Question

I am trying to read a binary file and store it into a database, however I get a segmentation fault when I try to store a string type into the database. To be exact, the error occurs inside the push function:

new_node->name = name;

I can’t seem to find a good solution on the web, and I’m aimlessly trying different things… any help would be appreciated.

// 
// loadbin.cpp
//

#include <iostream>
#include <fstream>
#include <string>
#include <vector>

using namespace std;

#include "studentsDB.h"

int main( int argc, char* argv[] ) {

    string name;
    string id;
    int numCourses;
    int crn;
    vector<int> crns;

    studentsDB sDB;
    studentsDB::node *students = 0;

    int in = 1;

    if( argc > 1 ) {

        ifstream infile(argv[in], ios::binary );

        while( !infile.eof() ) {
            infile.read( ( char* )(name.c_str()), sizeof( string ) );
            infile.read( ( char* )(id.c_str()), sizeof( string ) );
            infile.read( ( char* ) &numCourses, sizeof( int ) );

            do{
                crns.push_back( crn );
            }
            while( infile.read( ( char* ) &crn, sizeof( int ) ) );

            sDB.push( &students, (string)name, (string)id, numCourses, crns );
        }
        //sDB.printList( students );
    }


    else
        cout << "Not enough argument" << endl;
}

void studentsDB::push( struct node** head_ref, string name, string id,
                       int numCourses, vector<int>crns ) {

    struct node* new_node = ( struct node* ) malloc(sizeof(struct node));
    new_node->name = name;
    //new_node->id   = id;
    new_node->numCourses = numCourses;
    //new_node->crns = crns;
    new_node->next = (*head_ref);    
    (*head_ref)    = new_node;
    size++;
}

Answer 1

This code is bad:

        infile.read( ( char* )(name.c_str()), sizeof( string ) );

You can’t write to the buffer returned by c_str(), it is not guaranteed to be long enough to hold your result. sizeof(string) has nothing to do with the size the string can hold, by the way. You will need to allocate your own char[] buffer to hold the results of infile.read, then convert to a string afterwards.