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Matt Godbolt sold me on Rust by showing me C++

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Re: Matt Godbolt sold me on Rust by showing me C++

#221

Post by johnisgood »

zozbot234 wrote: post #40
dvratil wrote: post #8

The one thing that sold me on Rust (going from C++) was that there is a single way errors are propagated: the Result type. No need to bother with exceptions, functions returning bool, functions returning 0 on success, functions returning 0 on error, functions returning -1 on error, functions returning negative errno on error, functions taking optional pointer to bool to indicate error (optionally), functions taking r…

> The one thing that sold me on Rust (going from C++) was that there is a single way errors are propagated: the Result type. No need to bother with exceptions This isn't really true since Rust has panics. It would be nice to have out-of-the-box support for a "no panics" subset of Rust, which would also make it easier to properly support linear (no auto-drop) types.

I do not want a library to panic though, I want to handle the error myself.

Re: Matt Godbolt sold me on Rust by showing me C++

#222

Post by CJefferson »

jchw wrote: post #209
CJefferson wrote: post #206

Earlier quoted context omitted.

I had a look. In classic C++ style, if you use *x to get the ‘expected’ value, when it’s an error object (you forgot to check first and return the error), it’s undefined behaviour! Messing up error handling isn’t hard to do, so putting undefined behaviour here feels very dangerous to me, but it is the C++ way.

The reason it works this way is there's legitimately no easy way around it. You're not guaranteed a reasonable zero value for any type, so you can't do the slightly better Go thing (defined behavior but still wrong... Not great.) and you certainly can't do the Rust thing, because... There's no pattern matching. You can't conditionally enter a branch based on the presence of a value. There really is no reasonable work…

You could assert. You could throw. I can’t understand how, this modern age where so many programs end up getting hacked, that introducing more UB seems like a good idea.

This is one odd the major reasons I switched to rust, just to escape spending my whole life worrying about bugs caused by UB.

Re: Matt Godbolt sold me on Rust by showing me C++

#223

Post by mountainriver »

thrwyexecbrain wrote: post #132

The C++ code I write these days is actually pretty similar to Rust: everything is explicit, lots of strong types, very simple and clear lifetimes (arenas, pools), non-owning handles instead of pointers. The only difference in practice is that the build systems are different and that the Rust compiler is more helpful (both in catching bugs and reporting errors). Neither a huge deal if you have a proper build and testi…

I still find it basically impossible to get started with a C++ project.

I tried again recently for a proxy I was writing thinking surely things have evolved at this point. Every single package manager couldn’t handle my very basic and very popular dependencies. I mean I tried every single one. This is completely insane to me.

Not to mention just figuring out how to build it after that which was a massive headache and an ongoing one.

Compared to Rust it’s just night and day.

Outside of embedded programming or some special use cases I have literally no idea why anyone would ever write C++. I’m convinced it’s a bunch of masochists

Re: Matt Godbolt sold me on Rust by showing me C++

#224

Post by Seattle3503 »

nicoburns wrote: post #189
Seattle3503 wrote: post #61

Earlier quoted context omitted.

Absolutely, the compile times are the biggest drawback IMO. Everywhere I've been that built large systems in Rust eventually ends up spending a good amount of dev time trying to get CI/CD pipeline times to something sane. Besides developer productivity it can be an issue when you need a critical fix to go out quickly and your pipelines take 60+ minutes.

If you have the money to throw at it, you can get a long way optimising CI pipelines just by throwing faster hardware at it. The sort of server you could rent for ~$150/month might easily be ~5x faster than your typical Github Actions hosted runner.

Yes, this is often the best "low-hanging fruit" option, but it can get expensive. It depends how you value your developer time.

Re: Matt Godbolt sold me on Rust by showing me C++

#226

Post by johnisgood »

ryandv wrote: post #111
jasonjmcghee wrote: post #12

Earlier quoted context omitted.

unfortunately it's not so simple. that's the convention. depending on the library you're using it might be a special type of Error, or special type of Result, something needs to be transformed, `?` might not work in that case (unless you transform/map it), etc. I like rust, but its not as clean in practice, as you describe

There are patterns to address it such as creating your own Result type alias with the error type parameter (E) fixed to an error type you own: type Result = result::Result ; #[derive(Debug)] enum MyError { IOError(String) // ... } Your owned (i.e. not third-party) Error type is a sum type of error types that might be thrown by other libraries, with a newtype wrapper (`IOError`) on top. Then implement the `From` trait…

I scratch my head when people try to justify Rust's implementation of X. It looks absolutely horrendous, IMO.

I would rather have what OCaml has: https://ocaml.org/docs/error-handling.

Re: Matt Godbolt sold me on Rust by showing me C++

#227

Post by kanbankaren »

mb7733 wrote: post #200
kanbankaren wrote: post #188

Earlier quoted context omitted.

> Given C++, I can't help but hold things wrong and shoot myself Give an example. I have been programming in C/C++ for close to 30 years and the places where I worked had very strict guidelines on C++ usage. We could count the number of times we shot ourselves due to the language.

Isn't that their point though? They don't have 30 years of C/C++ experience and a workplace with very strict guidelines. They are just trying to write some code, and they run into trouble on C++'s sharper edges.

> with very strict guidelines.

Low level languages always came with a set of usage guidelines. Either you make the language safe for anyone that they can't shoot themselves in the foot and end up sacrificing performance, or provide guidelines on how to use it while retaining the ability to extract maximum performance from the hardware.

C/C++ shouldn't be approached like programming in Javascript/Python/Perl.

Re: Matt Godbolt sold me on Rust by showing me C++

#228

Post by jchw »

CJefferson wrote: post #222
jchw wrote: post #209

Earlier quoted context omitted.

The reason it works this way is there's legitimately no easy way around it. You're not guaranteed a reasonable zero value for any type, so you can't do the slightly better Go thing (defined behavior but still wrong... Not great.) and you certainly can't do the Rust thing, because... There's no pattern matching. You can't conditionally enter a branch based on the presence of a value. There really is no reasonable work…

You could assert. You could throw. I can’t understand how, this modern age where so many programs end up getting hacked, that introducing more UB seems like a good idea. This is one odd the major reasons I switched to rust, just to escape spending my whole life worrying about bugs caused by UB.

Assertions are debug-only. Exceptions are usually not guaranteed to be available and much of the standard library doesn't require them. You could std::abort, and that's about it.

I think the issue is that this just isn't particularly good either. If you do that, then you can't catch it like an exception, but you also can't statically verify that it won't happen.

C++ needs less of both undefined behavior and runtime errors. It needs more compile-time errors. It needs pattern matching.

Re: Matt Godbolt sold me on Rust by showing me C++

#229

Post by wyager »

kelnos wrote: post #67
zozbot234 wrote: post #40

Earlier quoted context omitted.

> The one thing that sold me on Rust (going from C++) was that there is a single way errors are propagated: the Result type. No need to bother with exceptions This isn't really true since Rust has panics. It would be nice to have out-of-the-box support for a "no panics" subset of Rust, which would also make it easier to properly support linear (no auto-drop) types.

I wish more people (and crate authors) would treat panic!() as it really should be treated: only for absolutely unrecoverable errors that indicate that some sort of state is corrupted and that continuing wouldn't be safe from a data- or program-integrity perspective. Even then, though, I do see a need to catch panics in some situations: if I'm writing some sort of API or web service, and there's some inconsistency in…

> only for absolutely unrecoverable errors

Unfortunately even the Rust core language doesn't treat them this way.

I think it's arguably the single biggest design mistake in the Rust language. It prevents a ton of useful stuff like temporarily moving out of mutable references.

They've done a shockingly good job with the language overall, but this is definitely a wart.

Re: Matt Godbolt sold me on Rust by showing me C++

#230

Post by brundolf »

frankwiles wrote: post #225
brundolf wrote: post #215

Wait, Godbolt is someone's name ?

Yes and he’s a really cool nice guy to boot!

I almost want to call this nominative determinism

I always thought it was called godbolt because it's like... Zeus blowing away the layers of compilation with his cosmic power, or something. Like it's a herculean task

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