How to read from a text file into a pointer array?

Question

I have abstract class (Service) with two derived classes (Court and Machine). I also have a pointer array of Service, and I'm trying to read from a text file that includes information for both Court and Machine. To identify which information is for which class, I'm using an if.

My code compiles, but when executing I receive a segmentation fault. I'm aware this means I'm accessing memory that I shouldn't, but I'm not sure what I'm doing wrong.

I've never worked with pointer arrays. Am I'm doing something wrong when trying to input objects? I made sure to include both classes at the start of the program.

Service *listServices[20];
ifstream ArchService;
ArchService.open("Services.txt");

while(!ArchService.eof()) 
{
    for (int iA = 0; iA < 20; iA++) 
    {

        string clave, descripcion, deporte;
        int tiempomax, maxpersonas; 
        char tipo;
        double costo;
        bool instructor;
        ArchService >> clave >> tiempomax >> tipo >> costo;

        if (tipo == 'C' || tipo == 'E' || tipo == 'B') 
        {
            ArchService >> instructor;
            ArchService.ignore();
            getline(ArchService, descripcion);
            listServices[iA] = new Machine(clave, tiempomax, tipo, costo, instructor, descripcion);
        }

        else 
        {
            ArchService >> maxpersonas;
            ArchService.ignore();
            getline(ArchService, deporte);
            listServices[iA] = new Court(clave, tiempomax, tipo, costo, maxpersonas, deporte);
        }
        listServices[iA]->print();
    }
    ArchService.close();
}

@Lorraine [Don't use `while(!ArchService.eof())`](http://stackoverflow.com/q/5605125/418066) — Biffen, Apr 28 '16 at 17:54
@Lorraine https://ericlippert.com/2014/03/05/how-to-debug-small-programs/ — Biffen, Apr 28 '16 at 17:54
I suggest you using valgrind (if you are on Linux) or drMemory (if you are on Windows) in order to find where is the problem. If your project has not many lines of code they can lead you directly to the line generating the problem. — Francesco Argese, Apr 28 '16 at 18:38

score 0 · Accepted Answer · answered Apr 29 '16 at 16:53

Every element of listServices is allocated over and over again, with old values not being deleted, so they just remain dangling references and form multiple memory leaks. Probably this is the root cause. As been mentioned before, you'd rather remove that while(!ArchService.eof()) loop if all you want is filling the array of 20 list services.

How to read from a text file into a pointer array?

1 Answers1