[New-bugs-announce] [issue22007] sys.stdout.write on OS X is not EINTR safe

Jonathan Stewmon report at bugs.python.org
Fri Jul 18 23:10:00 CEST 2014

New submission from Jonathan Stewmon:

Writing to sys.stdout on OS X can fail with IOError: [Errno 4] Interrupted system call.

I have observed this while trying to write to sys.stdout when SIGCHLD is received. The script below consistently reproduces the problem with python 2.7.2 on OS X 10.9.3.

import sys
import os
import signal
import subprocess
import time

children = {}
def claim_child():
    pid, status = os.wait()
    p = children.pop(pid)

def trap(sig, frame):

signal.signal(signal.SIGCHLD, trap)

running = 0
max_procs = 70
program = [sys.executable, '-c', 'import sys, time; print sys.version; time.sleep(3)']
f = sys.stdout # crashes with: IOError: [Errno 4] Interrupted system call
# f = file('/tmp/eintr.log', 'w') # works just fine
while True:
    while len(children) < max_procs:
        f.write('starting program: {}\n'.format(program))
        p = subprocess.Popen(program)
        children[p.pid] = p

components: IO
messages: 223435
nosy: jstewmon
priority: normal
severity: normal
status: open
title: sys.stdout.write on OS X is not EINTR safe
versions: Python 2.7

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