#include "iostream"

#ifndef XXXXXX
  #define XXXXXX 0
#endif

int main(){
  std::cout << XXXXXX << std::endl;
  return 0;
}



g++ micro002.cpp 
./a.out
0

g++ micro002.cpp  -DXXXXXX
./a.out
1

g++ micro002.cpp  -DXXXXXX=99
./a.out
99