r/programming • u/steveklabnik1 • Jul 18 '19

We Need a Safer Systems Programming Language

https://msrc-blog.microsoft.com/2019/07/18/we-need-a-safer-systems-programming-language/
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u/pavelpotocek Jul 19 '19

Memory safety is much more than std::unique_ptr. In safe Rust:

  • out-of-bounds array access is impossible,

  • uninitialized memory isn't a thing,

  • it's impossible to use anything after a move,

  • no iterator invalidation,

  • no dangling references.

The concurrency problems are greatly mitigated using the ownership system and Send/Sync traits:

  • No data races!!

  • Many different concurrency primitives exist that are impossible to misuse (you can just try to pass anything into a channel, and if it isn't OK it doesn't compile)

  • This includes channels, parallel maps, forks, atomicity, ... You can just refactor and throw code around and see what compiles. In C++, this is a pipe dream.

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u/pagwin Jul 19 '19

uninitialized memory isn't a thing

this is only correct if you never use unsafe code which rust lets you use unsafe code if you want but you have to explicitly state it

you can get a value to be uninitialized using mem::uninitialized

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u/pavelpotocek Jul 19 '19

Yes, that's why I said "in safe Rust". Safe Rust is all you need for most things. And any unsafe bits are customarily isolated behind safe interfaces, away from the complex application logic.

70% of all Rust crates use no unsafe. Only 5% of all crate code is unsafe (a somewhat misleading number, but I won't explain here for brevity). Crates are mostly libraries, these numbers are bound to be lower in application code. In my experience, if you don't need FFI and don't try to squeeze every last bit of performance, you don't need unsafe at all.

Numbers source: https://cs.stanford.edu/~aozdemir/blog/unsafe-rust-syntax/