Warning: comparison between pointer and integer?

[mwskz8]

Hi, I wrote a loop to read from start to end of a char[] in C (see partial code below). I was taught that a null char == '\0' == NULL. However, my gcc compiler gave me a warning: comparison between pointer and integer. I don't understand why I have to use '\0' to replace NULL in the while loop to get rid of the warning. Any help, please?

  char buf[32];
  sprintf(buf, "%d", 234);

  while (buf[i] != NULL){
        tmp = buf[i] - '0';
        result += tmp;
        i++;
  }  

[LB]

You are confusing two separate concepts. NULL is for pointers, whereas '\0' is for characters.

[keanedawg]

Interesting. I never realized that NULL is not the same for pointers as it is for characters ('\0') or for numbers (0).

[LB]

At machine code level and assembly level they are usually always the same, but the whole point of a type system is to prevent you from mixing types accidentally ;)