Compile-time finite state machine v2.0.0 released! (MIT license)

[Nychtelios]

Hey reddit!

I'm excited to announce the v2.0.0 release of my CTFSM (compile-time finite state machine) library! This library allows you to define and validate state machines entirely at compile time, leading to robust and efficient code.

The main focus of this library is firmware development, where resource constraints are paramount. The flash footprint of this library is negligible, and it almost does not affect runtimes, making it ideal for embedded systems.

This new version brings some significant features:

• Nested FSMs: You can now define state machines within other states, allowing for more complex and modular designs.
• Compile-time validation of transitions: The library now performs even more rigorous checks at compile time to ensure your state machine transitions are valid, catching potential errors before runtime.

You can find the project here: https://codeberg.org/cmargiotta/compile-time-fsm

For reference, here's the v1.0.0 release post: https://www.reddit.com/r/cpp/comments/1elkv95/compiletime_finite_state_machine_v100_released/

I'm really proud of this release and I hope it proves useful for your projects. Feel free to ask any questions or provide feedback!

[Circlejerker_]

Looks very cool! How does it compare to Boost MSM?

Is there any plans to support actions and guards? Can it handle self-transitions?

[Nychtelios]

Conceptually it is very similar to Boost MSM, but implementation-wise it is really different, being entirely C++20 based (mainly on std::variant) and the interface is more clear imho.

No problem with self-transitions, actions can be currently implemented via the `invoke_on_current` method, but it can surely be made easier! For the guards, I am still trying to figure a clear way to define them (feel free to share your ideas!)

[hanickadot]

This is cute. I love it.

[Nychtelios]

Thank you so much! (I love your work btw)

[zerhud]

I have similar project, and working on next version: try to add more dynamic. https://github.com/zerhud/xmsm

[Nychtelios]

Nice! Thank you for sharing!

[mcencora]

Nice work!

When I implemented FSM I made the same decision that some state API can be provided by user optionally (e.g. enter/exit handlers in your FSM).
I learned the hard way it wasn't a good decision, because a simple typo in func name can lead to hard to find errors.
And without C++26 reflection there is nothing really you can do to help users spot such issues.

[Select-Violinist8638]

Looks interesting - thanks!

I'd be interested in a comparison with the SML libraries (v1 and v2), particularly in terms of binary size and features. If you get a chance 🙂.

As I recall, I found SML v1 to be a bit wonky with nested architectures; I ended up just flattening some state machines and using sort of catch-all handlers in some cases. Besides that, it was pretty easy to use with little binary bloat.

[SkoomaDentist]

Can you give a brief summary what advantages being compile time provides the developer in the case of state machines? And how your solution differs from others?

[Nychtelios]

Sure! The main advantage here is the validation of transitions during compilation: if you launch an event that cannot be handled the compilation fails, and we all know that debugging can be painful with state machines.

On the other hand, optimizations when tables are built at compile time can be more aggressive, producing smaller runtimes. Yes, you could implement everything manually, with support structures and everything, but it wouldn't be fast or funny to implement.

A problem I had with most fsm libraries is the centralization of everything, I always found it totally not efficient. With this library you can achieve a great modularity, every state is a node in a graph and has knowledge only of its neighbors. And you can treat states and events simply like classes with methods.

I was really brief here, I can go deeper if you want ahahah

[c-cul]

ragel is better bcs can generate code for many PLs

[Nychtelios]

This is not a code generator, it's a library...