Thread: Sagmentation Fault pls help!

I'm writing a program that detects character entry and move a submarine that's on the display. here is the move code.
h moves left, j moves down, k moves up, l moves right.
the ocean is a 6x15 box. i understand that if i go out of boarder it will give me segmentation fault, but no matter where i go it ends the program with that msg.
Pls help!!!!!!!

test driver

Code:

#include<stdio.h>
main()
{
        int lat_s = 5;
        int long_s = 0;
        char c;
        int *lats, *longs;
        lats = &lat_s;
        longs = &long_s;
//      init_ocean();
//      show_boat(lat_s, long_s);
        c = getchar();
        while(c!= 'q')
        {
                printf("original lat is %d, long is %d\n", *lats, *longs);
                move_sub(c, *lats, *longs);
                printf("latitude is %d, longitude is %d\n", *lats, *longs);
                c = getchar();
        }
}

here's the move_sub code

Code:

void move_sub(char c, int *lats, int *longs);

void move_sub(char c, int *lats, int *longs)
{
        switch(c)
        {
                case'h': *longs = *longs - 1;
                         printf("longs is %d\n", *longs);
                         break;
                case'j': *lats  = *lats + 1;
                        printf("lats is %d\n", *lats);
                         break;
                case'k': *lats = *lats - 1;
                        printf("lat is %d\n", *lats);
                         break;
                case'l': *longs  = *longs + 1;
                        printf("longs is %d\n", *longs);
                         break;
                default: printf("Invalid Entry!");
                         break;
        }
}

I dont know where you are having your error message, but you are passing to move_sub a value that a pointer points to. Drop the * from lats and longs when passing them in.

That was magical!
Thanks
I thought I should pass the pointer value, and the pointer value will change according to entry. then it will change the value where it points to.
What's the difference?

The difference is before you were dereferencing some value (say 4), versus dereferencing an actual memory location that may happen to contain the value 4.