How to fix buffer overrun from char array variable?

Question

Im getting runtime error code #2 buffer overrun from pword char array. Any tips to help resolve isuue.

//Write a program to determine whether or not an entered 
//password is valid.Valid passwords consist of 10 characters,
//4 of which must be letters and the other 6 digits.
//The letters and digits can be arranged in any order.
//Only lowercase letters are allowed for valid passwords.
//Hints: use islower, isalpha, isdigit, and strlen.

#include<iostream>
#include<cctype>
#include<string>

using namespace std;

int main()
{
    const int Size = 10;
    char pword[Size];
    int count=0;
    int totall = 0;
    int totaln = 0;
    bool state = NULL;

    while(state != true) 
    {
    
        cout << "Enter a password up to 10 characters: " << endl;
        cin >> pword;

        int psize = strlen(pword);
        totall = 0;
        totaln = 0;
        while (pword[count] != '\0')

        {
            if (isalpha(pword[count]))
            {
                totall += 1;
            }

            if (isdigit(pword[count]))
            {
                totaln += 1;
            }
            count++;
        }
        if (totall > 4 || totaln > 6)
        {
            cout << " Error! Only enter 4 characters and 6 digits." << endl;
            state = false;
        }
        else
        {
            state = true;
        }
        count = 0;
        while(pword[count]!='\0')
        {
            if (!islower(pword[count]))
            {
                if (!isdigit(pword[count]))
                {
                    cout << "Error all characters must be lowercase!" << endl;
                    state = false;
                }
            }  
            count++;
        }

     
    }
   
        cout << "The password you entered is: " << pword << endl;
        cout << "The number of lower case letters in the password is " << totall << endl;
        cout << "The number of digits in the password is " << totaln << endl;
      
        return 0;
}

I tried dynamically allocating the char array by :

pword[Size]= (char*)malloc(sizeof(char))={};

failed though so I reverted the code back. I'm attempting to make a space on the heap for the char array indices 0-10 with null terminating character at 10 index. Looking at malloc though I don't see how I can make the array longer than a char this way?

The exact error message is "Run-Time Check Failure #2 - Stack around the variable 'pword' was corrupted." it occurs only when an incorrect password is entered then at completion the error occurs.

Answer 1

The main fix is to change this declaration:

int pword[Size];

To simply this:

string pword;

No more buffer overrun possibilities. Also bool state = NULL; doesn't sound like something that should compile, but perhaps the NULL coerces to false.

Some minor improvements to the code:

int main()
{
    string pword;
    int totall = 0;
    int totaln = 0;
    int isAllLowercase = true;
    bool state = false;

    while(state != true) 
    {
        cout << "Enter a password up to 10 characters: " << endl;
        cin >> pword;

        totall = 0;
        totaln = 0;
        isAllLowercase = true;

        for (char c : pword)
        {
            if (isalpha(c))
            {
                totall += 1;
            }

            if (isdigit(c))
            {
                totaln += 1;
            }
            isAllLowerCase = isAllLowerCase && (islower(c) || isdigit(c));
        }
        if (totall > 4 || totaln > 6)
        {
            cout << " Error! Only enter 4 characters and 6 digits." << endl;
        }
        else if (!isAllLowerCase)
        {
            cout << "Error all characters must be lowercase!" << endl;
        }
        else
        {
            state = true;
        }
    }
   
    cout << "The password you entered is: " << pword << endl;
    cout << "The number of lower case letters in the password is " << totall << endl;
    cout << "The number of digits in the password is " << totaln << endl;
      
    return 0;
}