text: // Copyright (c) 2006-2008 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_RAW_SCOPED_REFPTR_MISMATCH_CHECKER_H_
  #define BASE_RAW_SCOPED_REFPTR_MISMATCH_CHECKER_H_
  #pragma once
  
  #include "base/ref_counted.h"
  #include "base/template_util.h"
  #include "base/tuple.h"
  #include "build/build_config.h"
  
  // It is dangerous to post a task with a T* argument where T is a subtype of
  // RefCounted(Base|ThreadSafeBase), since by the time the parameter is used, the
  // object may already have been deleted since it was not held with a
  // scoped_refptr. Example: http://crbug.com/27191
  // The following set of traits are designed to generate a compile error
  // whenever this antipattern is attempted.
  
  namespace base {
  
  // This is a base internal implementation file used by task.h and callback.h.
  // Not for public consumption, so we wrap it in namespace internal.
  namespace internal {
  
  template <typename T>
  struct NeedsScopedRefptrButGetsRawPtr {
  #if defined(OS_WIN)
    enum {
      value = base::false_type::value
    };
  #else
    enum {
      // Human readable translation: you needed to be a scoped_refptr if you are a
      // raw pointer type and are convertible to a RefCounted(Base|ThreadSafeBase)
      // type.
      value = (is_pointer<T>::value &&
               (is_convertible<T, subtle::RefCountedBase*>::value ||
                is_convertible<T, subtle::RefCountedThreadSafeBase*>::value))
    };
  #endif
  };
  
  template <typename Params>
  struct ParamsUseScopedRefptrCorrectly {
    enum { value = 0 };
  };
  
  template <>
  struct ParamsUseScopedRefptrCorrectly<Tuple0> {
    enum { value = 1 };
  };
  
  template <typename A>
  struct ParamsUseScopedRefptrCorrectly<Tuple1<A> > {
    enum { value = !NeedsScopedRefptrButGetsRawPtr<A>::value };
  };
  
  template <typename A, typename B>
  struct ParamsUseScopedRefptrCorrectly<Tuple2<A, B> > {
    enum { value = !(NeedsScopedRefptrButGetsRawPtr<A>::value ||
                     NeedsScopedRefptrButGetsRawPtr<B>::value) };
  };
  
  template <typename A, typename B, typename C>
  struct ParamsUseScopedRefptrCorrectly<Tuple3<A, B, C> > {
    enum { value = !(NeedsScopedRefptrButGetsRawPtr<A>::value ||
                     NeedsScopedRefptrButGetsRawPtr<B>::value ||
                     NeedsScopedRefptrButGetsRawPtr<C>::value) };
  };
  
  template <typename A, typename B, typename C, typename D>
  struct ParamsUseScopedRefptrCorrectly<Tuple4<A, B, C, D> > {
    enum { value = !(NeedsScopedRefptrButGetsRawPtr<A>::value ||
                     NeedsScopedRefptrButGetsRawPtr<B>::value ||
                     NeedsScopedRefptrButGetsRawPtr<C>::value ||
                     NeedsScopedRefptrButGetsRawPtr<D>::value) };
  };
  
  template <typename A, typename B, typename C, typename D, typename E>
  struct ParamsUseScopedRefptrCorrectly<Tuple5<A, B, C, D, E> > {
    enum { value = !(NeedsScopedRefptrButGetsRawPtr<A>::value ||
                     NeedsScopedRefptrButGetsRawPtr<B>::value ||
                     NeedsScopedRefptrButGetsRawPtr<C>::value ||
                     NeedsScopedRefptrButGetsRawPtr<D>::value ||
                     NeedsScopedRefptrButGetsRawPtr<E>::value) };
  };
  
  template <typename A, typename B, typename C, typename D, typename E,
            typename F>
  struct ParamsUseScopedRefptrCorrectly<Tuple6<A, B, C, D, E, F> > {
    enum { value = !(NeedsScopedRefptrButGetsRawPtr<A>::value ||
                     NeedsScopedRefptrButGetsRawPtr<B>::value ||
                     NeedsScopedRefptrButGetsRawPtr<C>::value ||
                     NeedsScopedRefptrButGetsRawPtr<D>::value ||
                     NeedsScopedRefptrButGetsRawPtr<E>::value ||
                     NeedsScopedRefptrButGetsRawPtr<F>::value) };
  };
  
  template <typename A, typename B, typename C, typename D, typename E,
            typename F, typename G>
  struct ParamsUseScopedRefptrCorrectly<Tuple7<A, B, C, D, E, F, G> > {
    enum { value = !(NeedsScopedRefptrButGetsRawPtr<A>::value ||
                     NeedsScopedRefptrButGetsRawPtr<B>::value ||
                     NeedsScopedRefptrButGetsRawPtr<C>::value ||
                     NeedsScopedRefptrButGetsRawPtr<D>::value ||
                     NeedsScopedRefptrButGetsRawPtr<E>::value ||
                     NeedsScopedRefptrButGetsRawPtr<F>::value ||
                     NeedsScopedRefptrButGetsRawPtr<G>::value) };
  };
  
  template <typename A, typename B, typename C, typename D, typename E,
            typename F, typename G, typename H>
  struct ParamsUseScopedRefptrCorrectly<Tuple8<A, B, C, D, E, F, G, H> > {
    enum { value = !(NeedsScopedRefptrButGetsRawPtr<A>::value ||
                     NeedsScopedRefptrButGetsRawPtr<B>::value ||
                     NeedsScopedRefptrButGetsRawPtr<C>::value ||
                     NeedsScopedRefptrButGetsRawPtr<D>::value ||
                     NeedsScopedRefptrButGetsRawPtr<E>::value ||
                     NeedsScopedRefptrButGetsRawPtr<F>::value ||
                     NeedsScopedRefptrButGetsRawPtr<G>::value ||
                     NeedsScopedRefptrButGetsRawPtr<H>::value) };
  };
  
  }  // namespace internal
  
  }  // namespace base
  
  #endif  // BASE_RAW_SCOPED_REFPTR_MISMATCH_CHECKER_H_
  