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Comment by p1necone | Hacker News Reader

As far as I can tell most of the people complaining about Rust having painfully long compile times are just parroting second hand information and don't actually know. Kinda like the pervasive "but isn't Java really slow?" thing that still doesn't seem to have died either.

Edit: yes I know this article was written by someone who knows what they're talking about (and as they're a steward of the project I understand why they're calling this out for improvement, and somewhat exaggerating how bad it is). I was talking about the occasional comments I see on hacker news about how people aren't even bothering to try rust because compile times are "unusably" bad. 5 mins for a dev build of 2 million lines of code is not anywhere near reason to not even bother trying the language. No personal project or learning scratchpad is ever going to come close to 2 million lines. And it's not worse than many other languages that are used for large projects.

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I have a few beefs with this article, but to suggest Brian doesn’t know much about Rust is just plain incorrect. He is literally the #2 all time (human) contributor to the project: https://thanks.rust-lang.org/rust/all-time/

We do have experience, my C++ projects compile much faster than their rewrite in Rust.

On common laptops that you buy at the shopping mall, not compiler rigs.

I am not doing nothing special, other than all my third party artifacts are binary dependencies, not overusing templates, incremental compilation and incremental linking.

Cargo currently doesn't do binary dependencies, so already here I have to wait for the world to compile.

And while incremental compiling is already supported, lld still isn't supported on stable.

Plus I do have experience using other AOT compiled languages with modules support, since back in the day.

So we know what are talking about, and plenty of people on Rust team are quite aware of the problem, however not every can be fixed at the same time.

> We do have experience, my C++ projects compile much faster than their rewrite in Rust

Wow. And C++ projects can be quite slow to compile

They can, but you have to compile everything from scratch, not use binary dependencies, disable pre-compiled headers, not having an incremental compiler and linker available, and be an heavy meta-programming user.

> As far as I can tell most of the people complaining about Rust having painfully long compile times are just parroting second hand information and don't actually know.

My experience is the opposite. Most rust devs don't work on very large projects from what I can tell, so compile times tend to stay manageable. It's a small percentage that work on projects large enough to hit this problem, and when you hit it it hurts.

I think that it depends on where you are coming from. For Go, C#, Java devs and for those coming from dynamically typed languages, the compilation times will be unbearably slow. C++, scala, swift developers are probably used to slow compilation times.

C++ can be relatively fast when making use of binary dependencies and having a modular build.

This is the one place where Rust differs from many other languages: Dependencies and libraries are typically brought in a source-dependencies and built with your own code.

This typically makes the first build of any project considerably slower than for other languages, since you have to also build all your dependencies, but I think it allows for a really simple and predictable way to work, not to mention support any kind of architecture, across all packages.

It's obviously a trade-off, but I think it's a trade-off which is clearly worth it.

A trade off that requires buying a compiler rig, it is almost unusable to compile Rust stuff from scratch on my travel netbook.

If I plan to do some Rust coding on the go (no pun intended), better do a full build at home before packing.

A 5m C++ build turns into 30m Rust one, for the same project, ported across languages.

Not to mention that it means on a large team project everyone one is compiling the same stuff over and over again, given that cargo does not yet support code cache servers.

Yes there are some workarounds like sccache, but they are extra stuff one needs to install.

> Not to mention that it means on a large team project everyone one is compiling the same stuff over and over again,

That's a bit dramatical. You typically only compile your dependencies once during the project lifetime.

If you on your netbook have done a initial full build, you'll only get incremental builds from there on, just like with C++.

But unlike C++, dependency management isn't hell, and you are almost always guaranteed to have your dependency supported on the target you are building, OOB, without any fiddling or setup.

It's a trade-off, but I definitely think the Rust-team made the right decision here.

Dependency management isn't an issue when using OS packages, and Conan also does binary dependencies.

Compiling from source also does not solve the problem that a crate author hasn't taken a specific OS into account.

Yes I am being a bit dramatic, but this kind of issues do impact adoption, and there are many industries where shipping source is just not an option.

> Dependency management isn't an issue when using OS packages

Come on. What do you find most developer friendly?

1. "cargo build && done"

or 2. Try to uncover what dependencies this project really has, and then proceed to map out what the packages (and dev-packages) for those dependencies are called on the linux distro you are using (debian, ubuntu, fedora, arch, etc), not to mention what they are called on your specific version of that distro, root up, install all that stuff.... and then try ./configure yet again?

> but this kind of issues do impact adoption

Indeed. In 2020 I wouldn't bother adopting any kind of language which prefers the latter flow to the former one.

"cargo build && done" only works if every crate author has taken my OS into consideration and not used OS specific API or file locations.

And it is more like "cargo build && off to lunch".

I am usually on Windows, and most commercial vendors nicely sell us their already compiled binaries. No need to hunt for anything.

Regarding Linux distros, if it isn't on the official repositories, Conan provides exactly the same experience as cargo, only faster because it supports binary libraries.

And how many C/C++ projects use Conan by default, versus those who don't?

For comparison all rust projects uses cargo.

The ergonomic value of that is something you simply can not overstate.

For many users of AOT compiled languages, the ergonomic factor is being able to enjoy fast builds, without getting a compiler rig.

Turbo Pascal 7, which was already relatively complex, was already compiling several thousand lines per minute on a single core 4Mhz computer bounded to 640KB.

More modern examples with complexer type systems, are languages like Delphi, FreePascal, Ada/SPARK, D, F# via .NET AOT, OCaml.

So yeah cargo is nice, but not if I have to build everything from scratch, Rust isn't a scripting language.

>So yeah cargo is nice, but not if I have to build everything from scratch, Rust isn't a scripting language.

FWIW, Rust builds faster than node applications as my laptop can only handle so many iops.

And Rust compiles are in line with Ocaml (probably faster by now due to the optimization work over the past year)

> But unlike C++, dependency management isn't hell

There is nothing hell into C++ if you are using the right tools: meaning proper package manager, meaning Nix/Guix, Conan or Spack.

It is currently much more hell to integrate Rust+Cargo behind other build system ( behind pip/gem/npm for instance ) than it is with C++.

I think you wanted to reply to the upper comment. :)

>Regarding Linux distros, if it isn't on the official repositories, Conan provides exactly the same experience as cargo, only faster because it supports binary libraries.

Don't use the operating system binaries unless you are packaging your application for use by that same repo. Instead, use Conan or you will find yourself in dependency hell trying to get users running it on Fedora, Ubuntu 12.04, 14.04, 16.04, 18.04, 20.04, Debian, etc where they all use different versions of the dependencies you want.

The official repositories are for the sysadmin and for other packages in the official repositories.

I don't necessarily disagree, but this was written by one of the original authors of the Rust compiler, so I think he knows what he's talking about.

Well if you read the article you would have known the author is one of the co-founders of Rust.

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