check_cxx_source_compiles("
#include <string>
#include \"utf8.h\"

int main(int argc, char** argv) {
    std::string input = std::string(\"utfcpp\");
    const char * p = input.c_str();
    std::size_t len = input.length();
    utf8::is_valid(p, p + len);
}" HAVE_WORKING_UTFCPP)