Question

The code says at many places “invalid indirection”.Please help.

   int main()
    {

        char *s1,*s2,*position;
        printf("Enter string:\n");
        gets(s1);
        printf("Enter word to find:\n");
        gets(s2);
        *position=ststr(*s1,*s1);
        if(*position)
        printf("word is found at %c loc\n",*position);
        else
        printf("word not found");
        getch();
        return 0;

    }

char *strstr(char *s1,char *s2)
{
    int flag=1;
    char i,j;
    for(i=0; ;i++)
    {
        if(*s1[i]==*s2[0])
        for(j=i;*s2;j++)
        {
            if(*s1[j]!=*s2[j])
            flag=0;
        }

    }
    if(flag)
    return i;
    else
    return 0;
}

Answer 1

First, s1 and s2 in main have not been initialized to point anywhere meaningful. Either declare them as static arrays, or allocate memory to them at runtime using malloc() or calloc():

#define SIZE 20 // or some number big enough to hold your input
...
char s1[SIZE], s2[SIZE], *position; // s1 and s2 declared statically

Second, NEVER NEVER NEVER NEVER NEVER use gets(); it will introduce a point of failure in your program. Use fgets() instead:

if (fgets(s1, sizeof s1, stdin) != NULL)
  // process s1
else
  // check for EOF or error on read

EDIT

And like everyone else has pointed out, your comparison in the strstr() function needs to be either

*s1 == *s2

or

s1[i] == s2[i]

but first you need to deal with allocating your buffers in main properly.