Fixing #1531862: Do not close standard file descriptors in the

subprocess module.

Lib/subprocess.py

@@ -1000,14 +1000,10 @@ class Popen(object):
                     if errwrite:
                         os.dup2(errwrite, 2)
 
-                    # Close pipe fds.  Make sure we doesn't close the same
-                    # fd more than once.
-                    if p2cread:
-                        os.close(p2cread)
-                    if c2pwrite and c2pwrite not in (p2cread,):
-                        os.close(c2pwrite)
-                    if errwrite and errwrite not in (p2cread, c2pwrite):
-                        os.close(errwrite)
+                    # Close pipe fds.  Make sure we don't close the same
+                    # fd more than once, or standard fds.
+                    for fd in set((p2cread, c2pwrite, errwrite))-set((0,1,2)):
+                        if fd: os.close(fd)
 
                     # Close all other fds, if asked for
                     if close_fds:

Lib/test/test_subprocess.py

@@ -234,6 +234,48 @@ class ProcessTestCase(unittest.TestCase):
         stripped = remove_stderr_debug_decorations(output)
         self.assertEqual(stripped, "appleorange")
 
+    def test_stdout_filedes_of_stdout(self):
+        # stdout is set to sys.stdout.fileno() (#1531862).
+        cmd = r"import sys, os; sys.exit(os.write(sys.stderr.fileno(), '.\n'))"
+        rc = subprocess.call([sys.executable, "-c", cmd],
+                             stdout=sys.stdout.fileno())
+        self.assertEquals(rc, 2)
+
+    def test_stdout_fileobj_of_stdout(self):
+        # stdout is set to sys.stdout (#1531862).
+        cmd = r"import sys, os; sys.exit(os.write(sys.stderr.fileno(), '.\n'))"
+        rc = subprocess.call([sys.executable, "-c", cmd],
+                             stdout=sys.stdout)
+        self.assertEquals(rc, 2)
+
+    def test_stdout_fileobj_of_stderr(self):
+        # stdout is set to sys.stderr (#1531862).
+        cmd = r"import sys, os; sys.exit(os.write(sys.stderr.fileno(), '.\n'))"
+        rc = subprocess.call([sys.executable, "-c", cmd],
+                             stdout=sys.stderr)
+        self.assertEquals(rc, 2)
+
+    def test_stderr_filedes_of_stderr(self):
+        # stderr is set to sys.stderr.fileno() (#1531862).
+        cmd = r"import sys, os; sys.exit(os.write(sys.stderr.fileno(), '.\n'))"
+        rc = subprocess.call([sys.executable, "-c", cmd],
+                             stderr=sys.stderr.fileno())
+        self.assertEquals(rc, 2)
+
+    def test_stderr_fileobj_of_stderr(self):
+        # stderr is set to sys.stderr (#1531862).
+        cmd = r"import sys, os; sys.exit(os.write(sys.stderr.fileno(), '.\n'))"
+        rc = subprocess.call([sys.executable, "-c", cmd],
+                             stderr=sys.stderr)
+        self.assertEquals(rc, 2)
+
+    def test_stderr_fileobj_of_stdout(self):
+        # stderr is set to sys.stdout (#1531862).
+        cmd = r"import sys, os; sys.exit(os.write(sys.stderr.fileno(), '.\n'))"
+        rc = subprocess.call([sys.executable, "-c", cmd],
+                             stderr=sys.stdout)
+        self.assertEquals(rc, 2)
+
     def test_cwd(self):
         tmpdir = os.getenv("TEMP", "/tmp")
         # We cannot use os.path.realpath to canonicalize the path,

Misc/NEWS

@@ -37,6 +37,8 @@ Library
 - Bug #1541863: uuid.uuid1 failed to generate unique identifiers
   on systems with low clock resolution.
 
+- Bug #1531862: Do not close standard file descriptors in subprocess.
+
 
 Extension Modules
 -----------------