VC2005的返回值优化

先看一段代码：
#include
using namespace std;

class foo{
public:
    foo() { cout<<"default constructor calling."<    foo( const foo& p ) { cout<<"copy constructor calling."<    foo& operator=( const foo& p ) { cout<<"assigned operator calling."<    ~foo() { cout<<"destructor calling."<};

foo bar()
{
    foo t;
    return t;
}

int main(void)                                           
{
    {
        foo a = bar();
        // gcc3.4.2中
        //   default constructor calling.
        //   destructor calling.
        // VC2005（77626-009-0000007-41837）中
        //   default constructor calling.
        //   copy constructor calling.
        //   destructor calling.
        //   destructor calling.
    }
    cout << "--------" << endl;
    {
        foo b;
        b = bar();
        // gcc3.4.2中
        //   default constructor calling.
        //   default constructor calling.
        //   assigned operator calling.
        //   destructor calling.
        //   destructor calling.
        // VC2005（77626-009-0000007-41837）中
        //   default constructor calling.
        //   default constructor calling.
        //   copy constructor calling.
        //   destructor calling.
        //   assigned operator calling.
        //   destructor calling.
        //   destructor calling.
    }

    return 0;
}

问题就在
foo bar()
{
    foo t;
    return t;
}
中，return t 时调不调用拷贝构造函数？ 更一般的说，在最近的C++标准中，具名对象（且这个对象有side effects用途时）返回时应不应该优化？

争论太多了，留在这里“秋后问斩”^_^