cargo-geiger 0.3.0

Detects usage of unsafe Rust in your project and its dependencies.
cargo-geiger-0.3.0 is not a library.

cargo-geiger ☢

A program that list statistics related to usage of unsafe Rust code in a Rust crate and all its dependencies.

This project is in its current state a quick-n-dirty, glued together, remix of two other cargo plugin projects: and


  1. cargo install cargo-geiger
  2. Navigate to the same directory as the Cargo.toml you want to analyze.
  3. cargo geiger

Output examples

Default output format:

Example output

Why even care about unsafe Rust usage?

When and why to use unsafe Rust is out of scope for this project, it is simply a tool that provides information to aid auditing and hopefully to guide dependency selection. It is however the opinion of the author of this project that libraries choosing to abstain from unsafe Rust usage when possible should be promoted.

This project is an attempt to create pressure against unnecessary usage of unsafe Rust in public Rust libraries.

Why the name?

Unsafe Rust and ionizing radiation have something in common, they are both inevitable in some situations and both should preferably be safely contained!

Known issues

  • Unsafe code inside macros are not detected. Needs macro expansion(?).
  • Unsafe code generated by are probably not detected.
  • Error handling is missing for the most part and there are plenty of panics lurking.
  • Proper logging should be sorted out.
  • Command line flags needs some more review and refactoring for this project.
  • Will continue on syn parse errors. Needs a new command line flag and should default to exit on errors(?).
  • Could probably benefit from parallelization. One .rs file per core should be parsed at all times.
  • More on the github issue tracker.


  • Refactoring and general cleanup.
  • Proper error handling using Result.
  • An optional whitelist file at the root crate level to specify crates that are trusted to use unsafe (should only have an effect if placed in the root project).
  • Additional output formats



  • Intercepts rustc calls and reads the .d files generated by rustc to identify which .rs files are used by the build. This allows a crate that contains .rs files with unsafe code usage to pass as "green" if the unsafe code isn't used by the build.
  • Each metric is now printed as x/y, where x is the unsafe code used by the build and y is the total unsafe usage found in the crate.
  • Removed the --compact output format to avoid some code complexity. A new and better compact mode can be added later if requested.


  • (alexmaco) Table based default output format. Old format still available by --compact.


  • Initial experimental versions.
  • Mostly updates.