Run-Time Check Failure #2: Stack around the variable 'expression' was corrupted

Question

Following is my code for converting infix to postfix notation and later postfix is also being evaluated. This code works fine and gives right answer but in the end I am getting this error on run time.

Why this error is being caused? I am using Viusal C++ 2010.

Code:

#include<iostream>
#include<stack>
#include<string.h>

using namespace std;


int getPrecedence( char tmp )
{
    if(tmp=='+')
    {
        return 1;
    }
    else if(tmp == '-')
    {
        return 1;
    }
    else if(tmp == '*')
    {
        return 2;
    }
    else if(tmp == '/')
    {
        return 2;
    }
    else if(tmp == '=')
    {
        return 0;
    }
    else if(tmp == '(')
    {
        return -1;
    }
    else if(tmp == ')')
    {
        return -1;
    }
}

int main()
{

    stack<char> st;

    char expression[10];

    cout<<"Enter expression : ";
    //cin>>expression;
    strcpy(expression,"x=(0+1)+(y=2+3)");
    char postfix[100];  // its postfix string
    int counter=0;

    int i=0;

    int bracketCheck = 0;

    //(a+b)
    while( expression[i] != '\0' )  // iterate till '/0' does not come.
    {
        if(expression[i]== '+' || expression[i]== '-' || expression[i]== '*' || expression[i]== '/' || expression[i]== '='  )
        {
            if( st.empty() )
            {
                st.push(expression[i]);
            }
            else // when stack not empty
            {
                int topPrecedence = getPrecedence( st.top() );
                int expressionPrecedence = getPrecedence( expression[i] );


                while( !(topPrecedence < expressionPrecedence) )
                {
                    postfix[counter++] = st.top();
                    st.pop() ;

                    if(! st.empty() )
                    {
                        topPrecedence = getPrecedence( st.top() );
                    }
                    else
                    {
                        break;
                    }


                }

                //if( st.empty() )
                //{
                //  st.push( expression[i] );
                //}

                if( topPrecedence < expressionPrecedence )
                {
                    st.push( expression[i] );
                }


            }
        }
        else if( expression[i]=='(' )
        {
            st.push( expression[i] );
            bracketCheck++;
        }
        else if( expression[i]==')' )
        {
            int topPrecedence = getPrecedence( st.top() );
            int expressionPrecedence = getPrecedence( expression[i] );

            while( topPrecedence >= expressionPrecedence)   // +>=) --- 1 >= -1 ------- +>=) --- -1 >= -1
            {

                if( getPrecedence( st.top() ) != -1 )
                {
                    postfix[counter++] = st.top();
                }
                char BracketFound = st.top();
                st.pop();
                if( !st.empty() )
                    topPrecedence = getPrecedence( st.top() );
                if( st.empty() )   // break out of loop when stack is empty
                    break;
                if( BracketFound == '(' )
                    break;

            }

        }
        else // when its an alphabet 
        {
            postfix[counter++] = expression[i];
        }


        i++;
    } // outer while ends 

    while( ! st.empty() )
    {
        postfix[counter++] = st.top();
        st.pop();
    }


    postfix[counter] = '\0';
    i=0;

    while( postfix[i] != '\0' )
    {
        cout<<postfix[i]<<" ";
        i++;
    }

    stack<char> e; // eval stands for evaluation
    i=0;

    while( postfix[i] != '\0' )
    {
        if( postfix[i] == '+' )
        {
            int right = e.top();
            right = right - 48;  // 48 is ascii of 0 so 49-48=1
            e.pop();

            int left = e.top();
            left = left - 48;
            e.pop();

            int result = left + right;
            result = result + 48;   // sets to right ascii and in next line this ascii is type casted to char.
            e.push( result );

        }
        else if( postfix[i] == '-' )
        {
            int right = e.top();
            right = right - 48;  // 48 is ascii of 0 so 49-48=1
            e.pop();

            int left = e.top();
            left = left - 48;
            e.pop();

            int result = left - right;
            result = result + 48;   // sets to right ascii and in next line this ascii is type casted to char.
            e.push( result );
        }
        else if( postfix[i] == '*' )
        {
            int right = e.top();
            right = right - 48;  // 48 is ascii of 0 so 49-48=1
            e.pop();

            int left = e.top();
            left = left - 48;
            e.pop();

            int result = left * right;
            result = result + 48;   // sets to right ascii and in next line this ascii is type casted to char.
            e.push( result );
        }
        else if( postfix[i] == '/' )
        {
            int right = e.top();
            right = right - 48;  // 48 is ascii of 0 so 49-48=1
            e.pop();

            int left = e.top();
            left = left - 48;
            e.pop();

            int result = left / right;
            result = result + 48;   // sets to right ascii and in next line this ascii is type casted to char.
            e.push( result );
        }
        else if( postfix[i] == '=' )
        {
            int right = e.top();
            //left = left - 48;  // 48 is ascii of 0 so 49-48=1
            e.pop();

            int left = e.top();
            //right = right - 48;
            e.pop();


            //int result = right + left;
            //result = result + 48;   // sets to right ascii and in next line this ascii is type casted to char.
            e.push( right );

        }
        else
            e.push( postfix[i] );
        i++;
    }

    // while ends

    cout<<endl;
    cout<<"result= "<<e.top()<<endl;





    system("pause");
    return 0;
}

Answer 1

Well, the first problem I see is that you are copying 15 characters + null terminator into expression[10]. Basically, you are stuffing 16 pounds into a 10-pound sack.

Answer 2

char expression[10];

//<snip>

strcpy(expression,"x=(0+1)+(y=2+3)");

Look at the length of what you're copying into expression (don't forget the trailing \\0 ). You've allocated 10 spaces in your array, but you're trying to store 16 in it, and you're overflowing your buffer.