base::RefCounted now DCHECKs when referenced from multiple threads.

base/memory/ref_counted.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_REF_COUNTED_H_
 #define BASE_MEMORY_REF_COUNTED_H_
 
 #include <cassert>
 #include <iosfwd>
 
 #include "base/atomic_ref_count.h"
 #include "base/base_export.h"
 #include "base/compiler_specific.h"
 #ifndef NDEBUG
 #include "base/logging.h"
 #endif
+#include "base/threading/thread_checker.h"
 #include "base/threading/thread_collision_warner.h"
 #include "build/build_config.h"
 
 namespace base {
 
 namespace subtle {
 
 class BASE_EXPORT RefCountedBase {
  public:
   bool HasOneRef() const { return ref_count_ == 1; }
@@ skipping 11 matching lines @@
   #ifndef NDEBUG
     DCHECK(in_dtor_) << "RefCounted object deleted without calling Release()";
   #endif
   }
 
 
   void AddRef() const {
     // TODO(maruel): Add back once it doesn't assert 500 times/sec.
     // Current thread books the critical section "AddRelease"
     // without release it.
     // DFAKE_SCOPED_LOCK_THREAD_LOCKED(add_release_);

[noyau (Ping after 24h), 2015/03/24 09:01:21]

Since your code is now doing the same thing, it's probably a good idea to remove
those two TODOs.

   #ifndef NDEBUG
     DCHECK(!in_dtor_);
   #endif
     ++ref_count_;
   }
 
   // Returns true if the object should self-delete.
   bool Release() const {
     // TODO(maruel): Add back once it doesn't assert 500 times/sec.
     // Current thread books the critical section "AddRelease"
@@ skipping 53 matching lines @@
 //
 //   class MyFoo : public base::RefCounted<MyFoo> {
 //    ...
 //    private:
 //     friend class base::RefCounted<MyFoo>;
 //     ~MyFoo();
 //   };
 //
 // You should always make your destructor private, to avoid any code deleting
 // the object accidently while there are references to it.
+//
+// RefCounted objects are not thread-safe. To use a ref-counted object from more
+// than one thead, use a RefCountedThreadSafe.
 template <class T>
 class RefCounted : public subtle::RefCountedBase {
  public:
   RefCounted() {}
 
   void AddRef() const {
+    DCHECK(thread_checker_.CalledOnValidThread());
     subtle::RefCountedBase::AddRef();
   }
 
   void Release() const {
+    DCHECK(thread_checker_.CalledOnValidThread());
     if (subtle::RefCountedBase::Release()) {
       delete static_cast<const T*>(this);
     }
   }
 
  protected:
   ~RefCounted() {}
 
  private:
+  base::ThreadChecker thread_checker_;
+
   DISALLOW_COPY_AND_ASSIGN(RefCounted<T>);
 };
 
+// Same as RefCounted, but does not enforce thread safety. Subclasses of
+// UnsafeRefCounted probably have race conditions and should be fixed up, either
+// by ensuring they are only referenced from one thread (and moving to
+// RefCounted), or by moving to RefCountedThreadSafe.
+template <class T>
+class UnsafeRefCounted : public subtle::RefCountedBase {
+ public:
+  UnsafeRefCounted() {}
+
+  void AddRef() const { subtle::RefCountedBase::AddRef(); }
+
+  void Release() const {
+    if (subtle::RefCountedBase::Release())
+      delete static_cast<const T*>(this);
+  }
+
+ protected:
+  ~UnsafeRefCounted() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(UnsafeRefCounted<T>);
+};
+
 // Forward declaration.
 template <class T, typename Traits> class RefCountedThreadSafe;
 
 // Default traits for RefCountedThreadSafe<T>.  Deletes the object when its ref
 // count reaches 0.  Overload to delete it on a different thread etc.
 template<typename T>
 struct DefaultRefCountedThreadSafeTraits {
   static void Destruct(const T* x) {
     // Delete through RefCountedThreadSafe to make child classes only need to be
     // friend with RefCountedThreadSafe instead of this struct, which is an
@@ skipping 257 matching lines @@
 bool operator!=(const T* lhs, const scoped_refptr<U>& rhs) {
   return !operator==(lhs, rhs);
 }
 
 template <typename T>
 std::ostream& operator<<(std::ostream& out, const scoped_refptr<T>& p) {
   return out << p.get();
 }
 
 #endif  // BASE_MEMORY_REF_COUNTED_H_