Add InitializationStateDcheck, its base class, and their tests

util/misc/initialization_state.h

+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CRASHPAD_UTIL_MISC_INITIALIZATION_INITIALIZATION_STATE_H_
+#define CRASHPAD_UTIL_MISC_INITIALIZATION_INITIALIZATION_STATE_H_
+
+#include <stdint.h>
+
+namespace crashpad {
+
+//! \brief Tracks whether data are initialized.
+//!
+//! Objects of this type track whether the data they’re guarding are
+//! initialized. The three possible states are uninitialized (the initial
+//! state), initializing, and valid. As the guarded data are initialized, an
+//! InitializationState object will normally transition through these three
+//! states. A fourth state corresponds to the destruction of objects of this
+//! type, making it less likely that a use-after-free of an InitializationState
+//! object will appear in the valid state.
+//!
+//! If the only purpose for tracking the initialization state of guarded data is
+//! to DCHECK when the object is in an unexpected state, use
+//! InitializationStateDcheck instead.
+class InitializationState {
+ public:
+  //! \brief The object’s state.
+  enum State : uint8_t {

[Robert Sesek, 2014/08/13 20:13:37]

Is this necessary? Won't the compiler choose the best-fit type?

[Mark Mentovai, 2014/08/13 22:22:06]

rsesek wrote:
Not “best” fit, no. clang and gcc would choose int for this enum if you didn’t
hold their hands.

+    //! \brief The object has not yet been initialized.
+    kStateUninitialized = 0,
+
+    //! \brief The object is being initialized.
+    //!
+    //! This state protects against attempted reinitializaton of
+    //! partially-initialized objects whose initial initialization attempt
+    //! failed. This state is to be used while objects are initializing, but are
+    //! not yet fully initialized.
+    kStateInvalid,
+
+    //! \brief The object has been initialized.
+    kStateValid,
+
+    //! \brief The object has been destroyed.
+    kStateDestroyed,
+  };
+
+  InitializationState() : state_(kStateUninitialized) {}
+  ~InitializationState() { state_ = kStateDestroyed; }
+
+  //! \brief Returns `true` if the object’s state is #kStateUninitialized and it
+  //!     is safe to begin initializing it.
+  bool is_uninitialized() const { return state_ == kStateUninitialized; }
+
+  //! \brief Sets the object’s state to #kStateInvalid, marking initialization
+  //!     as being in process.
+  void set_invalid() { state_ = kStateInvalid; }
+
+  //! \brief Sets the object’s state to #kStateValid, marking it initialized.
+  void set_valid() { state_ = kStateValid; }
+
+  //! \brief Returns `true` if the the object’s state is #kStateValid and it has
+  //!     been fully initialized and may be used.
+  bool is_valid() const { return state_ == kStateValid; }
+
+ protected:
+  //! \brief Returns the object’s state.
+  //!
+  //! Consumers of this class should use an is_state_*() method instead.
+  State state() const { return state_; }
+
+  //! \brief Sets the object’s state.
+  //!
+  //! Consumers of this class should use a set_state_*() method instead.
+  void set_state(State state) { state_ = state; }
+
+ private:
+  State state_;

[Robert Sesek, 2014/08/13 20:13:36]

DISALLOW_COPY_AND_ASSIGN

+};
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_MISC_INITIALIZATION_INITIALIZATION_STATE_H_