
        }
    }

    Py_CLEAR(fut->fut_callbacks);
    return 0;
}


static int
future_init(FutureObj *fut, PyObject *loop)
{
    PyObject *res;
    int is_true;

    // Same to FutureObj_clear() but not clearing fut->dict
    Py_CLEAR(fut->fut_loop);
    Py_CLEAR(fut->fut_callback0);
    Py_CLEAR(fut->fut_context0);
    Py_CLEAR(fut->fut_callbacks);
    Py_CLEAR(fut->fut_result);
    Py_CLEAR(fut->fut_exception);
    Py_CLEAR(fut->fut_exception_tb);
    Py_CLEAR(fut->fut_source_tb);
    Py_CLEAR(fut->fut_cancel_msg);
    Py_CLEAR(fut->fut_cancelled_exc);

    fut->fut_state = STATE_PENDING;
    fut->fut_log_tb = 0;
    fut->fut_blocking = 0;

    if (loop == Py_None) {
        asyncio_state *state = get_asyncio_state_by_def((PyObject *)fut);
        loop = get_event_loop(state);
        if (loop == NULL) {
            return -1;
        }
    }
    else {
        Py_INCREF(loop);
    }
    fut->fut_loop = loop;

    res = PyObject_CallMethodNoArgs(fut->fut_loop, &_Py_ID(get_debug));
    if (res == NULL) {
        return -1;
    }
    is_true = PyObject_IsTrue(res);
    Py_DECREF(res);
    if (is_true < 0) {
        return -1;
    }
    if (is_true && !_Py_IsFinalizing()) {
        /* Only try to capture the traceback if the interpreter is not being
           finalized.  The original motivation to add a `_Py_IsFinalizing()`
           call was to prevent SIGSEGV when a Future is created in a __del__
           method, which is called during the interpreter shutdown and the
           traceback module is already unloaded.
        */
        asyncio_state *state = get_asyncio_state_by_def((PyObject *)fut);
        fut->fut_source_tb = PyObject_CallNoArgs(state->traceback_extract_stack);
        if (fut->fut_source_tb == NULL) {
            return -1;
        }
    }

    return 0;
}

static PyObject *
future_set_result(asyncio_state *state, FutureObj *fut, PyObject *res)
{
    if (future_ensure_alive(fut)) {
        return NULL;
    }

    if (fut->fut_state != STATE_PENDING) {
        PyErr_SetString(state->asyncio_InvalidStateError, "invalid state");
        return NULL;
    }

    assert(!fut->fut_result);
    fut->fut_result = Py_NewRef(res);
    fut->fut_state = STATE_FINISHED;

    if (future_schedule_callbacks(state, fut) == -1) {
        return NULL;
    }
    Py_RETURN_NONE;
}

static PyObject *
future_set_exception(asyncio_state *state, FutureObj *fut, PyObject *exc)
{
    PyObject *exc_val = NULL;

    if (fut->fut_state != STATE_PENDING) {
        PyErr_SetString(state->asyncio_InvalidStateError, "invalid state");
        return NULL;
    }

    if (PyExceptionClass_Check(exc)) {
        exc_val = PyObject_CallNoArgs(exc);
        if (exc_val == NULL) {
            return NULL;
        }
        if (fut->fut_state != STATE_PENDING) {
            Py_DECREF(exc_val);
            PyErr_SetString(state->asyncio_InvalidStateError, "invalid state");
            return NULL;
        }
    }
    else {
        exc_val = Py_NewRef(exc);
    }
    if (!PyExceptionInstance_Check(exc_val)) {
        Py_DECREF(exc_val);
        PyErr_SetString(PyExc_TypeError, "invalid exception object");
        return NULL;
    }
    if (Py_IS_TYPE(exc_val, (PyTypeObject *)PyExc_StopIteration)) {
        Py_DECREF(exc_val);
        PyErr_SetString(PyExc_TypeError,
                        "StopIteration interacts badly with generators "
                        "and cannot be raised into a Future");
        return NULL;
    }

    assert(!fut->fut_exception);
    assert(!fut->fut_exception_tb);
    fut->fut_exception = exc_val;
    fut->fut_exception_tb = PyException_GetTraceback(exc_val);
    fut->fut_state = STATE_FINISHED;

    if (future_schedule_callbacks(state, fut) == -1) {
        return NULL;
    }

    fut->fut_log_tb = 1;
    Py_RETURN_NONE;
}

static PyObject *
create_cancelled_error(asyncio_state *state, FutureObj *fut)
{
    PyObject *exc;
    if (fut->fut_cancelled_exc != NULL) {
        /* transfer ownership */
        exc = fut->fut_cancelled_exc;
        fut->fut_cancelled_exc = NULL;
        return exc;
    }
    PyObject *msg = fut->fut_cancel_msg;
    if (msg == NULL || msg == Py_None) {
        exc = PyObject_CallNoArgs(state->asyncio_CancelledError);
    } else {
        exc = PyObject_CallOneArg(state->asyncio_CancelledError, msg);
    }
    return exc;
}

static void
future_set_cancelled_error(asyncio_state *state, FutureObj *fut)
{
    PyObject *exc = create_cancelled_error(state, fut);
    if (exc == NULL) {
        return;
    }
    PyErr_SetObject(state->asyncio_CancelledError, exc);
    Py_DECREF(exc);
}

static int
future_get_result(asyncio_state *state, FutureObj *fut, PyObject **result)
{
    if (fut->fut_state == STATE_CANCELLED) {
        future_set_cancelled_error(state, fut);
        return -1;
    }

    if (fut->fut_state != STATE_FINISHED) {
        PyErr_SetString(state->asyncio_InvalidStateError,
                        "Result is not set.");
        return -1;
    }

    fut->fut_log_tb = 0;
    if (fut->fut_exception != NULL) {
        PyObject *tb = fut->fut_exception_tb;
        if (tb == NULL) {
            tb = Py_None;
        }
        if (PyException_SetTraceback(fut->fut_exception, tb) < 0) {
            return -1;
        }
        *result = Py_NewRef(fut->fut_exception);
        Py_CLEAR(fut->fut_exception_tb);
        return 1;
    }

    *result = Py_NewRef(fut->fut_result);
    return 0;
}

static PyObject *
future_add_done_callback(asyncio_state *state, FutureObj *fut, PyObject *arg,
                         PyObject *ctx)
{
    if (!future_is_alive(fut)) {
        PyErr_SetString(PyExc_RuntimeError, "uninitialized Future object");
        return NULL;
    }

    if (fut->fut_state != STATE_PENDING) {
        /* The future is done/cancelled, so schedule the callback
           right away. */
        if (call_soon(state, fut->fut_loop, arg, (PyObject*) fut, ctx)) {
            return NULL;
        }
    }
    else {
        /* The future is pending, add a callback.

           Callbacks in the future object are stored as follows:

              callback0 -- a pointer to the first callback
              callbacks -- a list of 2nd, 3rd, ... callbacks

           Invariants:

            * callbacks != NULL:
                There are some callbacks in in the list.  Just
                add the new callback to it.

            * callbacks == NULL and callback0 == NULL:
                This is the first callback.  Set it to callback0.

            * callbacks == NULL and callback0 != NULL:
                This is a second callback.  Initialize callbacks
                with a new list and add the new callback to it.
        */

        if (fut->fut_callbacks == NULL && fut->fut_callback0 == NULL) {
            fut->fut_callback0 = Py_NewRef(arg);
            fut->fut_context0 = Py_NewRef(ctx);
        }
        else {
            PyObject *tup = PyTuple_New(2);
            if (tup == NULL) {
                return NULL;
            }
            Py_INCREF(arg);
            PyTuple_SET_ITEM(tup, 0, arg);
            Py_INCREF(ctx);
            PyTuple_SET_ITEM(tup, 1, (PyObject *)ctx);

            if (fut->fut_callbacks != NULL) {
                int err = PyList_Append(fut->fut_callbacks, tup);
                if (err) {
                    Py_DECREF(tup);
                    return NULL;
                }
                Py_DECREF(tup);
            }
            else {
                fut->fut_callbacks = PyList_New(1);
                if (fut->fut_callbacks == NULL) {
                    Py_DECREF(tup);
                    return NULL;
                }

                PyList_SET_ITEM(fut->fut_callbacks, 0, tup);  /* borrow */
            }
        }
    }

    Py_RETURN_NONE;
}

static PyObject *
future_cancel(asyncio_state *state, FutureObj *fut, PyObject *msg)
{
    fut->fut_log_tb = 0;

    if (fut->fut_state != STATE_PENDING) {
        Py_RETURN_FALSE;
    }
    fut->fut_state = STATE_CANCELLED;

    Py_XINCREF(msg);
    Py_XSETREF(fut->fut_cancel_msg, msg);

    if (future_schedule_callbacks(state, fut) == -1) {
        return NULL;
    }

    Py_RETURN_TRUE;
}

/*[clinic input]
_asyncio.Future.__init__

    *
    loop: object = None

This class is *almost* compatible with concurrent.futures.Future.

    Differences:

    - result() and exception() do not take a timeout argument and
      raise an exception when the future isn't done yet.

    - Callbacks registered with add_done_callback() are always called
      via the event loop's call_soon_threadsafe().

    - This class is not compatible with the wait() and as_completed()
      methods in the concurrent.futures package.
[clinic start generated code]*/

static int
_asyncio_Future___init___impl(FutureObj *self, PyObject *loop)
/*[clinic end generated code: output=9ed75799eaccb5d6 input=89af317082bc0bf8]*/

{
    return future_init(self, loop);
}

static int
FutureObj_clear(FutureObj *fut)
{
    Py_CLEAR(fut->fut_loop);
    Py_CLEAR(fut->fut_callback0);
    Py_CLEAR(fut->fut_context0);
    Py_CLEAR(fut->fut_callbacks);
    Py_CLEAR(fut->fut_result);
    Py_CLEAR(fut->fut_exception);
    Py_CLEAR(fut->fut_exception_tb);
    Py_CLEAR(fut->fut_source_tb);
    Py_CLEAR(fut->fut_cancel_msg);
    Py_CLEAR(fut->fut_cancelled_exc);
    Py_CLEAR(fut->dict);
    return 0;
}

static int
FutureObj_traverse(FutureObj *fut, visitproc visit, void *arg)
{
    Py_VISIT(Py_TYPE(fut));
    Py_VISIT(fut->fut_loop);
    Py_VISIT(fut->fut_callback0);
    Py_VISIT(fut->fut_context0);
    Py_VISIT(fut->fut_callbacks);
    Py_VISIT(fut->fut_result);
    Py_VISIT(fut->fut_exception);
    Py_VISIT(fut->fut_exception_tb);
    Py_VISIT(fut->fut_source_tb);
    Py_VISIT(fut->fut_cancel_msg);
    Py_VISIT(fut->fut_cancelled_exc);
    Py_VISIT(fut->dict);
    return 0;
}

/*[clinic input]
_asyncio.Future.result

Return the result this future represents.

If the future has been cancelled, raises CancelledError.  If the
future's result isn't yet available, raises InvalidStateError.  If
the future is done and has an exception set, this exception is raised.
[clinic start generated code]*/

static PyObject *
_asyncio_Future_result_impl(FutureObj *self)
/*[clinic end generated code: output=f35f940936a4b1e5 input=49ecf9cf5ec50dc5]*/
{
    asyncio_state *state = get_asyncio_state_by_def((PyObject *)self);
    PyObject *result;

    if (!future_is_alive(self)) {
        PyErr_SetString(state->asyncio_InvalidStateError,
                        "Future object is not initialized.");
        return NULL;
    }

    int res = future_get_result(state, self, &result);

    if (res == -1) {
        return NULL;
    }

    if (res == 0) {
        return result;
    }

    assert(res == 1);

    PyErr_SetObject(PyExceptionInstance_Class(result), result);
    Py_DECREF(result);
    return NULL;
}

/*[clinic input]
_asyncio.Future.exception

    cls: defining_class
    /

Return the exception that was set on this future.

The exception (or None if no exception was set) is returned only if
the future is done.  If the future has been cancelled, raises
CancelledError.  If the future isn't done yet, raises
InvalidStateError.
[clinic start generated code]*/

static PyObject *
_asyncio_Future_exception_impl(FutureObj *self, PyTypeObject *cls)
/*[clinic end generated code: output=ce75576b187c905b input=3faf15c22acdb60d]*/
{
    if (!future_is_alive(self)) {
        asyncio_state *state = get_asyncio_state_by_cls(cls);
        PyErr_SetString(state->asyncio_InvalidStateError,
                        "Future object is not initialized.");
        return NULL;
    }

    if (self->fut_state == STATE_CANCELLED) {
        asyncio_state *state = get_asyncio_state_by_cls(cls);
        future_set_cancelled_error(state, self);
        return NULL;
    }

    if (self->fut_state != STATE_FINISHED) {
        asyncio_state *state = get_asyncio_state_by_cls(cls);
        PyErr_SetString(state->asyncio_InvalidStateError,
                        "Exception is not set.");
        return NULL;
    }

    if (self->fut_exception != NULL) {
        self->fut_log_tb = 0;
        return Py_NewRef(self->fut_exception);
    }

    Py_RETURN_NONE;
}

/*[clinic input]
_asyncio.Future.set_result

    cls: defining_class
    result: object
    /

Mark the future done and set its result.

If the future is already done when this method is called, raises
InvalidStateError.
[clinic start generated code]*/

static PyObject *
_asyncio_Future_set_result_impl(FutureObj *self, PyTypeObject *cls,
                                PyObject *result)
/*[clinic end generated code: output=99afbbe78f99c32d input=d5a41c1e353acc2e]*/
{
    asyncio_state *state = get_asyncio_state_by_cls(cls);
    ENSURE_FUTURE_ALIVE(state, self)
    return future_set_result(state, self, result);
}

/*[clinic input]
_asyncio.Future.set_exception

    cls: defining_class
    exception: object
    /

Mark the future done and set an exception.

If the future is already done when this method is called, raises
InvalidStateError.
[clinic start generated code]*/

static PyObject *
_asyncio_Future_set_exception_impl(FutureObj *self, PyTypeObject *cls,
                                   PyObject *exception)
/*[clinic end generated code: output=0a5e8b5a52f058d6 input=a245cd49d3df939b]*/
{
    asyncio_state *state = get_asyncio_state_by_cls(cls);
    ENSURE_FUTURE_ALIVE(state, self)
    return future_set_exception(state, self, exception);
}

/*[clinic input]
_asyncio.Future.add_done_callback

    cls: defining_class
    fn: object
    /
    *
    context: object = NULL

Add a callback to be run when the future becomes done.

The callback is called with a single argument - the future object. If
the future is already done when this is called, the callback is
scheduled with call_soon.
[clinic start generated code]*/

static PyObject *
_asyncio_Future_add_done_callback_impl(FutureObj *self, PyTypeObject *cls,
                                       PyObject *fn, PyObject *context)
/*[clinic end generated code: output=922e9a4cbd601167 input=599261c521458cc2]*/
{
    asyncio_state *state = get_asyncio_state_by_cls(cls);
    if (context == NULL) {
        context = PyContext_CopyCurrent();
        if (context == NULL) {
            return NULL;
        }
        PyObject *res = future_add_done_callback(state, self, fn, context);
        Py_DECREF(context);
        return res;
    }
    return future_add_done_callback(state, self, fn, context);
}

/*[clinic input]
_asyncio.Future.remove_done_callback

    cls: defining_class
    fn: object
    /

Remove all instances of a callback from the "call when done" list.

Returns the number of callbacks removed.
[clinic start generated code]*/

static PyObject *
_asyncio_Future_remove_done_callback_impl(FutureObj *self, PyTypeObject *cls,
                                          PyObject *fn)
/*[clinic end generated code: output=2da35ccabfe41b98 input=c7518709b86fc747]*/
{
    PyObject *newlist;
    Py_ssize_t len, i, j=0;
    Py_ssize_t cleared_callback0 = 0;

    asyncio_state *state = get_asyncio_state_by_cls(cls);
    ENSURE_FUTURE_ALIVE(state, self)

    if (self->fut_callback0 != NULL) {
        int cmp = PyObject_RichCompareBool(self->fut_callback0, fn, Py_EQ);
        if (cmp == -1) {
            return NULL;
        }
        if (cmp == 1) {
            /* callback0 == fn */
            Py_CLEAR(self->fut_callback0);
            Py_CLEAR(self->fut_context0);
            cleared_callback0 = 1;
        }
    }

    if (self->fut_callbacks == NULL) {
        return PyLong_FromSsize_t(cleared_callback0);
    }

    len = PyList_GET_SIZE(self->fut_callbacks);
    if (len == 0) {
        Py_CLEAR(self->fut_callbacks);
        return PyLong_FromSsize_t(cleared_callback0);
    }

    if (len == 1) {
        PyObject *cb_tup = PyList_GET_ITEM(self->fut_callbacks, 0);
        int cmp = PyObject_RichCompareBool(
            PyTuple_GET_ITEM(cb_tup, 0), fn, Py_EQ);
        if (cmp == -1) {
            return NULL;
        }
        if (cmp == 1) {
            /* callbacks[0] == fn */
            Py_CLEAR(self->fut_callbacks);
            return PyLong_FromSsize_t(1 + cleared_callback0);
        }
        /* callbacks[0] != fn and len(callbacks) == 1 */
        return PyLong_FromSsize_t(cleared_callback0);
    }

    newlist = PyList_New(len);
    if (newlist == NULL) {
        return NULL;
    }

    // Beware: PyObject_RichCompareBool below may change fut_callbacks.
    // See GH-97592.
    for (i = 0;
         self->fut_callbacks != NULL && i < PyList_GET_SIZE(self->fut_callbacks);
         i++) {
        int ret;
        PyObject *item = PyList_GET_ITEM(self->fut_callbacks, i);
        Py_INCREF(item);
        ret = PyObject_RichCompareBool(PyTuple_GET_ITEM(item, 0), fn, Py_EQ);
        if (ret == 0) {
            if (j < len) {
                PyList_SET_ITEM(newlist, j, item);
                j++;
                continue;
            }
            ret = PyList_Append(newlist, item);
        }
        Py_DECREF(item);
        if (ret < 0) {
            goto fail;
        }
    }

    // Note: fut_callbacks may have been cleared.
    if (j == 0 || self->fut_callbacks == NULL) {
        Py_CLEAR(self->fut_callbacks);
        Py_DECREF(newlist);
        return PyLong_FromSsize_t(len + cleared_callback0);
    }

    if (j < len) {
        Py_SET_SIZE(newlist, j);
    }
    j = PyList_GET_SIZE(newlist);
    len = PyList_GET_SIZE(self->fut_callbacks);
    if (j != len) {
        if (PyList_SetSlice(self->fut_callbacks, 0, len, newlist) < 0) {
            goto fail;
        }
    }
    Py_DECREF(newlist);
    return PyLong_FromSsize_t(len - j + cleared_callback0);

fail:
    Py_DECREF(newlist);
    return NULL;
}

/*[clinic input]
_asyncio.Future.cancel

    cls: defining_class
    /
    msg: object = None

Cancel the future and schedule callbacks.

If the future is already done or cancelled, return False.  Otherwise,
change the future's state to cancelled, schedule the callbacks and
return True.
[clinic start generated code]*/

static PyObject *
_asyncio_Future_cancel_impl(FutureObj *self, PyTypeObject *cls,
                            PyObject *msg)
/*[clinic end generated code: output=074956f35904b034 input=bba8f8b786941a94]*/
{
    asyncio_state *state = get_asyncio_state_by_cls(cls);
    ENSURE_FUTURE_ALIVE(state, self)
    return future_cancel(state, self, msg);
}

/*[clinic input]
_asyncio.Future.cancelled

Return True if the future was cancelled.
[clinic start generated code]*/

static PyObject *
_asyncio_Future_cancelled_impl(FutureObj *self)
/*[clinic end generated code: output=145197ced586357d input=943ab8b7b7b17e45]*/
{
    if (future_is_alive(self) && self->fut_state == STATE_CANCELLED) {
        Py_RETURN_TRUE;
    }
    else {
        Py_RETURN_FALSE;
    }
}

/*[clinic input]
_asyncio.Future.done

Return True if the future is done.

Done means either that a result / exception are available, or that the
future was cancelled.
[clinic start generated code]*/

static PyObject *
_asyncio_Future_done_impl(FutureObj *self)
/*[clinic end generated code: output=244c5ac351145096 input=28d7b23fdb65d2ac]*/
{
    if (!future_is_alive(self) || self->fut_state == STATE_PENDING) {
        Py_RETURN_FALSE;
    }
    else {
        Py_RETURN_TRUE;
    }
}

/*[clinic input]
_asyncio.Future.get_loop

    cls: defining_class
    /

Return the event loop the Future is bound to.
[clinic start generated code]*/

static PyObject *
_asyncio_Future_get_loop_impl(FutureObj *self, PyTypeObject *cls)
/*[clinic end generated code: output=f50ea6c374d9ee97 input=163c2c498b45a1f0]*/
{
    asyncio_state *state = get_asyncio_state_by_cls(cls);
    ENSURE_FUTURE_ALIVE(state, self)
    return Py_NewRef(self->fut_loop);
}

static PyObject *
FutureObj_get_blocking(FutureObj *fut, void *Py_UNUSED(ignored))
{
    if (future_is_alive(fut) && fut->fut_blocking) {
        Py_RETURN_TRUE;
    }
    else {
        Py_RETURN_FALSE;
    }
}

static int
FutureObj_set_blocking(FutureObj *fut, PyObject *val, void *Py_UNUSED(ignored))
{
    if (future_ensure_alive(fut)) {
        return -1;
    }
    if (val == NULL) {
        PyErr_SetString(PyExc_AttributeError, "cannot delete attribute");
        return -1;
    }

    int is_true = PyObject_IsTrue(val);
    if (is_true < 0) {
        return -1;
    }
    fut->fut_blocking = is_true;
    return 0;
}

static PyObject *
FutureObj_get_log_traceback(FutureObj *fut, void *Py_UNUSED(ignored))
{
    asyncio_state *state = get_asyncio_state_by_def((PyObject *)fut);
    ENSURE_FUTURE_ALIVE(state, fut)
    if (fut->fut_log_tb) {
        Py_RETURN_TRUE;
    }
    else {
        Py_RETURN_FALSE;
    }
}

static int
FutureObj_set_log_traceback(FutureObj *fut, PyObject *val, void *Py_UNUSED(ignored))
{
    if (val == NULL) {
        PyErr_SetString(PyExc_AttributeError, "cannot delete attribute");
        return -1;
    }
    int is_true = PyObject_IsTrue(val);
    if (is_true < 0) {
        return -1;
    }
    if (is_true) {
        PyErr_SetString(PyExc_ValueError,
                        "_log_traceback can only be set to False");
        return -1;
    }
    fut->fut_log_tb = is_true;
    return 0;
}

static PyObject *
FutureObj_get_loop(FutureObj *fut, void *Py_UNUSED(ignored))
{
    if (!future_is_alive(fut)) {
        Py_RETURN_NONE;
    }
    return Py_NewRef(fut->fut_loop);
}

static PyObject *
FutureObj_get_callbacks(FutureObj *fut, void *Py_UNUSED(ignored))
{
    asyncio_state *state = get_asyncio_state_by_def((PyObject *)fut);
    Py_ssize_t i;

    ENSURE_FUTURE_ALIVE(state, fut)

    if (fut->fut_callback0 == NULL) {
        if (fut->fut_callbacks == NULL) {
            Py_RETURN_NONE;
        }

        return Py_NewRef(fut->fut_callbacks);
    }

    Py_ssize_t len = 1;
    if (fut->fut_callbacks != NULL) {
        len += PyList_GET_SIZE(fut->fut_callbacks);
    }


    PyObject *new_list = PyList_New(len);
    if (new_list == NULL) {
        return NULL;
    }

    PyObject *tup0 = PyTuple_New(2);
    if (tup0 == NULL) {
        Py_DECREF(new_list);
        return NULL;
    }

    Py_INCREF(fut->fut_callback0);
    PyTuple_SET_ITEM(tup0, 0, fut->fut_callback0);
    assert(fut->fut_context0 != NULL);
    Py_INCREF(fut->fut_context0);
    PyTuple_SET_ITEM(tup0, 1, (PyObject *)fut->fut_context0);

    PyList_SET_ITEM(new_list, 0, tup0);

    if (fut->fut_callbacks != NULL) {
        for (i = 0; i < PyList_GET_SIZE(fut->fut_callbacks); i++) {
            PyObject *cb = PyList_GET_ITEM(fut->fut_callbacks, i);
            Py_INCREF(cb);
            PyList_SET_ITEM(new_list, i + 1, cb);
        }
    }

    return new_list;
}

static PyObject *
FutureObj_get_result(FutureObj *fut, void *Py_UNUSED(ignored))
{
    asyncio_state *state = get_asyncio_state_by_def((PyObject *)fut);
    ENSURE_FUTURE_ALIVE(state, fut)
    if (fut->fut_result == NULL) {
        Py_RETURN_NONE;
    }
    return Py_NewRef(fut->fut_result);
}

static PyObject *
FutureObj_get_exception(FutureObj *fut, void *Py_UNUSED(ignored))
{
    asyncio_state *state = get_asyncio_state_by_def((PyObject *)fut);
    ENSURE_FUTURE_ALIVE(state, fut)
    if (fut->fut_exception == NULL) {
        Py_RETURN_NONE;
    }
    return Py_NewRef(fut->fut_exception);
}

static PyObject *
FutureObj_get_source_traceback(FutureObj *fut, void *Py_UNUSED(ignored))
{
    if (!future_is_alive(fut) || fut->fut_source_tb == NULL) {
        Py_RETURN_NONE;
    }
    return Py_NewRef(fut->fut_source_tb);
}

static PyObject *
FutureObj_get_cancel_message(FutureObj *fut, void *Py_UNUSED(ignored))
{
    if (fut->fut_cancel_msg == NULL) {
        Py_RETURN_NONE;
    }
    return Py_NewRef(fut->fut_cancel_msg);
}

static int
FutureObj_set_cancel_message(FutureObj *fut, PyObject *msg,
                             void *Py_UNUSED(ignored))
{
    if (msg == NULL) {
        PyErr_SetString(PyExc_AttributeError, "cannot delete attribute");
        return -1;
    }
    Py_INCREF(msg);
    Py_XSETREF(fut->fut_cancel_msg, msg);
    return 0;
}

static PyObject *
FutureObj_get_state(FutureObj *fut, void *Py_UNUSED(ignored))
{
    asyncio_state *state = get_asyncio_state_by_def((PyObject *)fut);
    PyObject *ret = NULL;

    ENSURE_FUTURE_ALIVE(state, fut)

    switch (fut->fut_state) {
    case STATE_PENDING:
        ret = &_Py_ID(PENDING);
        break;
    case STATE_CANCELLED:
        ret = &_Py_ID(CANCELLED);
        break;
    case STATE_FINISHED:
        ret = &_Py_ID(FINISHED);
        break;
    default:
        assert (0);
    }
    return Py_XNewRef(ret);
}

static PyObject *
FutureObj_repr(FutureObj *fut)
{
    asyncio_state *state = get_asyncio_state_by_def((PyObject *)fut);
    ENSURE_FUTURE_ALIVE(state, fut)
    return PyObject_CallOneArg(state->asyncio_future_repr_func, (PyObject *)fut);
}

/*[clinic input]
_asyncio.Future._make_cancelled_error

Create the CancelledError to raise if the Future is cancelled.

This should only be called once when handling a cancellation since
it erases the context exception value.
[clinic start generated code]*/

static PyObject *
_asyncio_Future__make_cancelled_error_impl(FutureObj *self)
/*[clinic end generated code: output=a5df276f6c1213de input=ac6effe4ba795ecc]*/
{
    asyncio_state *state = get_asyncio_state_by_def((PyObject *)self);
    return create_cancelled_error(state, self);
}

static void
FutureObj_finalize(FutureObj *fut)
{
    PyObject *error_type, *error_value, *error_traceback;
    PyObject *context;
    PyObject *message = NULL;
    PyObject *func;

    if (!fut->fut_log_tb) {
        return;
    }
    assert(fut->fut_exception != NULL);
    fut->fut_log_tb = 0;

    /* Save the current exception, if any. */
    PyErr_Fetch(&error_type, &error_value, &error_traceback);

    context = PyDict_New();
    if (context == NULL) {
        goto finally;
    }

    message = PyUnicode_FromFormat(
        "%s exception was never retrieved", _PyType_Name(Py_TYPE(fut)));
    if (message == NULL) {
        goto finally;
    }

    if (PyDict_SetItem(context, &_Py_ID(message), message) < 0 ||
        PyDict_SetItem(context, &_Py_ID(exception), fut->fut_exception) < 0 ||
        PyDict_SetItem(context, &_Py_ID(future), (PyObject*)fut) < 0) {
        goto finally;
    }
    if (fut->fut_source_tb != NULL) {
        if (PyDict_SetItem(context, &_Py_ID(source_traceback),
                              fut->fut_source_tb) < 0) {
            goto finally;
        }
    }

    func = PyObject_GetAttr(fut->fut_loop, &_Py_ID(call_exception_handler));
    if (func != NULL) {
        PyObject *res = PyObject_CallOneArg(func, context);
        if (res == NULL) {
            PyErr_WriteUnraisable(func);
        }
        else {
            Py_DECREF(res);
        }
        Py_DECREF(func);
    }

finally:
    Py_XDECREF(context);
    Py_XDECREF(message);

    /* Restore the saved exception. */
    PyErr_Restore(error_type, error_value, error_traceback);
}

static PyMethodDef FutureType_methods[] = {
    _ASYNCIO_FUTURE_RESULT_METHODDEF
    _ASYNCIO_FUTURE_EXCEPTION_METHODDEF
    _ASYNCIO_FUTURE_SET_RESULT_METHODDEF
    _ASYNCIO_FUTURE_SET_EXCEPTION_METHODDEF
    _ASYNCIO_FUTURE_ADD_DONE_CALLBACK_METHODDEF
    _ASYNCIO_FUTURE_REMOVE_DONE_CALLBACK_METHODDEF
    _ASYNCIO_FUTURE_CANCEL_METHODDEF
    _ASYNCIO_FUTURE_CANCELLED_METHODDEF
    _ASYNCIO_FUTURE_DONE_METHODDEF
    _ASYNCIO_FUTURE_GET_LOOP_METHODDEF
    _ASYNCIO_FUTURE__MAKE_CANCELLED_ERROR_METHODDEF
    {"__class_getitem__", Py_GenericAlias, METH_O|METH_CLASS, PyDoc_STR("See PEP 585")},
    {NULL, NULL}        /* Sentinel */
};

static PyMemberDef FutureType_members[] = {
    {"__weaklistoffset__", T_PYSSIZET, offsetof(FutureObj, fut_weakreflist), READONLY},
    {"__dictoffset__", T_PYSSIZET, offsetof(FutureObj, dict), READONLY},
    {NULL},
};

#define FUTURE_COMMON_GETSETLIST                                              \
    {"_state", (getter)FutureObj_get_state, NULL, NULL},                      \
    {"_asyncio_future_blocking", (getter)FutureObj_get_blocking,              \
                                 (setter)FutureObj_set_blocking, NULL},       \
    {"_loop", (getter)FutureObj_get_loop, NULL, NULL},                        \
    {"_callbacks", (getter)FutureObj_get_callbacks, NULL, NULL},              \
    {"_result", (getter)FutureObj_get_result, NULL, NULL},                    \
    {"_exception", (getter)FutureObj_get_exception, NULL, NULL},              \
    {"_log_traceback", (getter)FutureObj_get_log_traceback,                   \
                       (setter)FutureObj_set_log_traceback, NULL},            \
    {"_source_traceback", (getter)FutureObj_get_source_traceback,             \
                          NULL, NULL},                                        \
    {"_cancel_message", (getter)FutureObj_get_cancel_message,                 \
                        (setter)FutureObj_set_cancel_message, NULL},

static PyGetSetDef FutureType_getsetlist[] = {
    FUTURE_COMMON_GETSETLIST
    {NULL} /* Sentinel */
};

static void FutureObj_dealloc(PyObject *self);

static PyType_Slot Future_slots[] = {
    {Py_tp_dealloc, FutureObj_dealloc},
    {Py_tp_repr, (reprfunc)FutureObj_repr},
    {Py_tp_doc, (void *)_asyncio_Future___init____doc__},
    {Py_tp_traverse, (traverseproc)FutureObj_traverse},
    {Py_tp_clear, (inquiry)FutureObj_clear},
    {Py_tp_iter, (getiterfunc)future_new_iter},
    {Py_tp_methods, FutureType_methods},
    {Py_tp_members, FutureType_members},
    {Py_tp_getset, FutureType_getsetlist},
    {Py_tp_init, (initproc)_asyncio_Future___init__},
    {Py_tp_new, PyType_GenericNew},
    {Py_tp_finalize, (destructor)FutureObj_finalize},

    // async slots
    {Py_am_await, (unaryfunc)future_new_iter},
    {0, NULL},
};

static PyType_Spec Future_spec = {
    .name = "_asyncio.Future",
    .basicsize = sizeof(FutureObj),
    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE |
              Py_TPFLAGS_IMMUTABLETYPE),
    .slots = Future_slots,
};

static void
FutureObj_dealloc(PyObject *self)
{
    FutureObj *fut = (FutureObj *)self;

    if (PyObject_CallFinalizerFromDealloc(self) < 0) {
        // resurrected.
        return;
    }

    PyTypeObject *tp = Py_TYPE(fut);
    PyObject_GC_UnTrack(self);

    if (fut->fut_weakreflist != NULL) {
        PyObject_ClearWeakRefs(self);
    }

    (void)FutureObj_clear(fut);
    tp->tp_free(fut);
    Py_DECREF(tp);
}


/*********************** Future Iterator **************************/

typedef struct {
    PyObject_HEAD
    FutureObj *future;
} futureiterobject;


#define FI_FREELIST_MAXLEN 255
static futureiterobject *fi_freelist = NULL;
static Py_ssize_t fi_freelist_len = 0;


static void
FutureIter_dealloc(futureiterobject *it)
{
    PyTypeObject *tp = Py_TYPE(it);
    PyObject_GC_UnTrack(it);
    tp->tp_clear((PyObject *)it);

    if (fi_freelist_len < FI_FREELIST_MAXLEN) {
        fi_freelist_len++;
        it->future = (FutureObj*) fi_freelist;
        fi_freelist = it;
    }
    else {
        PyObject_GC_Del(it);
        Py_DECREF(tp);
    }
}

static PySendResult
FutureIter_am_send(futureiterobject *it,
                   PyObject *Py_UNUSED(arg),
                   PyObject **result)
{
    /* arg is unused, see the comment on FutureIter_send for clarification */

    PyObject *res;
    FutureObj *fut = it->future;

    *result = NULL;
    if (fut == NULL) {
        return PYGEN_ERROR;
    }

    if (fut->fut_state == STATE_PENDING) {
        if (!fut->fut_blocking) {
            fut->fut_blocking = 1;
            *result = Py_NewRef(fut);
            return PYGEN_NEXT;
        }
        PyErr_SetString(PyExc_RuntimeError,
                        "await wasn't used with future");
        return PYGEN_ERROR;
    }

    it->future = NULL;
    res = _asyncio_Future_result_impl(fut);
    if (res != NULL) {
        Py_DECREF(fut);
        *result = res;
        return PYGEN_RETURN;
    }

    Py_DECREF(fut);
    return PYGEN_ERROR;
}

static PyObject *
FutureIter_iternext(futureiterobject *it)
{
    PyObject *result;
    switch (FutureIter_am_send(it, Py_None, &result)) {
        case PYGEN_RETURN:
            (void)_PyGen_SetStopIterationValue(result);
            Py_DECREF(result);
            return NULL;
        case PYGEN_NEXT:
            return result;
        case PYGEN_ERROR:
            return NULL;
        default:
            Py_UNREACHABLE();
    }
}

static PyObject *
FutureIter_send(futureiterobject *self, PyObject *unused)
{
    /* Future.__iter__ doesn't care about values that are pushed to the
     * generator, it just returns self.result().
     */
    return FutureIter_iternext(self);
}

static PyObject *
FutureIter_throw(futureiterobject *self, PyObject *const *args, Py_ssize_t nargs)
{
    PyObject *type, *val = NULL, *tb = NULL;
    if (!_PyArg_CheckPositional("throw", nargs, 1, 3)) {
        return NULL;
    }
    if (nargs > 1) {
        if (PyErr_WarnEx(PyExc_DeprecationWarning,
                            "the (type, exc, tb) signature of throw() is deprecated, "
                            "use the single-arg signature instead.",
                            1) < 0) {
            return NULL;
        }
    }

    type = args[0];
    if (nargs == 3) {
        val = args[1];
        tb = args[2];
    }
    else if (nargs == 2) {
        val = args[1];
    }

    if (tb != NULL && !PyTraceBack_Check(tb)) {
        PyErr_SetString(PyExc_TypeError, "throw() third argument must be a traceback");
        return NULL;
    }

    Py_INCREF(type);
    Py_XINCREF(val);
    Py_XINCREF(tb);

    if (PyExceptionClass_Check(type)) {
        PyErr_NormalizeException(&type, &val, &tb);
        /* No need to call PyException_SetTraceback since we'll be calling
           PyErr_Restore for `type`, `val`, and `tb`. */
    } else if (PyExceptionInstance_Check(type)) {
        if (val) {
            PyErr_SetString(PyExc_TypeError,
                            "instance exception may not have a separate value");
            goto fail;
        }
        val = type;
        type = PyExceptionInstance_Class(type);
        Py_INCREF(type);
        if (tb == NULL)
            tb = PyException_GetTraceback(val);
    } else {
        PyErr_SetString(PyExc_TypeError,
                        "exceptions must be classes deriving BaseException or "
                        "instances of such a class");
        goto fail;
    }

    Py_CLEAR(self->future);

    PyErr_Restore(type, val, tb);

    return NULL;

  fail:
    Py_DECREF(type);
    Py_XDECREF(val);
    Py_XDECREF(tb);
    return NULL;
}

static int
FutureIter_clear(futureiterobject *it)
{
    Py_CLEAR(it->future);
    return 0;
}

static PyObject *
FutureIter_close(futureiterobject *self, PyObject *arg)
{
    (void)FutureIter_clear(self);
    Py_RETURN_NONE;
}

static int
FutureIter_traverse(futureiterobject *it, visitproc visit, void *arg)
{
    Py_VISIT(Py_TYPE(it));
    Py_VISIT(it->future);
    return 0;
}

static PyMethodDef FutureIter_methods[] = {
    {"send",  (PyCFunction)FutureIter_send, METH_O, NULL},
    {"throw", _PyCFunction_CAST(FutureIter_throw), METH_FASTCALL, NULL},
    {"close", (PyCFunction)FutureIter_close, METH_NOARGS, NULL},
    {NULL, NULL}        /* Sentinel */
};

static PyType_Slot FutureIter_slots[] = {
    {Py_tp_dealloc, (destructor)FutureIter_dealloc},
    {Py_tp_getattro, PyObject_GenericGetAttr},
    {Py_tp_traverse, (traverseproc)FutureIter_traverse},
    {Py_tp_clear, FutureIter_clear},
    {Py_tp_iter, PyObject_SelfIter},
    {Py_tp_iternext, (iternextfunc)FutureIter_iternext},
    {Py_tp_methods, FutureIter_methods},

    // async methods
    {Py_am_send, (sendfunc)FutureIter_am_send},
    {0, NULL},
};

static PyType_Spec FutureIter_spec = {
    .name = "_asyncio.FutureIter",
    .basicsize = sizeof(futureiterobject),
    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
              Py_TPFLAGS_IMMUTABLETYPE),
    .slots = FutureIter_slots,
};

static PyObject *
future_new_iter(PyObject *fut)
{
    futureiterobject *it;

    asyncio_state *state = get_asyncio_state_by_def((PyObject *)fut);
    if (!Future_Check(state, fut)) {
        PyErr_BadInternalCall();
        return NULL;
    }

    ENSURE_FUTURE_ALIVE(state, fut)

    if (fi_freelist_len) {
        fi_freelist_len--;
        it = fi_freelist;
        fi_freelist = (futureiterobject*) it->future;
        it->future = NULL;
        _Py_NewReference((PyObject*) it);
    }
    else {
        it = PyObject_GC_New(futureiterobject, state->FutureIterType);
        if (it == NULL) {
            return NULL;
        }
    }

    it->future = (FutureObj*)Py_NewRef(fut);
    PyObject_GC_Track(it);
    return (PyObject*)it;
}


/*********************** Task **************************/


/*[clinic input]
class _asyncio.Task "TaskObj *" "&Task_Type"
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=719dcef0fcc03b37]*/

static int task_call_step_soon(asyncio_state *state, TaskObj *, PyObject *);
static PyObject * task_wakeup(TaskObj *, PyObject *);
static PyObject * task_step(asyncio_state *, TaskObj *, PyObject *);

/* ----- Task._step wrapper */

static int
TaskStepMethWrapper_clear(TaskStepMethWrapper *o)
{
    Py_CLEAR(o->sw_task);
    Py_CLEAR(o->sw_arg);
    return 0;
}

static void
TaskStepMethWrapper_dealloc(TaskStepMethWrapper *o)
{
    PyTypeObject *tp = Py_TYPE(o);
    PyObject_GC_UnTrack(o);
    (void)TaskStepMethWrapper_clear(o);
    Py_TYPE(o)->tp_free(o);
    Py_DECREF(tp);
}

static PyObject *
TaskStepMethWrapper_call(TaskStepMethWrapper *o,
                         PyObject *args, PyObject *kwds)
{
    if (kwds != NULL && PyDict_GET_SIZE(kwds) != 0) {
        PyErr_SetString(PyExc_TypeError, "function takes no keyword arguments");
        return NULL;
    }
    if (args != NULL && PyTuple_GET_SIZE(args) != 0) {
        PyErr_SetString(PyExc_TypeError, "function takes no positional arguments");
        return NULL;
    }
    asyncio_state *state = get_asyncio_state_by_def((PyObject *)o);
    return task_step(state, o->sw_task, o->sw_arg);
}

static int
TaskStepMethWrapper_traverse(TaskStepMethWrapper *o,
                             visitproc visit, void *arg)
{
    Py_VISIT(Py_TYPE(o));
    Py_VISIT(o->sw_task);
    Py_VISIT(o->sw_arg);
    return 0;
}

static PyObject *
TaskStepMethWrapper_get___self__(TaskStepMethWrapper *o, void *Py_UNUSED(ignored))
{
    if (o->sw_task) {
        return Py_NewRef(o->sw_task);
    }
    Py_RETURN_NONE;
}

static PyGetSetDef TaskStepMethWrapper_getsetlist[] = {
    {"__self__", (getter)TaskStepMethWrapper_get___self__, NULL, NULL},
    {NULL} /* Sentinel */
};

static PyType_Slot TaskStepMethWrapper_slots[] = {
    {Py_tp_getset, TaskStepMethWrapper_getsetlist},
    {Py_tp_dealloc, (destructor)TaskStepMethWrapper_dealloc},
    {Py_tp_call, (ternaryfunc)TaskStepMethWrapper_call},
    {Py_tp_getattro, PyObject_GenericGetAttr},
    {Py_tp_traverse, (traverseproc)TaskStepMethWrapper_traverse},
    {Py_tp_clear, (inquiry)TaskStepMethWrapper_clear},
    {0, NULL},
};

static PyType_Spec TaskStepMethWrapper_spec = {
    .name = "_asyncio.TaskStepMethWrapper",
    .basicsize = sizeof(TaskStepMethWrapper),
    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
              Py_TPFLAGS_IMMUTABLETYPE),
    .slots = TaskStepMethWrapper_slots,
};

static PyObject *
TaskStepMethWrapper_new(TaskObj *task, PyObject *arg)
{
    asyncio_state *state = get_asyncio_state_by_def((PyObject *)task);
    TaskStepMethWrapper *o;
    o = PyObject_GC_New(TaskStepMethWrapper, state->TaskStepMethWrapper_Type);
    if (o == NULL) {
        return NULL;
    }

    o->sw_task = (TaskObj*)Py_NewRef(task);
    o->sw_arg = Py_XNewRef(arg);

    PyObject_GC_Track(o);
    return (PyObject*) o;
}

/* ----- Task._wakeup implementation */

static  PyMethodDef TaskWakeupDef = {
    "task_wakeup",
    (PyCFunction)task_wakeup,
    METH_O,
    NULL
};

/* ----- Task introspection helpers */

static int
register_task(asyncio_state *state, PyObject *task)
{
    PyObject *res = PyObject_CallMethodOneArg(state->all_tasks,
                                                 &_Py_ID(add), task);
    if (res == NULL) {
        return -1;
    }
    Py_DECREF(res);
    return 0;
}


static int
unregister_task(asyncio_state *state, PyObject *task)
{
    PyObject *res = PyObject_CallMethodOneArg(state->all_tasks,
                                     &_Py_ID(discard), task);
    if (res == NULL) {
        return -1;
    }
    Py_DECREF(res);
    return 0;
}


static int
enter_task(asyncio_state *state, PyObject *loop, PyObject *task)
{
    PyObject *item;
    Py_hash_t hash;
    hash = PyObject_Hash(loop);
    if (hash == -1) {
        return -1;
    }
    item = _PyDict_GetItem_KnownHash(state->current_tasks, loop, hash);
    if (item != NULL) {
        Py_INCREF(item);
        PyErr_Format(
            PyExc_RuntimeError,
            "Cannot enter into task %R while another " \
            "task %R is being executed.",
            task, item, NULL);
        Py_DECREF(item);
        return -1;
    }
    if (PyErr_Occurred()) {
        return -1;
    }
    return _PyDict_SetItem_KnownHash(state->current_tasks, loop, task, hash);
}


static int
leave_task(asyncio_state *state, PyObject *loop, PyObject *task)
/*[clinic end generated code: output=0ebf6db4b858fb41 input=51296a46313d1ad8]*/
{
    PyObject *item;
    Py_hash_t hash;
    hash = PyObject_Hash(loop);
    if (hash == -1) {
        return -1;
    }
    item = _PyDict_GetItem_KnownHash(state->current_tasks, loop, hash);
    if (item != task) {
        if (item == NULL) {
            /* Not entered, replace with None */
            item = Py_None;
        }
        PyErr_Format(
            PyExc_RuntimeError,
            "Leaving task %R does not match the current task %R.",
            task, item, NULL);
        return -1;
    }
    return _PyDict_DelItem_KnownHash(state->current_tasks, loop, hash);
}

/* ----- Task */

/*[clinic input]
_asyncio.Task.__init__

    coro: object
    *
    loop: object = None
    name: object = None
    context: object = None

A coroutine wrapped in a Future.
[clinic start generated code]*/

static int
_asyncio_Task___init___impl(TaskObj *self, PyObject *coro, PyObject *loop,
                            PyObject *name, PyObject *context)
/*[clinic end generated code: output=49ac96fe33d0e5c7 input=924522490c8ce825]*/

{
    if (future_init((FutureObj*)self, loop)) {
        return -1;
    }

    asyncio_state *state = get_asyncio_state_by_def((PyObject *)self);
    int is_coro = is_coroutine(state, coro);
    if (is_coro == -1) {
        return -1;
    }
    if (is_coro == 0) {
        self->task_log_destroy_pending = 0;
        PyErr_Format(PyExc_TypeError,
                     "a coroutine was expected, got %R",
                     coro, NULL);
        return -1;
    }

    if (context == Py_None) {
        Py_XSETREF(self->task_context, PyContext_CopyCurrent());
        if (self->task_context == NULL) {
            return -1;
        }
    } else {
        self->task_context = Py_NewRef(context);
    }

    Py_CLEAR(self->task_fut_waiter);
    self->task_must_cancel = 0;
    self->task_log_destroy_pending = 1;
    self->task_num_cancels_requested = 0;
    Py_INCREF(coro);
    Py_XSETREF(self->task_coro, coro);

    if (name == Py_None) {
        name = PyUnicode_FromFormat("Task-%" PRIu64,
                                    ++state->task_name_counter);
    } else if (!PyUnicode_CheckExact(name)) {
        name = PyObject_Str(name);
    } else {
        Py_INCREF(name);
    }
    Py_XSETREF(self->task_name, name);
    if (self->task_name == NULL) {
        return -1;
    }

    if (task_call_step_soon(state, self, NULL)) {
        return -1;
    }
    return register_task(state, (PyObject*)self);
}

static int
TaskObj_clear(TaskObj *task)
{
    (void)FutureObj_clear((FutureObj*) task);
    Py_CLEAR(task->task_context);
    Py_CLEAR(task->task_coro);
    Py_CLEAR(task->task_name);
    Py_CLEAR(task->task_fut_waiter);
    return 0;
}

static int
TaskObj_traverse(TaskObj *task, visitproc visit, void *arg)
{
    Py_VISIT(Py_TYPE(task));
    Py_VISIT(task->task_context);
    Py_VISIT(task->task_coro);
    Py_VISIT(task->task_name);
    Py_VISIT(task->task_fut_waiter);
    FutureObj *fut = (FutureObj *)task;
    Py_VISIT(fut->fut_loop);
    Py_VISIT(fut->fut_callback0);
    Py_VISIT(fut->fut_context0);
    Py_VISIT(fut->fut_callbacks);
    Py_VISIT(fut->fut_result);
    Py_VISIT(fut->fut_exception);
    Py_VISIT(fut->fut_exception_tb);
    Py_VISIT(fut->fut_source_tb);
    Py_VISIT(fut->fut_cancel_msg);
    Py_VISIT(fut->fut_cancelled_exc);
    Py_VISIT(fut->dict);
    return 0;
}

static PyObject *
TaskObj_get_log_destroy_pending(TaskObj *task, void *Py_UNUSED(ignored))
{
    if (task->task_log_destroy_pending) {
        Py_RETURN_TRUE;
    }
    else {
        Py_RETURN_FALSE;
    }
}

static int
TaskObj_set_log_destroy_pending(TaskObj *task, PyObject *val, void *Py_UNUSED(ignored))
{
    if (val == NULL) {
        PyErr_SetString(PyExc_AttributeError, "cannot delete attribute");
        return -1;
    }
    int is_true = PyObject_IsTrue(val);
    if (is_true < 0) {
        return -1;
    }
    task->task_log_destroy_pending = is_true;
    return 0;
}

static PyObject *
TaskObj_get_must_cancel(TaskObj *task, void *Py_UNUSED(ignored))
{
    if (task->task_must_cancel) {
        Py_RETURN_TRUE;
    }
    else {
        Py_RETURN_FALSE;
    }
}

static PyObject *
TaskObj_get_coro(TaskObj *task, void *Py_UNUSED(ignored))
{
    if (task->task_coro) {
        return Py_NewRef(task->task_coro);
    }

    Py_RETURN_NONE;
}

static PyObject *
TaskObj_get_fut_waiter(TaskObj *task, void *Py_UNUSED(ignored))
{
    if (task->task_fut_waiter) {
        return Py_NewRef(task->task_fut_waiter);
    }

    Py_RETURN_NONE;
}

static PyObject *
TaskObj_repr(TaskObj *task)
{
    asyncio_state *state = get_asyncio_state_by_def((PyObject *)task);
    return PyObject_CallOneArg(state->asyncio_task_repr_func,
                               (PyObject *)task);
}


/*[clinic input]
_asyncio.Task._make_cancelled_error

Create the CancelledError to raise if the Task is cancelled.

This should only be called once when handling a cancellation since
it erases the context exception value.
[clinic start generated code]*/

static PyObject *
_asyncio_Task__make_cancelled_error_impl(TaskObj *self)
/*[clinic end generated code: output=55a819e8b4276fab input=52c0e32de8e2f840]*/
{
    FutureObj *fut = (FutureObj*)self;
    return _asyncio_Future__make_cancelled_error_impl(fut);
}


/*[clinic input]
_asyncio.Task.cancel

    msg: object = None

Request that this task cancel itself.

This arranges for a CancelledError to be thrown into the
wrapped coroutine on the next cycle through the event loop.
The coroutine then has a chance to clean up or even deny
the request using try/except/finally.

Unlike Future.cancel, this does not guarantee that the
task will be cancelled: the exception might be caught and
acted upon, delaying cancellation of the task or preventing
cancellation completely.  The task may also return a value or
raise a different exception.

Immediately after this method is called, Task.cancelled() will
not return True (unless the task was already cancelled).  A
task will be marked as cancelled when the wrapped coroutine
terminates with a CancelledError exception (even if cancel()
was not called).

This also increases the task's count of cancellation requests.
[clinic start generated code]*/

static PyObject *
_asyncio_Task_cancel_impl(TaskObj *self, PyObject *msg)
/*[clinic end generated code: output=c66b60d41c74f9f1 input=7bb51bf25974c783]*/
{
    self->task_log_tb = 0;

    if (self->task_state != STATE_PENDING) {
        Py_RETURN_FALSE;
    }

    self->task_num_cancels_requested += 1;

    // These three lines are controversial.  See discussion starting at
    // https://github.com/python/cpython/pull/31394#issuecomment-1053545331
    // and corresponding code in tasks.py.
    // if (self->task_num_cancels_requested > 1) {
    //     Py_RETURN_FALSE;
    // }

    if (self->task_fut_waiter) {
        PyObject *res;
        int is_true;

        res = PyObject_CallMethodOneArg(self->task_fut_waiter,
                                           &_Py_ID(cancel), msg);
        if (res == NULL) {
            return NULL;
        }

        is_true = PyObject_IsTrue(res);
        Py_DECREF(res);
        if (is_true < 0) {
            return NULL;
        }

        if (is_true) {
            Py_RETURN_TRUE;
        }
    }

    self->task_must_cancel = 1;
    Py_XINCREF(msg);
    Py_XSETREF(self->task_cancel_msg, msg);
    Py_RETURN_TRUE;
}

/*[clinic input]
_asyncio.Task.cancelling

Return the count of the task's cancellation requests.

This count is incremented when .cancel() is called
and may be decremented using .uncancel().
[clinic start generated code]*/

static PyObject *
_asyncio_Task_cancelling_impl(TaskObj *self)
/*[clinic end generated code: output=803b3af96f917d7e input=b625224d310cbb17]*/
/*[clinic end generated code]*/
{
    return PyLong_FromLong(self->task_num_cancels_requested);
}

/*[clinic input]
_asyncio.Task.uncancel

Decrement the task's count of cancellation requests.

This should be used by tasks that catch CancelledError
and wish to continue indefinitely until they are cancelled again.

Returns the remaining number of cancellation requests.
[clinic start generated code]*/

static PyObject *
_asyncio_Task_uncancel_impl(TaskObj *self)
/*[clinic end generated code: output=58184d236a817d3c input=68f81a4b90b46be2]*/
/*[clinic end generated code]*/
{
    if (self->task_num_cancels_requested > 0) {
        self->task_num_cancels_requested -= 1;
    }
    return PyLong_FromLong(self->task_num_cancels_requested);
}

/*[clinic input]
_asyncio.Task.get_stack

    cls: defining_class
    /
    *
    limit: object = None

Return the list of stack frames for this task's coroutine.

If the coroutine is not done, this returns the stack where it is
suspended.  If the coroutine has completed successfully or was
cancelled, this returns an empty list.  If the coroutine was
terminated by an exception, this returns the list of traceback
frames.

The frames are always ordered from oldest to newest.

The optional limit gives the maximum number of frames to
return; by default all available frames are returned.  Its
meaning differs depending on whether a stack or a traceback is
returned: the newest frames of a stack are returned, but the
oldest frames of a traceback are returned.  (This matches the
behavior of the traceback module.)

For reasons beyond our control, only one stack frame is
returned for a suspended coroutine.
[clinic start generated code]*/

static PyObject *
_asyncio_Task_get_stack_impl(TaskObj *self, PyTypeObject *cls,
                             PyObject *limit)
/*[clinic end generated code: output=6774dfc10d3857fa input=8e01c9b2618ae953]*/
{
    asyncio_state *state = get_asyncio_state_by_cls(cls);
    return PyObject_CallFunctionObjArgs(
        state->asyncio_task_get_stack_func, self, limit, NULL);
}

/*[clinic input]
_asyncio.Task.print_stack

    cls: defining_class
    /
    *
    limit: object = None
    file: object = None

Print the stack or traceback for this task's coroutine.

This produces output similar to that of the traceback module,
for the frames retrieved by get_stack().  The limit argument
is passed to get_stack().  The file argument is an I/O stream
to which the output is written; by default output is written
to sys.stderr.
[clinic start generated code]*/

static PyObject *
_asyncio_Task_print_stack_impl(TaskObj *self, PyTypeObject *cls,
                               PyObject *limit, PyObject *file)
/*[clinic end generated code: output=b38affe9289ec826 input=150b35ba2d3a7dee]*/
{
    asyncio_state *state = get_asyncio_state_by_cls(cls);
    return PyObject_CallFunctionObjArgs(
        state->asyncio_task_print_stack_func, self, limit, file, NULL);
}

/*[clinic input]
_asyncio.Task.set_result

    result: object
    /
[clinic start generated code]*/

static PyObject *
_asyncio_Task_set_result(TaskObj *self, PyObject *result)
/*[clinic end generated code: output=1dcae308bfcba318 input=9d1a00c07be41bab]*/
{
    PyErr_SetString(PyExc_RuntimeError,
                    "Task does not support set_result operation");
    return NULL;
}

/*[clinic input]
_asyncio.Task.set_exception

    exception: object
    /
[clinic start generated code]*/

static PyObject *
_asyncio_Task_set_exception(TaskObj *self, PyObject *exception)
/*[clinic end generated code: output=bc377fc28067303d input=9a8f65c83dcf893a]*/
{
    PyErr_SetString(PyExc_RuntimeError,
                    "Task does not support set_exception operation");
    return NULL;
}

/*[clinic input]
_asyncio.Task.get_coro
[clinic start generated code]*/

static PyObject *
_asyncio_Task_get_coro_impl(TaskObj *self)
/*[clinic end generated code: output=bcac27c8cc6c8073 input=d2e8606c42a7b403]*/
{
    return Py_NewRef(self->task_coro);
}

/*[clinic input]
_asyncio.Task.get_context
[clinic start generated code]*/

static PyObject *
_asyncio_Task_get_context_impl(TaskObj *self)
/*[clinic end generated code: output=6996f53d3dc01aef input=87c0b209b8fceeeb]*/
{
    return Py_NewRef(self->task_context);
}

/*[clinic input]
_asyncio.Task.get_name
[clinic start generated code]*/

static PyObject *
_asyncio_Task_get_name_impl(TaskObj *self)
/*[clinic end generated code: output=0ecf1570c3b37a8f input=a4a6595d12f4f0f8]*/
{
    if (self->task_name) {
        return Py_NewRef(self->task_name);
    }

    Py_RETURN_NONE;
}

/*[clinic input]
_asyncio.Task.set_name

    value: object
    /
[clinic start generated code]*/

static PyObject *
_asyncio_Task_set_name(TaskObj *self, PyObject *value)
/*[clinic end generated code: output=138a8d51e32057d6 input=a8359b6e65f8fd31]*/
{
    if (!PyUnicode_CheckExact(value)) {
        value = PyObject_Str(value);
        if (value == NULL) {
            return NULL;
        }
    } else {
        Py_INCREF(value);
    }

    Py_XSETREF(self->task_name, value);
    Py_RETURN_NONE;
}

static void
TaskObj_finalize(TaskObj *task)
{
    PyObject *context;
    PyObject *message = NULL;
    PyObject *func;
    PyObject *error_type, *error_value, *error_traceback;

    if (task->task_state != STATE_PENDING || !task->task_log_destroy_pending) {
        goto done;
    }

    /* Save the current exception, if any. */
    PyErr_Fetch(&error_type, &error_value, &error_traceback);

    context = PyDict_New();
    if (context == NULL) {
        goto finally;
    }

    message = PyUnicode_FromString("Task was destroyed but it is pending!");
    if (message == NULL) {
        goto finally;
    }

    if (PyDict_SetItem(context, &_Py_ID(message), message) < 0 ||
        PyDict_SetItem(context, &_Py_ID(task), (PyObject*)task) < 0)
    {
        goto finally;
    }

    if (task->task_source_tb != NULL) {
        if (PyDict_SetItem(context, &_Py_ID(source_traceback),
                              task->task_source_tb) < 0)
        {
            goto finally;
        }
    }

    func = PyObject_GetAttr(task->task_loop, &_Py_ID(call_exception_handler));
    if (func != NULL) {
        PyObject *res = PyObject_CallOneArg(func, context);
        if (res == NULL) {
            PyErr_WriteUnraisable(func);
        }
        else {
            Py_DECREF(res);
        }
        Py_DECREF(func);
    }

finally:
    Py_XDECREF(context);
    Py_XDECREF(message);

    /* Restore the saved exception. */
    PyErr_Restore(error_type, error_value, error_traceback);

done:
    FutureObj_finalize((FutureObj*)task);
}

static void TaskObj_dealloc(PyObject *);  /* Needs Task_CheckExact */

static PyMethodDef TaskType_methods[] = {
    _ASYNCIO_FUTURE_RESULT_METHODDEF
    _ASYNCIO_FUTURE_EXCEPTION_METHODDEF
    _ASYNCIO_FUTURE_ADD_DONE_CALLBACK_METHODDEF
    _ASYNCIO_FUTURE_REMOVE_DONE_CALLBACK_METHODDEF
    _ASYNCIO_FUTURE_CANCELLED_METHODDEF
    _ASYNCIO_FUTURE_DONE_METHODDEF
    _ASYNCIO_TASK_SET_RESULT_METHODDEF
    _ASYNCIO_TASK_SET_EXCEPTION_METHODDEF
    _ASYNCIO_TASK_CANCEL_METHODDEF
    _ASYNCIO_TASK_CANCELLING_METHODDEF
    _ASYNCIO_TASK_UNCANCEL_METHODDEF
    _ASYNCIO_TASK_GET_STACK_METHODDEF
    _ASYNCIO_TASK_PRINT_STACK_METHODDEF
    _ASYNCIO_TASK__MAKE_CANCELLED_ERROR_METHODDEF
    _ASYNCIO_TASK_GET_NAME_METHODDEF
    _ASYNCIO_TASK_SET_NAME_METHODDEF
    _ASYNCIO_TASK_GET_CORO_METHODDEF
    _ASYNCIO_TASK_GET_CONTEXT_METHODDEF
    {"__class_getitem__", Py_GenericAlias, METH_O|METH_CLASS, PyDoc_STR("See PEP 585")},
    {NULL, NULL}        /* Sentinel */
};

static PyMemberDef TaskType_members[] = {
    {"__weaklistoffset__", T_PYSSIZET, offsetof(TaskObj, task_weakreflist), READONLY},
    {"__dictoffset__", T_PYSSIZET, offsetof(TaskObj, dict), READONLY},
    {NULL},
};

static PyGetSetDef TaskType_getsetlist[] = {
    FUTURE_COMMON_GETSETLIST
    {"_log_destroy_pending", (getter)TaskObj_get_log_destroy_pending,
                             (setter)TaskObj_set_log_destroy_pending, NULL},
    {"_must_cancel", (getter)TaskObj_get_must_cancel, NULL, NULL},
    {"_coro", (getter)TaskObj_get_coro, NULL, NULL},
    {"_fut_waiter", (getter)TaskObj_get_fut_waiter, NULL, NULL},
    {NULL} /* Sentinel */
};

static PyType_Slot Task_slots[] = {
    {Py_tp_dealloc, TaskObj_dealloc},
    {Py_tp_repr, (reprfunc)TaskObj_repr},
    {Py_tp_doc, (void *)_asyncio_Task___init____doc__},
    {Py_tp_traverse, (traverseproc)TaskObj_traverse},
    {Py_tp_clear, (inquiry)TaskObj_clear},
    {Py_tp_iter, (getiterfunc)future_new_iter},
    {Py_tp_methods, TaskType_methods},
    {Py_tp_members, TaskType_members},
    {Py_tp_getset, TaskType_getsetlist},
    {Py_tp_init, (initproc)_asyncio_Task___init__},
    {Py_tp_new, PyType_GenericNew},
    {Py_tp_finalize, (destructor)TaskObj_finalize},

    // async slots
    {Py_am_await, (unaryfunc)future_new_iter},
    {0, NULL},
};

static PyType_Spec Task_spec = {
    .name = "_asyncio.Task",
    .basicsize = sizeof(TaskObj),
    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE |
              Py_TPFLAGS_IMMUTABLETYPE),
    .slots = Task_slots,
};

static void
TaskObj_dealloc(PyObject *self)
{
    TaskObj *task = (TaskObj *)self;

    if (PyObject_CallFinalizerFromDealloc(self) < 0) {
        // resurrected.
        return;
    }

    PyTypeObject *tp = Py_TYPE(task);
    PyObject_GC_UnTrack(self);

    if (task->task_weakreflist != NULL) {
        PyObject_ClearWeakRefs(self);
    }

    (void)TaskObj_clear(task);
    tp->tp_free(task);
    Py_DECREF(tp);
}

static int
task_call_step_soon(asyncio_state *state, TaskObj *task, PyObject *arg)
{
    PyObject *cb = TaskStepMethWrapper_new(task, arg);
    if (cb == NULL) {
        return -1;
    }

    int ret = call_soon(state, task->task_loop, cb, NULL, task->task_context);
    Py_DECREF(cb);
    return ret;
}

static PyObject *
task_set_error_soon(asyncio_state *state, TaskObj *task, PyObject *et,
                    const char *format, ...)
{
    PyObject* msg;

    va_list vargs;
    va_start(vargs, format);
    msg = PyUnicode_FromFormatV(format, vargs);
    va_end(vargs);

    if (msg == NULL) {
        return NULL;
    }

    PyObject *e = PyObject_CallOneArg(et, msg);
    Py_DECREF(msg);
    if (e == NULL) {
        return NULL;
    }

    if (task_call_step_soon(state, task, e) == -1) {
        Py_DECREF(e);
        return NULL;
    }

    Py_DECREF(e);
    Py_RETURN_NONE;
}

static inline int
gen_status_from_result(PyObject **result)
{
    if (*result != NULL) {
        return PYGEN_NEXT;
    }
    if (_PyGen_FetchStopIterationValue(result) == 0) {
        return PYGEN_RETURN;
    }

    assert(PyErr_Occurred());
    return PYGEN_ERROR;
}

static PyObject *
task_step_impl(asyncio_state *state, TaskObj *task, PyObject *exc)
{
    int res;
    int clear_exc = 0;
    PyObject *result = NULL;
    PyObject *coro;
    PyObject *o;

    if (task->task_state != STATE_PENDING) {
        PyErr_Format(state->asyncio_InvalidStateError,
                     "_step(): already done: %R %R",
                     task,
                     exc ? exc : Py_None);
        goto fail;
    }

    if (task->task_must_cancel) {
        assert(exc != Py_None);

        if (exc) {
            /* Check if exc is a CancelledError */
            res = PyObject_IsInstance(exc, state->asyncio_CancelledError);
            if (res == -1) {
                /* An error occurred, abort */
                goto fail;
            }
            if (res == 0) {
                /* exc is not CancelledError; reset it to NULL */
                exc = NULL;
            }
        }

        if (!exc) {
            /* exc was not a CancelledError */
            exc = create_cancelled_error(state, (FutureObj*)task);

            if (!exc) {
                goto fail;
            }
            clear_exc = 1;
        }

        task->task_must_cancel = 0;
    }

    Py_CLEAR(task->task_fut_waiter);

    coro = task->task_coro;
    if (coro == NULL) {
        PyErr_SetString(PyExc_RuntimeError, "uninitialized Task object");
        if (clear_exc) {
            /* We created 'exc' during this call */
            Py_DECREF(exc);
        }
        return NULL;
    }

    int gen_status = PYGEN_ERROR;
    if (exc == NULL) {
        gen_status = PyIter_Send(coro, Py_None, &result);
    }
    else {
        result = PyObject_CallMethodOneArg(coro, &_Py_ID(throw), exc);
        gen_status = gen_status_from_result(&result);
        if (clear_exc) {
            /* We created 'exc' during this call */
            Py_DECREF(exc);
        }
    }

    if (gen_status == PYGEN_RETURN || gen_status == PYGEN_ERROR) {
        PyObject *et, *ev, *tb;

        if (result != NULL) {
            /* The error is StopIteration and that means that
               the underlying coroutine has resolved */

            PyObject *tmp;
            if (task->task_must_cancel) {
                // Task is cancelled right before coro stops.
                task->task_must_cancel = 0;
                tmp = future_cancel(state, (FutureObj*)task,
                                    task->task_cancel_msg);
            }
            else {
                tmp = future_set_result(state, (FutureObj*)task, result);
            }

            Py_DECREF(result);

            if (tmp == NULL) {
                return NULL;
            }
            Py_DECREF(tmp);
            Py_RETURN_NONE;
        }

        if (PyErr_ExceptionMatches(state->asyncio_CancelledError)) {
            /* CancelledError */
            PyErr_Fetch(&et, &ev, &tb);
            assert(et);
            PyErr_NormalizeException(&et, &ev, &tb);
            if (tb != NULL) {
                PyException_SetTraceback(ev, tb);
                Py_DECREF(tb);
            }
            Py_XDECREF(et);

            FutureObj *fut = (FutureObj*)task;
            /* transfer ownership */
            fut->fut_cancelled_exc = ev;

            return future_cancel(state, fut, NULL);
        }

        /* Some other exception; pop it and call Task.set_exception() */
        PyErr_Fetch(&et, &ev, &tb);
        assert(et);
        PyErr_NormalizeException(&et, &ev, &tb);
        if (tb != NULL) {
            PyException_SetTraceback(ev, tb);
        }

        o = future_set_exception(state, (FutureObj*)task, ev);
        if (!o) {
            /* An exception in Task.set_exception() */
            Py_DECREF(et);
            Py_XDECREF(tb);
            Py_XDECREF(ev);
            goto fail;
        }
        assert(o == Py_None);
        Py_DECREF(o);

        if (PyErr_GivenExceptionMatches(et, PyExc_KeyboardInterrupt) ||
            PyErr_GivenExceptionMatches(et, PyExc_SystemExit))
        {
            /* We've got a KeyboardInterrupt or a SystemError; re-raise it */
            PyErr_Restore(et, ev, tb);
            goto fail;
        }

        Py_DECREF(et);
        Py_XDECREF(tb);
        Py_XDECREF(ev);

        Py_RETURN_NONE;
    }

    if (result == (PyObject*)task) {
        /* We have a task that wants to await on itself */
        goto self_await;
    }

    /* Check if `result` is FutureObj or TaskObj (and not a subclass) */
    if (Future_CheckExact(state, result) || Task_CheckExact(state, result)) {
        PyObject *wrapper;
        PyObject *tmp;
        FutureObj *fut = (FutureObj*)result;

        /* Check if `result` future is attached to a different loop */
        if (fut->fut_loop != task->task_loop) {
            goto different_loop;
        }

        if (!fut->fut_blocking) {
            goto yield_insteadof_yf;
        }

        fut->fut_blocking = 0;

        /* result.add_done_callback(task._wakeup) */
        wrapper = PyCFunction_New(&TaskWakeupDef, (PyObject *)task);
        if (wrapper == NULL) {
            goto fail;
        }
        tmp = future_add_done_callback(state,
            (FutureObj*)result, wrapper, task->task_context);
        Py_DECREF(wrapper);
        if (tmp == NULL) {
            goto fail;
        }
        Py_DECREF(tmp);

        /* task._fut_waiter = result */
        task->task_fut_waiter = result;  /* no incref is necessary */

        if (task->task_must_cancel) {
            PyObject *r;
            int is_true;
            r = PyObject_CallMethodOneArg(result, &_Py_ID(cancel),
                                             task->task_cancel_msg);
            if (r == NULL) {
                return NULL;
            }
            is_true = PyObject_IsTrue(r);
            Py_DECREF(r);
            if (is_true < 0) {
                return NULL;
            }
            else if (is_true) {
                task->task_must_cancel = 0;
            }
        }

        Py_RETURN_NONE;
    }

    /* Check if `result` is None */
    if (result == Py_None) {
        /* Bare yield relinquishes control for one event loop iteration. */
        if (task_call_step_soon(state, task, NULL)) {
            goto fail;
        }
        return result;
    }

    /* Check if `result` is a Future-compatible object */
    if (_PyObject_LookupAttr(result, &_Py_ID(_asyncio_future_blocking), &o) < 0) {
        goto fail;
    }
    if (o != NULL && o != Py_None) {
        /* `result` is a Future-compatible object */
        PyObject *wrapper;
        PyObject *tmp;

        int blocking = PyObject_IsTrue(o);
        Py_DECREF(o);
        if (blocking < 0) {
            goto fail;
        }

        /* Check if `result` future is attached to a different loop */
        PyObject *oloop = get_future_loop(state, result);
        if (oloop == NULL) {
            goto fail;
        }
        if (oloop != task->task_loop) {
            Py_DECREF(oloop);
            goto different_loop;
        }
        Py_DECREF(oloop);

        if (!blocking) {
            goto yield_insteadof_yf;
        }

        /* result._asyncio_future_blocking = False */
        if (PyObject_SetAttr(
                result, &_Py_ID(_asyncio_future_blocking), Py_False) == -1) {
            goto fail;
        }

        wrapper = PyCFunction_New(&TaskWakeupDef, (PyObject *)task);
        if (wrapper == NULL) {
            goto fail;
        }

        /* result.add_done_callback(task._wakeup) */
        PyObject *add_cb = PyObject_GetAttr(
            result, &_Py_ID(add_done_callback));
        if (add_cb == NULL) {
            Py_DECREF(wrapper);
            goto fail;
        }
        PyObject *stack[2];
        stack[0] = wrapper;
        stack[1] = (PyObject *)task->task_context;
        EVAL_CALL_STAT_INC_IF_FUNCTION(EVAL_CALL_API, add_cb);
        tmp = PyObject_Vectorcall(add_cb, stack, 1, state->context_kwname);
        Py_DECREF(add_cb);
        Py_DECREF(wrapper);
        if (tmp == NULL) {
            goto fail;
        }
        Py_DECREF(tmp);

        /* task._fut_waiter = result */
        task->task_fut_waiter = result;  /* no incref is necessary */

        if (task->task_must_cancel) {
            PyObject *r;
            int is_true;
            r = PyObject_CallMethodOneArg(result, &_Py_ID(cancel),
                                             task->task_cancel_msg);
            if (r == NULL) {
                return NULL;
            }
            is_true = PyObject_IsTrue(r);
            Py_DECREF(r);
            if (is_true < 0) {
                return NULL;
            }
            else if (is_true) {
                task->task_must_cancel = 0;
            }
        }

        Py_RETURN_NONE;
    }

    Py_XDECREF(o);
    /* Check if `result` is a generator */
    res = PyObject_IsInstance(result, (PyObject*)&PyGen_Type);
    if (res < 0) {
        goto fail;
    }
    if (res) {
        /* `result` is a generator */
        o = task_set_error_soon(
            state, task, PyExc_RuntimeError,
            "yield was used instead of yield from for "
            "generator in task %R with %R", task, result);
        Py_DECREF(result);
        return o;
    }

    /* The `result` is none of the above */
    o = task_set_error_soon(
        state, task, PyExc_RuntimeError, "Task got bad yield: %R", result);
    Py_DECREF(result);
    return o;

self_await:
    o = task_set_error_soon(
        state, task, PyExc_RuntimeError,
        "Task cannot await on itself: %R", task);
    Py_DECREF(result);
    return o;

yield_insteadof_yf:
    o = task_set_error_soon(
        state, task, PyExc_RuntimeError,
        "yield was used instead of yield from "
        "in task %R with %R",
        task, result);
    Py_DECREF(result);
    return o;

different_loop:
    o = task_set_error_soon(
        state, task, PyExc_RuntimeError,
        "Task %R got Future %R attached to a different loop",
        task, result);
    Py_DECREF(result);
    return o;

fail:
    Py_XDECREF(result);
    return NULL;
}

static PyObject *
task_step(asyncio_state *state, TaskObj *task, PyObject *exc)
{
    PyObject *res;

    if (enter_task(state, task->task_loop, (PyObject*)task) < 0) {
        return NULL;
    }

    res = task_step_impl(state, task, exc);

    if (res == NULL) {
        PyObject *et, *ev, *tb;
        PyErr_Fetch(&et, &ev, &tb);
        leave_task(state, task->task_loop, (PyObject*)task);
        _PyErr_ChainExceptions(et, ev, tb); /* Normalizes (et, ev, tb) */
        return NULL;
    }
    else {
        if (leave_task(state, task->task_loop, (PyObject*)task) < 0) {
            Py_DECREF(res);
            return NULL;
        }
        else {
            return res;
        }
    }
}

static PyObject *
task_wakeup(TaskObj *task, PyObject *o)
{
    PyObject *et, *ev, *tb;
    PyObject *result;
    assert(o);

    asyncio_state *state = get_asyncio_state_by_def((PyObject *)task);
    if (Future_CheckExact(state, o) || Task_CheckExact(state, o)) {
        PyObject *fut_result = NULL;
        int res = future_get_result(state, (FutureObj*)o, &fut_result);

        switch(res) {
        case -1:
            assert(fut_result == NULL);
            break; /* exception raised */
        case 0:
            Py_DECREF(fut_result);
            return task_step(state, task, NULL);
        default:
            assert(res == 1);
            result = task_step(state, task, fut_result);
            Py_DECREF(fut_result);
            return result;
        }
    }
    else {
        PyObject *fut_result = PyObject_CallMethod(o, "result", NULL);
        if (fut_result != NULL) {
            Py_DECREF(fut_result);
            return task_step(state, task, NULL);
        }
        /* exception raised */
    }

    PyErr_Fetch(&et, &ev, &tb);
    assert(et);
    PyErr_NormalizeException(&et, &ev, &tb);
    if (tb != NULL) {
        PyException_SetTraceback(ev, tb);
    }

    result = task_step(state, task, ev);

    Py_DECREF(et);
    Py_XDECREF(tb);
    Py_XDECREF(ev);

    return result;
}


/*********************** Functions **************************/


/*[clinic input]
_asyncio._get_running_loop

Return the running event loop or None.

This is a low-level function intended to be used by event loops.
This function is thread-specific.

[clinic start generated code]*/

static PyObject *
_asyncio__get_running_loop_impl(PyObject *module)
/*[clinic end generated code: output=b4390af721411a0a input=0a21627e25a4bd43]*/
{
    PyObject *loop;
    asyncio_state *state = get_asyncio_state(module);
    if (get_running_loop(state, &loop)) {
        return NULL;
    }
    if (loop == NULL) {
        /* There's no currently running event loop */
        Py_RETURN_NONE;
    }
    return loop;
}

/*[clinic input]
_asyncio._set_running_loop
    loop: 'O'
    /

Set the running event loop.

This is a low-level function intended to be used by event loops.
This function is thread-specific.
[clinic start generated code]*/

static PyObject *
_asyncio__set_running_loop(PyObject *module, PyObject *loop)
/*[clinic end generated code: output=ae56bf7a28ca189a input=4c9720233d606604]*/
{
    asyncio_state *state = get_asyncio_state(module);
    if (set_running_loop(state, loop)) {
        return NULL;
    }
    Py_RETURN_NONE;
}

/*[clinic input]
_asyncio.get_event_loop

Return an asyncio event loop.

When called from a coroutine or a callback (e.g. scheduled with
call_soon or similar API), this function will always return the
running event loop.

If there is no running event loop set, the function will return
the result of `get_event_loop_policy().get_event_loop()` call.
[clinic start generated code]*/

static PyObject *
_asyncio_get_event_loop_impl(PyObject *module)
/*[clinic end generated code: output=2a2d8b2f824c648b input=9364bf2916c8655d]*/
{
    asyncio_state *state = get_asyncio_state(module);
    return get_event_loop(state);
}

/*[clinic input]
_asyncio.get_running_loop

Return the running event loop.  Raise a RuntimeError if there is none.

This function is thread-specific.
[clinic start generated code]*/

static PyObject *
_asyncio_get_running_loop_impl(PyObject *module)
/*[clinic end generated code: output=c247b5f9e529530e input=2a3bf02ba39f173d]*/
{
    PyObject *loop;
    asyncio_state *state = get_asyncio_state(module);
    if (get_running_loop(state, &loop)) {
        return NULL;
    }
    if (loop == NULL) {
        /* There's no currently running event loop */
        PyErr_SetString(
            PyExc_RuntimeError, "no running event loop");
    }
    return loop;
}

/*[clinic input]
_asyncio._register_task

    task: object

Register a new task in asyncio as executed by loop.

Returns None.
[clinic start generated code]*/

static PyObject *
_asyncio__register_task_impl(PyObject *module, PyObject *task)
/*[clinic end generated code: output=8672dadd69a7d4e2 input=21075aaea14dfbad]*/
{
    asyncio_state *state = get_asyncio_state(module);
    if (register_task(state, task) < 0) {
        return NULL;
    }
    Py_RETURN_NONE;
}


/*[clinic input]
_asyncio._unregister_task

    task: object

Unregister a task.

Returns None.
[clinic start generated code]*/

static PyObject *
_asyncio__unregister_task_impl(PyObject *module, PyObject *task)
/*[clinic end generated code: output=6e5585706d568a46 input=28fb98c3975f7bdc]*/
{
    asyncio_state *state = get_asyncio_state(module);
    if (unregister_task(state, task) < 0) {
        return NULL;
    }
    Py_RETURN_NONE;
}


/*[clinic input]
_asyncio._enter_task

    loop: object
    task: object

Enter into task execution or resume suspended task.

Task belongs to loop.

Returns None.
[clinic start generated code]*/

static PyObject *
_asyncio__enter_task_impl(PyObject *module, PyObject *loop, PyObject *task)
/*[clinic end generated code: output=a22611c858035b73 input=de1b06dca70d8737]*/
{
    asyncio_state *state = get_asyncio_state(module);
    if (enter_task(state, loop, task) < 0) {
        return NULL;
    }
    Py_RETURN_NONE;
}


/*[clinic input]
_asyncio._leave_task

    loop: object
    task: object

Leave task execution or suspend a task.

Task belongs to loop.

Returns None.
[clinic start generated code]*/

static PyObject *
_asyncio__leave_task_impl(PyObject *module, PyObject *loop, PyObject *task)
/*[clinic end generated code: output=0ebf6db4b858fb41 input=51296a46313d1ad8]*/
{
    asyncio_state *state = get_asyncio_state(module);
    if (leave_task(state, loop, task) < 0) {
        return NULL;
    }
    Py_RETURN_NONE;
}


/*********************** PyRunningLoopHolder ********************/


static PyRunningLoopHolder *
new_running_loop_holder(asyncio_state *state, PyObject *loop)
{
    PyRunningLoopHolder *rl = PyObject_GC_New(
        PyRunningLoopHolder, state->PyRunningLoopHolder_Type);
    if (rl == NULL) {
        return NULL;
    }

#if defined(HAVE_GETPID) && !defined(MS_WINDOWS)
    rl->rl_pid = getpid();
#endif
    rl->rl_loop = Py_NewRef(loop);

    PyObject_GC_Track(rl);
    return rl;
}


static int
PyRunningLoopHolder_clear(PyRunningLoopHolder *rl)
{
    Py_CLEAR(rl->rl_loop);
    return 0;
}


static int
PyRunningLoopHolder_traverse(PyRunningLoopHolder *rl, visitproc visit,
                             void *arg)
{
    Py_VISIT(Py_TYPE(rl));
    Py_VISIT(rl->rl_loop);
    return 0;
}


static void
PyRunningLoopHolder_tp_dealloc(PyRunningLoopHolder *rl)
{
    asyncio_state *state = get_asyncio_state_by_def((PyObject *)rl);
    if (state->cached_running_holder == (PyObject *)rl) {
        state->cached_running_holder = NULL;
    }
    PyTypeObject *tp = Py_TYPE(rl);
    PyObject_GC_UnTrack(rl);
    PyRunningLoopHolder_clear(rl);
    PyObject_GC_Del(rl);
    Py_DECREF(tp);
}


static PyType_Slot PyRunningLoopHolder_slots[] = {
    {Py_tp_getattro, PyObject_GenericGetAttr},
    {Py_tp_dealloc, (destructor)PyRunningLoopHolder_tp_dealloc},
    {Py_tp_traverse, (traverseproc)PyRunningLoopHolder_traverse},
    {Py_tp_clear, PyRunningLoopHolder_clear},
    {0, NULL},
};


static PyType_Spec PyRunningLoopHolder_spec = {
    .name = "_asyncio._RunningLoopHolder",
    .basicsize = sizeof(PyRunningLoopHolder),
    .slots = PyRunningLoopHolder_slots,
    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
              Py_TPFLAGS_IMMUTABLETYPE),
};


/*********************** Module **************************/


static void
module_free_freelists(void)
{
    PyObject *next;
    PyObject *current;

    next = (PyObject*) fi_freelist;
    while (next != NULL) {
        assert(fi_freelist_len > 0);
        fi_freelist_len--;

        current = next;
        next = (PyObject*) ((futureiterobject*) current)->future;
        PyObject_GC_Del(current);
    }
    assert(fi_freelist_len == 0);
    fi_freelist = NULL;
}

static int
module_traverse(PyObject *mod, visitproc visit, void *arg)
{
    asyncio_state *state = get_asyncio_state(mod);

    Py_VISIT(state->FutureIterType);
    Py_VISIT(state->TaskStepMethWrapper_Type);
    Py_VISIT(state->FutureType);
    Py_VISIT(state->TaskType);
    Py_VISIT(state->PyRunningLoopHolder_Type);

    Py_VISIT(state->asyncio_mod);
    Py_VISIT(state->traceback_extract_stack);
    Py_VISIT(state->asyncio_future_repr_func);
    Py_VISIT(state->asyncio_get_event_loop_policy);
    Py_VISIT(state->asyncio_iscoroutine_func);
    Py_VISIT(state->asyncio_task_get_stack_func);
    Py_VISIT(state->asyncio_task_print_stack_func);
    Py_VISIT(state->asyncio_task_repr_func);
    Py_VISIT(state->asyncio_InvalidStateError);
    Py_VISIT(state->asyncio_CancelledError);

    Py_VISIT(state->all_tasks);
    Py_VISIT(state->current_tasks);
    Py_VISIT(state->iscoroutine_typecache);

    Py_VISIT(state->context_kwname);

    // Visit freelist.
    PyObject *next = (PyObject*) fi_freelist;
    while (next != NULL) {
        PyObject *current = next;
        Py_VISIT(current);
        next = (PyObject*) ((futureiterobject*) current)->future;
    }
    return 0;
}

static int
module_clear(PyObject *mod)
{
    asyncio_state *state = get_asyncio_state(mod);

    Py_CLEAR(state->FutureIterType);
    Py_CLEAR(state->TaskStepMethWrapper_Type);
    Py_CLEAR(state->FutureType);
    Py_CLEAR(state->TaskType);
    Py_CLEAR(state->PyRunningLoopHolder_Type);

    Py_CLEAR(state->asyncio_mod);
    Py_CLEAR(state->traceback_extract_stack);
    Py_CLEAR(state->asyncio_future_repr_func);
    Py_CLEAR(state->asyncio_get_event_loop_policy);
    Py_CLEAR(state->asyncio_iscoroutine_func);
    Py_CLEAR(state->asyncio_task_get_stack_func);
    Py_CLEAR(state->asyncio_task_print_stack_func);
    Py_CLEAR(state->asyncio_task_repr_func);
    Py_CLEAR(state->asyncio_InvalidStateError);
    Py_CLEAR(state->asyncio_CancelledError);

    Py_CLEAR(state->all_tasks);
    Py_CLEAR(state->current_tasks);
    Py_CLEAR(state->iscoroutine_typecache);

    Py_CLEAR(state->context_kwname);

    module_free_freelists();

    return 0;
}

static void
module_free(void *mod)
{
    (void)module_clear((PyObject *)mod);
}

static int
module_init(asyncio_state *state)
{
    PyObject *module = NULL;

    state->asyncio_mod = PyImport_ImportModule("asyncio");
    if (state->asyncio_mod == NULL) {
        goto fail;
    }

    state->current_tasks = PyDict_New();
    if (state->current_tasks == NULL) {
        goto fail;
    }

    state->iscoroutine_typecache = PySet_New(NULL);
    if (state->iscoroutine_typecache == NULL) {
        goto fail;
    }


    state->context_kwname = Py_BuildValue("(s)", "context");
    if (state->context_kwname == NULL) {
        goto fail;
    }

#define WITH_MOD(NAME) \
    Py_CLEAR(module); \
    module = PyImport_ImportModule(NAME); \
    if (module == NULL) { \
        goto fail; \
    }

#define GET_MOD_ATTR(VAR, NAME) \
    VAR = PyObject_GetAttrString(module, NAME); \
    if (VAR == NULL) { \
        goto fail; \
    }

    WITH_MOD("asyncio.events")
    GET_MOD_ATTR(state->asyncio_get_event_loop_policy, "get_event_loop_policy")

    WITH_MOD("asyncio.base_futures")
    GET_MOD_ATTR(state->asyncio_future_repr_func, "_future_repr")

    WITH_MOD("asyncio.exceptions")
    GET_MOD_ATTR(state->asyncio_InvalidStateError, "InvalidStateError")
    GET_MOD_ATTR(state->asyncio_CancelledError, "CancelledError")

    WITH_MOD("asyncio.base_tasks")
    GET_MOD_ATTR(state->asyncio_task_repr_func, "_task_repr")
    GET_MOD_ATTR(state->asyncio_task_get_stack_func, "_task_get_stack")
    GET_MOD_ATTR(state->asyncio_task_print_stack_func, "_task_print_stack")

    WITH_MOD("asyncio.coroutines")
    GET_MOD_ATTR(state->asyncio_iscoroutine_func, "iscoroutine")

    WITH_MOD("traceback")
    GET_MOD_ATTR(state->traceback_extract_stack, "extract_stack")

    PyObject *weak_set;
    WITH_MOD("weakref")
    GET_MOD_ATTR(weak_set, "WeakSet");
    state->all_tasks = PyObject_CallNoArgs(weak_set);
    Py_CLEAR(weak_set);
    if (state->all_tasks == NULL) {
        goto fail;
    }

    Py_DECREF(module);
    return 0;

fail:
    Py_CLEAR(module);
    return -1;

#undef WITH_MOD
#undef GET_MOD_ATTR
}

PyDoc_STRVAR(module_doc, "Accelerator module for asyncio");

static PyMethodDef asyncio_methods[] = {
    _ASYNCIO_GET_EVENT_LOOP_METHODDEF
    _ASYNCIO_GET_RUNNING_LOOP_METHODDEF
    _ASYNCIO__GET_RUNNING_LOOP_METHODDEF
    _ASYNCIO__SET_RUNNING_LOOP_METHODDEF
    _ASYNCIO__REGISTER_TASK_METHODDEF
    _ASYNCIO__UNREGISTER_TASK_METHODDEF
    _ASYNCIO__ENTER_TASK_METHODDEF
    _ASYNCIO__LEAVE_TASK_METHODDEF
    {NULL, NULL}
};

static int
module_exec(PyObject *mod)
{
    asyncio_state *state = get_asyncio_state(mod);

#define CREATE_TYPE(m, tp, spec, base)                                  \
    do {                                                                \
        tp = (PyTypeObject *)PyType_FromMetaclass(NULL, m, spec,        \
                                                  (PyObject *)base);    \
        if (tp == NULL) {                                               \
            return -1;                                                  \
        }                                                               \
    } while (0)

    CREATE_TYPE(mod, state->TaskStepMethWrapper_Type, &TaskStepMethWrapper_spec, NULL);
    CREATE_TYPE(mod, state->PyRunningLoopHolder_Type, &PyRunningLoopHolder_spec, NULL);
    CREATE_TYPE(mod, state->FutureIterType, &FutureIter_spec, NULL);
    CREATE_TYPE(mod, state->FutureType, &Future_spec, NULL);
    CREATE_TYPE(mod, state->TaskType, &Task_spec, state->FutureType);

#undef CREATE_TYPE

    if (PyModule_AddType(mod, state->FutureType) < 0) {
        return -1;
    }

    if (PyModule_AddType(mod, state->TaskType) < 0) {
        return -1;
    }
    // Must be done after types are added to avoid a circular dependency
    if (module_init(state) < 0) {
        return -1;
    }

    if (PyModule_AddObjectRef(mod, "_all_tasks", state->all_tasks) < 0) {
        return -1;
    }

    if (PyModule_AddObjectRef(mod, "_current_tasks", state->current_tasks) < 0) {
        return -1;
    }


    return 0;
}

static struct PyModuleDef_Slot module_slots[] = {
    {Py_mod_exec, module_exec},
    {0, NULL},
};

static struct PyModuleDef _asynciomodule = {
    .m_base = PyModuleDef_HEAD_INIT,
    .m_name = "_asyncio",
    .m_doc = module_doc,
    .m_size = sizeof(asyncio_state),
    .m_methods = asyncio_methods,
    .m_slots = module_slots,
    .m_traverse = module_traverse,
    .m_clear = module_clear,
    .m_free = (freefunc)module_free,
};

PyMODINIT_FUNC
PyInit__asyncio(void)
{
    return PyModuleDef_Init(&_asynciomodule);
}