3 files changed, 66 insertions, 0 deletions
diff --git a/test/unit/input/bysyncify-stackOverflow.wast b/test/unit/input/bysyncify-stackOverflow.wast
new file mode 100644
index 000000000..a36a06b40
--- /dev/null
+++ b/test/unit/input/bysyncify-stackOverflow.wast
@@ -0,0 +1,22 @@
+(module
+  (memory 1 2)
+  (import "env" "sleep" (func $sleep))
+  (export "memory" (memory 0))
+  (func "many_locals" (param $x i32) (result i32)
+    (local $y i32)
+    (local $z i32)
+    (local.set $y
+      (i32.add (local.get $x) (i32.const 10))
+    )
+    (local.set $z
+      (i32.add (local.get $y) (i32.const 20))
+    )
+    (call $sleep)
+    (select
+      (local.get $y)
+      (local.get $z)
+      (local.get $x)
+    )
+  )
+)
+
diff --git a/test/unit/input/bysyncify.js b/test/unit/input/bysyncify.js
index 2e1bb4895..be6d32903 100644
--- a/test/unit/input/bysyncify.js
+++ b/test/unit/input/bysyncify.js
@@ -252,10 +252,53 @@ function coroutineTests() {
   ]), 'check yielded values')
 }
 
+function stackOverflowAssertTests() {
+  console.log('\nstack overflow assertion tests\n\n');
+
+  // Get and compile the wasm.
+
+  var binary = fs.readFileSync('c.wasm');
+
+  var module = new WebAssembly.Module(binary);
+
+  var DATA_ADDR = 4;
+
+  var instance = new WebAssembly.Instance(module, {
+    env: {
+      sleep: function() {
+        console.log('sleep...');
+        exports.bysyncify_start_unwind(DATA_ADDR);
+        view[DATA_ADDR >> 2] = DATA_ADDR + 8;
+        // The end of the stack will be reached as the stack is tiny.
+        view[DATA_ADDR + 4 >> 2] = view[DATA_ADDR >> 2] + 1;
+      }
+    }
+  });
+
+  var exports = instance.exports;
+  var view = new Int32Array(exports.memory.buffer);
+  exports.many_locals();
+  assert(view[DATA_ADDR >> 2] > view[DATA_ADDR + 4 >> 2], 'should have wrote past the end of the stack');
+  // All API calls should now fail, since we wrote past the end of the
+  // stack
+  var fails = 0;
+  ['bysyncify_stop_unwind', 'bysyncify_start_rewind', 'bysyncify_stop_rewind', 'bysyncify_start_unwind'].forEach(function(name) {
+    try {
+      exports[name](DATA_ADDR);
+      console.log('no fail on', name);
+    } catch (e) {
+      console.log('expected fail on', name);
+      fails++;
+    }
+  });
+  assert(fails == 4, 'all 4 should have failed');
+}
+
 // Main
 
 sleepTests();
 coroutineTests();
+stackOverflowAssertTests();
 
 console.log('\ntests completed successfully');
 
diff --git a/test/unit/test_bysyncify.py b/test/unit/test_bysyncify.py
index 8d5a780e8..407f3f7f9 100644
--- a/test/unit/test_bysyncify.py
+++ b/test/unit/test_bysyncify.py
@@ -10,6 +10,7 @@ class BysyncifyTest(BinaryenTestCase):
       print(args)
       run_process(WASM_OPT + args + [self.input_path('bysyncify-sleep.wast'), '--bysyncify', '-o', 'a.wasm'])
       run_process(WASM_OPT + args + [self.input_path('bysyncify-coroutine.wast'), '--bysyncify', '-o', 'b.wasm'])
+      run_process(WASM_OPT + args + [self.input_path('bysyncify-stackOverflow.wast'), '--bysyncify', '-o', 'c.wasm'])
       print('  file size: %d' % os.path.getsize('a.wasm'))
       run_process([NODEJS, self.input_path('bysyncify.js')])