Extract and Modify Field in a 32-bit Register

#include <stdio.h>
#include <stdint.h>

uint32_t update_register(uint32_t reg) {
    struct me{
        unsigned int a :10;
        unsigned int b :5;
        unsigned int c :17;
    
    };
    struct me * nan= (struct me *) &reg;
if( nan->b <31) nan->b++;
return reg;
}

int main() {
    uint32_t reg;
    scanf("%u", &reg);
    uint32_t updated = update_register(reg);
    printf("%u", updated);
    return 0;
}