The clang compiler supports source based coverage tracking, but the default reporting options are very basic. This tools allows for converting a llvm coverage file into a nice HTML report.

First compile your program with coverage tracking:

clang -O0 -fprofile-instr-generate -fcoverage-mapping test/switch.cpp -o test/switch

Now execute the program and write the coverage for that run into a file (here: rc.profraw):

LLVM_PROFILE_FILE="rc.profraw" test/switch

The coverage from one or more runs can be finalized with llvm-profdata:

llvm-profdata merge -sparse rc.profraw -o rc.profdata

The finalized coverage file is now converted into an HTML report using llvmcov2html:

mkdir -p tmp
bin/llvmcov2html tmp test/switch rc.profdata

The coverage percentage is printed to stdout and the HTML files are written into the tmp directory. Start with index.html to get an overview.

llvmcov2html requires LLVM 12 and a C++17 compiler. Both plain make and cmake are supported.