...

// Henri: required
#include "mount.h" // set_root_dir()
#include "getopt++/StringOption.h" // RootOption
extern StringOption RootOption;

...

// Henri: original function replaced by this one (more clear than modifying the existing function)
#if 1
io_stream *
UserSettings::open_settings (const char *filename, std::string &pathname)
{
/*
  Obtain user settings (last-action, last-cache -- aka local directory, last-mirror etc.) from /etc/setup/setup.rc
   - at startup (setup.exe), the root directory may have been specified explicitly (-R) or it may have been specified
     implicitly by starting setup.exe from the root directory, or its value may be present in registry ("rootdir")
   - if all options fail, it will default to either X:\Cygwin64 or X:\Cygwin (where X is the system drive)
   Note:
   - although the value of the root directory can be overruled in the Root Page later on, /etc/setup/setup.rc is read
     at startup from the root directory as explained above
   - however, said value can NOT be overruled in case of "Download to Local directory"
   Algorithm:
   - read /etc/setup/setup.rc from the specified root directory (-R) and if file exists
    - note: the root directory is NOT the Unix root; it is the Windows directory where the Cygwin packages
      have been, or will be installed
   - else read /etc/setup/setup.rc from the current directory and if file exists
    - this makes only sense if the current directory equals the root directory (i.e. this is the directory where
      the file /etc/setup/setup.rc will be written!)
   - else fall back to the whacky default (rootdir from registry)
 */
  io_stream *f = NULL; // Henri
  bool found = false; // Henri

  // Henri: take root directory seriously if explicitly specified (-R) ! ... setup mount_table (mount.cc)
  std::string my_RD;
  if (std::string (RootOption).size ()) {
    my_RD = std::string (RootOption);
    //LogPlainPrintf("UserSettings::open_settings: my_RD = %s\n", my_RD.c_str() );
    pathname = "file://" + my_RD + "/etc/setup/" + filename;
    f = io_stream::open(pathname, "rt", 0);
    //LogPlainPrintf("UserSettings::open_settings: 1. pathname = %s\n", pathname.c_str() );
    if (f) {
        found = true;
        set_root_dir(my_RD); // required in case of download
    }
  }

  // Henri: current directory (should!) equals the root directory ... setup mount_table
  // Henri: this is specifying the root directory implicitly ...
  if (found == false) {
  // Henri:  original code + correction (basically a daft option)
    pathname = "file://";
    pathname += cwd;
    if (!isdirsep (cwd[cwd.size () - 1]) && !isdirsep (filename[0]))
        pathname += "/";
    pathname += "etc/setup/"; // Henri: heck! "etc/setup/" was missing in pathname ...
    pathname += filename;
    //LogPlainPrintf("UserSettings::open_settings: 2. pathname = %s\n", pathname.c_str() );
    f = io_stream::open(pathname, "rt", 0);
    if (f) {
        found = true;
        set_root_dir(cwd); // required in case of download
    }
  }
  
  if (!f) // found == false
    {
      pathname = "cygfile:///etc/setup/";
      pathname += filename;
      //LogPlainPrintf(" *** WARNING *** UserSettings::open_settings: 3. pathname = %s\n", pathname.c_str() );
#if 0
      LogPlainPrintf(" *** WARNING ***\n");
      LogPlainPrintf("     rootdir from registry will be used as the root directory. Defaults will be\n");
      LogPlainPrintf("     obtained from /etc/setup/setup.rc over there.\n");
      LogPlainPrintf("     Defaults will also be written over there, unless another root directory is\n");
      LogPlainPrintf("     chosen later on (Not possible in case of Download to Local Directory).\n");
      LogPlainPrintf(" END WARNING\n");
#endif
      f = io_stream::open (pathname, "rt", 0); // Henri: creates mount_table where / maps to rootdir from registry
    }
  //if (!f) pathname = ""; // Henri: dont lie! (however, lying is prerequisite to keep setup.exe working)
  /*
   - ignore error if file does not exist ...
   - an exception occured if the file did not exist ... however, a non-existing mount-point was fine ... Hark!
    - a null pointer is returned if the file does not exist, while a (valid) pointer is returned in case of a
      non-existing mount-point ...
   - this software is garbage
   */

  return f;
}
#endif // Henri: end replace open_settings

#if 0 // Henri: put out the garbage ...
io_stream *
UserSettings::open_settings (const char *filename, std::string &pathname)
{
  pathname = "file://";
  pathname += cwd;
  if (!isdirsep (cwd[cwd.size () - 1]) && !isdirsep (filename[0]))
    pathname += "/"; // Henri: WRONG: missing "etc/setup/" in pathname!
  pathname += filename;
  io_stream *f = io_stream::open(pathname, "rt", 0);
  if (!f)
    {
      pathname = "cygfile:///etc/setup/";
      pathname += filename;
      f = io_stream::open (pathname, "rt", 0);
    }
  return f; // Henri: no reset of pathname if a null pointer is returned
            // Henri: Oh hell, a (valid) pointer is returned in case of a NON-existing mount-point ...
}
#endif

// Henri: relevance of cwd? As local directory: None! As root directory, only if the current directory equals the root directory
// Henri: why? /etc/setup/setup.rc is eventually written out to /etc/setup/setup.rc in the root directory; by definition the root
// Henri: can be equal to the current directory (start directory of setup.exe), but it does not require that!
// Henri: it is a daft option! And only useful if one wants to escape the dictation by registry.
UserSettings::UserSettings (std::string local_dir) // Henri: basically the start directory (cwd) of setup.exe is provided here
  : table (NULL), table_len (-1), cwd (local_dir)
{
  global = this;
  extend_table (0);
  io_stream *f = open_settings ("setup.rc", filename); // Henri: Jezus C.! This initializes the member variable ... Tada!
...

=====