翻转数字最后n位

 #include<stdio.h>
 int turn_n(int ,int);
 int main(void)
 {
     int test,a=-,b=0xfffffffe,c=;
     printf("%x\n%d\n%x\n",a,b,c);
     test=turn_n(-,);
     printf("%d\n",test);
     return ;
 }
 int turn_n(int num,int bits)
 {
     int mask=;
     int bitval=;
     while(bits-->)
     {
         mask |=bitval;
         bitval <<=;
     }
     return num^mask;
 }