1 files changed, 43 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/gc/weakmap-expose.js b/js/src/jit-test/tests/gc/weakmap-expose.js
new file mode 100644
index 0000000000..45ebc7d5a9
--- /dev/null
+++ b/js/src/jit-test/tests/gc/weakmap-expose.js
@@ -0,0 +1,43 @@
+// Test that WeakMap.get() doesn't return a gray GC thing.
+
+function checkNotGray(value) {
+  // Assigning a gray GC thing to an object propery will assert.
+  let test = {};
+  test.property = value;
+}
+
+// 1. Make a black WeakMap with a gray key and gray value.
+
+gczeal(0);
+
+let key = {};
+let value = {};
+
+let map = new WeakMap();
+map.set(key, value);
+
+let gray = grayRoot();
+gray.key = key;
+
+addMarkObservers([map, key, value]);
+
+gray = null;
+key = null;
+value = null;
+
+gc();
+
+let marks = getMarks();
+assertEq(marks[0], "black");
+assertEq(marks[1], "gray");
+assertEq(marks[2], "gray");
+
+// 2. Get our key back, which will expose it and mark it black.
+
+key = nondeterministicGetWeakMapKeys(map)[0];
+checkNotGray(key);
+
+// 3. Look up the value in the map and check it's not gray.
+
+value = map.get(key);
+checkNotGray(value);