genmask_function.c

#include<stdio.h>

//// Begin copy //////////////////////
#ifndef GENMASK

#ifndef U32_C 
#define U32_C(x) x ## U
#endif /* U32_C */

/*
 * Create a contiguous bitmask starting at bit position @l and ending at
 * position @h. For example
 * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
 */
#define GENMASK(h, l)       (((U32_C(1) << ((h) - (l) + 1)) - 1) << (l))
//#define GENMASK_ULL(h, l)   (((U64_C(1) << ((h) - (l) + 1)) - 1) << (l))

#endif /* GENMASK */
//// End copy //////////////////////

int main() {
    printf("1: %x\n", GENMASK(39,21) ); // should output only 32bit
    printf("2: %x\n", GENMASK(14,2) );  
}