读取、写入和AS_字节函数

在第11章的编程和原则中，作者给出了以下代码来演示二进制：

#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<cmath>


#include<sstream>
#include <fstream>
#include <iomanip>
using namespace std;
    template<class T>
    char* as_bytes(T& i) // treat a T as a sequence of bytes
{
    void* addr = &i; // get the address of the first byte
    // of memory used to store the object
    return static_cast<char*>(addr); // treat that memory as bytes
}
int main()
{
    // open an istream for binary input from a file:
    cout << "Please enter input file name\n";
    string iname;
    cin >> iname;
    ifstream ifs {iname,ios_base::binary}; // note: stream mode
    // binary tells the stream not to try anything clever with the bytes
    // open an ostream for binary output to a file:
    cout << "Please enter output file name\n";
    string oname;
    cin >> oname;
    ofstream ofs {oname,ios_base::binary}; // note: stream mode
    // binary tells the stream not to try anything clever with the bytes

    vector<int> v;

    // read from binary file:
    for(int x; ifs.read(as_bytes(x),sizeof(int)); ) // note: reading bytes
        v.push_back(x);
    // . . . do something with v . . .
    // write to binary file:
    for(int x : v)
        ofs.write(as_bytes(x),sizeof(int)); // note: writing bytes
    return 0;
}

我有一些问题：

为什么他要读取一个未初始化变量的地址？ 为什么程序在文件末尾切断了一些字符？ 为什么以及如何将未初始化的变量推送到向量中？