Why is this printing out 0 back in main but 6 when it is inside of the strcmp function?

  7 int main()
  8 {
  9 char* str = "test string";
 10 char* str2 = "test strong";
 11 //printf("string length = %d\n",strlen(str));
 12 
 13 int num = strcmp(str,str2);
 14 
 15 printf("num = %d\n",num);
 16 }




 29 int strcmp(char* str, char* str2)
 30 {
 31   if(*str == '\0' && *str2 == '\0')
 32     return 0;
 33   if(*str2 - *str == 0)
 34   {
 35     strcmp(str+1,str2+1);
 36   }
 37   else
 38   {
 39     int num = *str2 - *str;
 40     cout << "num = " <<num<<endl;
 41     return num;
 42     }
 43 }

The output is:

num = 6 num = 0

Why is it printing 0 when obviously the value that it should be returning is 6?