c – 小的ref-counting缓冲类中的内存损坏

#include <algorithm>

template<typename T>
struct buffer
{
    // create a buffer of length n
    buffer(unsigned n) : rc(*(new unsigned(1))),data(new T[n]) { }

    buffer(const buffer<T> & rhs) : rc(++rhs.rc),data(rhs.data) { }

    buffer<T>& operator=(buffer<T> rhs)
    {
        std::swap(rc,rhs.rc);
        std::swap(data,rhs.data);
        return *this;
    }

    ~buffer()
    {
        if (--rc == 0) {
            delete [] data;
            delete (&rc);
        }
    }

private:
    mutable unsigned & rc;
    T * data;
};


int main() {
    typedef buffer<int> numbers;
    numbers n1(10);
    numbers n2(20);
    numbers n3(30);
    n1 = n2 = n3 = n2;
}

我没有看到代码有任何问题.但Visual Studio和valgrind抱怨内存损坏.

我现在盯着这段代码已经太久了.谁能发现错误？