def copy_tb(base_tb, tb_next):
# TracebackType has no public constructor, so allocate one the hard way
try:
raise ValueError
except ValueError as exc:
new_tb = exc.__traceback__
c_new_tb = CTraceback.from_address(id(new_tb))
# At the C level, tb_next either pointer to the next traceback or is
# NULL. c_void_p and the .tb_next accessor both convert NULL to None,
# but we shouldn't DECREF None just because we assigned to a NULL
# pointer! Here we know that our new traceback has only 1 frame in it,
# so we can assume the tb_next field is NULL.
assert c_new_tb.tb_next is None
# If tb_next is None, then we want to set c_new_tb.tb_next to NULL,
# which it already is, so we're done. Otherwise, we have to actually
# do some work:
if tb_next is not None:
_ctypes.Py_INCREF(tb_next)
c_new_tb.tb_next = id(tb_next)
assert c_new_tb.tb_frame is not None
_ctypes.Py_INCREF(base_tb.tb_frame)
old_tb_frame = new_tb.tb_frame
c_new_tb.tb_frame = id(base_tb.tb_frame)
_ctypes.Py_DECREF(old_tb_frame)
c_new_tb.tb_lasti = base_tb.tb_lasti
c_new_tb.tb_lineno = base_tb.tb_lineno
return new_tb
def set_aio_task_coro(
task: "asyncio.Task[Any]", new_coro: Coroutine[Any, Any, Any]
) -> None:
try:
task._coro = new_coro # type: ignore
return
except AttributeError as ex:
if sys.implementation.name != "cpython": # pragma: no cover
raise
if "is not writable" not in str(ex): # pragma: no cover
raise
# If using the C accelerator on CPython, the setter isn't
# even present and we need to use ctypes to change the
# coroutine field.
global aio_task_coro_c_offset
import ctypes
old_coro = get_aio_task_coro(task)
if aio_task_coro_c_offset is None:
# Deduce the offset by scanning the task object representation
# for id(task._coro)
aio_task_coro_c_offset = _aligned_ptr_offset_in_object(task, old_coro)
if aio_task_coro_c_offset is None: # pragma: no cover
raise RuntimeError("Couldn't determine C offset of asyncio.Task._coro")
# (Explanation copied from trio._core._multierror, applies equally well here.)
# How to handle refcounting? I don't want to use ctypes.py_object because
# I don't understand or trust it, and I don't want to use
# ctypes.pythonapi.Py_{Inc,Dec}Ref because we might clash with user code
# that also tries to use them but with different types. So private _ctypes
# APIs it is!
import _ctypes # type: ignore
coro_field = ctypes.c_size_t.from_address(id(task) + aio_task_coro_c_offset)
assert coro_field.value == id(old_coro)
_ctypes.Py_INCREF(new_coro)
coro_field.value = id(new_coro)
_ctypes.Py_DECREF(old_coro)
