[C++] Segmentation Fault {Novice C++ Programmer}

[INFERNO2K]

Hello folks.

In the following function, cleanSpace [which takes in a string such as

this      is\ta\ta          a        test

. It cleans it up. I am recieving a segmentation fault on one line when I apply it to a second program [my second school assignment]. I do not understand what the problem is here.

Problem is on the bolded line.

int Account::cleanSpace(char c[])
{
    int i=0,
        j=0,
        k=0, 
        m=0; 
        
   /* Ultimately this loop will scan for new lines and tabs and replace them 
   with spaces. */
    for(i=0; c[i]; i++)
    {   
	    if(c[i] == '\n' || c[i] == '\t')
	    c[i] = ' ';     
    }

   /* For loop finds character starting point. */
    for(i=0; c[i] == ' '; i++)
    {
        c[m] = c[i+1];
    }         
	     
   /* For loop moves all characters next to the first found character. */
    for(i++; c[i]; i++)
    {
        c[++m] = c[i];
    }

   /* For loop removes trailing spaces. */
    for(i = strlen(c) - 1; c[i] == ' '; i--)
    {
        c[i] = '\0';
    }

   /*For loop removes excess spaces. */
    for(i = 0; c[i]; i++)
    {
        if(c[i] == ' ' && c[i+1] == ' ')
        {
            j = i;
            
    	    while(c[j] == ' ')
            {
	           j++;
            } 
	    
    	    for(k = i + 1; c[k]; k++, j++)
            {
    		      c[k] = c[j];
    	    }
        j=0;                           
	   }
    }
    return strlen(c);
}

The problem is on the bolded line.

Here is my header file, if its needed here.

#ifndef ACCOUNT_H
#define ACCOUNT_H

class Account
{
      private: 
               char customer[251];
               char accountNumber[16];
               int balance;
      public:
               Account(){init(",,,;","000000000000000",0);} //Default constructor
               Account(char c[], char num[], int b){init(c, num, b);} //Overloaded constructor
               void init(char c[], char num[], int b); //Initialization function
               int cleanSpace(char c[]); //Cleanspace function
               int changeCustomerInfo(char c[]); //Change customer info
               void changeAccountNumber(char num[]){strcpy(this->accountNumber, num);}
               void changeBalance(int b){this->balance = b;}
               void getLastName(char st[]); //Retrieves the last name
               void getFirstName(char st[]); //Retrieves the first name
               void getCity(char st[]); //Retrieves the city name
               void getPhoneNumber(char st[]); //Retrieves the phone number
               const char* getCustomer() const{return customer;}
               const char* getAccountNumber() const{return accountNumber;}
               int getBalance()const{return balance;}
               ~Account(){} //Destructor
};
#endif

I would appreciate any help, and thanks in advance.

[Darryl]

Maybe you are passing in a char array that's not zero terminated. You will have to run it through the debugger to see whats going on.

Also, a better solution might be to pass in the size as well. Passing in the buffer your way is consider a major security hole.

[Deo]

you know if you used a temp character array in your cleanup function you could probably reduce your code to one for loop with a couple of if statements. Would eliminate the need for 7 separate loops which could equal a lot of wasted time if your string is long. Would make your code more readible and rid of the potential problems with altering the array you are processing on.

As for you problem.. sorry I can't help.. I'm a retard without the aid of my trusty debugger

[INFERNO2K]

Function worked fine in my previous program.

[Darryl]

Just because it worked, doesn't necessarily mean it was right. Post the code that is calling this function.

[INFERNO2K]

#include <stdio.h>
#include <string.h>
#include "Account.h"
#include "Account.cpp"

int initTest(Account& a, Account& b);
int test1(Account& in);
void test2(Account& in);
void test3(Account& in);
void test4(Account& in);
void message();

int main()
{
	Account one;
	if (test1(one))
	{
		char d[] = "   xxxxx  xxxxxxxxxxxxxxxxxxx"
				   "xxxxxxxxxxxxxxxxxxxxxxxxx"
				   "xxxxxxxxxxxxxxxxxxxxxxxxx"
				   "xxxxxxxxxxxxxxxxxxxxxxxxx"
				   "xxxxxxxxxxxxxxxxxxxxxxxxx"
				   "xxxxxxxxxxxxxxxxxxxxxxxxx"
				   "xxxxxxxxxxxxxxxxxxxxxxxxx"
				   "xxxxxxxxxxxxxxxxxxxxxxxxx"
				   "xxxxxxxxxxxxxxxxxxxxxxxxx"
				   "xxxxxxxxxxxxxxxxxxxxxxxxx"
				   "xxxxxxxxxxxxxxxxxxxxxxxxx";
		char num[] = "aw0000000000000"; 
		Account two(d, num, 5347);
		Account three;
		three.init(d, num, 5347);
		if (initTest(two,three))
		{
			 printf("Failed init test\n"
					"fix your init function\n");
		}
		else
		{
			test2(two);
		}
	}
	return 0;
}

[Darryl]

Ok and how about the code that calls: Account::cleanSpace(char c[])

[INFERNO2K]

int Account::changeCustomerInfo(char c[])
{   
    int result = 0;
    char temp[251];
    result = strlen(c) - 250; 

    cleanSpace(c); //Calls the cleanSpace function
         
    if(strlen(c) <= 250){
           strcpy(this->customer, c);
    }    
        else{
            for(int i = 0; i < 250; i++){
                    temp[i] = c[i];
            }
        strcpy(this->customer, temp);}
             
        if(strlen(c) > 250){
            return result;}
            
        else return 0;  
}

[Darryl]

Ok, this is getting silly, I am trying trace your array through your program, from where it gets handed to your class in main to where it gives you the error in cleanspace ...so now lets see what calls changeCustomerInfo() and any other calls as well in between so that I can trace it the whole way through.

[INFERNO2K]

Ok, I also discovered the problem [as via asking my professor]. He told me it may because I am being passed a string literal. The function is working on the string and cleaning it when it is already clean. The function is acting on a string that does not need changing.

To fix this issue, I am confused.

[hk_mp5kpdw]

Ok, I also discovered the problem [as via asking my professor]. He told me it may because I am being passed a string literal. The function is working on the string and cleaning it when it is already clean. The function is acting on a string that does not need changing.

To fix this issue, I am confused.

Don't use the string literal directly in your program, copy it into an array or to a pointer you've allocated memory for.

[INFERNO2K]

so at the begining of cleanspace, I would declare a temp array and set it to st, and work on the temp array?

[INFERNO2K]

This is how I call changeCustomerinfo.

Looks like a problem the more I look at it

void Account::init(char c[], char num[], int b)
{
     changeCustomerInfo(c);       
     changeAccountNumber(num);
     changeBalance(b);
}

[INFERNO2K]

Yeah that is forsure the problem.

I am acting on a string literal

[hk_mp5kpdw]

Changing the use of a string literal so it doesn't break your code could be as easy as changing something like this:

void func(char *cptr)
{
    // Do something with cptr
}

int main()
{
    func("Hello");  // "Hello" is a string literal
    return 0;
}

.. to this:

void func(char *cptr)
{
    // Do something with cptr
}

int main()
{
    char data[] = "Hello";  // data is not a string literal
    func(data);  // Use char array instead of the string literal    
    return 0;
}