Class preexec_func

cpp-subprocess/subprocess.hpp:1014–1041

// aiming for. If you know, then please do let me know.

class preexec_func
{
public:
  preexec_func() {}

  template <typename Func>
  explicit preexec_func(Func f): holder_(new FuncHolder<Func>(std::move(f)))
  {}

  void operator()() {
    (*holder_)();
  }

private:
  struct HolderBase {
    virtual void operator()() const = 0;
    virtual ~HolderBase(){};
  };
  template <typename T>
  struct FuncHolder: HolderBase {
    FuncHolder(T func): func_(std::move(func)) {}
    void operator()() const override { func_(); }
    // The function pointer/reference
    T func_;
  };

  std::unique_ptr<HolderBase> holder_ = nullptr;
};

// ~~~~ End Popen Args ~~~~