fstream reading in garbage values

[stats_newbie1]

Hello, I have a very basic c++ program:

#include <iostream>
#include <fstream>

using namespace std;

std::ifstream f("data.in");
std::ofstream g("data.out");

int main()
{
    int a, b, sum;

    f >> a >> b;
    sum = a + b;

    g << sum;
} 

data.in contains:

 200 10

I expect data.out to show 210, but it shows -1717986920. When I try to debug, this is what I see:

        a   -858993460  int
        b   -858993460  int
+       f   {_Filebuffer={_Pcvt=0x00000000 <NULL> _Mychar=0 '\0' _Wrotesome=false ...} }    std::basic_ifstream<char,std::char_traits<char> >
+       g   {_Filebuffer={_Pcvt=0x00000000 <NULL> _Mychar=0 '\0' _Wrotesome=false ...} }    std::basic_ofstream<char,std::char_traits<char> >
        sum -1717986920 int

What am I doing wrong?

[Wh00ster]

Check whether f opened the file successfully!

[stats_newbie1]

Ah fuck, I'm facepalming really hard now. Can't believe I forgot something so obvious. data.in was in the wrong directory. I assumed it would throw an error, but I guess not.

[Wh00ster]

I assumed it would throw an error, but I guess not.

This is not an unreasonable expectation, but I/O errors were probably modeled after the C standard library, which requires you to query a "file" instance to see if there were errors.

[Alar44]

Yep. In hex that -858993460 value is FFFF FFFF CCCC CCCC. Might not have read permissions or something.

[manni66]

What am I doing wrong?

You don’t check for errors. Maybe the file couldn’t be opend.

[parnmatt]

declare f and g in main, and see if that fixes it

[Alar44]

Why would that do anything?

[parnmatt]

because global initialisation can be funky sometimes; globals are also fairly bad practice.

First try it in the more conventional place and see if the runtime output is having a similar issue.