Thread: corrupted stack

hi. i wrote this program:

Code:

/*
* A program to find prime number pairs, triplets etc.
* Prime number pairs are two prime numbers which are an exact number apart.
*/

#include <stdio.h>
#include <stdlib.h>

int checkprime(int, int, int, int);

struct asettings {
	int high, low, difference, number;
};

int main(int argc, char *argv[])
{
	/* Command line arguments */
	struct asettings my_settings;
	my_settings.high = 100;
	my_settings.low = 1;
	my_settings.difference = 2;
	my_settings.number = 2;
	int i;
	
	if (argc != 1) {
		for (i = 1; i <argc; i + 2) {
			if (argv[i][0] == '-') {
				switch (argv[i][1]) {
					case 'h':
						my_settings.high = atoi(argv[i+1]);
						i = i + 1;
						break;
					case 'l':
						my_settings.low = atoi(argv[i+1]);
						i = i + 1;
						break;
					case 'd':
						my_settings.difference = atoi(argv[i+1]);
						i = i + 1;
						break;
					case 'n':
						my_settings.number = atoi(argv[i+1]);
						i = i + 1;
						break;
					default:
						printf("Usage: %s -h highest_number -l lowest_number -d difference -n number_per_group\n", argv[0]);
						exit(EXIT_FAILURE);
				}
			}
			else {
				printf("Usage: %s -h highest_number -l lowest_number -d difference -n number_per_group\n", argv[0]);
				exit(EXIT_FAILURE);
			}
			break;
		}
	}
	
	printf("This is a program to find groups of prime numbers separated by a fixed value.\n\n");
	printf("Your current settings are: \n");
	printf("Range for prime number search: %d and %d\n", my_settings.low, my_settings.high);
	printf("Difference between prime numbers: %d\n", my_settings.difference);
	printf("Number of prime numbers per group: %d\n", my_settings.number);
	printf("Program will begin");
	getchar();
	/* Error occurs here */
	
	int number = my_settings.low;
	int yes = 1;
	int counter = 0;
	int temp, j;
	while (number < my_settings.high) {
		yes = checkprime(number, my_settings.difference, my_settings.number, 1);
		if (yes == 0) {
			temp = number;
			counter = counter + 1;
			printf("%d", number);
			for (j = 1; j <= my_settings.number; j ++) {
				temp = temp + my_settings.difference;
				printf(", %d", temp);
			}
			printf(" are a prime number group\n");
		}
		number = number + 2;
	}
	
	printf("Total %d groups between %d and %d\n\nEnd of program\n", counter, my_settings.low, my_settings.high);
	getchar();
	
	exit(EXIT_SUCCESS);
}

int checkprime(int numb, int diff, int total, int current)
{
	int divisor;
	int check;
	divisor = numb / 2;
	
	for (;;) {
		if (numb % divisor == 0) {
			break;
		}
		else {
			divisor = divisor - 1;
		}
		if (divisor == 1) {
			if (numb % divisor == 0) {
				break;
			}
			else {
				if (current < total) {
					check = checkprime(numb + diff, diff, total, current + 1);
					if (check == 0) {
						return (0);
					}
				}
				else if (current == total) {
					return (0);
				}
				break;
			}
		}
	}
	
	return(1);
}

it compiles fine, but when its running i get a corrupted stack/core dumped error. it occurs at the comment where i stated.

why doesnt it work? thx for the help!

Shouldn't this:

Code:

for (i = 1; i <argc; i + 2) {

really say:

Code:

for (i = 1; i <argc; i += 2) {

Secondly, you either need to do the above add, or do the i = i + 1 at each case, (and change it to i += 2), but don't do both. I reckon you are indexing past the end of the argv array.

I would also validate the proper number of args before I assumed argv[i+1] existed.

Todd

Since each of the 4 cases have exactly the same code, you could use switch's fallthrough instead to only write the code once:

Code:

  case 'h':
  case 'l':
  case 'd':
  case 'n':
    my_settings.high = atoi(argv[i+1]);
    ++i;
    break;

Originally Posted by robatino

Since each of the 4 cases have exactly the same code, you could use switch's fallthrough instead to only write the code once:

Code:

  case 'h':
  case 'l':
  case 'd':
  case 'n':
    my_settings.high = atoi(argv[i+1]);
    ++i;
    break;

Look again. The four cases are not exactly the same. They are all unique. With your version, only settings.high would ever get set.

Todd

Originally Posted by Todd Burch

Look again. The four cases are not exactly the same. They are all unique. With your version, only settings.high would ever get set.

Todd

You're right, sorry about that.

i commented out the entire command line argument part but still get the same error:

Code:

Error while dumping state (probably corrupted stack)
Segmentation fault (core dumped)