Simulating nullptr & nullptr_t for GCC 4.5.3 - c++

Question

Due to some legacy reasons I'm stuck with MIPS-GCC 4.5.3. But the code which I'm trying to compile uses C++11 nullptr & nullptr_t heavily which is a missing feature in GCC 4.5.3.
After some googling & getting into the usage I ended up creating a nullptr wrapper like below, but unfortunately it doesn't satisfy some of the use case,
namespace std {
class nullptr_t {
public:
nullptr_t() { }
template <typename T> nullptr_t(const T&) { }
template <class T> nullptr_t(const T*) { }
template <class T> nullptr_t(T*) { }
template <typename T, typename U> nullptr_t(const typename T::U*) { }
template<typename T> operator T*() { return 0;}
template<typename T1, typename T2> operator T1 T2::*() { return 0; }
operator int() const { return 0; }
operator unsigned() const { return 0; }
operator bool() const { return false; }
bool operator == (unsigned i) const { return i == 0; }
bool operator != (unsigned i) const { return i != 0; }
bool operator !() const { return true; }
} nullptr = {};
}
using std::nullptr;
template<typename T> struct DummyContainer {
DummyContainer(T* ptr)
: m_ptr(ptr) { }
DummyContainer(std::nullptr_t)
: m_ptr(0) { }
T& operator = (std::nullptr_t) { return *m_ptr; }
private: T* m_ptr;
};
int main(int argc, char** argv)
{
const char* case1 = nullptr; // working
// I think for below case std::unique_ptr has to be modified to take std::nullptr_t during construction & operator =
std::unique_ptr<char> case2 = nullptr; // not working.
DummyContainer<char> case3 = nullptr; // working
case3 = nullptr; //working
unsigned* case4 = argc > 1 ? nullptr : nullptr; //works
unsigned* case5 = argc > 2 ? (unsigned*)0 : nullptr; //not working. (It is the major issue as of now)
return 0;
}
Here the major case is unsigned* case5 = argc > 2 ? (unsigned*)0 : nullptr;
IDEONE snapshot : http://ideone.com/m1mhtB
(Thanks to http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2431.pdf)
Any tips/suggestions will be appreciated :)
(Note: please avoid answers like upgrade your gcc)

Answer 1

Below solution seems to be working,
Original source: https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit/Source/wtf/NullPtr.h
namespace std {
class nullptr_t {
public:
// Required in order to create const nullptr_t objects without an
// explicit initializer in GCC 4.5, a la:
//
// const std::nullptr_t nullptr;
nullptr_t() { }
// Make nullptr convertible to any pointer type.
template<typename T> operator T*() const { return 0; }
// Make nullptr convertible to any member pointer type.
template<typename C, typename T> operator T C::*() { return 0; }
private:
// Do not allow taking the address of nullptr.
void operator&();
};
}
const std::nullptr_t nullptr;
IDEOne: http://ideone.com/Bnp6th