4 ms·

> And some application developers prefer having an "I don't care, just give me the backtrace" error wrapper for everything, to speed up the development and not

> And some application developers prefer having an "I don't care, just give me the backtrace" error wrapper for everything, to speed up the development and not spend time on micro-managing error types. That's me tbh. I actually love Rust's error story atm, I always use an Error enum and I have made it do everything I want.. except one thing: Low (no?) cost backtraces. My error enums give me all the API-level specifics I want, but often I make the variants grouped by general code area. It's guided by my program flow, not debug introspection. So if I don't need to branch a codepath from an error object, it typically just goes into a single variant and I shove some message in there. What I'd love is to be able to easily and quickly just bake backtraces into this "non-program flow defining type". Bonus points if it could be done at compile time. I've thought about using a macro at error creation time to make it a compile-time poor mans backtrace, but I'm unsure if just one level of stack trace is all that beneficial. Either way I know I want something that's no more costly than: foreign_err.map(|foreign_err| MyError::Dump(format!("some description: {}", foreign_err))) edit: I should add, internally my perspective is coming from Go, so wrapping repeatedly in strings is fairly welcome to me. Just adding some low-cost default context to this would be a huge help.

shepmaster 7y ago
An unstable `std::backtrace::Backtrace` (https://doc.rust-lang.org/nightly/std/backtrace/struct.Backtrace.html https://doc.rust-lang.org/nightly/std/backtrace/struct.Backt...) exists in nightly Rust. If you cannot require nightly, you can use the backtrace crate (https://docs.rs/backtrace/0.3.40/backtrace/ https://docs.rs/backtrace/0.3.40/backtrace/) on stable. Crates like my SNAFU (https://docs.rs/snafu/0.6.0/snafu/ https://docs.rs/snafu/0.6.0/snafu/) help abstract this away. Whenever the standard library implementation stabilizes, you will likely see many more errors including backtraces.
- asdkhadsj 7y ago
  Are you familiar with how costly backtrace is? I fear bubbling an error up and repeatedly adding a stack trace or some junk like that. Admittedly I have not looked too much into Backtrace, but I hope my concern makes sense.
  - shepmaster 7y ago
    I do believe it's non-zero, as the stack has to be walked and potentially symbols are looked up. The symbols can be delayed until display time, but the stalk walk is "now or never", as I understand it. SNAFU addresses this by allowing `Option<Backtrace>` in the error struct. The backtrace is only captured when an environment variable is set by the end user.
    - amluto 7y ago
      It would be interesting for someone to port the Linux kernel’s ORC to user code. ORC backtraces are exact and more than an order of magnitude faster than DWARF.
  - DarthGhandi 7y ago
    > Are you familiar with how costly... Checks the username of who you responded too: I'll blindly bet yes to that question for any amount you desire.

shepmaster 7y ago

An unstable `std::backtrace::Backtrace` (https://doc.rust-lang.org/nightly/std/backtrace/struct.Backtrace.html https://doc.rust-lang.org/nightly/std/backtrace/struct.Backt...) exists in nightly Rust. If you cannot require nightly, you can use the backtrace crate (https://docs.rs/backtrace/0.3.40/backtrace/ https://docs.rs/backtrace/0.3.40/backtrace/) on stable. Crates like my SNAFU (https://docs.rs/snafu/0.6.0/snafu/ https://docs.rs/snafu/0.6.0/snafu/) help abstract this away. Whenever the standard library implementation stabilizes, you will likely see many more errors including backtraces.

asdkhadsj 7y ago
Are you familiar with how costly backtrace is? I fear bubbling an error up and repeatedly adding a stack trace or some junk like that. Admittedly I have not looked too much into Backtrace, but I hope my concern makes sense.
- shepmaster 7y ago
  I do believe it's non-zero, as the stack has to be walked and potentially symbols are looked up. The symbols can be delayed until display time, but the stalk walk is "now or never", as I understand it. SNAFU addresses this by allowing `Option<Backtrace>` in the error struct. The backtrace is only captured when an environment variable is set by the end user.
  - amluto 7y ago
    It would be interesting for someone to port the Linux kernel’s ORC to user code. ORC backtraces are exact and more than an order of magnitude faster than DWARF.
- DarthGhandi 7y ago
  > Are you familiar with how costly... Checks the username of who you responded too: I'll blindly bet yes to that question for any amount you desire.