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Lachlan Partington · Guest

I noticed a difference in how overloaded operators are resolved
between Visual C++ 6 and VC 2003 in a particular situation involving
operator overloading, namespaces and inheritance. The new behaviour
in VC 2003 is somewhat perplexing.

Is anyone able to explain from a language perspective why the
following example is behaving correctly, or how it should be behaving
if incorrect?

namespace ns
{
struct B
{
B& operator<<(const void* v) // <----- 1
{
return *this;
}
};

B& operator<<(B& b, const char* s) // <----- 2
{
return b;
}
}

//using namespace ns; // <----- 3

struct D : public ns::B
{
D()
{
// If using declaration at 3 is defined,
// calls 2 otherwise calls 1
*this << "test";
}
};

void f()
{
D d;

// Always calls 2 regardless of whether using declaration
// at 3 is defined.
d << "test";
}

I would have thought that operator<< at 2 should always be called
(that is certainly the intended behaviour) regardless of whether the
call is made from a member function of D or not.

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