C++ changing value of wrong array

Question

I'm ultimately trying to create a video game and am having this issue in C++ where the wrong array is being changed. Here's the code that's going wrong:

 #include "stdafx.h"
 #include <iostream>
 #include <string>

 using namespace std;

 string commonNames[] = {""};
 string xCommonNames[] = {""};

 int commonIndex = 0;
 int xCommonIndex = 0;

 void placeName(string name, string placement)
 {
if(placement == "common"){
    commonNames[commonIndex] = name;
    commonIndex++;
}
else if(placement == "xCommon"){
    xCommonNames[xCommonIndex] = name;
    xCommonIndex++;
}

 }

 int _tmain(int argc, _TCHAR* argv[])
 {

placeName("Nathan","common");
placeName("Alex","xCommon");
placeName("Alyssa","common");


cout << commonNames[0] << endl;
cout << commonNames[1] << endl;
cout << xCommonNames[0] << endl;

system("pause");
return 0;
 }

I get this as the output:

 Nathan
 Alyssa
 Alyssa

Something's not right, it should turn out:

 Nathan
 Alyssa
 Alex

In the Game, there are different types like legendary and xLegendary which have the same problem. I even checked if they had the same address and they didn't. What am I doing wrong?

juanchopanza · Accepted Answer · 2014-03-08 16:20:27Z

5

This is a size 1 array:

string commonNames[] = {""};

You then access it as if it had more than one element. That out of bounds access is undefined behaviour. You might want to look at std::vector<std::string> instead. For example

std::vector<std::string> commonNames;
std::vector<std::string> xCommonNames;

void placeName(const std::string& name, const std::string& placement)
{
  if(placement == "common"){
    commonNames.push_back(name)
  }
  else if(placement == "xCommon"){
    xCommonNames.push_back(name);
  }

}

edited Mar 8, 2014 at 16:20

answered Mar 8, 2014 at 16:11

juanchopanza

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