[C++-sig] why does the "shared_ptr<X> const&" silently become 0xCCCCCCCC

[ZaeX]

Hi, All:

I used a "shared_ptr<A> const&" to store a ref of A in B;
Well, the constructor of B seems ok, the share_ptr<A> seems to be well
initialized;
but after the constructor, I found the the pointer silently become
0xCCCCCCCC

///////////////////////////////////// below are the simplified class
definitions
class A{};

class B
{
private:
   shared_ptr<A> const& m_ptr;
public:
   B(shared_ptr<A> const& ptr):m_ptr(ptr) {cout<<m_ptr.get()<<endl;}
   void ShowPtr(cout<<m_ptr.get()<<endl;)
}
/////////////////////////////////// below are my exporting code

    class_<B, auto_ptr<B> >("B",  init<shared_ptr<A> const&>())
       .def("ShowPtr", &B::ShowPtr)
    ;
    class_<A, shared_ptr<A>, noncopyable >("A")
    ;
/////////////////////////////////// below are python code
 a = A()
 b = B(a)  #cout output the ptr of a
 b.ShowPtr()  #cout output 0xCCCCCCCC

============================================
I'm quite confused by the behaviors here. Could you tell me what goes wrong?

-- 
Time is mana, we must hurry
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