C++语言中的一些小点

#include <iostream>
using namespace std;
void func(int *x) {
  cout << __PRETTY_FUNCTION__ << endl;
  cout << x << endl;
}
void func(int x) {
  cout << __PRETTY_FUNCTION__ << endl;
  cout << x << endl;
}
int main() {
  //func(NULL); //编译报错，因为NULL即代表0又代表空地址
  func(nullptr);  //nullptr代表空地址
  return 0;
}

int main() {
  int a = 10;
  int &b = a; //左值：有内存、有名字  右值：没名字、没内存
  //int &&c = a;//无法将左值绑定到右值引用上
  /*
  int tmp = 20;
  const int &c = tmp;
  */
  const int &c = 20;
  /*
  int tmp = 20;
  int &&d = tmp;
  */
  int &&d = 20;//可以把右值绑定到右值引用上
  //int &&f = d;//一个右值引用变量，本身是一个左值，无法绑定到右值引用上
  int &f = d;
  return 0;
}

auto_ptr<int> ptr1(new int);
auto_ptr<int> ptr2(ptr1);
*ptr2 = 20;
cout << *ptr1 << endl;//非法

//auto_ptr源码
auto_ptr(_Myt& _Right) _THROW0()
    : _Myptr(_Right.release())
    { // construct by assuming pointer from _Right auto_ptr
    }
_Ty *release() _THROW0()
    { // return wrapped pointer and give up ownership
    _Ty *_Tmp = _Myptr;
    _Myptr = 0;
    return (_Tmp);
    }

scoped_ptr<const scoped_ptr<T>&> = delete;
scoped_ptr<T>& operator=(const scoped_ptr<T>&) = delete;

/*
  unique_ptr(const unique_ptr<T>&) = delete;
  unique_ptr<T>& operator=(const unique_ptr<T>&) = delete;
  unique_ptr(unique_ptr<T> &&src);
  unique_ptr(T)& operator=(unique_ptr<T> &&src)
  tempate<typename T>
  unique_ptr<T> getSmartPtr()
  {
    unique_ptr<T> ptr(new T());
    return ptr;
  }
  unique_ptr<int> ptr1 = getSmartPtr<int>();
  ptr1 = getSmartPtr<int>();
  */
  unique_ptr<int> p1(new int);
  unique_ptr<int> p2(std::move(p1));