"Yeah, I think that the standard Rust API may simply not be acceptable inside the kernel, if it has similar behavior to the (completely broken) C++ 'new' operator." ouch.
Conversation
Replying to
I agree with him. You can't have compilers doing magic random allocations, it leads to state-explosion. Almost as stupid as kernel true-type parsing.
1
Asking for pure curiosity. In C++ i guess he refers to implicit allocations done by copy operators etc. Which are not random but they could be hard to spot. Rust isn’t that bad in that aspect, with more explicit semantics for what is copied or moved. The only exception is drop
1
Rust's high-level standard library has a choice between APIs using panic (unwinding or abort) or reporting an error.
The low-level subset of the standard library doesn't provide dynamic allocation. If you're using that, then you can choose to only provide APIs reporting errors.
1
The proof of concept kernel Rust implementation doesn't use the high-level standard library. They used the liballoc library as a placeholder and that comes with both forms of methods (panic and error reporting). They explained they'll only be providing error reporting variants.
1
Unlike C, Rust has standard support for using it as a freestanding language and with a low-level subset of the standard library.
The language fully supports implementing the allocation APIs via the kernel allocators and only providing the variants of those APIs not using panic.
1
1
It is annoying that you lose all the standard dynamically allocated collections, etc. and need to fork the libraries if you don't want method variants panicking on OOM.
So, for example, you'd want Vec::push(x) to return Option<T> or Result<T, E> to get back `x` on alloc failure.
As a language, it fully supports it. It fits well into the idiomatic error handling system based on sum types (typically Result) including syntactic sugar for bubbling up the errors.
Unlike C++, no-unwind support is standard, but high level stdlib mostly relies on panic on OOM.
1
The high level stdlib has no relevance to the kernel usage because it MUST use $![no_std] (freestanding) code. The high-level stdlib (libstd) uses lower-level standard libraries (libcore, liballoc, etc.) and they can use some of those, but they will need a stripped down liballoc.
1
Show replies