Migration Guides

The guides in this section document all possibly breaking changes in the library for that last versions of CAF.

0.8 to 0.9

Version 0.9 included a lot of changes and improvements in its implementation, but it also made breaking changes to the API.

self has been removed

This is the biggest library change since the initial release. The major problem with this keyword-like identifier is that it must have a single type as it’s implemented as a thread-local variable. Since there are so many different kinds of actors (event-based or blocking, untyped or typed), self needs to perform type erasure at some point, rendering it ultimately useless. Instead of a thread-local pointer, you can now use the first argument in functor-based actors to “catch” the self pointer with proper type information.

actor_ptr has been replaced

CAF now distinguishes between handles to actors, i.e., typed_actor<...> or simply actor, and addresses of actors, i.e., actor_addr. The reason for this change is that each actor has a logical, (network-wide) unique address, which is used by the networking layer of CAF. Furthermore, for monitoring or linking, the address is all you need. However, the address is not sufficient for sending messages, because it doesn’t have any type information. The function current_sender() now returns the address of the sender. This means that previously valid code such as send(current_sender(), ...) will cause a compiler error. However, the recommended way of replying to messages is to return the result from the message handler.

The API for typed actors is now similar to the API for untyped actors

The APIs of typed and untyped actors have been harmonized. Typed actors can now be published in the network and also use all operations untyped actors can.

0.9 to 0.10 (libcppa to CAF)

The first release under the new name CAF is an overhaul of the entire library. Some classes have been renamed or relocated, others have been removed. The purpose of this refactoring was to make the library easier to grasp and to make its API more consistent. All classes now live in the namespace caf and all headers have the top level folder “caf” instead of “cppa”. For example, #include "cppa/actor.hpp" becomes #include "caf/actor.hpp". Further, the convenience header to get all parts of the user API is now "caf/all.hpp". The networking has been separated from the core library. To get the networking components, simply include "caf/io/all.hpp" and use the namespace caf::io, e.g., caf::io::remote_actor.

Version 0.10 still includes the header cppa/cppa.hpp to make the transition process for users easier and to not break existing code right away. The header defines the namespace cppa as an alias for caf. Furthermore, it provides implementations or type aliases for renamed or removed classes such as cow_tuple. You won’t get any warning about deprecated headers with 0.10. However, we will add this warnings in the next library version and remove deprecated code eventually.

Even when using the backwards compatibility header, the new library has breaking changes. For instance, guard expressions have been removed entirely. The reasoning behind this decision is that we already have projections to modify the outcome of a match. Guard expressions add little expressive power to the library but a whole lot of code that is hard to maintain in the long run due to its complexity. Using projections to not only perform type conversions but also to restrict values is the more natural choice.

any_tuple => message

This type is only being used to pass a message from one actor to another. Hence, message is the logical name.

partial_function => message_handler

Technically, it still is a partial function. However, we wanted to put emphasize on its use case.

cow_tuple => X

We want to provide a streamlined, simple API. Shipping a full tuple abstraction with the library does not fit into this philosophy. The removal of cow_tuple implies the removal of related functions such as tuple_cast.

cow_ptr => X

This pointer class is an implementation detail of message and should not live in the global namespace in the first place. It also had the wrong name, because it is intrusive.

X => message_builder

This new class can be used to create messages dynamically. For example, the content of a vector can be used to create a message using a series of append calls.

accept_handle, connection_handle, publish, remote_actor,
max_msg_size, typed_publish, typed_remote_actor, publish_local_groups,
new_connection_msg, new_data_msg, connection_closed_msg, acceptor_closed_msg

These classes concern I/O functionality and have thus been moved to caf::io

0.10 to 0.11

Version 0.11 introduced new, optional components. The core library itself, however, mainly received optimizations and bugfixes with one exception: the member function on_exit is no longer virtual. You can still provide it to define a custom exit handler, but you must not use override.

0.11 to 0.12

Version 0.12 removed two features:

  • Type names are no longer demangled automatically. Hence, users must explicitly pass the type name as first argument when using announce, i.e., announce<my_class>(...) becomes announce<my_class>("my_class", ...).
  • Synchronous send blocks no longer support continue_with. This feature has been removed without substitution.

0.12 to 0.13

This release removes the (since 0.9 deprecated) cppa headers and deprecates all *_send_tuple versions (simply use the function without _tuple suffix). local_actor::on_exit once again became virtual.

In case you were using the old cppa::options_description API, you can migrate to the new API based on extract (see Extracting Command Line Options).

Most importantly, version 0.13 slightly changes last_dequeued and last_sender. Both functions will now cause undefined behavior (dereferencing a nullptr) instead of returning dummy values when accessed from outside a callback or after forwarding the current message. Besides, these function names were not a good choice in the first place, since “last” implies accessing data received in the past. As a result, both functions are now deprecated. Their replacements are named current_message and current_sender (see Messaging Interfaces).

0.13 to 0.14

The function timed_sync_send has been removed. It offered an alternative way of defining message handlers, which is inconsistent with the rest of the API.

The policy classes broadcast, random, and round_robin in actor_pool were removed and replaced by factory functions using the same name.

0.14 to 0.15

Version 0.15 replaces the singleton-based architecture with actor_system. Most of the free functions in namespace caf are now member functions of actor_system (see Environment / Actor Systems). Likewise, most functions in namespace caf::io are now member functions of middleman (see Middleman). The structure of CAF applications has changed fundamentally with a focus on configurability. Setting and fine-tuning the scheduler, changing parameters of the middleman, etc. is now bundled in the class actor_system_config. The new configuration mechanism is also easily extensible.

Patterns are now limited to the simple notation, because the advanced features (1) are not implementable for statically typed actors, (2) are not portable to Windows/MSVC, and (3) drastically impact compile times. Dropping this functionality also simplifies the implementation and improves performance.

The blocking_api flag has been removed. All variants of spawn now auto-detect blocking actors.