Issue #12098: multiprocessing on Windows now starts child processes

  using the same sys.flags as the current process.
Backport from default branch.

2 files changed, 34 insertions, 17 deletions

diff --git a/Lib/test/test_multiprocessing.py b/Lib/test/test_multiprocessing.py
index 9b3f0a9..8091a9f 100644
--- a/Lib/test/test_multiprocessing.py
+++ b/Lib/test/test_multiprocessing.py
@@ -2400,11 +2400,43 @@ class TestNoForkBomb(unittest.TestCase):
             self.assertEqual('', err.decode('ascii'))
 
 #
+# Issue 12098: check sys.flags of child matches that for parent
+#
+
+class TestFlags(unittest.TestCase):
+    @classmethod
+    def run_in_grandchild(cls, conn):
+        conn.send(tuple(sys.flags))
+
+    @classmethod
+    def run_in_child(cls):
+        import json
+        r, w = multiprocessing.Pipe(duplex=False)
+        p = multiprocessing.Process(target=cls.run_in_grandchild, args=(w,))
+        p.start()
+        grandchild_flags = r.recv()
+        p.join()
+        r.close()
+        w.close()
+        flags = (tuple(sys.flags), grandchild_flags)
+        print(json.dumps(flags))
+
+    def test_flags(self):
+        import json, subprocess
+        # start child process using unusual flags
+        prog = ('from test.test_multiprocessing import TestFlags; ' +
+                'TestFlags.run_in_child()')
+        data = subprocess.check_output(
+            [sys.executable, '-E', '-S', '-O', '-c', prog])
+        child_flags, grandchild_flags = json.loads(data.decode('ascii'))
+        self.assertEqual(child_flags, grandchild_flags)
+#
 #
 #
 
 testcases_other = [OtherTest, TestInvalidHandle, TestInitializers,
-                   TestStdinBadfiledescriptor, TestTimeouts, TestNoForkBomb]
+                   TestStdinBadfiledescriptor, TestTimeouts, TestNoForkBomb,
+                   TestFlags]
 
 #
 #
diff --git a/Lib/test/test_support.py b/Lib/test/test_support.py
index 034a374..b3076c1 100644
--- a/Lib/test/test_support.py
+++ b/Lib/test/test_support.py
@@ -1344,22 +1344,7 @@ def py3k_bytes(b):
 def args_from_interpreter_flags():
     """Return a list of command-line arguments reproducing the current
     settings in sys.flags."""
-    flag_opt_map = {
-        'bytes_warning': 'b',
-        'dont_write_bytecode': 'B',
-        'ignore_environment': 'E',
-        'no_user_site': 's',
-        'no_site': 'S',
-        'optimize': 'O',
-        'py3k_warning': '3',
-        'verbose': 'v',
-    }
-    args = []
-    for flag, opt in flag_opt_map.items():
-        v = getattr(sys.flags, flag)
-        if v > 0:
-            args.append('-' + opt * v)
-    return args
+    return subprocess._args_from_interpreter_flags()
 
 def strip_python_stderr(stderr):
     """Strip the stderr of a Python process from potential debug output