C++ over-aligned memory allocation

#include <cstdio>
#include <cstdlib>
#include <new>
struct S{
    char buff[10];
};
 
int main()
{
    S* p1 = new S;
    std::printf("default-aligned address:   %p\n", static_cast<void*>(p1));
 
    S* p2 = new (std::align_val_t{32}) S;
    std::printf("over-aligned address:   %p\n", static_cast<void*>(p2));
}

new运算符支持指定按什么对齐了。over-aligned意思是超过默认的对齐的尺寸。std::max_align_t是个类型，其对齐大小为标量当中最大的那个

#include <new>
#include <iostream>
int main()
{
   std::cout << alignof(std::max_align_t) << '\n';
}

经测试，MS上的值为8。其它平台的典型值为8或16。

参考：https://ask.helplib.com/others/post_12363048

http://en.cppreference.com/w/cpp/memory/new/operator_new