C：对象切片和异常

但是现在我正在尝试进行实验,但是在按值捕获时我找不到切片的示例.切片的常规场景(不是例外)是这样的：

Derived d1;
Derived d2;
Base& b1 = d1;
Base& b2 = d2;
b1 = b2;

在最后一行中调用Base的赋值运算符,它只复制Derived对象的Base部分.因此,b1的基础部分是从d2复制的,而b1的派生部分是从d2复制的.坏.

但是,当按价值捕获异常时,这怎么会发生？

我尝试了这个代码(同时使用：g和Sun CC编译器)：

struct Base
{
    virtual void print() const
    {
        cout << "{ Base: " << m << " }" << endl;
    }

    Base(int _m = 0) : m(_m) {}

    int m;
};

struct Derived : Base
{
    Derived(int _m = 0,int _n = 0) : Base(_m),n(_n) {}

    void print() const
    {
        cout << "{ Base: " << m << ",Derived: " << n << " }" << endl;
    }

    int n;
};

int main()
{
    try
    {
        try
        {
            throw Derived(3,300);
        }
        catch(Base x)
        {
            cout << "Inner catch: ";
            x.print();
            throw;
        }
    }
    catch(Derived y)
    {
        cout << "Outer catch: ";
        y.print();
    }    
}

输出是：

Inner catch: { Base: 3 }
Outer catch: { Base: 3,Derived: 300 }

所以我抛出Derived异常,捕获它的Base BY VALUE并重新抛出,然后捕获Derived BY VALUE并且一切正常,没有任何切片.
那个怎么样？

并且有人可以提供捕获BY VALUE时的切片示例吗？