C++, Array - Windows Error Crash but no Compiler Error

Question

Ok so here's my code. I'm getting no errors in the compiler, however when I run this program it lets me input 2 names then crashes with a Window's Error. What in the heck am I doing wrong?!

#include <iostream>

using namespace std;

//declaration of variables

int i; // Loop Counter
int x; // Number of Family Members

int main()
{

string FamilyName[x]; // Array of Names


cout << "Enter Number of Family Members" <<endl;
cin >> x;

for (i = 0 ; i < x ; i++){
        cout << "Enter Family Member's Name: " <<endl;
        cin >> FamilyName[i];
}
for (i = 0 ; i < x ; i++){
    cout << FamilyName[i] <<endl;
}

return 0;
}

This should ideally not compile as array size(x in the string FamilyName[x]) should be a constant expression. Which compiler are you using? — Arun
– Arun, Commented Dec 9, 2014 at 3:08
@KickButtowski "filename.exe has stopped working A problem caused the program to stop working correctly. Windows will close the program and notify you if a solution is available. " — Osiris Clash
– Osiris Clash, Commented Dec 9, 2014 at 3:08
@musical_coder Array declarations allocate space (so long as x > 0) — M.M
– M.M, Commented Dec 9, 2014 at 3:32

Arun · Accepted Answer · 2014-12-09 03:15:21Z

1

You can solve the problem in two ways, allocate the array to a large size(x should be initialized...and it should be a constant value) and then the code becomes:

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

//declaration of variables

int i; // Loop Counter
const int x = 500; // MAX Number of Family Members

int main()
{

string FamilyName[x]; // Array of Names

int count;
cout << "Enter Number of Family Members" <<endl;
cin >> count;

for (i = 0 ; i < count ; i++){
        cout << "Enter Family Member's Name: " <<endl;
        cin >> FamilyName[i];
}
for (i = 0 ; i < count ; i++){
    cout << FamilyName[i] <<endl;
}

return 0;
}

Or use dynamic memory allocation to read the number of family member first and then do the allocation:

int main()
{

int count;
cout << "Enter Number of Family Members" <<endl;
cin >> count;

auto FamilyName = new string[count];

for (i = 0 ; i < count ; i++){
        cout << "Enter Family Member's Name: " <<endl;
        cin >> FamilyName[i];
}
for (i = 0 ; i < count ; i++){
    cout << FamilyName[i] <<endl;

    delete[] FamilyName;
}

Hope this helps

answered Dec 9, 2014 at 3:15

Arun

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1 Comment

M.M Over a year ago

The second version should use vector to manage the memory, there is no reason to use raw pointers (especially not hidden behind auto)

Adam Forbis · Accepted Answer · 2014-12-09 03:08:54Z

0

You are not allocating any memory to your string array, on this line string FamilyName[x]; // Array of Names x is not defined. It also may be a good idea to set a max array size or have some way of pushing on to the end of the array.

answered Dec 9, 2014 at 3:08

Adam Forbis

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Comments

zachyee · Accepted Answer · 2014-12-09 03:19:32Z

0

The size of your array should be constant.

Maybe use a vector of strings since vectors can grow dynamically.

string name;
vector<string> FamilyName;
for(int i = 0; i < x; i++)
{
    cin >> name;
    FamilyName.push_back(name);
}

Either that or give your array a constant size larger than any family size you might encounter.

string FamilyName[100];

if you wouldn't ever get a family with over 100 members.

edited Dec 9, 2014 at 3:19

answered Dec 9, 2014 at 3:14

zachyee

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Comments

neutrino · Accepted Answer · 2014-12-09 03:19:49Z

0

You need to either allocate reasonable memory for FamilyName or use STL:

string[] FamilyName;
//after get x
FamilyName = new string[x];

or

vector<string> FamilyName;
cin << temp_string;
FamilyName.push_back(temp_string);

answered Dec 9, 2014 at 3:19

neutrino

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