Rust – What made it “click” for me (Ownership and memory internals)(deavid.wordpress.com) |
Rust – What made it “click” for me (Ownership and memory internals)(deavid.wordpress.com) |
The immeasurable success of Rust certainly lies in its clear communication and forcing developers to learn about the basics of hardware.
I can't help but to feel validated in thinking that every developer worth its salt should know about these basics anyway. But I have to admit that not everybody comes with a CS background.
Something doesn't sit quite right with me to describe the "basics of hardware" as being something that comes with a "CS background".
I come from a formal CS background, and we spent more time dealing with finite state automatons, programming language theory, and other aspects of abstract computation. Getting down and dirty with data sizes, system components, and bit fiddling was an available, but optional path. We all spent one or two courses dealing with the practical nature of computers, but it was largely drowned out by theory, at least in my program.
But the reality is, I still can't tell you what Computer Science actually is. Is it:
- About understanding how to control computers (which are fast electronic machines)
- About inventing programming, from the ground up. (A weird sub-discipline of mathematics and category theory)
or
- Learning to make software in order to improves the lives of humans
We sort of need to learn all three aspects. Haskell programs run slower than C++ programs because haskell isn't written in harmony with the physical CPU cores we've made. Making fast programs is pointless if our software doesn't solve user needs. And solving user needs are impossible if we can't express ourselves clearly to the computer - which programming language theorists are obsessed with.
I think the basics of hardware is part of CS, but maybe a CS undergraduate degree doesn't give anyone enough time to really go broad in the field. I dunno!
But manually managing memory lifetimes you only learn from a lot of exposure to C/asm.
In my first 3 months of Rust, I spent an equal amount of time with the type-checker and the borrow-checker. A year in and I don’t really have a separate phase of resolving borrow-check errors before I can compile.
People with more C exposure tend to think that way already.
Why C? It is not any lower than Rust, one might even argue that Rust is lower-level than C due to it having control over SIMD and the like without non-portable compiler extensions.
Memory management in C was too high level at that time ;)
You can get very far writing software without even being aware that your language is even doing something called garbage collection for you, or without even having a basic concept of memory being tied to values, sizes, etc. If you lack this context a borrow checker just seems like a pointless nuisance.
Once you get your head around the borrow checker, Rust takes a lot of that cognitive load off you, by tracking things for you at compile time and dinging you on it if you get something wrong.
their salt
Ultimately we are all still just writing nicer versions of C. The fundamental model of pretty much all high level languages remains the same. You can still explain and think about the vast majority of memory related goings-on in a program as using the basic abstraction of the pointer and contiguous arrays of bytes. Even languages that have different paradigms, be they functional, logical, or object oriented can be described in terms of pointers--one easy way to understand pretty much every other programming language paradigm is basically just to ask "how would I implement this using pointers?". It's a shared history and approach to computing we have yet to move on from.
I thought, “I wish there was a way to prove to the compiler that it will be there when I access it, rather than having to tell it to trust me.”
And that’s when lifetimes in Rust really clicked for me. I know it’s not exactly the same thing but the value of describing the valid lifetime of a thing at compile time began making a lot more sense.
As a Rust beginner, that's a handy thing to remember! Thinking of variable passing in terms of least privilege seems much better than just trying to use the simplest syntax (changing ownership by passing the variable rather than a pointer to it) all the time.
LOL, sure borrow-checked reference counted pointers that can't equal null to mark the beginning or end of a chain are exactly what I am looking for when I want to build a linked list or tree. Why are you like this, Rust?
I understand what the claims advantages of Rust are, but I can't understand those cult-like passions.
This does not work in Rust. But the counterpart in C kind of does:
int &p_a = 0x100;
int a = \*p_a;
probably dont want to actually use that code...
let a: String = "Hello world".to_string();
There are almost no application domains in which you need to conform to some insane borrowing protocol for the entire software.
Your analogy is stupid beyond belief; and terms of the safety of the circuit itself that is behind the outlet, yes I can plug in anything without worrying there will be a fire in the wall. I live in the first world, where we have electrical codes and circuit breakers.
For some software (eg browsers, operating systems), time spent making our programs correct and fast is worth the effort.
But at the same time, I don't want to invest so much time into learning a language which I probably am not going to use.
I am probably being disrespectful. I understand a lot of people use C, including Linux kernel devs, but I cannot imagine developing new apps with an old language such as C.
It won't take you too long either! Compared to modern languages, C is very small and very simple and likely won't take as long as learning any other popular language in use today. You can learn all of C in the amount of time it takes most people to learn just the basics of a borrow checker. If you only focus on the aspects related to memory (stack, heap, sizing, arrays, pointers) it would likely only take half a day, if that.
If you are responsible for your own memory, it makes you more aware of issues such as indirection and cyclic dependencies.
Good luck with a browser without javascript.
Borrowing Through Faith
Rust Prevails!
I'm not convinced Rust & C++ have as much in common as you think. Rust is really familar to OCaml or Haskell users.
Contributing to world class projects such as Postgres sounds cool, but doesn't it take years of experience?
Of course there are other benefit of learning C as you noted.
> Ownership is completely inadequate for operating systems.
The linux kernel is adding rust support as a first class language. In time I wouldn't be surprised if large parts of the linux kernel were written in rust. Obviously linux will always have a lot of unsafe code, but unsafe is part of rust too. Its surprising how infrequently you need it.
[1] https://security.googleblog.com/2023/01/supporting-use-of-ru...
Computer Systems Engineering
> About inventing programming, from the ground up. (A weird sub-discipline of mathematics and category theory)
Computer Science
> Learning to make software in order to improves the lives of humans
Software Engineering
Otherwise, where do operating systems fall? Are they systems engineering? They don't seem to be entirely about the hardware to me, and they were a core part of my CS program. What about SeL4 - which is a formally verified operating system project?
How about programming languages like C or Rust? Is that computer science, or systems engineering? How about Excel - the world's most popular programming language - that happens to be functional? Are financial planners doing computer science when they program a spreadsheet?
The lines are blurry everywhere. My CS program offered 3 different degrees, like you said - Computer engineering, Computer Science and Software Engineering. The only difference was the CS degree had a lot of electives, and the other two filled those electives in with (different) required subjects.
Maybe CS is just "lets play with some cool things on computers!". And there's a big playpen of things to explore. Thats more or less how it feels to me.
Computer Science is about understanding what computation can and cannot achieve, and more importantly, how to achieve it (that is where it differs from Mathematics, where mathematicians are usually not interested in the how part). Under this definition, we can put typical college subjects into consideration:
* Data Structures and Algorithms: about studying how to manipulate data to solve a task efficiently.
* Complexity Theory: about formal classification of hardness of problems. What makes a computational problem "hard" or "easy"?
* Computer System: about how to construct a software system to achieve certain purposes. What are the constraints in a system (performance, security, privacy, correctness, fault tolerance, etc), and how to design a system to address such constraints? What tradeoffs to be made when you cannot meet all the desired requirements?
* Distributed System: how to design system with a few to massive number of computers that are connected in a network? How do you reason about fault tolerance, consistency, sharding, and so on?
* Operating System: about how to create abstraction to the hardware, that allows for other softwares to interact with it without having to explicitly deal with the hardware?
The list could go on, but I just give a couple of examples.
This is not a discipline that I am aware of
- Learning to make software in order to make the lives of humans miserable
This is a discipline, but not quite Computer Science
- Learning to make software so that great engineers become average engineers, and incompetent engineers become managers
This is software engineering
The lines between academic fields are primarily administrative. Their main purpose is to facilitate undergraduate education. They are also fuzzy and vary between institutions. A person working in a CS department could find their home in the mathematics department at another university. Or physics. Or economics. Or biology. Or somewhere else. No matter what CS was at your university, it can be something very different at another.
You can't plug a device that pulls 10kW into a plug and have it work, because the circuit breaker stops you from overloading your circuits. You can't plug in a device that attaches the live to your left hand and the neutral to your right, immediately stopping your heart, because such a device is forbidden by electrical codes, and everyone who makes electrical devices has to follow these.
Or, else, what is your point?
In both cases, it should be clear to you that you are behaving in a possibly dangerous manner, that you should know what you're doing and that you are responsible for not endangering others with whatever you're doing.
Making safe things unsafe: rusterfuck.
Leaks are not a security concern (besides DOS attacks).
What on earth constitutes "recent" language and where did you se me mentioning "resent"? Anyways, does C++17 qualify? What about PHP8, ECMAScript of latter editions, newer versions of C#, Java etc. etc. ?
If I understand your thinking correct let me help you with your question: what native high performance language with no GC, memory / lifetime management and with the stable release after 2015 is used by all large tech companies. Nice try.
Also what FAANGs do with their choice of tech is their own worries. They have needs that will never be encountered by majority of the rest of the world's programming.
No, language versions are not languages.
> If I understand your thinking correct let me help you with your question: what native high performance language with no GC, memory / lifetime management and with the stable release after 2015 is used by all large tech companies. Nice try.
I meant in general, which languages that were created in the last 20 years are used by all big tech companies.
> Also what FAANGs do with their choice of tech is their own worries. They have needs that will never be encountered by majority of the rest of the world's programming.
I was arguing that Rust is popular since it has quite a bit of adoption, as demonstrated for example by it's usage by big tech. Also, no, there is a dire need for good systems languages.