Getting useful GCov results for header-only libraries

Question

For my header-only C++ library (lots of templates etc) I use GCov to check test coverage. However, it reports 100% coverage for all headers because the unused functions aren't generated by the compiler in the first place. Manually spotting uncovered functions is easy but defeats the purpose of continuous integration…

How does one solve this automatically? Should I just use "lines hit / LOC" as my coverage metric and just never reach 100% again?

Answer 1

Apart from the usual flags to GCC controlling inlining;

--coverage -fno-inline -fno-inline-small-functions -fno-default-inline 

You can instantiate your template classes at the top of your unit test files;

template class std::map<std::string, std::string>; 

This will generate code for every method in that template class making the coverage tools work perfectly.

Also, make sure that you initialise your *.gcno files (so for lcov)

lcov -c -i -b ${ROOT} -d . -o Coverage.baseline <run your tests here> lcov -c -d . -b ${ROOT} -o Coverage.out lcov -a Coverage.baseline -a Coverage.out -o Coverage.combined genhtml Coverage.combined -o HTML