1 files changed, 53 insertions, 0 deletions
diff --git a/js/src/vm/ProfilingStack.cpp b/js/src/vm/ProfilingStack.cpp
new file mode 100644
index 0000000000..289bdd9d83
--- /dev/null
+++ b/js/src/vm/ProfilingStack.cpp
@@ -0,0 +1,53 @@
+/* -*- 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 "js/ProfilingStack.h"
+
+#include "mozilla/IntegerRange.h"
+#include "mozilla/MathAlgorithms.h"
+
+#include <algorithm>
+
+using namespace js;
+
+ProfilingStack::~ProfilingStack() {
+  // The label macros keep a reference to the ProfilingStack to avoid a TLS
+  // access. If these are somehow not all cleared we will get a
+  // use-after-free so better to crash now.
+  MOZ_RELEASE_ASSERT(stackPointer == 0);
+
+  delete[] frames;
+}
+
+void ProfilingStack::ensureCapacitySlow() {
+  MOZ_ASSERT(stackPointer >= capacity);
+  const uint32_t kInitialCapacity = 4096 / sizeof(ProfilingStackFrame);
+
+  uint32_t sp = stackPointer;
+
+  uint32_t newCapacity;
+  if (!capacity) {
+    newCapacity = kInitialCapacity;
+  } else {
+    size_t memoryGoal =
+        mozilla::RoundUpPow2(capacity * 2 * sizeof(ProfilingStackFrame));
+    newCapacity = memoryGoal / sizeof(ProfilingStackFrame);
+  }
+  newCapacity = std::max(sp + 1, newCapacity);
+
+  auto* newFrames = new js::ProfilingStackFrame[newCapacity];
+
+  // It's important that `frames` / `capacity` / `stackPointer` remain
+  // consistent here at all times.
+  for (auto i : mozilla::IntegerRange(capacity)) {
+    newFrames[i] = frames[i];
+  }
+
+  js::ProfilingStackFrame* oldFrames = frames;
+  frames = newFrames;
+  capacity = newCapacity;
+  delete[] oldFrames;
+}