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      1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef BASE_MEMORY_RAW_SCOPED_REFPTR_MISMATCH_CHECKER_H_
      6 #define BASE_MEMORY_RAW_SCOPED_REFPTR_MISMATCH_CHECKER_H_
      7 
      8 #include "base/memory/ref_counted.h"
      9 #include "base/template_util.h"
     10 #include "base/tuple.h"
     11 #include "build/build_config.h"
     12 
     13 // It is dangerous to post a task with a T* argument where T is a subtype of
     14 // RefCounted(Base|ThreadSafeBase), since by the time the parameter is used, the
     15 // object may already have been deleted since it was not held with a
     16 // scoped_refptr. Example: http://crbug.com/27191
     17 // The following set of traits are designed to generate a compile error
     18 // whenever this antipattern is attempted.
     19 
     20 namespace base {
     21 
     22 // This is a base internal implementation file used by task.h and callback.h.
     23 // Not for public consumption, so we wrap it in namespace internal.
     24 namespace internal {
     25 
     26 template <typename T>
     27 struct NeedsScopedRefptrButGetsRawPtr {
     28 #if defined(OS_WIN)
     29   enum {
     30     value = base::false_type::value
     31   };
     32 #else
     33   enum {
     34     // Human readable translation: you needed to be a scoped_refptr if you are a
     35     // raw pointer type and are convertible to a RefCounted(Base|ThreadSafeBase)
     36     // type.
     37     value = (is_pointer<T>::value &&
     38              (is_convertible<T, subtle::RefCountedBase*>::value ||
     39               is_convertible<T, subtle::RefCountedThreadSafeBase*>::value))
     40   };
     41 #endif
     42 };
     43 
     44 template <typename Params>
     45 struct ParamsUseScopedRefptrCorrectly {
     46   enum { value = 0 };
     47 };
     48 
     49 template <>
     50 struct ParamsUseScopedRefptrCorrectly<Tuple<>> {
     51   enum { value = 1 };
     52 };
     53 
     54 template <typename Head, typename... Tail>
     55 struct ParamsUseScopedRefptrCorrectly<Tuple<Head, Tail...>> {
     56   enum { value = !NeedsScopedRefptrButGetsRawPtr<Head>::value &&
     57                  ParamsUseScopedRefptrCorrectly<Tuple<Tail...>>::value };
     58 };
     59 
     60 }  // namespace internal
     61 
     62 }  // namespace base
     63 
     64 #endif  // BASE_MEMORY_RAW_SCOPED_REFPTR_MISMATCH_CHECKER_H_
     65