New issue 3042: crash when reading non-blocking subprocess output
https://bitbucket.org/pypy/pypy/issues/3042/crash-when-reading-non-blocking-subprocess
Jacob Lifshay:
Output:
```
RPython traceback:
File "pypy_interpreter.c", line 37926, in BuiltinCode_funcrun_obj
File "pypy_module__io_1.c", line 11207, in W_BufferedReader_readline_w
File "implement_2.c", line 32105, in dispatcher_70
File "pypy_module__io.c", line 15998, in W_BufferedReader__raw_read
Traceback (most recent call last):
File "pypy_bug.py", line 10, in <module>
s = p.stdout.readline()
SystemError: unexpected internal exception (please report a bug):
<BlockingIOError object at 0x7f9481569f00>; internal traceback was dumped to
stderr
```
Versions:
Python 3.6.1 \(7a2e437acfce, Mar 21 2019, 13:39:41\)
\[PyPy 7.2.0-beta0 with GCC 6.2.0 20160901\]
Ubuntu 18.04 x86\_64
reproducable using:
```python
import subprocess
import fcntl
import os
from select import select
p = subprocess.Popen(["/bin/bash", "-c", "printf ''"],
stdin=subprocess.DEVNULL, stdout=subprocess.PIPE, stderr=None)
fl = fcntl.fcntl(p.stdout, fcntl.F_GETFL)
fcntl.fcntl(p.stdout, fcntl.F_SETFL, fl | os.O_NONBLOCK)
while True:
s = p.stdout.readline()
print(s)
if len(s) == 0:
if p.poll() is not None:
break
try:
select([p.stdout], [], [], 1.0)
except InterruptedError:
pass
```
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