gcov2lcov

Convert golang test coverage to lcov format (which can for example be uploaded to coveralls).

See gcov2lcov-action for a github action which uses this tool.

Credits

This tool is based on covfmt and uses some parts of goveralls.

Installation

Binary download

Download a version for your platform from the Releases page.

You may have noticed that the file gcov2lcov-linux-amd64.tar.gz does not follow the naming convention used for other artifacts. This particular file is provided for backward compatibility with the gcov2lcov-action and can be disregarded for general use.

Compile from source

$ go install github.com/jandelgado/gcov2lcov@latest

Usage

Usage of ./gcov2lcov:
  -infile string
        go coverage file to read, default: <stdin>
  -outfile string
        lcov file to write, default: <stdout>
  -use-absolute-source-path
        use absolute paths for source file in lcov output, default: false

Example

$ go test -coverprofile=coverage.out && \
gcov2lcov -infile=coverage.out -outfile=coverage.lcov

GOROOT

It might be necessary to set the GOROOT environment variable properly before calling gcov2lcov. If you see cannot find GOROOT directory warnings like e.g.

022/05/23 16:00:58 warn: go/build: importGo github.com/pashagolub/pgxmock/: exit status 2
go: cannot find GOROOT directory: /opt/hostedtoolcache/go/1.13.15/x64

Then call gcov2lcov with

$ GOROOT=$(go env GOROOT) gcov2lcov -infile=coverage.out -outfile=coverage.lcov

Build and Test

make test to run tests
make build to build binary in bin/ directory

Tracefile format reference

The following desription is taken from the geninfo manpage of the lcov homepage:

A tracefile is made up of several human-readable lines of text, divided into
sections. If available, a tracefile begins with the testname which is stored in
the following format:

TN:<test name>

For each source file referenced in the .da file, there is a section containing
filename and coverage data:

SF:<absolute path to the source file>

Following is a list of line numbers for each function name found in the source file:

FN:<line number of function start>,<function name>

Next, there is a list of execution counts for each instrumented function:

FNDA:<execution count>,<function name>

This list is followed by two lines containing the number of functions found and hit:

FNF:<number of functions found> FNH:<number of function hit>

Branch coverage information is stored which one line per branch:

BRDA:<line number>,<block number>,<branch number>,<taken>

Block number and branch number are gcc internal IDs for the branch. Taken is
either '-' if the basic block containing the branch was never executed or a
number indicating how often that branch was taken.

Branch coverage summaries are stored in two lines:

BRF:<number of branches found> BRH:<number of branches hit>

Then there is a list of execution counts for each instrumented line (i.e. a
line which resulted in executable code):

DA:<line number>,<execution count>[,<checksum>]

Note that there may be an optional checksum present for each instrumented line.
The current geninfo implementation uses an MD5 hash as checksumming algorithm.

At the end of a section, there is a summary about how many lines were found and
how many were actually instrumented:

LH:<number of lines with a non-zero execution count> LF:<number of instrumented lines>

Each sections ends with:

end_of_record

In addition to the main source code file there are sections for all #included
files which also contain executable code.

Note that the absolute path of a source file is generated by interpreting the
contents of the respective .bb file (see gcov (1) for more information on this
file type). Relative filenames are prefixed with the directory in which the .bb
file is found.

Note also that symbolic links to the .bb file will be resolved so that the
actual file path is used instead of the path to a link. This approach is
necessary for the mechanism to work with the /proc/gcov files.