Array of strings question

Hey guys I woke up early this morning and finished this code. Check out the working changes, and thanks to ItCbitC and MK27 for getting me over this hump. I owe you two my life!
p.s. figuring out that non duplicate algo was a pain in the rear

Code:

---

dupArray = (char**)malloc(val*sizeof(char*));

  fseek(finp_dat, seek_val, SEEK_SET);
  while((fread(&eof_test, sizeof(char), 1, finp_dat))!= NULL)
    {
      fseek(finp_dat, -1, SEEK_CUR);

      fread(test_string, sizeof(char),len, finp_dat);
      dupArray[j] = strdup(test_string);

      j++;

      fseek(finp_dat, advance_val, SEEK_CUR);
    }

  for(i=0;i<5;i++)
    {
      for(k=i;k<5;k++)
        {
          if((i!= k) && ((strcmp(dupArray[i], dupArray[k])==0)))
            {
              dupArray[k] = "dup";
              //printf("%s\n", dupArray[k]);
            }
        }
    }
  for(i=0;i<5;i++)
    {
      if(dupArray[i]!= "dup")
        printf("%s\n", dupArray[i]);
    }



    for(i=0;i<val;i++)
      {
        free(dupArray[i]);
      }
    free(dupArray);
}

---

Quote:

---

dupArray[k] = "dup";

---

when you will free this pointer - your program will crash

I agree with vart, dupArray[k] now points to a string literal so trying to free() a pointer that has not been allocated dynamically is undefined behaviour. IMHO a better design would be to free(dupArray[k]) and then set it to NULL. Doing it this way, conditionally print only those elements that are not NULL.