Issues with fstream and eof() (have spent a combined 5 hours debugging, searching for a solution, and testing)

Question

int i = 0;
while(!fin.eof())
{

    fin >> fname;
    fin >> lname;
    fin >> id;

    customer[i].setFname(fname);
    customer[i].setLname(lname);
    customer[i].setId(id);

    i++;
}
fin.close();

When my program gets to the fourth iteration of this while loop (and runs out of text from my input .txt file) visual studio prompts me with this:

Unhandled exception at 0x754bc41f in program5.exe: Microsoft C++ exception: std::ios_base::failure at memory location 0x003ceb64..

I'm clueless as to why. I've tried replacing !fin.eof() with (fin >> x) where x is an int, I've tried a do-while instead of a while, I've tried using get, getline. I thought it might be an issue that eof wasn't triggering with my >> operator so I added fin.peek(); at the very end of the loop so it would trigger eof when it peeked. I just have no idea what I'm doing wrong. Assume my customer class works properly, I've tested outside of this loop at it works perfectly.

Spend some time on this website. There are *hundreds* of questions, answers and comments telling you that *using `eof()` is always an error and doesn't do what you think*. — Kerrek SB, Jul 01 '13 at 22:03
I've spent hours on this site and still haven't resolved my issue, care to refer me to a specific post? Even if this is the case why did my other debugging attempts not work? fin >> x, etc — Stefan Theard, Jul 01 '13 at 22:05
still identical issue occurs with your suggestion 0x499602D2 — Stefan Theard, Jul 01 '13 at 22:08
@DavidSchwartz yes I thought that might be an issue, it won't trigger, so why did adding an fin.peek(); at the end not trigger it? — Stefan Theard, Jul 01 '13 at 22:09

score 1 · Answer 1 · answered Jul 01 '13 at 22:16

If I recall, one of the idioms when working with streams is to make loops like

while (cin >> x){
   //do something...

You should be checking the state of the stream while you read in the values. You could do something like

while(fin >> fname && fin >> lname && fin >> id){
...

This could probably be made more elegant

Issues with fstream and eof() (have spent a combined 5 hours debugging, searching for a solution, and testing)

1 Answers1