1 files changed, 52 insertions, 0 deletions
diff --git a/js/src/jsapi-tests/testExternalStrings.cpp b/js/src/jsapi-tests/testExternalStrings.cpp
new file mode 100644
index 0000000000..59c1029fb2
--- /dev/null
+++ b/js/src/jsapi-tests/testExternalStrings.cpp
@@ -0,0 +1,52 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "jsapi-tests/tests.h"
+#include "util/Text.h"
+
+static const char16_t arr[] = u"hi, don't delete me";
+static const size_t arrlen = js_strlen(arr);
+
+static int finalized1 = 0;
+static int finalized2 = 0;
+
+struct ExternalStringCallbacks : public JSExternalStringCallbacks {
+  int* finalizedCount = nullptr;
+
+  explicit ExternalStringCallbacks(int* finalizedCount)
+      : finalizedCount(finalizedCount) {}
+
+  void finalize(char16_t* chars) const override {
+    MOZ_ASSERT(chars == arr);
+    (*finalizedCount)++;
+  }
+
+  size_t sizeOfBuffer(const char16_t* chars,
+                      mozilla::MallocSizeOf mallocSizeOf) const override {
+    MOZ_CRASH("Unexpected call");
+  }
+};
+
+static const ExternalStringCallbacks callbacks1(&finalized1);
+static const ExternalStringCallbacks callbacks2(&finalized2);
+
+BEGIN_TEST(testExternalStrings) {
+  const unsigned N = 1000;
+
+  for (unsigned i = 0; i < N; ++i) {
+    CHECK(JS_NewExternalString(cx, arr, arrlen, &callbacks1));
+    CHECK(JS_NewExternalString(cx, arr, arrlen, &callbacks2));
+  }
+
+  JS_GC(cx);
+
+  // a generous fudge factor to account for strings rooted by conservative gc
+  const unsigned epsilon = 10;
+
+  CHECK((N - finalized1) < epsilon);
+  CHECK((N - finalized2) < epsilon);
+
+  return true;
+}
+END_TEST(testExternalStrings)