Define #define constant for compile time in gcc

define_const.c

#include <stdio.h>

#define _2_0     (1)
#define _2_1     (_2_0*2)
#define _2_2     (_2_1*2)
#define _2_3     (_2_2*2)
#define _2_4     (_2_3*2)
#define _2_5     (_2_4*2)
#define _2_6     (_2_5*2)
#define _2_7     (_2_6*2)
#define _2_8     (_2_7*2)

#define TWO_ORDER(n) _2_##n 

#define MAX_VAL 40

#if TWO_ORDER(1) > MAX_VAL
#define ORDER (0)
#elif TWO_ORDER(2) > MAX_VAL
#define ORDER (1)
#elif TWO_ORDER(3) > MAX_VAL
#define ORDER (2)
#elif TWO_ORDER(4) > MAX_VAL
#define ORDER (3)
#elif TWO_ORDER(5) > MAX_VAL
#define ORDER (4)
#elif TWO_ORDER(6) > MAX_VAL
#define ORDER (5)
#elif TWO_ORDER(7) > MAX_VAL
#define ORDER (6)
#elif TWO_ORDER(8) > MAX_VAL
#define ORDER (7)
#else
#error "Can not support value."
#endif

int main(void)
{
    printf("2' order value = %d\n", ORDER);
    return 0;
}