bin+lib grcov

Rust tool to collect and aggregate code coverage data for multiple source files

17 releases

✓ Uses Rust 2018 edition

new 0.5.12 Mar 26, 2020
0.5.9 Jan 9, 2020
0.5.7 Dec 23, 2019
0.5.5 Oct 7, 2019
0.3.0 Oct 9, 2018

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Build Status Build status codecov crates.io

grcov collects and aggregates code coverage information for multiple source files. grcov processes .gcda files which can be generated from llvm/clang or gcc. Linux, OSX and Windows are supported.

This is a project initiated by Mozilla to gather code coverage results on Firefox.

Table of Contents

man grcov:

    grcov [FLAGS] [OPTIONS] <paths>...

        --branch                          Enables parsing branch coverage information
    -h, --help                            Prints help information
        --ignore-not-existing             Ignore source files that can't be found on the disk
        --llvm                            Speeds-up parsing, when the code coverage information is exclusively coming
                                          from a llvm build
    -V, --version                         Prints version information

        --commit-sha <COMMIT HASH>                   Sets the hash of the commit used to generate the code coverage data
        --filter <filter>
            Filters out covered/uncovered files. Use 'covered' to only return covered files, 'uncovered' to only return
            uncovered files [possible values: covered, uncovered]
        --ignore <PATH>...                           Ignore files/directories specified as globs
        --log <LOG>
            Set the file where to log (or stderr or stdout). Defaults to 'stderr' [default: stderr]

    -o, --output-file <FILE>                         Specifies the output file
    -t, --output-type <OUTPUT TYPE>
            Sets a custom output type [default: lcov]  [possible values: ade, lcov, coveralls, coveralls+, files,
            covdir, html]
        --path-mapping <PATH>...
    -p, --prefix-dir <PATH>
            Specifies a prefix to remove from the paths (e.g. if grcov is run on a different machine than the one that
            generated the code coverage information)
        --service-job-id <SERVICE JOB ID>            Sets the service job id [aliases: service-job-number]
        --service-name <SERVICE NAME>                Sets the service name
        --service-number <SERVICE NUMBER>            Sets the service number
        --service-pull-request <SERVICE PULL REQUEST>
                                                     Sets the service pull request number

    -s, --source-dir <DIRECTORY>                     Specifies the root directory of the source files
        --threads <NUMBER>                            [default: 16]
        --token <TOKEN>
            Sets the repository token from Coveralls, required for the 'coveralls' and 'coveralls+' formats

        --vcs-branch <VCS BRANCH>
            Set the branch for coveralls report. Defaults to 'master' [default: master]

    <paths>...    Sets the input paths to use

How to get grcov

Grcov can be downloaded from releases or, if you have Rust installed, you can run cargo install grcov.

Example: How to generate .gcda files for from C/C++

Pass --coverage to clang or gcc (or for older gcc versions pass -ftest-coverage and -fprofile-arcs options (see gcc docs).

Example: How to generate .gcda fiels for a Rust project

  1. Ensure that the following environment variables are set up:
export RUSTFLAGS="-Zprofile -Ccodegen-units=1 -Cinline-threshold=0 -Clink-dead-code -Coverflow-checks=off -Zno-landing-pads"

These will ensure that things like dead code elimination do not skew the coverage.

  1. Build your code:

cargo build

If you look in target/debug/deps dir you will see .gcno files have appeared. These are the locations that could be covered.

  1. Run your tests:

cargo test

In the target/debug/deps/ dir you will now also see .gcda files. These contain the hit counts on which of those locations have been reached. Both sets of files are used as inputs to grcov.

Generate a coverage report from .gcda files

Generate a html coverage report like this:

grcov ./target/debug/ -s . -t html --llvm --branch --ignore-not-existing -o ./target/debug/coverage/

You can see the report in target/debug/coverage/index.html.

(or alterntatively with -t lcov grcov will output a lcov compatible coverage report that you could then feed into lcov's genhtml command).

lcov's genhtml

By passing -t lcov you could generate an lcov.info file and pass it to genhtml:

genhtml -o ./target/debug/coverage/ --show-details --highlight --ignore-errors source --legend ./target/debug/lcov.info

Coveralls/Codecov output

Coverage can also be generated in coveralls format:

grcov ./target/debug -t coveralls -s . --token YOUR_COVERALLS_TOKEN > coveralls.json

grcov with Travis

Here is an example of .travis.yml file

language: rust

  - curl -L https://github.com/mozilla/grcov/releases/latest/download/grcov-linux-x86_64.tar.bz2 | tar jxf -

    - os: linux
      rust: nightly

    - export CARGO_INCREMENTAL=0
    - export RUSTFLAGS="-Zprofile -Ccodegen-units=1 -Cinline-threshold=0 -Clink-dead-code -Coverflow-checks=off -Zno-landing-pads"
    - cargo build --verbose $CARGO_OPTIONS
    - cargo test --verbose $CARGO_OPTIONS
    - |
      zip -0 ccov.zip `find . \( -name "YOUR_PROJECT_NAME*.gc*" \) -print`;
      ./grcov ccov.zip -s . -t lcov --llvm --branch --ignore-not-existing --ignore "/*" -o lcov.info;
      bash <(curl -s https://codecov.io/bash) -f lcov.info;

Alternative reports

grcov provides the following output types:

Output Type -t Description
lcov (default) lcov's INFO format that is compatible with the linux coverage project.
ade ActiveData-ETL format. Only useful for Mozilla projects.
coveralls Generates coverage in Coveralls format.
coveralls+ Like coveralls but with function level information.
files Output a file list of covered or uncovered source files.
covdir Provides coverage in a recursive JSON format.
html Output a HTML coverage report.


This project is using pre-commit. Please run pre-commit install to install the git pre-commit hooks on your clone. Instructions on how to install pre-commit can be found here.

Every time you will try to commit, pre-commit will run checks on your files to make sure they follow our style standards and they aren't affected by some simple issues. If the checks fail, pre-commit won't let you commit.

Build & Test

Build with:

cargo build

To run unit tests:

cargo test --lib

To run integration tests, it is suggested to use the Docker image defined in tests/Dockerfile. Simply build the image to run them:

docker build -t marcocas/grcov -f tests/Dockerfile .

Otherwise, if you don't want to use Docker, the only prerequisite is to install GCC 7, setting the GCC_CXX environment variable to g++-7 and the GCOV environment variable to gcov-7. Then run the tests with:

cargo test

Minimum requirements

  • GCC 4.9 or higher is required (if parsing coverage artifacts generated by GCC).


Published under the MPL 2.0 license.


~188K SLoC