You can do this (if you want to be evil!)

struct fstr { constexpr fstr(const char* s) { for (length = 0; s[length] ; length++) data[length] = s[length]; }

    char data[256] = {0};
    size_t length = 0;

};

template <fstr sz> struct log { log() { std::cout << std::string_view{ sz.data, sz.length } << std::endl; } };

int main() { log<fstr(std::source_location::current().file_name())> _; }