Authors:David Herman
Time:2:40 pm - 3:20 pm

A Haiku to describe Rust:

a systems language

pursuing the trifecta

safe, concurrent, fast

Mozilla Research is interested in the platform side of the web: Boot To Gecko, for example. And at a lower level, thinking about how they’d design things for the future. Looking at a set of tabs in a browser, you think about them in terms of security and sandboxing, but Mozilla Research thinks about them in term of threading, performance, etc: like the browser is an operating system that provides a bunch of stuff for “apps”.

So why Rust? Mozilla’s codebase is huge, and lots of C++, which is not designed for security, etc. Started working on Rust in 2009, self hosting on LLVM in 2011. Rust is the love child of C++, Erlang, and Caml, and Haskell.


Sometimes abstractions remove duplicated code, but introduce performance issues. Rust strives to provide zero cost abstractions. For example, lambdas are aggressively inlined, and you can annotate code to push the compiler towards inlining. Rust also provides C++ like structured data: direct access instead of indirection. [Shows example of a Point(x,y) struct. You can deal with the indirection if you needed. Rust is currently calling these “borrowed pointers” to reinforce the idea that they’re on the stack, and not necessarily long lived. Rust also provides syntax for allocating on the heap, when needed. These can be passed as borrowed pointers, if needed.

Four ways to use a structure:

  • Directly
  • Borrowed Pointer (*)
  • Heap Pointer (&)
  • Unique (Owned) Pointers (~)

You can “move” ownership of pointers; doing so effectively eliminates the local variable so you no longer have access.


Actor-like language, so you allocate tasks. When you create a stack, you have a small stack allocated, which will dynamically grow. Task creation is pretty cheap. Tasks can not have pointers to data in other tasks, so they can be garbage collected independently. [Sounds like they’re roughly the same as processes.] Tasks can allocate unique pointers, which are created on the shared heap. When a Task needs to communicate with another Task, it simply moves the pointer to the other Task. This pointer pass is very cheap. And because it’s a unique pointer, you’re guaranteed that no other Task points to it.


Rust has generics (parametric polymorphism). “Classes” are flat structs, and you can attach methods after the fact.

You can declare traits which provide a way to do Type Classes [feels like interfaces to me].

ARCs (“Automic Reference Counting”) structs require that the data within it must be deeply immutable. These can be freely shared between Tasks.

Even though Rust is designed for safety, there’s no such thing as a completely safe language: every language has a way to do something “unsafe”. Rust has that, too, but they’re branded with a huge hazmat sign, and if you touch them, your code is branded unsafe.

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