为什么我的班级的规模为零？如何确保不同的对象具有不同的地址？

问题描述

我创建了一个类，但它的大小为零。现在，如何确保所有对象具有不同的地址？ （我们知道，空类的大小非零。）

I created a class but its size is zero. Now, how can I be sure that all objects have different addresses? (As we know, empty classes have a non-zero size.)

#include<cstdio>
#include<iostream>
using namespace std;
class Test
{
    int arr[0];//Why is the sizezero?
};

int main()
{
    Test a,b;  
      cout <<"size of class"<<sizeof(a)<<endl;
       if (&a == &b)// now how we ensure about address of objects ?
          cout << "impossible " << endl;
       else
          cout << "Fine " << endl;//Why isn't the address the same? 

        return 0;
}        

推荐答案

C ++不允许在任何上下文中大小为 0 的数组声明。但是，即使你使你的类定义完全空， sizeof 仍然需要评估为非零值。

Your class definition is illegal. C++ does not allow array declarations with size 0 in any context. But even if you make your class definition completely empty, the sizeof is still required to evaluate to a non-zero value.

换句话说，如果你的编译器接受类定义，并将上面的 sizeof 归零，那么该编译器超出了标准C ++语言的范围。它必须是与标准C ++无关的编译器扩展。

In other words, if your compiler accepts the class definition and evaluates the above sizeof to zero, that compiler is going outside of scope of standard C++ language. It must be a compiler extension that has no relation to standard C++.

因此，在这种情况下，唯一的答案是为什么问题是：因为这是它的方式是在你的编译器中实现的。

So, the only answer to the "why" question in this case is: because that's the way it is implemented in your compiler.

我没有看到它与确保不同的对象具有不同的地址有关。无论对象大小是否为零，编译器都可以轻松实施此操作。

I don't see what it all has to do with ensuring that different objects have different addresses. The compiler can easily enforce this regardless of whether object size is zero or not.

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