C++ undefined reference using fstream

Question

So I had to make quick code in just a few minutes for a TSP type problem, but when I tried to read in the file, my compiler freaked out. Here is the sample code, what causes this error?

#include <cstdlib>
#include <iostream>
#include <fstream> 
using namespace std;

int tour_cost (int start, int end, int* array, int* tour) //calculate tour cost
{
    int cost = 0;
    for (int i = start; i < end; i++) 
        cost += array[tour[i] * tour[i] + tour[i + 1]];
    return cost;
}

int main()   
{
    int array [625];
    int tour [25];
    int dist = 0;   
    ifstream infile ("cities.txt");
    for (int i = 0; i < 25; i++) {
        for (int j = 0; j < 25; j++ ) {
            infile >> dist;
            array[i*i + j] = dist;
        }
        tour[i] = i;
    }
    cout << tour_cost (0,24,array,tour);
    return 0;
}

Sample error:

ps2.cpp:(.text+0xc0): undefined reference to `std::basic_ifstream<char, std::char_traits<char> >::basic_ifstream(char const*, std::_Ios_Openmode)'
ps2.cpp:(.text+0xe8): undefined reference to `std::istream::operator>>(int&)'

How are you compiling it? It compiled just fine for me with the default settings. — John Odom
– John Odom, Commented Feb 10, 2014 at 22:31

6502 · Accepted Answer · 2014-02-10 22:33:10Z

6

When compiling C++ code you must use g++, not gcc.

answered Feb 10, 2014 at 22:33

6502

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3 Comments

ptgrimes Over a year ago

Alas I thought I was going crazy

Mooing Duck Over a year ago

I don't think that would cause these errors would it? It wouldn't understand the C++ syntax. This is a linker thing... Right?

6502 Over a year ago

@MooingDuck: IIUC the compiler is indeed the same, it's the linking phase that is c++ specific.

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