Segmentation Fault Error (Using Pointers) in C

Question

So apparently, when I compile this program on my own computer it seems to work. However, on another compiler it gives Segmentation Fault Errors. I've used pointers here, and I might have used them wrong, however, logically everything should work without error. If anyone could point out some errors, it would be greatly appreciated.

contains.c

#include <string.h>

int contains(char *s, char *t)
{
    if (!t)
        return 0;

    if (!*t)
        return 0;

    if (s)
    {
        char *k;
        int n = 0;
        int l = t;
        int len = strlen(t);
        int counter = 0;

        printf("%d", len);

        for(k=s; *k; k++)
        {

            printf("S: %c ", *k);
            printf("T: %c ", *t);
            if (*k == *t)
            {
                printf("Si: %c ", *k);
                printf("Ti: %c ", *t);
                t++;
                counter++;
            }
            else
            {
                counter = 0;
                t = l;
                if (*k == *t)
                {
                    t++;
                    counter++;
                    printf("Si: %c ", *k);
                    printf("Ti: %c ", *t);
                }

            }

            printf("%d\n", len);
            printf("%d", counter);
            if (counter >= len)
            {
                    n++;
                    t = l;
                    counter = 0;
                    if (*k == *t)
                    {
                        t++;
                        counter++;

                        printf("Si: %c ", *k);
                        printf("Ti: %c ", *t);
                    }
            }
        }

        return n;
    }
    else
        return 0;



}

main.c

#include <stdio.h>

int contains(char *s, char *t);

int main(void)
{
  printf ("%d\n", contains ("I wanna shoot something!", "thing"));
  printf ("%d\n", contains ("Let's get in range!", "ge"));
  printf ("%d\n", contains ("Wanna see the fireworks?", "wanna"));
  printf ("%d\n", contains ("Look at the pretty explosions!", " "));
  printf ("%d\n", contains ("Kaboom!", ""));

  printf ("%d\n", contains ((char *) 0, "aaa"));
  printf ("%d\n", contains ("aaa", (char *) 0));
  printf ("%d\n", contains ((char *) 0, (char *) 0));

  return 0;
}

Fix your code until no more warnings are issued by the compiler. — alk
– alk, Commented Nov 15, 2013 at 7:41

JIghtuse · Accepted Answer · 2013-11-15 07:32:34Z

3

You assign integer to pointer and pointer to integer. It is wrong at least:

int l = t;
...
t = l

answered Nov 15, 2013 at 7:32

JIghtuse

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7 Comments

WhozCraig Over a year ago

+1 This is the biggest hitch in this code, and running it on different implementations where sizeof(int) and sizeof(char*) differ (or are the same) will exhibit the behavior seen. Changing int l to intptr_t l and including <stdint.h> is one potential work-around, but I would have to look more to be confident in that. In either case, the compiler should have warned the OP if configured properly.

Maaz Over a year ago

I'm simply setting the location that t is pointing to to l as an int? Then I retrieve it later on... What's wrong with that exactly?

WhozCraig Over a year ago

@Maaz what do you suppose happens when the physical size of a pointer in memory is larger than an int (such as a 32bit int and a 64bit pointer)?

Maaz Over a year ago

So it's just a size of the integer that's being the limitation here? For example if I used long int or something, would that fix this issue? Furthermore, using int* l = t fix the error?

Maaz Over a year ago

Oops sorry, I meant char* l = t

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