[SOLVED] How to pass a spooled file, uploaded from a file upload widget, to a C FILE *f pointer

I need to pass some text files, uploaded from a Wt file upload widget, as arguments to some C function for processing their data. Unless that I really can't find a proper way to open a file using the spooled file name (converted from std::string to a char *) as the first fopen()'s argument, I realized that I have not understood the file handling methods provided by Wt. I.e., where a spooled file is stored?. I tried to use std::string WtFileUpload::spoolFileName() const just after the file upload is finished (I provide a button to be clicked when the progress bar reaches the end), but by digging the errno number, I found that the file didn't exists.

Please, suggest me a proper way to proceed on this (provide some code if you can) and help me to understand the way Wt handles files uploaded with this widget.

Thanks in advance.

UPDATE: My file upload and handling code:

//Declared in the application class:
Wt::WFileUpload *RORUpload;
Wt::WPushButton *RORUploadButton;

//Create file upload widget and add handlers for it in application constructor:
root()->addWidget(new Wt::WText("RINEX File Loaders "));
new Wt::WBreak(root());
//RINEX observation data file from rover station uploader.
new Wt::WBreak(root());
RORUpload = new Wt::WFileUpload();
RORUpload->setFileTextSize(40);
root()->addWidget(new Wt::WText("RINEX Rover Observation Data "));
new Wt::WBreak(root());
RORUploadButton = new Wt::WPushButton("Upload", root());
root()->addWidget(RORUpload);
//Upload when the button is clicked.
RORUploadButton->clicked().connect(RORUpload, &Wt::WFileUpload::upload);
RORUploadButton->clicked().connect(RORUploadButton, &Wt::WPushButton::disable);
// Upload automatically when the user entered a file.
RORUpload->changed().connect(RORUpload, &Wt::WFileUpload::upload); // !!! do not rename this 'upload'
RORUpload->changed().connect(RORUploadButton, &Wt::WPushButton::disable);
// React to a succesfull upload.
RORUpload->uploaded().connect(RORUpload, (Wt::WObject::Method) &Wt::WFileUpload::uploaded);
//React to a fileupload problem.
RORUpload->fileTooLarge().connect(RORUpload, (Wt::WObject::Method) &Wt::WFileUpload::fileTooLarge);

//When user presses a "submit" button, a connection function will be called.
const std::string Nameofror = RORUpload->spoolFileName();
const char *CNameofror = Nameofror.c_str();

I wonder if the problem is related with my (Wt::WObjectMethod) cast. EDIT: See my comment on this question.

UPDATE 2: Forgot to say that i get a program crash when I click the "submit" button Code for this:

//Create button into application constructor:
  SubmitButton = new Wt::WPushButton("Submit", root());
SubmitButton->clicked().connect(SubmitButton, &Wt::WPushButton::disable);
SubmitButton->clicked().connect(this, &GOPApplication::definedOptions);

//definedOptions:

void GOPApplication::definedOptions()
{

int Posmode = PTGroup->checkedId();  //Value selection from PTContainer (checked radio button id).

     //int singlemoving;                                              //Value selection from SPContainer (checked radio button id).
int Frequencies = FGroup->checkedId();                  //Value selection from FContainer (checked radio button id).
const Wt::WString WElmask = EMedit->text();             //Value selection from EMw (given number).
std::string SElmask = WElmask.narrow();                 //Value selection from EMw (given number).
const char *CElmask = SElmask.c_str();                  //Value selection from EMw (given number).
float Elmask = atof(CElmask);                           //Value selection from EMw (given number).
int Height = HGroup->checkedId();                       //Value selection from HContainer (checked radio button id).
int Soltype = STGroup->checkedId();                     //Value selection from STContainer (checked radio button id).
int Sateph = SAGroup->checkedId();                      //Value selection from SEContainer (checked radio button id).
int Basestatcoord = BSCGroup->checkedId();              //Value selection from BSCContainer (checked radio button id).
int Ionerror = IEGroup->checkedId();                    //Value selection from IEContainer (checked radio button id).
int Troperror = TEGroup->checkedId();                   //Value selection from TEContainer (checked radio button id).
int Receiverapcpvc = RAGroup->checkedId();              //Value selection from RAContainer (checked radio button id).
int Satelliteapvc = SAGroup->checkedId();               //Value selection from SAContainer (checked radio button id).
int Earthtidescorr = ETCGroup->checkedId();             //Value selection from ETCContainer (checked radio button id).
int Ambresstr = STRGroup->checkedId();                  //Value selection from STRContainer (checked radio button id).
const Wt::WString WMinlockcount = MLCedit->text();      //Value selection from MLCw (given number).
std::string SMinlockcount = WMinlockcount.narrow();     //Value selection from MLCw (given number).
const char *CMinlockcount = SMinlockcount.c_str();      //Value selection from MLCw (given number).
float Minlockcount = atof(CMinlockcount);               //Value selection from MLCw (given number).
const Wt::WString WMinfixcount = MFCedit->text();       //Value selection from MFCw (given number).
std::string SMinfixcount = WMinfixcount.narrow();       //Value selection from MFCw (given number).
const char *CMinfixcount = SMinfixcount.c_str();        //Value selection from MFCw (given number).
float Minfixcount = atof(CMinfixcount);                 //Value selection from MFCw (given number)
const Wt::WString WThreshold = Tedit->text();           //Value selection from Tw (given number).
std::string SThreshold = WThreshold.narrow();           //Value selection from Tw (given number).
const char *CThreshold = SThreshold.c_str();            //Value selection from Tw (given number).
float Threshold = atof(CThreshold);                     //Value selection from Tw (given number).
const Wt::WString WMinelevangle = MEAedit->text();      //Value selection from MEAw (given number).
std::string SMinelevangle = WMinelevangle.narrow();     //Value selection from Tw (given number).
const char *CMinelevangle = SMinelevangle.c_str();      //Value selection from Tw (given number).
float Minelevangle = atof(CMinelevangle);               //Value selection from Tw (given number).
int Settimesystem = STSGroup->checkedId();              //Value selection from STSContainer (checked radio button id).
int Outputresiduals = ORGroup->checkedId();             //Value selection from ORContainer (checked radio button id).
int Settimeformat = STFGroup->checkedId();              //Value selection from STFContainer (checked radio button id).
//What about RINEX files obtaining?
//Maybe... (see notebook for infos about spoolFileName() usage)
const std::string Nameofror = RORUpload->spoolFileName();
const char *CNameofror = Nameofror.c_str();
printf("\n\n============= %s =============\n\n", CNameofror);
//const std::string Nameofrob = ROBUpload->spoolFileName();
//const char *CNameofrob = Nameofrob.c_str();
//const std::string Nameofrn = RNUpload->spoolFileName();
//const char *CNameofrn = Nameofrn.c_str();
//post-processing(Posmode,Frequencies,Elmask,Height,Soltype,Sateph,Basestatcoord,Ionerror,Troperror,Receiverapcpvc,
//              Satelliteapvc,Earthtidescor,Ambresstr,Minlockcount,Minfixcount,Threshold,Minelevangle,Settimesystem,Outputresiduals,Settimeformat);
 }