How to resolve int variable before passing to C/C++ Macros? [closed]

Answer 1

You need another layer of indirection and for id to be a macro, not a variable (it can't work with a variable -- macros work at the token level; they can't know the value of a C variable, only the value of a preprocessor macro).

The following modified code works (i.e., prints 10):

#include 
using namespace std;

#define channel1 10
#define channel_(id) channel##id
#define channel(id) channel_(id)
#define id 1
int main(){
        cout << channel(id)<<"\n"; 
        return 0;
}