bpo-31471: Fix assertion failure in subprocess.Popen() on Windows, in case env has a bad keys() method. (#3580)

Author: orenmn

Lib/test/test_subprocess.py

@@ -2742,6 +2742,15 @@ def test_invalid_args(self):
  stdout=subprocess.PIPE,
  close_fds=True)
 
+ @support.cpython_only
+ def test_issue31471(self):
+ # There shouldn't be an assertion failure in Popen() in case the env
+ # argument has a bad keys() method.
+ class BadEnv(dict):
+ keys = None
+ with self.assertRaises(TypeError):
+ subprocess.Popen([sys.executable, "-c", "pass"], env=BadEnv())
+
  def test_close_fds(self):
  # close file descriptors
  rc = subprocess.call([sys.executable, "-c",

Misc/NEWS.d/next/Core and Builtins/2017-09-14-19-47-57.bpo-31471.0yiA5Q.rst

@@ -0,0 +1,2 @@
+Fix an assertion failure in `subprocess.Popen()` on Windows, in case the env
+argument has a bad keys() method. Patch by Oren Milman.

Modules/_winapi.c

@@ -723,9 +723,13 @@ getenvironment(PyObject* environment)
  }
 
  keys = PyMapping_Keys(environment);
+ if (!keys) {
+ return NULL;
+ }
  values = PyMapping_Values(environment);
- if (!keys || !values)
+ if (!values) {
  goto error;
+ }
 
  envsize = PySequence_Fast_GET_SIZE(keys);
  if (PySequence_Fast_GET_SIZE(values) != envsize) {