lcov is a graphical front-end application to gcov, a code coverage generating utility intended to work with the gcc suite of tools. When compiling and generating test code coverage data with the clang/llvm tool suite, the output data format and versions are incompatible, leading to a failure in generating code coverage reports, as in backend-cmocka build #1089.

In the clang/llvm case, the llvm-cov utility, along with supporting report formats, allows working in gcov compatibility mode and produces gcov format output.

What projects generally appear to do is install a wrapper for gcov, which tests for the compiler in use, and passes arguments to the correct utility, or just llvm-cov in gcov mode, if it is available.