1 files changed, 27 insertions, 0 deletions
diff --git a/xpcom/ds/nsTArray.cpp b/xpcom/ds/nsTArray.cpp
new file mode 100644
index 0000000000..3c193ece91
--- /dev/null
+++ b/xpcom/ds/nsTArray.cpp
@@ -0,0 +1,27 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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 "nsTArray.h"
+#include "nsXPCOM.h"
+#include "nsCycleCollectionNoteChild.h"
+#include "nsDebug.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/IntegerPrintfMacros.h"
+
+// Ensure this is sufficiently aligned so that Elements() and co don't create
+// unaligned pointers, or slices with unaligned pointers for empty arrays, see
+// https://github.com/servo/servo/issues/22613.
+alignas(8) const nsTArrayHeader sEmptyTArrayHeader = {0, 0, 0};
+
+bool IsTwiceTheRequiredBytesRepresentableAsUint32(size_t aCapacity,
+                                                  size_t aElemSize) {
+  using mozilla::CheckedUint32;
+  return ((CheckedUint32(aCapacity) * aElemSize) * 2).isValid();
+}
+
+void ::detail::SetCycleCollectionArrayFlag(uint32_t& aFlags) {
+  aFlags |= CycleCollectionEdgeNameArrayFlag;
+}