std::vector

I have some weird issues I cannot figure out. When I run the code below which takes a file.txt reads it line by line into a vector<string> and then compares each index to string "--" it does not make it to the comparison stage.

Further more, in the convert_file() under the for loop string m, has some weird behavior: string m = "1"; m+= "--"; ('--' inside vector) m+= "2"; will print to console 2--; which makes me think something is bugging out the vector. The 2 is replacing the 1, the first character. This makes it look like the vector is bugged.

#include <iostream>
#include <sstream>
#include <fstream>
#include <string>
#include <vector>
using namespace std;

vector<string> get_file(const char* file){
      int SIZE=256, ln=0;
      char str[SIZE];
      vector<string> strs;
      ifstream in(file, ios::in);
      if(!in){
        return strs;
      } else {
        while(in.getline(str,SIZE)){
          strs.push_back(string(str));
          ln++;
        }
      }
      in.close();
      return strs;
    }

void convert_file(const char* file){
      vector<string> s = get_file(file);

      vector<string> d;
      int a, b;
      bool t = false;
      string comp = "--";

      for(int i=0; i<s.size(); i++){
        string m = "1";
        m+= string(s.at(i));
        m+= "2";
        cout << m << endl;
        if(s.at(i) == comp){
          cout << "s[i] == '--'" << endl;
        }
      }
    }

int main(){
  convert_file("test.txt");
  return 0;
}

now when I run a test file to check a similar program:

#include <iostream>
#include <string>
#include <vector>
using namespace std;

int main(){
  vector<string> s;
  s.push_back("--");
  s.push_back("a");

  for(int i=0; i<s.size(); i++){
    cout << "1" << s.at(i) << "2" << endl;
    if(s.at(i) == "--"){
      cout << i << "= --" << endl;
    }
  }
  return 0;
}

prints off 1--2, 0= --, 1a2. it works, it prints properly, and does the comparison. This leads me to think something is happening when I pull the line into a string.

Windows 7, cygwin64
g++ version 4.9.3
compile: D:\projects\test>g++ -o a -std=c++11 test.cpp