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> Android has ported a lot of the Bluetooth code to Rust. This is a demonstration of why they need to put more resources into porting the rest of the code into

> Android has ported a lot of the Bluetooth code to Rust. This is a demonstration of why they need to put more resources into porting the rest of the code into Rust. I like how they snuck that in there :-D As someone who spent years writing C and C++, but no experience with Rust, with this porting from C to Rust, how much refactoring is required? That might should be two different questions: 1. How closely does C translate directly over to Rust? Does Rust require some reorganization/refactoring? 2. How is Google approaching this? Are they trying to closely "translate" it as much as possible, or is this an opportunity for major rewrite/refactor? Also very curious if anyone knows, will the Android Bluetooth stack ever be usable on a standard Linux distro desktop system?

deleted 3y ago
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meibo 3y ago
It's likely pretty far from a 1:1 port, you'll be rearchitecting a lot of what you are writing. It's unavoidable due to the way Rust guarantees memory safety.
tommiegannert 3y ago
I was recently trying to port a PIC microcontroller simulator from C++ to Rust as an (unfinished) experiment. Because there were lots of cyclic references (modules talking to each other over "signal busses" with callbacks,) I think I ended up fighting Rust more than it helped. It ended up requiring a lot of Box (pointers to heap) for things where I could store the data inline in C++. My conclusion is that if you're writing a simple CLI or request-response thing, Rust is probably an easy port. More generally, if your code structure could work well with arena allocations, moving to lifetime-tagging of references isn't a big deal. But if you're writing (admitted ugly) code with cyclic references the way a C programmer would :), Rust will feel like an uphill battle and is not the place to start. I need to start by restructuring the C++ code, moving ownership to a common parent. I think that'll make things better. Iteratively learning more about Rust, but continuing to work in C++ until the code has a better correspondance to Rust. Edit: forgot the word simulator, and changed RefCell to Box.
- steveklabnik 3y ago
  > It ended up requiring a lot of RefCell (pointers to heap) Just so you know, RefCell does not inherently point to the heap. If you put a Box or something inside, sure, but on its own, it doesn't allocate.
  - tommiegannert 3y ago
    Ah, thanks, I changed it to a Box. I confused the two, since I had to use them in conjunction.
    - steveklabnik 3y ago
      It's all good. For what it's worth, I agree with you generally that a lot of the C code I see is like, "differently shaped" than the Rust, so it's not super simple to port directly over.

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meibo 3y ago

It's likely pretty far from a 1:1 port, you'll be rearchitecting a lot of what you are writing. It's unavoidable due to the way Rust guarantees memory safety.

tommiegannert 3y ago

I was recently trying to port a PIC microcontroller simulator from C++ to Rust as an (unfinished) experiment. Because there were lots of cyclic references (modules talking to each other over "signal busses" with callbacks,) I think I ended up fighting Rust more than it helped. It ended up requiring a lot of Box (pointers to heap) for things where I could store the data inline in C++. My conclusion is that if you're writing a simple CLI or request-response thing, Rust is probably an easy port. More generally, if your code structure could work well with arena allocations, moving to lifetime-tagging of references isn't a big deal. But if you're writing (admitted ugly) code with cyclic references the way a C programmer would :), Rust will feel like an uphill battle and is not the place to start. I need to start by restructuring the C++ code, moving ownership to a common parent. I think that'll make things better. Iteratively learning more about Rust, but continuing to work in C++ until the code has a better correspondance to Rust. Edit: forgot the word simulator, and changed RefCell to Box.

steveklabnik 3y ago
> It ended up requiring a lot of RefCell (pointers to heap) Just so you know, RefCell does not inherently point to the heap. If you put a Box or something inside, sure, but on its own, it doesn't allocate.
- tommiegannert 3y ago
  Ah, thanks, I changed it to a Box. I confused the two, since I had to use them in conjunction.
  - steveklabnik 3y ago
    It's all good. For what it's worth, I agree with you generally that a lot of the C code I see is like, "differently shaped" than the Rust, so it's not super simple to port directly over.