C++ limit of unsigned int through template

Question

I'm using a template to convert integral types into a string representation of their binary values. I used the following:

template<typename T>
std::string ToBinary(const T& value)
{
    const std::bitset<std::numeric_limits<T>::digits + 1> bs(value);
    const std::string s(bs.to_string());

    return s;
}

It works for int but doesn't compile with unsigned int :

unsigned int buffer_u[10];
int buffer_i[10];
...
ToBinary(buffer_i[1]); //compile and works
ToBinary(buffer_u[1]); //doesn't compile -- ambiguous overload

Could you explain why?

EDIT:

Yes, I'm using VS2010

Answer 1

Not your ToBinary call is ambiguous, its the constructor call of bitset with an unsigned value. Unfortunately this is a VC++ Bug: http://connect.microsoft.com/VisualStudio/feedback/details/532897/problems-constructing-a-bitset-from-an-unsigned-long-in-the-vc-rc

Edit - Workaround:

template<>
std::string ToBinary<unsigned int>(const unsigned int& value)
{
    const std::bitset<std::numeric_limits<unsigned int>::digits> bs(static_cast<unsigned long long>(value));
    return bs.to_string();
}