// declare interface's constructors and destructor

protected:

explicit IPlugin(const std::filesystem::path& path) {};

// deconstructor apparently needs to be defined, not just declared (with = 0)

virtual ~IPlugin() = default;

public:

virtual std::filesystem::path path() const = 0;

virtual int apiLevel() const = 0;

virtual PLUGIN_TYPE pluginType() const = 0;

virtual std::string pluginTypeString() const = 0;

virtual int run(const std::filesystem::path& appDirPath) = 0;