smacro.cpp

constexpr {
    bool debug = /*...*/;
    log->(std::meta::expression<const char*> c,  std::meta::expression<>... args) {
            if(debug) {
                -> { 
                   printf(->c, (->args)...); 
               };
         }
    }
}

void foo() {
    log("Hello %", "World");  //expand to printf("Hello World")  only and only if debug is true
}