Rust doesn't assume an allocator. The Rust standard library (to have things like growable strings) requires an allocator but the language and its core do not.
And Rust doesn't assume threading either. The default stuff isn't even thread safe, it's just that in Rust when you introduce threading and still try to use stuff that isn't thread safe the compiler will tell you that can't work.
You can deliberately write stuff that won't do what you meant of course, but they're trying to make it harder to do that by accident. I have a set of Rust types which defy logical behaviour (for example type whose members always compare as equal yet hash differently) and as intended if you use those in otherwise safe code your program might not work but it doesn't cause random craziness. For example maybe your attempt to binary search an ordered list of my data types that claim they form a total order and yet always reply "I'm smaller" when asked how they compare to anything, even themselves - will become an infinite loop, but it won't suddenly execute environment variables as code or anything like that whereas in C all bets are off.
> And Rust doesn't assume threading either. The default stuff isn't even thread safe
Right, and Rust doesn't even know what a thread is actually. It's all implemented in the standard library. The only thing Rust know, is that there exist some special Traits (Send and Sync) which are automatically implemented if a struct field implements it itself. And that's it.
And Rust doesn't assume threading either. The default stuff isn't even thread safe, it's just that in Rust when you introduce threading and still try to use stuff that isn't thread safe the compiler will tell you that can't work.
You can deliberately write stuff that won't do what you meant of course, but they're trying to make it harder to do that by accident. I have a set of Rust types which defy logical behaviour (for example type whose members always compare as equal yet hash differently) and as intended if you use those in otherwise safe code your program might not work but it doesn't cause random craziness. For example maybe your attempt to binary search an ordered list of my data types that claim they form a total order and yet always reply "I'm smaller" when asked how they compare to anything, even themselves - will become an infinite loop, but it won't suddenly execute environment variables as code or anything like that whereas in C all bets are off.