Rust Error Output

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This is a reference to help answer this question: “what will my Rust program print if something goes wrong?”

The examples were compiled with Rust 1.95.0. All output in these examples goes to stderr, nothing goes to stdout.

Setup code for stable_eyre

fn make_error() -> Result<(), stable_eyre::eyre::Report> {
    Ok(std::fs::remove_file("/this/file/does/not/exist")?)
}

fn install_hook() -> stable_eyre::eyre::Result<()> {
    let hook =
        stable_eyre::HookBuilder::default().capture_backtrace_by_default(true);
    hook.install()
}

Debug

fn main() {
    install_hook().unwrap();
    eprintln!("{:?}", make_error().unwrap_err())
}

No such file or directory (os error 2)

Stack backtrace:
   0: stable_eyre::HookBuilder::make_handler
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/stable-eyre-0.2.2/src/lib.rs:145:18
   1: stable_eyre::HookBuilder::install::{{closure}}
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/stable-eyre-0.2.2/src/lib.rs:168:63
   2: eyre::capture_handler
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/eyre-0.6.12/src/lib.rs:601:23
   3: eyre::error::::from_std
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/eyre-0.6.12/src/error.rs:90:28
   4: eyre::error:: for eyre::Report>::from
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/eyre-0.6.12/src/error.rs:496:9
   5:  as core::ops::try_trait::FromResidual>>::from_residual
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/result.rs:2189:27
   6: stable_eyre_debug::make_error
             at /home/runner/work/rust-error-output/rust-error-output/gen/src/bin/stable_eyre_debug.rs:2:8
   7: stable_eyre_debug::main
             at /home/runner/work/rust-error-output/rust-error-output/gen/src/bin/stable_eyre_debug.rs:12:23
   8: core::ops::function::FnOnce::call_once
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/ops/function.rs:250:5
   9: std::sys::backtrace::__rust_begin_short_backtrace
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/sys/backtrace.rs:166:18
  10: std::rt::lang_start::{{closure}}
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:206:18
  11: <&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe as core::ops::function::FnOnce<()>>::call_once
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/ops/function.rs:287:21
      std::panicking::catch_unwind::do_call::<&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe, i32>
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:581:40
      std::panicking::catch_unwind:: + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe>
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:544:19
      std::panic::catch_unwind::<&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe, i32>
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panic.rs:359:14
      std::rt::lang_start_internal::{closure#0}
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:175:24
      std::panicking::catch_unwind::do_call::
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:581:40
      std::panicking::catch_unwind::
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:544:19
      std::panic::catch_unwind::
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panic.rs:359:14
      std::rt::lang_start_internal
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:171:5
  12: std::rt::lang_start
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:205:5
  13: main
  14: __libc_start_call_main
  15: __libc_start_main@@GLIBC_2.34
  16: _start

Display

fn main() {
    install_hook().unwrap();
    eprintln!("{}", make_error().unwrap_err())
}

No such file or directory (os error 2)

Alternate Display

fn main() {
    install_hook().unwrap();
    eprintln!("{:#}", make_error().unwrap_err())
}

No such file or directory (os error 2)

Unwrap

fn main() {
    install_hook().unwrap();
    make_error().unwrap();
}

thread 'main' (556677) panicked at src/bin/stable_eyre_unwrap.rs:12:18:
called `Result::unwrap()` on an `Err` value: No such file or directory (os error 2)

Stack backtrace:
   0: stable_eyre::HookBuilder::make_handler
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/stable-eyre-0.2.2/src/lib.rs:145:18
   1: stable_eyre::HookBuilder::install::{{closure}}
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/stable-eyre-0.2.2/src/lib.rs:168:63
   2: eyre::capture_handler
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/eyre-0.6.12/src/lib.rs:601:23
   3: eyre::error::::from_std
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/eyre-0.6.12/src/error.rs:90:28
   4: eyre::error:: for eyre::Report>::from
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/eyre-0.6.12/src/error.rs:496:9
   5:  as core::ops::try_trait::FromResidual>>::from_residual
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/result.rs:2189:27
   6: stable_eyre_unwrap::make_error
             at /home/runner/work/rust-error-output/rust-error-output/gen/src/bin/stable_eyre_unwrap.rs:2:8
   7: stable_eyre_unwrap::main
             at /home/runner/work/rust-error-output/rust-error-output/gen/src/bin/stable_eyre_unwrap.rs:12:5
   8: core::ops::function::FnOnce::call_once
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/ops/function.rs:250:5
   9: std::sys::backtrace::__rust_begin_short_backtrace
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/sys/backtrace.rs:166:18
  10: std::rt::lang_start::{{closure}}
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:206:18
  11: <&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe as core::ops::function::FnOnce<()>>::call_once
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/ops/function.rs:287:21
      std::panicking::catch_unwind::do_call::<&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe, i32>
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:581:40
      std::panicking::catch_unwind:: + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe>
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:544:19
      std::panic::catch_unwind::<&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe, i32>
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panic.rs:359:14
      std::rt::lang_start_internal::{closure#0}
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:175:24
      std::panicking::catch_unwind::do_call::
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:581:40
      std::panicking::catch_unwind::
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:544:19
      std::panic::catch_unwind::
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panic.rs:359:14
      std::rt::lang_start_internal
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:171:5
  12: std::rt::lang_start
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:205:5
  13: main
  14: __libc_start_call_main
  15: __libc_start_main@@GLIBC_2.34
  16: _start

note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Expect

fn main() {
    install_hook().unwrap();
    make_error().expect("oh no");
}

thread 'main' (556677) panicked at src/bin/stable_eyre_expect.rs:12:18:
oh no: No such file or directory (os error 2)

Stack backtrace:
   0: stable_eyre::HookBuilder::make_handler
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/stable-eyre-0.2.2/src/lib.rs:145:18
   1: stable_eyre::HookBuilder::install::{{closure}}
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/stable-eyre-0.2.2/src/lib.rs:168:63
   2: eyre::capture_handler
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/eyre-0.6.12/src/lib.rs:601:23
   3: eyre::error::::from_std
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/eyre-0.6.12/src/error.rs:90:28
   4: eyre::error:: for eyre::Report>::from
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/eyre-0.6.12/src/error.rs:496:9
   5:  as core::ops::try_trait::FromResidual>>::from_residual
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/result.rs:2189:27
   6: stable_eyre_expect::make_error
             at /home/runner/work/rust-error-output/rust-error-output/gen/src/bin/stable_eyre_expect.rs:2:8
   7: stable_eyre_expect::main
             at /home/runner/work/rust-error-output/rust-error-output/gen/src/bin/stable_eyre_expect.rs:12:5
   8: core::ops::function::FnOnce::call_once
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/ops/function.rs:250:5
   9: std::sys::backtrace::__rust_begin_short_backtrace
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/sys/backtrace.rs:166:18
  10: std::rt::lang_start::{{closure}}
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:206:18
  11: <&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe as core::ops::function::FnOnce<()>>::call_once
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/ops/function.rs:287:21
      std::panicking::catch_unwind::do_call::<&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe, i32>
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:581:40
      std::panicking::catch_unwind:: + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe>
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:544:19
      std::panic::catch_unwind::<&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe, i32>
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panic.rs:359:14
      std::rt::lang_start_internal::{closure#0}
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:175:24
      std::panicking::catch_unwind::do_call::
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:581:40
      std::panicking::catch_unwind::
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:544:19
      std::panic::catch_unwind::
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panic.rs:359:14
      std::rt::lang_start_internal
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:171:5
  12: std::rt::lang_start
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:205:5
  13: main
  14: __libc_start_call_main
  15: __libc_start_main@@GLIBC_2.34
  16: _start

note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Return

fn main() -> Result<(), stable_eyre::eyre::Report> {
    install_hook()?;
    make_error()
}

Error: No such file or directory (os error 2)

Stack backtrace:
   0: stable_eyre::HookBuilder::make_handler
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/stable-eyre-0.2.2/src/lib.rs:145:18
   1: stable_eyre::HookBuilder::install::{{closure}}
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/stable-eyre-0.2.2/src/lib.rs:168:63
   2: eyre::capture_handler
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/eyre-0.6.12/src/lib.rs:601:23
   3: eyre::error::::from_std
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/eyre-0.6.12/src/error.rs:90:28
   4: eyre::error:: for eyre::Report>::from
             at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/eyre-0.6.12/src/error.rs:496:9
   5:  as core::ops::try_trait::FromResidual>>::from_residual
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/result.rs:2189:27
   6: stable_eyre_return::make_error
             at /home/runner/work/rust-error-output/rust-error-output/gen/src/bin/stable_eyre_return.rs:2:8
   7: stable_eyre_return::main
             at /home/runner/work/rust-error-output/rust-error-output/gen/src/bin/stable_eyre_return.rs:12:5
   8: core::ops::function::FnOnce::call_once
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/ops/function.rs:250:5
   9: std::sys::backtrace::__rust_begin_short_backtrace
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/sys/backtrace.rs:166:18
  10: std::rt::lang_start::{{closure}}
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:206:18
  11: <&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe as core::ops::function::FnOnce<()>>::call_once
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/ops/function.rs:287:21
      std::panicking::catch_unwind::do_call::<&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe, i32>
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:581:40
      std::panicking::catch_unwind:: + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe>
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:544:19
      std::panic::catch_unwind::<&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe, i32>
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panic.rs:359:14
      std::rt::lang_start_internal::{closure#0}
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:175:24
      std::panicking::catch_unwind::do_call::
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:581:40
      std::panicking::catch_unwind::
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:544:19
      std::panic::catch_unwind::
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panic.rs:359:14
      std::rt::lang_start_internal
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:171:5
  12: std::rt::lang_start
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/rt.rs:205:5
  13: main
  14: __libc_start_call_main
  15: __libc_start_main@@GLIBC_2.34
  16: _start