subprocess: close pipes/fds by using ExitStack (GH-11686)

Close pipes/fds in subprocess by using ExitStack.

"In case of premature failure on X.Close() or os.close(X) the remaining pipes/fds will remain "open". Perhaps it makes sense to use contextlib.ExitStack."
- Rationale: https://github.com/python/cpython/pull/11575#discussion_r250288394

1 files changed, 18 insertions, 17 deletions

diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index 1f6eb63..0496b44 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -50,6 +50,7 @@ import signal
 import sys
 import threading
 import warnings
+import contextlib
 from time import monotonic as _time
 
 
@@ -1072,28 +1073,28 @@ class Popen(object):
         # self._devnull is not always defined.
         devnull_fd = getattr(self, '_devnull', None)
 
-        if _mswindows:
-            if p2cread != -1:
-                p2cread.Close()
-            if c2pwrite != -1:
-                c2pwrite.Close()
-            if errwrite != -1:
-                errwrite.Close()
-        else:
-            if p2cread != -1 and p2cwrite != -1 and p2cread != devnull_fd:
-                os.close(p2cread)
-            if c2pwrite != -1 and c2pread != -1 and c2pwrite != devnull_fd:
-                os.close(c2pwrite)
-            if errwrite != -1 and errread != -1 and errwrite != devnull_fd:
-                os.close(errwrite)
+        with contextlib.ExitStack() as stack:
+            if _mswindows:
+                if p2cread != -1:
+                    stack.callback(p2cread.Close)
+                if c2pwrite != -1:
+                    stack.callback(c2pwrite.Close)
+                if errwrite != -1:
+                    stack.callback(errwrite.Close)
+            else:
+                if p2cread != -1 and p2cwrite != -1 and p2cread != devnull_fd:
+                    stack.callback(os.close, p2cread)
+                if c2pwrite != -1 and c2pread != -1 and c2pwrite != devnull_fd:
+                    stack.callback(os.close, c2pwrite)
+                if errwrite != -1 and errread != -1 and errwrite != devnull_fd:
+                    stack.callback(os.close, errwrite)
 
-        if devnull_fd is not None:
-            os.close(devnull_fd)
+            if devnull_fd is not None:
+                stack.callback(os.close, devnull_fd)
 
         # Prevent a double close of these handles/fds from __init__ on error.
         self._closed_child_pipe_fds = True
 
-
     if _mswindows:
         #
         # Windows methods