Why am I getting a segfault?

[Tduck]

My current assignment tasks me with using fstream, which I now finally understand to an extent, but now I have a problem which I haven't seen since I learned Python. How can I stop this program from segfaulting? breakfasts.txt lists the name of a food item on one line, then the cost of the food item on the next, and my program should be taking, line by line, a string equal to the line on the text file, though instead I get an error, segmentation fault. What piece of illegal memory am I accessing here?

#include <iostream>
#include <fstream>
#include <iomanip>
#include <string>

using namespace std;

int main()
{
    ifstream inFile;
    cout << fixed << showpoint << setprecision(2);
    
    inFile.open("breakfasts.txt");

    if(!inFile)
    { cout << "Cannot open the input file. Program Terminates!" << endl; return 1; }
    
    string foodName[8];
    string foodCost[8];

    //We need to record the value by using getline(inFile,foodName[i]);
    //Now we need to skip the first line, and get getline(inFile,foodCost[i]);
    //Repeat this, incrementing the number of lines skipped by 1 each time.  
    
    for(int i = 0; i < 16; i++)
    {
        if(16 % (i+1) != 0)
        {
            getline(inFile,foodName[i]);
        }
        else if(16 % (i+1) == 0)
        {
            getline(inFile,foodCost[i]);
        }
    }
    return 0;
}

[keskiverto]

Your arrays have 8 elements. Valid indices are thus 0..7.
The indices that you do use, are in range 0..15.

[Tduck]

Why is my code starting at line 10?
Here is the breakfasts.txt file

Plain Egg
1.45
Bacon and Egg
2.45
Muffin
0.99
French Toast
1.99
Fruit Basket
2.49
Cereal
0.69
Coffee
0.50
Tea
0.75

#include <iostream>
#include <fstream>
#include <iomanip>
#include <string>

using namespace std;

int main()
{
    ifstream inFile;
    cout << fixed << showpoint << setprecision(2);
    
    inFile.open("breakfasts.txt");

    if(!inFile)
    { cout << "Cannot open the input file. Program Terminates!" << endl; return 1; }
    
    string line[16];  //we'll later turn these into foodName[8] and foodCost[8]
    string foodName[8];
    string foodCost[8]; 
    //if statement evaluates odd/even, if odd j++, if even, k++
    for(int i = 0, j = 0, k = 0; i < 16; i++)
    {
        getline(inFile,line[i]);
        cout << "Line " << i << ":  " << line[i] << endl;
    }
    //We need to record the value by using getline(inFile,foodName[i]);
    //Now we need to skip the first line, and get getline(inFile,foodCost[i]);
    //Repeat this, incrementing the number of lines skipped by 1 each time.  
    //Get value[0], get value2[0], 
    return 0;
}

[keskiverto]

Why is my code starting at line 10?

??? Please explain.


Yes, your input data has 16 lines. However, it contains only 8 entries, where an entry is a pair of name and cost.

std::string name;
std::string cost;

// this reads one entry (but two lines):
std::getline( inFile, name );
std::getline( inFile, cost );

This loop reads at most 8 entries, but will stop earlier if any read fails:

size_t entry = 0;
while ( entry < 8 and std::getline( inFile, name ) and std::getline( inFile, cost ) ) {
  std::cout << "Entry " << entry << ": " << name << ' ' << cost << '\n';
  ++entry;
}

The wording in your instructions is a bit peculiar (the "we need to skip the first line" that makes no real sense).