【c++11关键字】 alignas alignof

/*
 * c++11关键字
 * alignas 设置对其方式
 * alignof 对其方式大小
*/
#include <QCoreApplication>
#include <iostream>
using namespace  std;
struct alignas(8) S //S至少是八个字节的对其方式
{

};
struct alignas(1) U //BAD
{
 S s;
};
struct Foo
{
  int i;
  float f;
  char c;
};
struct Empty
{

};
struct alignas(64) Empty64
{

};
struct alignas(1) Double
{
  double d;
};
struct Obj
{
    char a;
    int b;
};
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    cout << sizeof(Obj) << " "<< alignof(Obj);
    cout << "Alignment of " << "\n"
         << "-char " << alignof(char) << "\n"
         << "-pointer " << alignof(char*) << "\n"
         << "-Foo " << alignof(Foo) << "\n"
         << "-Empty " << alignof(Empty) << "\n"
         << "- alignas(64) Empty64 " << alignof(Empty64) << "\n"
         << "-alignas(1) Double " << alignof(Double) << "\n";
    return a.exec();
}