Union size/alignment with bitfield member

[fuhsnn]

#include <stdio.h>
#include <stdint.h>
union S{
   int8_t a;
   int64_t:37;
};
int main(void){
  printf("%d,", sizeof(union S));
  printf("%d\n", _Alignof(union S));
  // expect 5,1; got 8,8
}