lcov

LCOV is a graphical front end for the GNU Compiler Collection’s gcov code coverage tool. It is used with C and C++ projects to collect and present coverage data that indicates which parts of the source code were exercised by tests. LCOV itself processes the data produced by gcov and helps generate readable reports across multiple source files.

LCOV operates by parsing the coverage data generated by gcov, which creates .gcno and .gcda files during program execution. The lcov tool collects this information into a consolidated coverage data file (commonly lcov.info) and can merge data from several runs or multiple source trees. In addition to text data, LCOV provides the option to create HTML reports via the genhtml utility, offering a browsable, file-by-file view of coverage results, including line, function, and, where supported, branch coverage.

Key features include support for line and function coverage, optional branch coverage, the ability to merge coverage data from multiple runs, and filtering or excluding specific files or directories. Users can specify directories to scan, reset counters, or capture baseline data, enabling incremental coverage analysis. LCOV can generate both summary information and detailed per-file reports, and the resulting lcov.info file can be used with other tools or stored for traceability.

Typical workflow involves compiling the program with coverage instrumentation flags (such as --coverage or -fprofile-arcs -ftest-coverage), running the test suite to exercise the code, and invoking lcov to capture and possibly merge data, followed by genhtml to produce HTML reports. LCOV is widely used in continuous integration and development workflows to monitor test coverage over time.

LCOV is open source and commonly distributed with GNU tools; it works with GCC and compatible gcov data formats and is maintained to support contemporary coverage analysis needs in C and C++ projects.