a = first_word;
b = second_word;
while [a] == [b] && [a] != 0 {
  a += 1;
  b += 1;
}

if [a] < [b] {
  output(first_word);
} else {
  output(second_word);
}

// or slightly translated:
a = first_word;
b = second_word;
loop: {
  left = [a];
  right = [b];
  a += 1;
  b += 1;
  if left - right != 0 {
    goto endloop;
  }
  if left == 0 {
    goto endloop;
  }
}
goto loop:
endloop:

if left - right < 0 {
  output(first_word);
} else {
  output(second_word);
}

// musl strcmp for reference:
int strcmp(const char *l, const char *r)
{
	for (/*nothing*/; *l==*r && *l; l++, r++);
	return *(unsigned char *)l - *(unsigned char *)r;
}

// but don't be scared about the above for syntax, it means:
/*nothing*/;
while *l == *r && *l != 0 {
  l++;
  r++;
}