"A light wrapper around rr, the time-travelling debugger

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Development tools cargo-rr
Overview

cargo-rr

Crates.io MIT Licensed

A light wrapper around rr, the time-travelling debugger.

Do you find yourself running the same test over and over in the debugger, trying to figure out how the code got in a bad state? We have a tool for you! Easy to install and setup, it will record an execution trace, and that gives magical new powers to gdb. Step backwards, run backwards, see where variables changed their value or when a function was last called on an object (using conditional breakpoints). (source)

Suppose we ran a test and got a failure. We first re-run the test under rr to record the entire execution (including everything else on your system the test interacts with).

> cargo rr test my_test

thread 'main' panicked at 'assertion failed: `(left == right)`
  left: `1`,
 right: `2`', tests/tests.rs:100

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 2 filtered out; finished in 0.06s

Let's replay the recording.

> cargo rr replay

(rr) continue

thread 'main' panicked at 'assertion failed: `(left == right)`
  left: `1`,
 right: `42`', tests/tests.rs:100

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 2 filtered out; finished in 0.06s

We'll go backwards until we return to the failed assertion so we can have a look at a and b.

(rr) break tests/tests.rs:100
(rr) reverse-continue
Continuing.

Breakpoint 1, tests::main () at tests/tests.rs:100
100         assert_eq!(a, b);

(rr) print a
$1 = 1

(rr) print b
$2 = 42

I wonder where a is set to 1?

(rr) watch -l a
(rr) reverse-continue

Old value = 1
New value = -1992923200
0x000055dcac485ed9 in tests::main () at tests/tests.rs:30
30          let a = some_calculation();

Note that since we're going in reverse the old and new values are backwards. -1992923200 is whatever used to be at the address 0x000055dcac485ed9 before it was used for a.

Comments
  • Unit tests in main.rs (or submodule of main.rs) aren't detected

    Unit tests in main.rs (or submodule of main.rs) aren't detected

    cargo rr test fails when running on a project using cargo workspaces. cargo-rr prouces the following error:

    Error: cargo-rr: No test artifacts built.

    I was testing on the following code, for reference: https://git.sr.ht/~zethra/license

    opened by zethra 13
  • Add installation instructions

    Add installation instructions

    I tried my hand at writing some instructions, which could go into the readme.

    While at it, I also made two minor changes to your readme. Feel free to accept or decline those as you prefer!

    opened by grunweg 6
  • Unify `rr-opts` and `gdb-opts` behavior.

    Unify `rr-opts` and `gdb-opts` behavior.

    This is a continuation to #12.

    I think the arguments should have the same syntax for specifying them.

    Now, both can be specified with their specific flag:

    cargo rr replay --rr-opts="-s 1234" --gdb-opts="-a" Note that equal signs are required to eliminate ambiguity. Otherwise clap would parse --rr-opts "-s 1234" as specifying the -s flag.

    In the unified-across-commands branch I have also adjusted the behavior to be consistent, you can decide if that makes sense, given that the other commands do not support gdb-opts and only rr-opts

    opened by DrRuhe 3
  • Can't pass rr-opts

    Can't pass rr-opts

    No matter what I try to do, I can't pass options to rr. For example:

    ❯ cargo rr replay mytrace -s 1234 
error: Found argument '-s' which wasn't expected, or isn't valid in this context

USAGE:
    cargo rr replay [trace] [rr-opts] [-- <gdb-opts>...]

For more information try --help
    opened by NickHu 2
  • No test artifacts built

    No test artifacts built

    Hi, thanks for the rr-wrapper! This is very convenient :) Unfortunately I get an error when trying to run a test: Error: cargo-rr: No test artifacts built.

    Steps to reproduce:

    cargo new --lib bla
cd bla
cargo rr test it_works
    opened by obraunsdorf 1
  • use other variable to configure log level

    use other variable to configure log level

    The log output will break the interactive selection of cargo rr test. Therefore use other variable so that users that have RUST_LOG set in their development environment can still use it.

    opened by DrRuhe 0
  • Workspaces aren't supported

    Workspaces aren't supported

    I get an error like the following when I try to directly run a test executable

    /home/daniel/.cargo_target/debug/deps/license_codegen-f799eb14e6783cf2: error while loading shared libraries: libtest-a3b2353c72e89634.so: cannot open shared object file: No such file or directory
    opened by danielzfranklin 0
Releases(v0.2.0)
Owner
Daniel Franklin
Daniel Franklin
GitHub
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