8 ms·

Rust seems to have inherited two favorite C++ development process features: long compilation times and incomprehensible error messages that aren't really relate

by izacus 5y ago

Rust seems to have inherited two favorite C++ development process features: long compilation times and incomprehensible error messages that aren't really related to the actual issue (e.g. just how C++ barfed out a bunch of template errors, borrow checker really loves to barf out very obscure error messages when there's an issue with lifetimes).

estebank 5y ago
If you encounter incomprehensible error messages, I would encourage you to file a ticket at http://github.com/rust-lang/rust/issues http://github.com/rust-lang/rust/issues. We consider them bugs and are diligent about dealing with them.
- ogoffart 5y ago
  The worst error message was basically no error message. After I made some big refactoring to my project, cargo would just exit with: error: could not compile `the_project`. And nothing else. No hint of what the problem is. It then took me a long time to try to comment out code here and there to find out what was causing the error. When I finally found out the problem, I took the time to fill a bug report. I don't know if anyone looked at it. https://github.com/rust-lang/rust/issues/73026 https://github.com/rust-lang/rust/issues/73026
  - estebank 5y ago
    Thank you for the great report. It indeed seems to have fallen through the cracks, with no one touching it (it's missing the T-compiler tag, which means I didn't triage it) since it was first cathegorized. I wouldn't call that lack of output representative of the experience of using rustc though, if I'm allowed to let my pride on my work flare up a bit.
    - ogoffart 5y ago
      Sorry, I did not mean to say that this was representative of the overall experience. On the contrary, I'm usually quite satisfied with the compiler messages. Thanks for your work!
      - estebank 5y ago
        Thank you! The "bad" thing about having high standards is that when it isn't met it is quite jarring, more so than if it were homogeneously bad or meh, and that ends up bring more frustrating.
Ygg2 5y ago
What the hell are you on about? Saying in it inherited them, just proves you probably didn't use either. While compilation times are longer than say Go, they definitely never felt too long, compared to say Java. But your comment around errors takes the cake. Like maybe, if you use some combination of macros expansion and traits it could get confused. But Rust errors are on par with Elm. They show the line, they show what went wrong and how to fix. This is a far cry from C++, where using even a bit of templates, results in unintelligible mess.
- brabel 5y ago
  > they definitely never felt too long, compared to say Java. Woah... now I am the one who have to ask: what the hell are you on about?? I work on Rust and Java projects, if you exclude running tests, Java compiles very very fast compared to pretty much any language... Rust is a lot slower to compile even on the much smaller projects I've worked on... in this post, a very small project (I think it's like 16,000 LoC, it's mentioned in the beginning) was taking over a minute even on hot builds... To get a build to take this long in Java you would need to have several million LoC! Even if you don't use something like Gradle to cache compilation units and just compile everything from scratch with javac.
  - dmitriid 5y ago
    > Java compiles very very fast compared to pretty much any language In my experience C# compiles faster, but I still agree with you on all points.
    - yawaramin 5y ago
      Not surprising, considering the chief architect of C# is the guy famous for making Turbo Pascal.
    - emn13 5y ago
      Build times have regressed considerably the past few releases (at least for me). Not that I'm complaining about the tradeoffs, the new features are generally worth it. Whats most annoying is that it's often hard to tell which features are expensive until you've already wasted a bunch of time introducing em. But I've got to say I'm super jealous of the level of introspection the rust compiler allows here. I'd definitely be willing to change a few C# coding patterns in code bases I maintain to benefit build times, but as is, that's a really painful trial and error process. And sometimes you get lucky finding the root cause, but if you don't... well, it's not a great experience.
Uther 5y ago
While compilation time is a well known Rust pain point, Rust error messages are really one of the best part of the language. Complicated error messages are clearly no a common occurrence unless you rely heavily on meta-programming tricks, and that is not common in Rust, unlike C++.
- estebank 5y ago
  And the intention is to improve those too. It's hard, and I would prefer crate writers show more restrain than they do, but we have to meet users where they are.
space_rock 5y ago
Someone has never used Rust
ModernMech 5y ago
I teach C++ and Rust to college students, and their number one praise of Rust over C++ is how much more helpful the error messages are. It’s really night and day, so I can’t even fathom how you would equate the two.
- izacus 5y ago
  It's easy to fathom once you go beyond the school examples and start working on bigger codebases. The error messages are verbose and simple until you hit cases where borrow checker complains about an error in a completely different part of the codebase than where the actual issue here is. This is where it behaves similar to C++ (and, honestly, some other languages) and there all the verbosity in the world doesn't help.
  - UtherII 5y ago
    Have you really used Rust on big codebases? One of the big advantage of Rust is especially that it fails far earlier than C++. Borrow checker error are local error that prevent bad behavior to propagate and cause problem on unexpected part.
mlindner 5y ago
Rust has some of the best compiler error messages out there so not sure what you're talking about there. And C++'s compiler error message issue stopped being an issue since like GCC 4.

by izacus 5y ago

estebank 5y ago

If you encounter incomprehensible error messages, I would encourage you to file a ticket at http://github.com/rust-lang/rust/issues http://github.com/rust-lang/rust/issues. We consider them bugs and are diligent about dealing with them.

ogoffart 5y ago
The worst error message was basically no error message. After I made some big refactoring to my project, cargo would just exit with: error: could not compile `the_project`. And nothing else. No hint of what the problem is. It then took me a long time to try to comment out code here and there to find out what was causing the error. When I finally found out the problem, I took the time to fill a bug report. I don't know if anyone looked at it. https://github.com/rust-lang/rust/issues/73026 https://github.com/rust-lang/rust/issues/73026
- estebank 5y ago
  Thank you for the great report. It indeed seems to have fallen through the cracks, with no one touching it (it's missing the T-compiler tag, which means I didn't triage it) since it was first cathegorized. I wouldn't call that lack of output representative of the experience of using rustc though, if I'm allowed to let my pride on my work flare up a bit.
  - ogoffart 5y ago
    Sorry, I did not mean to say that this was representative of the overall experience. On the contrary, I'm usually quite satisfied with the compiler messages. Thanks for your work!
    - estebank 5y ago
      Thank you! The "bad" thing about having high standards is that when it isn't met it is quite jarring, more so than if it were homogeneously bad or meh, and that ends up bring more frustrating.

Ygg2 5y ago

What the hell are you on about? Saying in it inherited them, just proves you probably didn't use either. While compilation times are longer than say Go, they definitely never felt too long, compared to say Java. But your comment around errors takes the cake. Like maybe, if you use some combination of macros expansion and traits it could get confused. But Rust errors are on par with Elm. They show the line, they show what went wrong and how to fix. This is a far cry from C++, where using even a bit of templates, results in unintelligible mess.

brabel 5y ago
> they definitely never felt too long, compared to say Java. Woah... now I am the one who have to ask: what the hell are you on about?? I work on Rust and Java projects, if you exclude running tests, Java compiles very very fast compared to pretty much any language... Rust is a lot slower to compile even on the much smaller projects I've worked on... in this post, a very small project (I think it's like 16,000 LoC, it's mentioned in the beginning) was taking over a minute even on hot builds... To get a build to take this long in Java you would need to have several million LoC! Even if you don't use something like Gradle to cache compilation units and just compile everything from scratch with javac.
- dmitriid 5y ago
  > Java compiles very very fast compared to pretty much any language In my experience C# compiles faster, but I still agree with you on all points.
  - yawaramin 5y ago
    Not surprising, considering the chief architect of C# is the guy famous for making Turbo Pascal.
  - emn13 5y ago
    Build times have regressed considerably the past few releases (at least for me). Not that I'm complaining about the tradeoffs, the new features are generally worth it. Whats most annoying is that it's often hard to tell which features are expensive until you've already wasted a bunch of time introducing em. But I've got to say I'm super jealous of the level of introspection the rust compiler allows here. I'd definitely be willing to change a few C# coding patterns in code bases I maintain to benefit build times, but as is, that's a really painful trial and error process. And sometimes you get lucky finding the root cause, but if you don't... well, it's not a great experience.

Uther 5y ago

While compilation time is a well known Rust pain point, Rust error messages are really one of the best part of the language. Complicated error messages are clearly no a common occurrence unless you rely heavily on meta-programming tricks, and that is not common in Rust, unlike C++.

estebank 5y ago
And the intention is to improve those too. It's hard, and I would prefer crate writers show more restrain than they do, but we have to meet users where they are.

space_rock 5y ago

Someone has never used Rust

ModernMech 5y ago

I teach C++ and Rust to college students, and their number one praise of Rust over C++ is how much more helpful the error messages are. It’s really night and day, so I can’t even fathom how you would equate the two.

izacus 5y ago
It's easy to fathom once you go beyond the school examples and start working on bigger codebases. The error messages are verbose and simple until you hit cases where borrow checker complains about an error in a completely different part of the codebase than where the actual issue here is. This is where it behaves similar to C++ (and, honestly, some other languages) and there all the verbosity in the world doesn't help.
- UtherII 5y ago
  Have you really used Rust on big codebases? One of the big advantage of Rust is especially that it fails far earlier than C++. Borrow checker error are local error that prevent bad behavior to propagate and cause problem on unexpected part.

mlindner 5y ago

Rust has some of the best compiler error messages out there so not sure what you're talking about there. And C++'s compiler error message issue stopped being an issue since like GCC 4.