Getting "error: cannot convert 'std::__cxx11::string* {aka std::__cxx11::basic_string<char>*}' to 'const char*' error while passing a path as argument

I am new to programming.I want to access all the directories and sub-directories from default installed directory,but it is failing in traversing the folder, here i am passing path to constant char.Below is the code

using namespace std;


int reading(const char *d_path)
{
    cout<<"In Reading"<<endl;

    /*bfs::path pathSource("c:\\Program Files\\");*/
    struct stat info; //

    DIR *dir;
    struct dirent *ent;
    dir= opendir (d_path);
    cout<<dir<<endl;
  if ((dir = opendir (d_path)) != NULL)
  {
      cout<<"in IF"<<endl;
       while ((ent = readdir (dir)) != NULL)
       {
          if (ent->d_name[0] != NULL)
          {
              cout<<"New"<<endl;
              string path = string (d_path) + string(ent->d_name) + '\\' ;
              cout<< "Entry = "<<path<<endl;
              stat (path,&info);
              if(S_ISDIR(info.st_mode))
              {
                  reading(path);
              }


          }
       }
       closedir (dir);
  }
  /* print all the files and directories within directory */

 else
    {
  /* could not open directory */
      perror ("");

    }

return 0;
}