Create the Goanna Runtime Environment

1 files changed, 166 insertions, 0 deletions

diff --git a/system/framework/GuardObjects.h b/system/framework/GuardObjects.h
new file mode 100644
index 000000000..38523114b
--- /dev/null
+++ b/system/framework/GuardObjects.h
@@ -0,0 +1,166 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+/* Implementation of macros to ensure correct use of RAII Auto* objects. */
+
+#ifndef mozilla_GuardObjects_h
+#define mozilla_GuardObjects_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Move.h"
+#include "mozilla/Types.h"
+
+#ifdef __cplusplus
+
+#ifdef DEBUG
+
+/**
+ * A custom define is used rather than |mozPoisonValue()| due to cascading
+ * build failures relating to how mfbt is linked on different operating
+ * systems. See bug 1160253.
+ */
+#define MOZ_POISON uintptr_t(-1)
+
+namespace mozilla {
+namespace detail {
+
+/*
+ * The following classes are designed to cause assertions to detect
+ * inadvertent use of guard objects as temporaries. In other words,
+ * when we have a guard object whose only purpose is its constructor and
+ * destructor (and is never otherwise referenced), the intended use
+ * might be:
+ *
+ *   AutoRestore savePainting(mIsPainting);
+ *
+ * but is is easy to accidentally write:
+ *
+ *   AutoRestore(mIsPainting);
+ *
+ * which compiles just fine, but runs the destructor well before the
+ * intended time.
+ *
+ * They work by adding (#ifdef DEBUG) an additional parameter to the
+ * guard object's constructor, with a default value, so that users of
+ * the guard object's API do not need to do anything. The default value
+ * of this parameter is a temporary object. C++ (ISO/IEC 14882:1998),
+ * section 12.2 [class.temporary], clauses 4 and 5 seem to assume a
+ * guarantee that temporaries are destroyed in the reverse of their
+ * construction order, but I actually can't find a statement that that
+ * is true in the general case (beyond the two specific cases mentioned
+ * there). However, it seems to be true.
+ *
+ * These classes are intended to be used only via the macros immediately
+ * below them:
+ *
+ *   MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER declares (ifdef DEBUG) a member
+ *     variable, and should be put where a declaration of a private
+ *     member variable would be placed.
+ *   MOZ_GUARD_OBJECT_NOTIFIER_PARAM should be placed at the end of the
+ *     parameters to each constructor of the guard object; it declares
+ *     (ifdef DEBUG) an additional parameter. (But use the *_ONLY_PARAM
+ *     variant for constructors that take no other parameters.)
+ *   MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL should likewise be used in
+ *     the implementation of such constructors when they are not inline.
+ *   MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT should be used in
+ *     the implementation of such constructors to pass the parameter to
+ *     a base class that also uses these macros
+ *   MOZ_GUARD_OBJECT_NOTIFIER_INIT is a statement that belongs in each
+ *     constructor. It uses the parameter declared by
+ *     MOZ_GUARD_OBJECT_NOTIFIER_PARAM.
+ *
+ * For more details, and examples of using these macros, see
+ * https://developer.mozilla.org/en/Using_RAII_classes_in_Mozilla
+ */
+class GuardObjectNotifier
+{
+private:
+  bool* mStatementDone;
+
+public:
+  GuardObjectNotifier()
+    : mStatementDone(reinterpret_cast<bool*>(MOZ_POISON))
+  {
+  }
+
+  ~GuardObjectNotifier()
+  {
+    // Assert that the GuardObjectNotifier has been properly initialized by
+    // using the |MOZ_GUARD_OBJECT_NOTIFIER_INIT| macro. A poison value is
+    // used rather than a null check to appease static analyzers that were
+    // (incorrectly) detecting null pointer dereferences.
+    MOZ_ASSERT(mStatementDone != reinterpret_cast<bool*>(MOZ_POISON));
+    *mStatementDone = true;
+  }
+
+  void setStatementDone(bool* aStatementIsDone)
+  {
+    mStatementDone = aStatementIsDone;
+  }
+};
+
+class GuardObjectNotificationReceiver
+{
+private:
+  bool mStatementDone;
+
+public:
+  GuardObjectNotificationReceiver() : mStatementDone(false) { }
+
+  ~GuardObjectNotificationReceiver() {
+    /*
+     * Assert that the guard object was not used as a temporary.  (Note that
+     * this assert might also fire if init is not called because the guard
+     * object's implementation is not using the above macros correctly.)
+     */
+    MOZ_ASSERT(mStatementDone);
+  }
+
+  void init(GuardObjectNotifier& aNotifier)
+  {
+    aNotifier.setStatementDone(&mStatementDone);
+  }
+};
+
+} /* namespace detail */
+} /* namespace mozilla */
+
+#undef MOZ_POISON
+
+#endif /* DEBUG */
+
+#ifdef DEBUG
+#  define MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER \
+     mozilla::detail::GuardObjectNotificationReceiver _mCheckNotUsedAsTemporary;
+#  define MOZ_GUARD_OBJECT_NOTIFIER_PARAM \
+     , mozilla::detail::GuardObjectNotifier&& _notifier = \
+         mozilla::detail::GuardObjectNotifier()
+#  define MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM \
+     mozilla::detail::GuardObjectNotifier&& _notifier = \
+         mozilla::detail::GuardObjectNotifier()
+#  define MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL \
+     , mozilla::detail::GuardObjectNotifier&& _notifier
+#  define MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_IN_IMPL \
+     mozilla::detail::GuardObjectNotifier&& _notifier
+#  define MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT \
+     , mozilla::Move(_notifier)
+#  define MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_TO_PARENT \
+       mozilla::Move(_notifier)
+#  define MOZ_GUARD_OBJECT_NOTIFIER_INIT \
+     do { _mCheckNotUsedAsTemporary.init(_notifier); } while (0)
+#else
+#  define MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
+#  define MOZ_GUARD_OBJECT_NOTIFIER_PARAM
+#  define MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM
+#  define MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL
+#  define MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_IN_IMPL
+#  define MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_TO_PARENT
+#  define MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT
+#  define MOZ_GUARD_OBJECT_NOTIFIER_INIT do { } while (0)
+#endif
+
+#endif /* __cplusplus */
+
+#endif /* mozilla_GuardObjects_h */