For examples: It does not follow the Linux rules for pathname separators, but mixes in Windows-isms. It doesn't properly check whether std::atomic<bool> is actually signal safe on the target architecture. Its unique filename generation has an all-too-common failure mode. It passes by reference only to then make local value copies anyway. It does not correctly follow the XDG Base Directory Specification.

https://en.wikipedia.org/wiki/Contemporary_art

Instead of

    static bool file_exists(const std::string &p) {
        struct stat st{}; return ::stat(p.c_str(), &st) == 0;
    }
      

    std::filesystem::exists(path);