New submission from jimbo1qaz_ via Gmail <jimbo1...@gmail.com>:
Windows 10 1709 x64, Python 3.7.1. Minimal example and stack traces at https://gist.github.com/jimbo1qaz/75d7a40cac307f8239ce011fd90c86bf Essentially I create a subprocess.Popen, using a process (msys2 head.exe) which closes its stdin after some amount of input, then write nothing but b"\n"*1000 bytes to its stdin. If the bufsize is small (1000 bytes), I always get OSError: [Errno 22] Invalid argument If the bufsize is large (1 million bytes), I always get BrokenPipeError: [Errno 32] Broken pipe. (This happens whether I write 1 million newlines or 1000 at a time). Originally I created a ffmpeg->ffplay pipeline with a massive bufsize (around 1280*720*3 * 2 frames), then wrote 1280*720*3 bytes of video frames at a time. Closing ffplay's window usually created BrokenPipeError, but occasionally OSError. This was actually random. ------------ It seems that this is known to some extent, although I couldn't find any relevant issues on the bug tracker, and "having to catch 2 separate errors" isn't explained on the documentation. (Is it intended though undocumented behavior?) Popen._communicate() calls Popen._stdin_write(), but specifically ignores BrokenPipeError and OSError where exc.errno == errno.EINVAL == 22 (the 2 cases I encountered). But I don't call Popen.communicate() but instead write directly to stdin, since I have a loop that outputs 1 video frame at a time, and rely on pipe blocking to stop my application from running too far ahead of ffmpeg/ffplay. ------------ popen.stdin is a <_io.BufferedWriter name=3>. https://docs.python.org/3/library/io.html#io.BufferedIOBase.write >Write the given bytes-like object, b, and return the number of bytes written >(always equal to the length of b in bytes, since if the write fails an OSError >will be raised). Depending on the actual implementation, these bytes may be >readily written to the underlying stream, or held in a buffer for performance >and latency reasons. The page doesn't mention BrokenPipeError at all (Ctrl+F). So why do I *sometimes* get a BrokenPipeError (subclasses ConnectionError subclasses OSError) instead? ---------- messages: 333792 nosy: jimbo1qaz_ priority: normal severity: normal status: open title: When writing/closing a closed Popen.stdin, I get OSError vs. BrokenPipeError randomly or depending on bufsize versions: Python 3.7 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue35754> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
