Question

I fail to understand why the following program wrong:

 int& getID(){
   static int r = 0;
   return r++;
 }

main:

 int main(){
   int a = getID();
   std::cout << "a=" << a << std::endl;
   return 0;
 }

Why returning a static variable as described creates problems and not returning
the wanted value?

Answer 1

You are using post-increment(r++ as opposed to ++r). The result of post-increment is a temporary, and you are trying to return a reference to that temporary. You can’t do that. If you want to return a reference to r, then you can use pre-increment, or you can just do the increment, then in a separate statement, return r.