isalpha causing a "Debug Assertion Failed" in c++

Question

I have a short program designed to count the number of consonants in a string by first testing to see if the character in the array is an alpha character (to skip any white space or punctuation). I keep getting a Debug Assertion Failed for my "if (isalpha(strChar))" line of code.

"strChar" is a variable that is assigned the char value in a for loop

Sorry if this is a remedial issue, but I'm not sure where I'm going wrong. Thanks in advance for any help!

#include <iostream>
#include <cctype>
using namespace std;
int ConsCount(char *string, const int size);


int main()
{
    const int SIZE = 81; //Size of array
    char iString[SIZE]; //variable to store the user inputted string

    cout << "Please enter a string of no more than " << SIZE - 1 << " characters:" << endl;
    cin.getline(iString, SIZE);

    cout << "The total number of consonants is " << ConsCount(iString, SIZE) << endl;
}

int ConsCount(char *string, const int size)
{
    int count;
    int totalCons = 0;
    char strChar;

    for (count = 0; count < size; count++)
    {
        strChar = string[count];
        if (isalpha(strChar))
            if (toupper(strChar) != 'A' || toupper(strChar) != 'E' || toupper(strChar) != 'I' || toupper(strChar) != 'O' || toupper(strChar) != 'U')
            totalCons++;
    }
    return totalCons;
}

Answer 1

The function ConsCount(char* string, const int size) should be like this:

int ConsCount(char *string, const int size)
{
    int consCount = 0;

    char* begin = string;
    for (char* itr = begin; *itr != '\0'; ++itr)
    {
        if (isalpha(*itr)) {
            char ch = toupper(*itr);

            switch(ch) {
                case 'A':
                case 'E':
                case 'I':
                case 'O':
                case 'U':
                    break; // If ch is any of 'A', 'E', 'I', 'O', 'U'
                default:
                    ++consCount;
            }
        }
    }

    return consCount;
}

As you can see I replaced the if statement with switch for better readability and using char* as a iterator to iterate the string. You can remove the unused parameter int size in your code.

And also I suggest you to use std::string for the safe-code. It also provides you a iterator class to iterate over the std::string.