Thread: Still more problems with argv and argc

I know I've posted this code a couple of times now so I feel really stupid asking again for help but the requirements for the challenge that I'm working on changed a little bit on me.

What I now need to do is take in a list of numbers, assuming it will be an even numbered list of numbers, and compute the cycle length of the pairs of numbers given. But when I accept the numbers at the command line, the program crashes. I know it's because of my inexperience with pointers and arrays of pointers.
Here is the link to the challenge that I'm working on.

Code:

/*
program overflows @ command line
*/
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{

	int *inci;	//holds the incremental value of i
	int *origi;	//hold the original value of i to increment
	int *num1, *num2; //numbers to be compared
	int count = 0;	//count is the more permanent storage for counting cycle length
	int temp = 0;	//temp is the temporary storage for testing greatest cycle length

 
	while(argc > 1)
	{	
		int i = 1;	
		*origi = atoi(argv[i]);
		*inci = atoi(argv[i]);
		*num1 = atoi(argv[i]);
		*num2 = atoi(argv[i+1]);
			
		while(*num1 <= *num2)
			{
				while(*num1 != 1)
				{
					if(*num1 % 2)//if i is odd
					{
						*num1 = (3 * (*num1))+1;
						++temp;
					}
				
					else // assumes that i is even
					{
						*num1 = (*num1)/2;
						++temp;
					}		
				
					if(temp > count) //stores the largest temp number into count to be printed later
					{
						count = temp;
						temp = 0;	
					}
				}
				*num1 = ++(*inci);
				argc -= 2;
				argv += 2;
			}
		printf("%d %d %d \n", *origi, *num2, count);
	}
	return 0;
}

Hehe, well I was always curious about how the wheel worked.
I thought I was taking integers from the command line.
Am I not?

if argc == 2
argv[2] will be NULL

so atoi(argv[2] ) will crash

Using pointers without allocating them
So why do you think you need to use pointers in the code?

Originally Posted by Elysia

So why do you think you need to use pointers in the code?

I thought I needed to use pointers because I was using argv.

So is there any special reason why argv is so special it needs to use pointers, then?

Originally Posted by Elysia

So is there any special reason why argv is so special it needs to use pointers, then?

I thought that because it is an array of pointers it would be easier to use pointers to use it.
Or I'm just so anxious to write really sophisticated programs I blindly decided to use pointers where they where unnecessary.
Or both.

I see. It is certainly possible to use pointers to it, but you got the concept wrong.
Pointers store memory addresses, so you would assign to the actual pointer, and not the pointee.

So the way I did it, i was playing with the address not the value, correct?

Just remove every single asterisk in that piece of code. Except this one:

Code:

int main(int argc, char *argv[])

You didn't need to add any pointers of your own.

Originally Posted by MikeyIckey

So the way I did it, i was playing with the address not the value, correct?

You were trying to assign to a pointer to which you hadn't set a valid address.