Does anyone know why fstream crashes at this line?

Question

This is the first time i ran into this problem so I have no idea how to fix it. EDIT: Nevermind. Look like an off by one error in my constructor caused this to happen somehow

#include <iostream>
#include <fstream>
#include "graphm.h"

using namespace std;

int main() {

   ifstream infile1("data31.txt");

   for(;;){
      GraphM G;
      G.buildGraph(infile1);
      if (infile1.eof()) 
         break;
}

void GraphM::buildGraph(ifstream& infile){
    int i = 0;
    infile >> i;     //it crashes here
}

my text file is just 1 line: 5

Can you post constructor and destructor for `GraphM` and the rest of the `for` loop. The first call to `G.buildGraph()` won't set `eof()` so a second iteration of the loop will be performed. — hmjd, Oct 18 '12 at 08:06

score 4 · Answer 1 · answered Oct 18 '12 at 08:09

The problem might be related to the file not being open. You should always check whether a file has been successfully opened:

ifstream infile1("data31.txt");

if ( !infile1 )
{
    // Failed to open data31.txt
    return -1;
}

or you can use an explicit function instead of overloaded operator!

if ( infile1.fail() ) 
{
    return -1;
}

score 1 · Answer 2 · edited May 23 '17 at 12:12

1

What is the error that you get? Make sure that the file is open by checking the infile.is_open() function. you can find the sample code here:

http://www.cplusplus.com/reference/iostream/ifstream/is_open/

You can also check this thread:

Using C++ ifstream extraction operator>> to read formatted data from a file

It has a useful instructions for using ifstream.

edited May 23 '17 at 12:12

Community

1
1

answered Oct 18 '12 at 08:14

manman

4,743
3
30
42

score 0 · Answer 3 · answered Oct 18 '12 at 08:14

0

Possible problems with the code:

1. Unopenable file/unopened file
2. Unopenable file/unopened file
3. Unopenable file/unopened file
4. Unopenable file/unopened file

How to get around this problem? Follow @MaximSkurydin's code.

answered Oct 18 '12 at 08:14

Aniket Inge

25,375
5
50
78

Does anyone know why fstream crashes at this line?

3 Answers3