this is my first cpython PR, let me know what else needs to be done to get this into any other releases it's required in.

Since _asinciomodule is compiled with python interpreter, it can use private macro APIs
(_PyObject_GC_TRACK and _PyObject_GC_UNTRACK).

Oh, sorry, macro version API broke Windows build and you used public APIs to fix it.

Could you add news entry?
https://devguide.python.org/committing/#what-s-new-and-news-entries

added news and reverted LRU change

should we put as many fixes as we can in this PR, or create another PR with as many as we can? I need the defaultdict one too...and maybe even others as who knows what third party libraries do. I feel like we've opened a pandoras box of crashers :)

I already created #2974.
More pull request for updating document is welcome.

The latest revision LGTM. But can you use blurb to generate the NEWS entry?

@1st1 should I remove the one in NEWS? Also was hoping I could add a testcase for Task but couldn't figure out how to repro it, especially given Task inherits from Future so I don't want to trigger the Future's crash

@1st1 should I remove the one in NEWS?

Yes, please!

Also was hoping I could add a testcase for Task but couldn't figure out how to repro it, especially given Task inherits from Future so I don't want to trigger the Future's crash

I'm trying to come up with a test.

The following test crashes unpatched CPython:

    import gc

    def test_task_del_collect(self):
        async def coro():
            return Evil()

        class Evil:
            def __del__(self):
                gc.collect()

        for i in range(100):
            task = self.new_task(self.loop, coro())
            self.loop.run_until_complete(task)

The test also fails if we fix only Task, but not Future.

so I had something similar but it doesn't crash:

import gc
import asyncio

class Evil:
    def __del__(self):
        gc.collect()


async def run():
    return Evil()


loop = asyncio.get_event_loop()

for i in range(100):
    loop.run_until_complete(asyncio.Task(run()))
#    f = asyncio.Future()
#    f.set_result(Evil())

ah, figured it out, had to have multiple tasks pending in the run loop.

ya realized as I was going to work, this should fix it

this set of PRs is a massive win for Python. It would be nice if a core dev could look and find a way to nip it at the bud to avoid these hacky calls, as shown they're highly error prone. Who knows how many third party modules are missing them too.

GH-2984 is a backport of this pull request to the 3.6 branch.

Do we have C Task/Future in 3.5?

No. asyncio speedup is introduced at 3.6