Thread: malloc problem

Hi,

Just for fun (I have been out of C for some weeks) I coded some programs. In one of them I used this:

Code:

int decs[512];

I decided to replace it by:

Code:

int *decs = (int *) malloc(NUMBER_OF_INTS_NEEDED * sizeof(int));

I use this in a program to convert roman numbers to decimal numbers. When I use the second line, XLV = 45 (that's ok) but MCI = 1076 and MM = 1983 ?? It's late here, so it could be a stupid mistake.

Maybe NUMBER_OF_INTS_NEEDED has the wrong value. If you get the correct values for MCI and MM when using an array (int decs[512]), then that could be the problem.

NUMBER_OF_INTS_NEEDED is the number of roman numbers (MM = 2 ints needed) + 1 for a terminating zero to indicate the end of the array.

When I set NUMBER_OF_INTS_NEEDED = 512, all numbers are correctly calculated.

When I set NUMBER_OF_INTS_NEEDED = 4 (3 chars + 1 zero) the program produces invalid output using MCI as input and valid output using XLV as input. It's not a segmentation error. Even when I input MMMMMMM (NUMBER_OF_INTS_NEEDED = 4) it doesn't segfault.

I use the int array like a reverted enum:

Code:

ptr = rn; // rn: ( char rn[512] = MCI; for example)
	while(*ptr != '\0')
	{
		if(*ptr == 'M')
			decs[l] = 1000;
		else if(*ptr == 'D')
			decs[l] = 500;
		else if(*ptr == 'C')
			decs[l] = 100;
		else if(*ptr == 'L')
			decs[l] = 50;
		else if(*ptr == 'X')
			decs[l] = 10;
		else if(*ptr == 'V')
			decs[l] = 5;
		else if(*ptr == 'I')
			decs[l] = 1;
		++l;
		*ptr++;
	}

Like brewbuck said, you probably have a bug elsewhere in your code. By the way:
> *ptr++;

ptr++;
would work just fine here.