More unittests to test stack scanning

src/core/thread.d

@@ -4415,6 +4415,86 @@ unittest
     expect(fib, "delegate");
 }
 
+
+// stress testing GC stack scanning
+unittest
+{
+    import core.memory;
+
+    static void unreferencedThreadObject()
+    {
+        static void sleep() { Thread.sleep(dur!"msecs"(100)); }
+        auto thread = new Thread(&sleep);
+        thread.start();
+    }
+    unreferencedThreadObject();
+    GC.collect();
+
+    static class Foo
+    {
+        this(int value)
+        {
+            _value = value;
+        }
+
+        int bar()
+        {
+            return _value;
+        }
+
+        int _value;
+    }
+
+    static void collect()
+    {
+        auto foo = new Foo(2);
+        assert(foo.bar() == 2);
+        GC.collect();
+        Fiber.yield();
+        GC.collect();
+        assert(foo.bar() == 2);
+    }
+
+    auto fiber = new Fiber(&collect);
+
+    fiber.call();
+    GC.collect();
+    fiber.call();
+
+    // thread reference
+    auto foo = new Foo(2);
+
+    void collect2()
+    {
+        assert(foo.bar() == 2);
+        GC.collect();
+        Fiber.yield();
+        GC.collect();
+        assert(foo.bar() == 2);
+    }
+
+    fiber = new Fiber(&collect2);
+
+    fiber.call();
+    GC.collect();
+    fiber.call();
+
+    static void recurse(size_t cnt)
+    {
+        --cnt;
+        Fiber.yield();
+        if (cnt)
+        {
+            auto fib = new Fiber(() { recurse(cnt); });
+            fib.call();
+            GC.collect();
+            fib.call();
+        }
+    }
+    fiber = new Fiber(() { recurse(20); });
+    fiber.call();
+}
+
 }
 
 version( AsmX86_64_Posix )