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I have never used Arc<T>/Rc<T> in my embedded work, and rarely in my non-embedded work.

elcritch 4y ago
Ah true, I probably overstate the amount of Arc<T>/Rc<T> in Rust code. C++ uses shared_ptr<T> a lot in the code I've been dealing with lately, so maybe its biased me. Though it's partly up to the skill/experience of the programmer too.
- estebank 4y ago
  For what is worth, I rarely need to use Arc or RefCell, but I also rarely write complex async code where it is more prevalent.
zozbot234 4y ago
Rc/Arc requires allocation, which limits its usefulness for embedded programming. It may become more useful once local allocators get stabilized, which would mean allocations can be made even absent a general heap.
robocat 4y ago
And Steve said, "Let there be borrowing," and there was borrowing. And Steve saw that the borrowing was good.”. Tongue-in-cheek. My guess is that your experience and skills perhaps can’t be projected on to the average developer.
- steveklabnik 4y ago
  Nah. As the sibling says, these types do heap allocation, and a lot of embedded programs simply don't have a heap. As esteban says, these types do get used more often in async code, which I don't write a ton of at the moment. But more importantly, I think that if a beginner tries to use arc/rc to "get around the borrow checker" it introduces even more pain. It's not a beginner's tool, it's a possible misleading path. I left a comment a few years back with a practical example here; while the root cause isn't refcounting, look at how much ceremony they add https://news.ycombinator.com/item?id=24992537 https://news.ycombinator.com/item?id=24992537 If we were talking about clone, however, that would be a different story: clone is often a great tool for beginners who are struggling with a design that fits into what Rust wants. And even then, the comment didn't qualify as "beginner code" or "expert code": it said that Rust programs generally "make heavy use of reference counting" and that's simply not my experience, nothing more, nothing less. Not only with my own code, but code I see others write, and libraries that I and others use. YMMV, as always.
surajrmal 4y ago
Agreed, it's easy to avoid if you architect your code to avoid sharing state, or stick to only sharing state with children that will always be outlived by the parent.

Ah true, I probably overstate the amount of Arc<T>/Rc<T> in Rust code. C++ uses shared_ptr<T> a lot in the code I've been dealing with lately, so maybe its biased me. Though it's partly up to the skill/experience of the programmer too.

estebank 4y ago
For what is worth, I rarely need to use Arc or RefCell, but I also rarely write complex async code where it is more prevalent.

zozbot234 4y ago

Rc/Arc requires allocation, which limits its usefulness for embedded programming. It may become more useful once local allocators get stabilized, which would mean allocations can be made even absent a general heap.

robocat 4y ago

And Steve said, "Let there be borrowing," and there was borrowing. And Steve saw that the borrowing was good.”. Tongue-in-cheek. My guess is that your experience and skills perhaps can’t be projected on to the average developer.

steveklabnik 4y ago
Nah. As the sibling says, these types do heap allocation, and a lot of embedded programs simply don't have a heap. As esteban says, these types do get used more often in async code, which I don't write a ton of at the moment. But more importantly, I think that if a beginner tries to use arc/rc to "get around the borrow checker" it introduces even more pain. It's not a beginner's tool, it's a possible misleading path. I left a comment a few years back with a practical example here; while the root cause isn't refcounting, look at how much ceremony they add https://news.ycombinator.com/item?id=24992537 https://news.ycombinator.com/item?id=24992537 If we were talking about clone, however, that would be a different story: clone is often a great tool for beginners who are struggling with a design that fits into what Rust wants. And even then, the comment didn't qualify as "beginner code" or "expert code": it said that Rust programs generally "make heavy use of reference counting" and that's simply not my experience, nothing more, nothing less. Not only with my own code, but code I see others write, and libraries that I and others use. YMMV, as always.

surajrmal 4y ago

Agreed, it's easy to avoid if you architect your code to avoid sharing state, or stick to only sharing state with children that will always be outlived by the parent.