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by inferiorhuman 957 days ago
You definitely can use rust in an embedded space. I rather liked having traits and proper types instead of a giant mess of integer constants. In general I think a lot of the so-called bloat you see with Rust binaries is due to a combination of not using a shared standard library and generics – the former is a non-issue in an embedded context and the latter is well under your control.

Sure, ELF includes a lot of fluff but you're not deploying ELF on a microcontroller.
1 comments
fusslo 957 days ago
yeah I think I just need to write some stuff to figure it out.

I was mostly trying to figure a 1:1 comparison. For example, If I write a Feature Control module in c and in rust, using the same design, are outputs similar?

seems like either no one has a good sense of that comparison, or it's a bad comparison and I don't understand why.

What I'm trying to avoid is having a space-saving task be "rewrite rust module X in c to save code memory"

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inferiorhuman 957 days ago
IMO it would be good to familiarize yourself with the rust quirks/features (check out the rust book) and then poke at some of the embedded specific groups. Once you get a handle on the common types and patterns it's probably easier to find the information you're looking for, e.g.:

https://github.com/rust-lang/rust/issues/46213

In general Rust chases a "zero cost abstraction" ethos, so a lot of the type system niceties have no code or memory cost because the heavy lifting is done at compile time, not run time. For instance using specific traits for each GPIO pin ensures you won't accidentally apply some meaning meant for another pin, but the compiler will compile it right down to integers anyhow.

Things like options (how Rust deals with "null" values) are enums and usually incur a one byte penalty, but in some cases they can be compiled down to no overhead at all.

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steveklabnik 957 days ago
> it's a bad comparison and I don't understand why

Different languages are different, and so it's tough to compare. You don't generally write Rust code in the same way you write C, and so a "using the same design" constraint on a comparison means that some folks will not consider it to be an accurate one.

In general, similar constructs have the same amount of overhead, that is, zero. Rust has additional features that are useful that can increase code size if you're not careful, but getting that back down doesn't necessarily mean abandoning Rust, but it may lead to "write the Rust closer to C." I am thinking of generics specifically here, monomorphization can blow up your code size, but you could either not use generics or use a few techniques to minimize it.

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