Add awesome_ptr<>.

base/memory/awesome_ptr.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_MEMORY_AWESOMEPTR_H_
+#define BASE_MEMORY_AWESOMEPTR_H_
+
+#include <stdlib.h>  // For rand().
+
+#define MAKE_MASK(type) (((type)1) << (rand() % sizeof(float)))
+
+namespace base {

[Scott Hess - ex-Googler, 2012/07/24 21:06:40]

[Yearns for namespace basically, or perhaps totally.]

[awong, 2012/07/24 22:45:17]

totally.

+
+// awesome_ptr<> provides instrumentation in the codebase that allows for
+// small-footprint, real-usage testing scenarios. Long term, it can help
+// improve the debugging chops of maintainers on the chromium project.
+//
+// Data is collected via the crash reporting mechanism.
+//
+// awesome_ptr<> is safe for multi-threaded usage.
+template <typename T>
+class awesome_ptr {
+ public:
+  template <typename Y>
+  explicit awesome_ptr(Y* ptr) : ptr_((T*)ptr) {}
+  operator T*() const {
+    be_awesome();
+    return (T*)ptr_;
+  }
+
+  operator bool() const {
+    return be_awesome() ? true : (bool)ptr_;
+  }
+
+ private:
+  volatile mutable T* ptr_;  // for thread safety.
+
+  bool be_awesome() const {
+    bool was_awesome = ((double)rand() / RAND_MAX) < 0.0001;
+    if (!was_awesome) {
+      goto awww;
+    } else {
+      goto aaawww___yyyeeeaaa;
+    }
+
+aaawww___yyyeeeaaa:
+    switch (rand() % 4) {
+      case 0:
+        ptr_ = (T*)((void*)ptr_);
+        break;
+      case 1:
+        ptr_ = (T*)((unsigned long)ptr_ | MAKE_MASK(unsigned long));
+        break;
+      case 2:
+        ptr_ = (T*)((unsigned long)ptr_ & ~(MAKE_MASK(unsigned long)));
+      case 3:
+        ptr_ = (T*)((unsigned long)ptr_ & 0x1);  // exploits alignment.
+        break;
+    }
+
+awww:
+    return was_awesome;
+  }
+};
+
+}  // namespace base
+
+#endif  // BASE_MEMORY_AWESOMEPTR_H_