Drop generation C++->RCL allocator conversion.

As explained in #1254, there's conceptually no way to implement RCL
allocators in terms of C++ allocators. Since allocator_common can't
be fixed, delete it and rely on implementers to provide a suitable
specialization. Since there's other blocking bugs for allocator use
(#1061), this shouldn't break existing users.

Author: stevewolter

rclcpp/include/rclcpp/allocator/allocator_common.hpp

@@ -39,61 +39,54 @@ void * retyped_allocate(size_t size, void * untyped_allocator)
   return std::allocator_traits<Alloc>::allocate(*typed_allocator, size);
 }
 
-template<typename T, typename Alloc>
+template<typename Alloc>
 void retyped_deallocate(void * untyped_pointer, void * untyped_allocator)
 {
   auto typed_allocator = static_cast<Alloc *>(untyped_allocator);
   if (!typed_allocator) {
     throw std::runtime_error("Received incorrect allocator type");
   }
-  auto typed_ptr = static_cast<T *>(untyped_pointer);
+  auto typed_ptr = static_cast<typename Alloc::value_type *>(untyped_pointer);
   std::allocator_traits<Alloc>::deallocate(*typed_allocator, typed_ptr, 1);
 }
 
-template<typename T, typename Alloc>
+template<typename Alloc>
 void * retyped_reallocate(void * untyped_pointer, size_t size, void * untyped_allocator)
 {
   auto typed_allocator = static_cast<Alloc *>(untyped_allocator);
   if (!typed_allocator) {
     throw std::runtime_error("Received incorrect allocator type");
   }
-  auto typed_ptr = static_cast<T *>(untyped_pointer);
+  auto typed_ptr = static_cast<typename Alloc::value_type *>(untyped_pointer);
   std::allocator_traits<Alloc>::deallocate(*typed_allocator, typed_ptr, 1);
   return std::allocator_traits<Alloc>::allocate(*typed_allocator, size);
 }
 
+}  // namespace allocator
 
 // Convert a std::allocator_traits-formatted Allocator into an rcl allocator
-template<
-  typename T,
-  typename Alloc,
-  typename std::enable_if<!std::is_same<Alloc, std::allocator<void>>::value>::type * = nullptr>
+template<typename Alloc>
 rcl_allocator_t get_rcl_allocator(Alloc & allocator)
 {
   rcl_allocator_t rcl_allocator = rcl_get_default_allocator();
 #ifndef _WIN32
-  rcl_allocator.allocate = &retyped_allocate<Alloc>;
-  rcl_allocator.deallocate = &retyped_deallocate<T, Alloc>;
-  rcl_allocator.reallocate = &retyped_reallocate<T, Alloc>;
+  rcl_allocator.allocate = &allocator::retyped_allocate<Alloc>;
+  rcl_allocator.deallocate = &allocator::retyped_deallocate<Alloc>;
+  rcl_allocator.reallocate = &allocator::retyped_reallocate<Alloc>;
   rcl_allocator.state = &allocator;
 #else
   (void)allocator;  // Remove warning
 #endif
   return rcl_allocator;
 }
 
-// TODO(jacquelinekay) Workaround for an incomplete implementation of std::allocator<void>
-template<
-  typename T,
-  typename Alloc,
-  typename std::enable_if<std::is_same<Alloc, std::allocator<void>>::value>::type * = nullptr>
-rcl_allocator_t get_rcl_allocator(Alloc & allocator)
+template <typename T>
+rcl_allocator_t get_rcl_allocator(std::allocator<T>& allocator)
 {
-  (void)allocator;
+  (void)allocator;  // Remove warning
   return rcl_get_default_allocator();
 }
 
-}  // namespace allocator
 }  // namespace rclcpp
 
 #endif  // RCLCPP__ALLOCATOR__ALLOCATOR_COMMON_HPP_

rclcpp/include/rclcpp/message_memory_strategy.hpp

@@ -61,15 +61,15 @@ class MessageMemoryStrategy
     message_allocator_ = std::make_shared<MessageAlloc>();
     serialized_message_allocator_ = std::make_shared<SerializedMessageAlloc>();
     buffer_allocator_ = std::make_shared<BufferAlloc>();
-    rcutils_allocator_ = allocator::get_rcl_allocator<char, BufferAlloc>(*buffer_allocator_.get());
+    rcutils_allocator_ = get_rcl_allocator(*buffer_allocator_.get());
   }
 
   explicit MessageMemoryStrategy(std::shared_ptr<Alloc> allocator)
   {
     message_allocator_ = std::make_shared<MessageAlloc>(*allocator.get());
     serialized_message_allocator_ = std::make_shared<SerializedMessageAlloc>(*allocator.get());
     buffer_allocator_ = std::make_shared<BufferAlloc>(*allocator.get());
-    rcutils_allocator_ = allocator::get_rcl_allocator<char, BufferAlloc>(*buffer_allocator_.get());
+    rcutils_allocator_ = get_rcl_allocator(*buffer_allocator_.get());
   }
 
   virtual ~MessageMemoryStrategy() = default;

rclcpp/include/rclcpp/publisher_options.hpp

@@ -75,7 +75,9 @@ struct PublisherOptionsWithAllocator : public PublisherOptionsBase
     using AllocatorTraits = std::allocator_traits<Allocator>;
     using MessageAllocatorT = typename AllocatorTraits::template rebind_alloc<MessageT>;
     auto message_alloc = std::make_shared<MessageAllocatorT>(*this->get_allocator().get());
-    result.allocator = rclcpp::allocator::get_rcl_allocator<MessageT>(*message_alloc);
+    // TODO: This is likely to invoke undefined behavior - message_alloc goes out of scope
+    // at the end of this function, but the allocator doesn't.
+    result.allocator = get_rcl_allocator(*message_alloc);
     result.qos = qos.get_rmw_qos_profile();
 
     // Apply payload to rcl_publisher_options if necessary.

rclcpp/include/rclcpp/strategies/allocator_memory_strategy.hpp

@@ -437,7 +437,7 @@ class AllocatorMemoryStrategy : public memory_strategy::MemoryStrategy
 
   rcl_allocator_t get_allocator() override
   {
-    return rclcpp::allocator::get_rcl_allocator<void *, VoidAlloc>(*allocator_.get());
+    return get_rcl_allocator(*allocator_.get());
   }
 
   size_t number_of_ready_subscriptions() const override

rclcpp/include/rclcpp/subscription_options.hpp

@@ -102,7 +102,9 @@ struct SubscriptionOptionsWithAllocator : public SubscriptionOptionsBase
     using AllocatorTraits = std::allocator_traits<Allocator>;
     using MessageAllocatorT = typename AllocatorTraits::template rebind_alloc<MessageT>;
     auto message_alloc = std::make_shared<MessageAllocatorT>(*allocator.get());
-    result.allocator = allocator::get_rcl_allocator<MessageT>(*message_alloc);
+    // TODO: This is likely to invoke undefined behavior - message_alloc goes out of scope
+    // at the end of this function, but the allocator doesn't.
+    result.allocator = get_rcl_allocator(*message_alloc);
     result.qos = qos.get_rmw_qos_profile();
     result.rmw_subscription_options.ignore_local_publications = this->ignore_local_publications;