c++ - Does order matter when #defines are using other #defines? -

according answer this question, following code legit:

#define 3 three #define 9 three*3  int main() {     std::cout << nine;     return 0; } 

and sure, compiles , runs fine. however, answer mentioned question states 1 should careful order of such #define directives, , 1 used in other #defines should defined before them. following code:

#define 9 three*3 #define 3 three  int main() {     std::cout << nine;     return 0; } 

also compiles , runs fine, , prints "9".

is compiler letting me off easy, or order indeed not matter #defines use other #defines? compilation fail on more complicated project?

one thing worth mentioning mentioned question speaks of c, whilst code in c++. (supposed) differences in behavior come from?

three macro need defined before use of nine macro. can change three before every use of nine:

#define 9 three*3 #define 3 three  int main() {     std::cout << nine; //9 #undef 3 #define 3 4     std::cout << nine; //12 #undef 3     //no `three` macro defined here     int 3 = 2;     std::cout << nine; //three * 3 == 6     return 0; }