Issue #1731717: Fixed the problem where subprocess.wait() could cause an

OSError exception when The OS had been told to ignore SIGCLD in our process
or otherwise not wait for exiting child processes.

diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index ac46ce85c07610addcef06449e97c21593889975..452611c5a9a108cb990ca92bbd22a57d92c64eb0 100644 (file)
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -1295,7 +1295,11 @@ class Popen(object):
                 os.close(errpipe_read)
 
             if data:
-                _eintr_retry_call(os.waitpid, self.pid, 0)
+                try:
+                    _eintr_retry_call(os.waitpid, self.pid, 0)
+                except OSError as e:
+                    if e.errno != errno.ECHILD:
+                        raise
                 try:
                     exception_name, hex_errno, err_msg = data.split(b':', 2)
                 except ValueError:
@@ -1358,7 +1362,15 @@ class Popen(object):
             """Wait for child process to terminate.  Returns returncode
             attribute."""
             if self.returncode is None:
-                pid, sts = _eintr_retry_call(os.waitpid, self.pid, 0)
+                try:
+                    pid, sts = _eintr_retry_call(os.waitpid, self.pid, 0)
+                except OSError as e:
+                    if e.errno != errno.ECHILD:
+                        raise
+                    # This happens if SIGCLD is set to be ignored or waiting
+                    # for child processes has otherwise been disabled for our
+                    # process.  This child is dead, we can't get the status.
+                    sts = 0
                 self._handle_exitstatus(sts)
             return self.returncode
 

diff --git a/Lib/test/subprocessdata/sigchild_ignore.py b/Lib/test/subprocessdata/sigchild_ignore.py
new file mode 100644 (file)
index 0000000..1d03303
--- /dev/null
+++ b/Lib/test/subprocessdata/sigchild_ignore.py
@@ -0,0 +1,6 @@
+import signal, subprocess, sys
+# On Linux this causes os.waitpid to fail with OSError as the OS has already
+# reaped our child process.  The wait() passing the OSError on to the caller
+# and causing us to exit with an error is what we are testing against.
+signal.signal(signal.SIGCLD, signal.SIG_IGN)
+subprocess.Popen([sys.executable, '-c', 'print("albatross")']).wait()

diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index 0804a1322542750497c60c91182c84f3acc3ccd9..1e97bac0189d0a4750ab5de50829d78ea2532209 100644 (file)
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -1073,6 +1073,16 @@ class POSIXProcessTestCase(BaseTestCase):
                         close_fds=False, pass_fds=(fd, )))
             self.assertIn('overriding close_fds', str(context.warning))
 
+    def test_wait_when_sigchild_ignored(self):
+        # NOTE: sigchild_ignore.py may not be an effective test on all OSes.
+        sigchild_ignore = support.findfile("sigchild_ignore.py",
+                                           subdir="subprocessdata")
+        p = subprocess.Popen([sys.executable, sigchild_ignore],
+                             stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+        stdout, stderr = p.communicate()
+        self.assertEqual(0, p.returncode, "sigchild_ignore.py exited"
+                         " non-zero with this error:\n%s" % stderr)
+
 
 @unittest.skipUnless(mswindows, "Windows specific tests")
 class Win32ProcessTestCase(BaseTestCase):

diff --git a/Misc/NEWS b/Misc/NEWS
index d2a2c42b87971833cfa60906a0fc8fe5855e9ca3..981b53f49a75e9f11bc57ba6f53f482735e66dd2 100644 (file)
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -33,6 +33,10 @@ Library
   added in 3.2beta1) to allow specifying a specific list of file descriptors
   to keep open in the child process.
 
+- Issue #1731717: Fixed the problem where subprocess.wait() could cause an
+  OSError exception when The OS had been told to ignore SIGCLD in our process
+  or otherwise not wait for exiting child processes.
+
 
 What's New in Python 3.2 Beta 1?
 ================================