mitogen: Use pty.STD*_FILENO constants

Makes it more obvious and easier to find where stdin, stdout, and stderr file
descriptors are being interacted with.

ansible_mitogen/target.py

@@ -42,6 +42,7 @@ import json
 import logging
 import operator
 import os
+import pty
 import pwd
 import re
 import signal
@@ -120,7 +121,7 @@ def subprocess__Popen__close_fds(self, but):
             continue
 
         fd = int(name, 10)
-        if fd > 2 and fd != but:
+        if fd > pty.STDERR_FILENO and fd != but:
             try:
                 os.close(fd)
             except OSError:

mitogen/core.py

@@ -74,6 +74,7 @@ import logging
 import os
 import pickle as py_pickle
 import pstats
+import pty
 import signal
 import socket
 import struct
@@ -544,8 +545,8 @@ def set_cloexec(fd):
     they must be explicitly closed through some other means, such as
     :func:`mitogen.fork.on_fork`.
     """
+    assert fd > pty.STDERR_FILENO, 'fd %r <= 2 (STDERR_FILENO)' % (fd,)
     flags = fcntl.fcntl(fd, fcntl.F_GETFD)
-    assert fd > 2, 'fd %r <= 2' % (fd,)
     fcntl.fcntl(fd, fcntl.F_SETFD, flags | fcntl.FD_CLOEXEC)
 
 
@@ -4019,7 +4020,9 @@ class ExternalContext(object):
         in_fp = os.fdopen(os.dup(in_fd), 'rb', 0)
         os.close(in_fd)
 
-        out_fp = os.fdopen(os.dup(self.config.get('out_fd', 1)), 'wb', 0)
+        out_fd = self.config.get('out_fd', pty.STDOUT_FILENO)
+        out_fd2 = os.dup(out_fd)
+        out_fp = os.fdopen(out_fd2, 'wb', 0)
         self.stream = MitogenProtocol.build_stream(
             self.router,
             parent_id,
@@ -4103,7 +4106,11 @@ class ExternalContext(object):
         Open /dev/null to replace stdio temporarily. In case of odd startup,
         assume we may be allocated a standard handle.
         """
-        for stdfd, mode in ((0, os.O_RDONLY), (1, os.O_RDWR), (2, os.O_RDWR)):
+        for stdfd, mode in [
+                (pty.STDIN_FILENO, os.O_RDONLY),
+                (pty.STDOUT_FILENO, os.O_RDWR),
+                (pty.STDERR_FILENO, os.O_RDWR),
+        ]:
             fd = os.open('/dev/null', mode)
             if fd != stdfd:
                 os.dup2(fd, stdfd)
@@ -4119,8 +4126,9 @@ class ExternalContext(object):
         avoid receiving SIGHUP.
         """
         try:
-            if os.isatty(2):
-                self.reserve_tty_fp = os.fdopen(os.dup(2), 'r+b', 0)
+            if os.isatty(pty.STDERR_FILENO):
+                reserve_tty_fd = os.dup(pty.STDERR_FILENO)
+                self.reserve_tty_fp = os.fdopen(reserve_tty_fd, 'r+b', 0)
                 set_cloexec(self.reserve_tty_fp.fileno())
         except OSError:
             pass
@@ -4140,13 +4148,16 @@ class ExternalContext(object):
         self._nullify_stdio()
 
         self.loggers = []
-        for name, fd in (('stdout', 1), ('stderr', 2)):
-            log = IoLoggerProtocol.build_stream(name, fd)
+        for stdfd, name in [
+                (pty.STDOUT_FILENO, 'stdout'),
+                (pty.STDERR_FILENO, 'stderr'),
+        ]:
+            log = IoLoggerProtocol.build_stream(name, stdfd)
             self.broker.start_receive(log)
             self.loggers.append(log)
 
         # Reopen with line buffering.
-        sys.stdout = os.fdopen(1, 'w', 1)
+        sys.stdout = os.fdopen(pty.STDOUT_FILENO, 'w', 1)
 
     def main(self):
         self._setup_master()

mitogen/fakessh.py

@@ -95,6 +95,7 @@ Sequence:
 import getopt
 import inspect
 import os
+import pty
 import shutil
 import socket
 import subprocess
@@ -354,8 +355,9 @@ def _fakessh_main(dest_context_id, econtext):
               control_handle, stdin_handle)
 
     process = Process(econtext.router,
-                      stdin=os.fdopen(1, 'w+b', 0),
-                      stdout=os.fdopen(0, 'r+b', 0))
+        stdin=os.fdopen(pty.STDOUT_FILENO, 'w+b', 0),
+        stdout=os.fdopen(pty.STDIN_FILENO, 'r+b', 0),
+    )
     process.start_master(
         stdin=mitogen.core.Sender(dest, stdin_handle),
         control=mitogen.core.Sender(dest, control_handle),

mitogen/parent.py

@@ -43,6 +43,7 @@ import inspect
 import logging
 import os
 import re
+import pty
 import signal
 import socket
 import struct
@@ -406,12 +407,14 @@ def _acquire_controlling_tty():
     if sys.platform in ('linux', 'linux2'):
         # On Linux, the controlling tty becomes the first tty opened by a
         # process lacking any prior tty.
-        os.close(os.open(os.ttyname(2), os.O_RDWR))
+        tty_path = os.ttyname(pty.STDERR_FILENO)
+        tty_fd = os.open(tty_path, os.O_RDWR)
+        os.close(tty_fd)
     if hasattr(termios, 'TIOCSCTTY') and not mitogen.core.IS_WSL and not IS_SOLARIS:
         # #550: prehistoric WSL does not like TIOCSCTTY.
         # On BSD an explicit ioctl is required. For some inexplicable reason,
         # Python 2.6 on Travis also requires it.
-        fcntl.ioctl(2, termios.TIOCSCTTY)
+        fcntl.ioctl(pty.STDERR_FILENO, termios.TIOCSCTTY)
 
 
 def _linux_broken_devpts_openpty():
@@ -1415,7 +1418,7 @@ class Connection(object):
     #   w: write side of core_src FD.
     #   C: the decompressed core source.
 
-    # Final os.close(2) to avoid --py-debug build from corrupting stream with
+    # Final os.close(STDOUT_FILENO) to avoid --py-debug build corrupting stream with
     # "[1234 refs]" during exit.
     @staticmethod
     def _first_stage():