[windows] fix multiprocess dill issue

btest

@@ -65,6 +65,12 @@ DEFAULT_CONFIG_NAME = "btest.cfg"
 
 ConfigDefault = os.environ.get("BTEST_CFG", DEFAULT_CONFIG_NAME)
 
+# These regexes have fixed patterns and are used in child processes, so they
+# must be module-level constants to survive multiprocess spawn on Windows.
+RE_INPUT = re.compile(r"%INPUT")
+RE_DIR = re.compile(r"%DIR")
+RE_ENV = re.compile(r"\$\{(\w+)}")
+
 
 def normalize_path(path):
     """Ensures that paths on Windows convert backslashes to forward slashes, to
@@ -440,9 +446,6 @@ class TestManager(mp_managers.SyncManager):
         mgr_data["Options"] = Options
         mgr_data["TestBase"] = TestBase
         mgr_data["TmpDir"] = TmpDir
-        mgr_data["RE_INPUT"] = RE_INPUT
-        mgr_data["RE_DIR"] = RE_DIR
-        mgr_data["RE_ENV"] = RE_ENV
 
         output_handler.prepare(self)
         self._output_handler = output_handler
@@ -567,6 +570,15 @@ class TestManager(mp_managers.SyncManager):
             for global_key, global_value in mgr_data.items():
                 globals()[global_key] = global_value
 
+            # multiprocess/dill may reconstruct this method with its own globals
+            # dict, separate from the module-level globals used by functions like
+            # replaceEnvs. Also set globals in __mp_main__, which is where
+            # multiprocess imports the script in spawned child processes.
+            mp_main = sys.modules.get("__mp_main__")
+            if mp_main is not None:
+                for global_key, global_value in mgr_data.items():
+                    setattr(mp_main, global_key, global_value)
+
         while True:
             # Pull the next test from the list that was built at startup. This may
             # be more than one test if there were alternatives requested in the
@@ -3275,9 +3287,6 @@ if __name__ == "__main__":
 
     CommandPrefix = getOption("CommandPrefix", "@TEST-")
 
-    RE_INPUT = re.compile(r"%INPUT")
-    RE_DIR = re.compile(r"%DIR")
-    RE_ENV = re.compile(r"\$\{(\w+)}")
     RE_PART = re.compile(r"^(.*)#([0-9]+)$")
     RE_IGNORE = re.compile(CommandPrefix + "IGNORE")
     RE_START_NEXT_TEST = re.compile(CommandPrefix + "START-NEXT")