Question

As a c++ beginner I’ve written the following code:

int main(void){
struct car{
    char * make[200];
    int manfYear;
};

int num=0;

cout << "How many cars do you wish to catalogue? ";
cin >> num;
car * Cars = new car [num]; 

for (int i=1;i<=num;i++){
    cout << "Car #" << i << ":" << endl << "Please enter the make: ";
    cin.getline(*Cars->make,200);
    cout << "Please enter the year made: ";
    cin >> Cars->manfYear;
}

My problem is that I can’t get my head round a problem where I get a segfault when running the program at the point I need to enter the model of the car. Can someone please explain what I’m doing wrong?

As far as I understand it I’m passing a pointer to the array “make” which should make it work. Is my understanding way off?

Thanks in advance
Dan

Answer 1

Four issues I see right away:

Issue 1

In your struct, you have:

char * make[200];

In English, this is saying, “create an array of 200 pointers to character”, when I think you want to say, “create an array of 200 characters.” So you should have instead:

char make[200].

Issue 2

You are looping by starting at 1. This will skip the first car in the array – remember arrays are zero-indexed. So you should have instead:

for (int i = 0 ; i < num ; i++)

and for display purposes, you could say:

cout << "Car #" << (i+1) << ":" << endl << "Please enter the make: ";

Issue 3

Where you say:

cin.getline(*Cars->make,200);

and

cin >> Cars->manfYear;

Where in these lines are you specifying which car the user is populating? Nowhere. If you are looping with i, then you need to actually mention i. These should work:

cin.getline(Cars[i].make,200);

and

cin >> Cars[i].manfYear;

Notice that we are using ., not ->. This is because the items in the Cars array are actual instances, not pointers. The Cars array is itself a pointer, but not its contents.

Issue 4

All credit to @Ben C who pointed this out first: mixing the >> operator with getline() function on cin can lead to strange behavior, with leftover CR‘s from >> going into the getline() call. You could use either all >> (disadvantage: you don’t have the 200 limit enforced when reading the make) or all cin.getline() (disadvantage: you will have to use string buffers and then convert them for number of cars and year), or put cin.ignore() after each invocation of >>, like so:

cin >> num;
cin.ignore();

and

cin >> Cars[i].manfYear;
cin.ignore();

Again, all credit to @Ben C for noticing this first.

Last But Not Least

By convention, classes/structs have capital names, and variables have lowercase / camelcase names. Consider renaming the struct from car to Car, and the array from Cars to cars. In other words, the reverse of the capitalization you have right now.

Finally, I concur with all the other posters here: you should consider using string instead of char arrays.