issue7213: Open the pipes used by subprocesses with the FD_CLOEXEC flag from

the C code, using pipe2() when available.  Adds unittests for close_fds and
cloexec behaviors.

Lib/test/test_subprocess.py

@@ -10,6 +10,7 @@ import time
 import re
 import sysconfig
 import warnings
+import select
 try:
     import gc
 except ImportError:
@@ -964,6 +965,83 @@ class POSIXProcessTestCase(BaseTestCase):
         exitcode = subprocess.call([program, "-c", "pass"], env=envb)
         self.assertEqual(exitcode, 0)
 
+    def test_pipe_cloexec(self):
+        sleeper = support.findfile("input_reader.py", subdir="subprocessdata")
+        fd_status = support.findfile("fd_status.py", subdir="subprocessdata")
+
+        p1 = subprocess.Popen([sys.executable, sleeper],
+                              stdin=subprocess.PIPE, stdout=subprocess.PIPE,
+                              stderr=subprocess.PIPE, close_fds=False)
+
+        self.addCleanup(p1.communicate, b'')
+
+        p2 = subprocess.Popen([sys.executable, fd_status],
+                              stdout=subprocess.PIPE, close_fds=False)
+
+        output, error = p2.communicate()
+        result_fds = set(map(int, output.split(b',')))
+        unwanted_fds = set([p1.stdin.fileno(), p1.stdout.fileno(),
+                            p1.stderr.fileno()])
+
+        self.assertFalse(result_fds & unwanted_fds,
+                         "Expected no fds from %r to be open in child, "
+                         "found %r" %
+                              (unwanted_fds, result_fds & unwanted_fds))
+
+    def test_pipe_cloexec_real_tools(self):
+        qcat = support.findfile("qcat.py", subdir="subprocessdata")
+        qgrep = support.findfile("qgrep.py", subdir="subprocessdata")
+
+        subdata = b'zxcvbn'
+        data = subdata * 4 + b'\n'
+
+        p1 = subprocess.Popen([sys.executable, qcat],
+                              stdin=subprocess.PIPE, stdout=subprocess.PIPE,
+                              close_fds=False)
+
+        p2 = subprocess.Popen([sys.executable, qgrep, subdata],
+                              stdin=p1.stdout, stdout=subprocess.PIPE,
+                              close_fds=False)
+
+        self.addCleanup(p1.wait)
+        self.addCleanup(p2.wait)
+        self.addCleanup(p1.terminate)
+        self.addCleanup(p2.terminate)
+
+        p1.stdin.write(data)
+        p1.stdin.close()
+
+        readfiles, ignored1, ignored2 = select.select([p2.stdout], [], [], 10)
+
+        self.assertTrue(readfiles, "The child hung")
+        self.assertEqual(p2.stdout.read(), data)
+
+    def test_close_fds(self):
+        fd_status = support.findfile("fd_status.py", subdir="subprocessdata")
+
+        fds = os.pipe()
+        self.addCleanup(os.close, fds[0])
+        self.addCleanup(os.close, fds[1])
+
+        open_fds = set(fds)
+
+        p = subprocess.Popen([sys.executable, fd_status],
+                             stdout=subprocess.PIPE, close_fds=False)
+        output, ignored = p.communicate()
+        remaining_fds = set(map(int, output.split(b',')))
+
+        self.assertEqual(remaining_fds & open_fds, open_fds,
+                         "Some fds were closed")
+
+        p = subprocess.Popen([sys.executable, fd_status],
+                             stdout=subprocess.PIPE, close_fds=True)
+        output, ignored = p.communicate()
+        remaining_fds = set(map(int, output.split(b',')))
+
+        self.assertFalse(remaining_fds & open_fds,
+                         "Some fds were left open")
+        self.assertIn(1, remaining_fds, "Subprocess failed")
+
 
 @unittest.skipUnless(mswindows, "Windows specific tests")
 class Win32ProcessTestCase(BaseTestCase):