dylint 0.1.0-pre.1

A tool for running Rust lints from dynamic libraries
Documentation

Dylint

A tool for running Rust lints from dynamic libraries

cargo install cargo-dylint --version '>=0.1.0-pre'

Dylint is a Rust linting tool, similar to Clippy. But whereas Clippy runs a predetermined, static set of lints, Dylint runs lints from user-specified, dynamic libraries. Thus, Dylint allows developers to have their own personal lint collections.

Contents

Quick start

cargo install cargo-dylint dylint-link --version '>=0.1.0-pre' # Install cargo-dylint and dylint-link
git clone https://github.com/trailofbits/dylint                # Clone the Dylint repository
cd dylint/examples/allow_clippy                                # Go to one of the example lint libraries
cargo build                                                    # Build the library
cargo dylint allow_clippy -- --manifest-path ../../Cargo.toml  # Run the library's lint on the Dylint source code

You can start writing your own Dylint libraries by forking the dylint-template repository.

Library requirements

A Dylint library must satisfy four requirements. Note: before trying to satisfy these explicitly, see Utilities below.

  1. Have a filename of the form:

    DLL_PREFIX LIBRARY_NAME '@' TOOLCHAIN DLL_SUFFIX

    The following is a concrete example on Linux:

    libquestion_mark_in_expression@nightly-2021-03-11-x86_64-unknown-linux-gnu.so

    The filename components are as follows:

    • DLL_PREFIX and DLL_SUFFIX are OS-specific strings. For example, on Linux, they are lib and .so, respectively.
    • LIBARY_NAME is a name chosen by the library's author.
    • TOOLCHAIN is the Rust toolchain for which the library is compiled, e.g., nightly-2021-03-11-x86_64-unknown-linux-gnu.

  2. Export a dylint_version function:

    extern "C" fn dylint_version() -> *mut std::os::raw::c_char

    This function should return the Dylint version the library is compiled for. The current Dylint version is 0.1.0-pre.1.

  3. Export a register_lints function:

    fn register_lints(sess: &rustc_session::Session, lint_store: &mut rustc_lint::LintStore)

    This is a function called by the Rust compiler. It is documented here.

  4. Link against the rustc_driver dynamic library. This ensures the library uses Dylint's copies of the Rust compiler crates. This requirement can be satisfied by including the following declaration in your libraries lib.rs file:

    extern crate rustc_driver;

Dylint provides utilities to help meet the above requirements. If your library uses the dylint-link tool and the dylint_library! macro, then all you should have to do is implement the register_lints function.

How libraries are found

When Dylint is started, the following locations are searched:

  • the colon-separated paths in DYLINT_LIBRARY_PATH (if set)
  • the current package's target/debug directory (if in a package)
  • the current package's target/release directory (if in a package)

Any file found in the above locations with a name of the form DLL_PREFIX LIBRARY_NAME '@' TOOLCHAIN DLL_SUFFIX is considered a Dylint library.

In an invocation of the form cargo dylint [names], each name in names is compared to the libraries found in the above manner. If name matches a discovered library's LIBRARY_NAME, then name resolves to that library. It is considered an error if a name resolves to multiple libraries.

If the above process does not resolve name to a library, then name is treated as a path.

If --lib name is used, then name is is treated only as a library name, and not as a path.

If --path name is used, then name is is treated only as a path, and not as a library name.

Utilities

The following utilities can be helpful for writing Dylint libraries:

  • dylint-link is a wrapper around Rust's default linker (cc) that creates a copy of your library with a filename that Dylint recognizes.
  • dylint_library! is a macro that automatically defines the dylint_version function and adds the extern crate rustc_driver declaration.
  • ui_test is a function that can be used to test Dylint libraries. It provides convenient access to the compiletest_rs package.
  • clippy_utils is a collection of utilities to make writing lints easier. It is generously provided by the Rust Clippy Developers.

References

Useful references for writing lints include: