subprocess.communicate never returns when the subprocess outputs more than 0xFFFF + 1 bytes

[riouh]

• uvloop version: uvloop==0.14.0
• Python version: Python 3.8.6
• Platform: MacOS
• Can you reproduce the bug with PYTHONASYNCIODEBUG in env?: yes
• Does uvloop behave differently from vanilla asyncio? How?: yes. vanilla asyncio just works

The following code never returns with uvloop :

import asyncio
from asyncio.subprocess import PIPE
import uvloop
import logging

logging.basicConfig(level=logging.DEBUG)


async def main():
    proc = await asyncio.create_subprocess_exec("/bin/cat", stdin=PIPE, stderr=PIPE, stdout=PIPE)
    stdin = b'x' * 65_537
    stdout, stderr = await proc.communicate(stdin)
    print(stdout)


uvloop.install()
asyncio.run(main())

changing 65_537 to 65_536 makes the script work as expected and returns immediately.

The debug output is :

 % PYTHONASYNCIODEBUG=1 python xxx.py
DEBUG:asyncio:<Process 13746> communicate: feed stdin (65537 bytes)
DEBUG:asyncio:<Process 13746> communicate: close stdin
DEBUG:asyncio:<Process 13746> communicate: read stdout
DEBUG:asyncio:<Process 13746> communicate: read stderr

[lovasoa]

I can reproduce the issue with the latest version of uvloop published on pypi (v0.14.0, which is almost one year old), but I cannot reproduce it with the latest development version ( 6ef69a7 ). It looks like the issue has been fixed by some other change. It would be nice if a new version could be published on pypi soon.

[fantix]

Closed by #364. Please feel free to reopen if the issue persists.

[lovasoa]

@fantix : The issue was already fixed in master when it was opened. The problem is that the latest released version is old and contains the bug: https://pypi.org/project/uvloop/#history

[fantix]

Right, thanks for the reminder - this links to how we close issues. I'm leaning towards marking issues closed to reflect the situation in the master branch, and PyPI releases could reference the issues fixed in each version. People with the same issue could still find this ticket and understand the release by comparing the Git tags in logs. But @1st1 may have a different opinion

[1st1]

But @1st1 may have a different opinion

Closing as soon as it's fixes in master is IMO ok, but then I typically add a comment saying when the release is scheduled and then go back and update the issue again once the release has been made.

[lovasoa]

Yes, I also think this is the right thing to do. So, is there a new release planned ? The last one was in November 2019.

[fantix]

Yes! I'll push for a new release after the first 3 columns on this board are cleared.