From 00cd2cab74947602c38a232c2076b6857b74dd83 Mon Sep 17 00:00:00 2001
From: Armin Rigo <arigo@tunes.org>
Date: Fri, 26 Feb 2021 10:39:29 +0100
Subject: Tests (passing) for _continulet switching to a different thread

---
 pypy/module/_continuation/interp_continuation.py  |  2 +-
 pypy/module/_continuation/test/test_translated.py | 80 +++++++++++++++++++++++
 2 files changed, 81 insertions(+), 1 deletion(-)

diff --git a/pypy/module/_continuation/interp_continuation.py b/pypy/module/_continuation/interp_continuation.py
index f00fff154b..db1724986d 100644
--- a/pypy/module/_continuation/interp_continuation.py
+++ b/pypy/module/_continuation/interp_continuation.py
@@ -24,7 +24,7 @@ class W_Continulet(W_Root):
         ec = self.space.getexecutioncontext()
         if ec.stacklet_thread is not self.sthread:
             global_state.clear()
-            raise geterror(self.space, "inter-thread support is missing")
+            raise geterror(self.space, "cannot switch to a different thread")
 
     def descr_init(self, w_callable, __args__):
         if self.sthread is not None:
diff --git a/pypy/module/_continuation/test/test_translated.py b/pypy/module/_continuation/test/test_translated.py
index a2f83d0b8f..5f4bdfb76b 100644
--- a/pypy/module/_continuation/test/test_translated.py
+++ b/pypy/module/_continuation/test/test_translated.py
@@ -117,6 +117,86 @@ class AppTestWrapper:
         _vmprof.disable()
         f.close()
 
+    def test_thread_switch_to_sub(self):
+        try:
+            import thread, time
+        except ImportError:
+            py.test.skip("no threads")
+        c_list = []
+        lock = thread.allocate_lock()
+        lock.acquire()
+        lock2 = thread.allocate_lock()
+        lock2.acquire()
+        #
+        def fn():
+            c = _continuation.continulet(lambda c_main: c_main.switch())
+            c.switch()
+            c_list.append(c)
+            lock.release()
+            lock2.acquire()
+        #
+        thread.start_new_thread(fn, ())
+        lock.acquire()
+        [c] = c_list
+        py.test.raises(_continuation.error, c.switch)
+        #
+        lock2.release()
+        time.sleep(0.5)
+        py.test.raises(_continuation.error, c.switch)
+
+    def test_thread_switch_to_sub_nonstarted(self):
+        try:
+            import thread, time
+        except ImportError:
+            py.test.skip("no threads")
+        c_list = []
+        lock = thread.allocate_lock()
+        lock.acquire()
+        lock2 = thread.allocate_lock()
+        lock2.acquire()
+        #
+        def fn():
+            c = _continuation.continulet(lambda c_main: None)
+            c_list.append(c)
+            lock.release()
+            lock2.acquire()
+        #
+        thread.start_new_thread(fn, ())
+        lock.acquire()
+        [c] = c_list
+        py.test.raises(_continuation.error, c.switch)
+        #
+        lock2.release()
+        time.sleep(0.5)
+        py.test.raises(_continuation.error, c.switch)
+
+    def test_thread_switch_to_main(self):
+        try:
+            import thread, time
+        except ImportError:
+            py.test.skip("no threads")
+        c_list = []
+        lock = thread.allocate_lock()
+        lock.acquire()
+        lock2 = thread.allocate_lock()
+        lock2.acquire()
+        #
+        def fn():
+            def in_continulet(c_main):
+                c_list.append(c_main)
+                lock.release()
+                lock2.acquire()
+            c = _continuation.continulet(in_continulet)
+            c.switch()
+        #
+        thread.start_new_thread(fn, ())
+        lock.acquire()
+        [c] = c_list
+        py.test.raises(_continuation.error, c.switch)
+        #
+        lock2.release()
+        time.sleep(0.5)
+        py.test.raises(_continuation.error, c.switch)
 
 def _setup():
     for _i in range(20):
-- 
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