C++ Code Dumping "random" data - c++

Question

I will start by saying I am reasonably new as a C++ programmer.
However I understand PHP and VBA, so have a good understanding of the aspects of programming fundamentals.
Because I use CSV's quite often in my day to day job, I thought it would be a good learning exercise to write a library that manipulates CSV Files.
I wrote this function:
int getHeaders(ifstream & os, vector<string> & head2){
string STRING;
getline(os,STRING);
cout << STRING << endl;
STRING.erase(remove(STRING.begin(), STRING.end(), '\"'), STRING.end());
string::iterator it = STRING.begin();
int x = 0;
for (int index = 0; it < STRING.end(); it++, index++) {
if (*it == ',') {
head2.push_back(STRING.substr(0,index));
STRING.erase(0,index+1);
cout << endl << head2[x];
cout << endl << STRING;
x++;
}
}
return head2.size();
}
Which is called by the following:
int addRowCount = 0;
vector<string> head1;
ifstream outfile;
outfile.open("default.csv", ios_base::app);
cout << getHeaders(outfile, head1) << endl;
cout << head1[0] << endl << head1[1] << endl;
But when I run the program, the program just dumps a load of random rubbish to the console (and crashes the application)
I am using windows so cannot use valgrind.
Does anyone know why this may be happening? Obviously this "dump" is not what I want the application to do. I am hoping someone can point out the part of my code which would make this happen.
Thanks in advance.

Answer 1

When you call erase on a string, iterators into that string are invalidated, so it is an error to use it after the call to STRING.erase().
Hint: When you look at the documentation for a method on a class that supports iterators, keep an eye out for notes about invalidating iterators. On this page, for example, read the section titled Iterator validity
[not related to the answer, but a style issue: Using ALL CAPS for a variable name like STRING is generally considered bad style in C and C++. All caps names are used for #defined symbols]

Answer 2

So it turns out that head2[1] wasn't set so it was some sort of memory leak.
Here is the finished function after a few further amendments for the advice in the comments section:
int getHeaders(ifstream & os, vector<string> & head2){
string STRING;
getline(os,STRING);
STRING.erase(remove(STRING.begin(), STRING.end(), '\"'), STRING.end());
int strle = count(STRING.begin(),STRING.end(), ',') + 1;
for(int x = 0; x != strle; x++){
if (count(STRING.begin(), STRING.end(), ',') > 0) {
head2.push_back(STRING.substr(0,STRING.find_first_of(',')));
} else {
head2.push_back(STRING.substr(0,STRING.length()));
}
STRING.erase(0,STRING.find_first_of(',')+1);
}
return head2.size();
}