Internal Program Version: lcov v2.3 (The man files)

LCOV is an extension of GCOV, a GNU tool which provides information about
what parts of a program are actually executed (i.e. "covered") while running
a particular test case. The extension consists of a set of Perl scripts
which build on the textual GCOV output to implement the following enhanced
functionality:
- HTML based output: coverage rates are additionally indicated using bar
  graphs and specific colors.
- Support for large projects: overview pages allow quick browsing of
  coverage data by providing three levels of detail: directory view,
  file view and source code view.

https://github.com/linux-test-project/lcov