Bug in Visual Studio 2010 SP1 C++ compiler by Ben171280

Please consider the following code:

int _tmain(int argc, _TCHAR* argv[])
{
    char c = 0xC3;
    char* pc = &c;
    unsigned short s = *pc;
    if(s > 0xFF)
        cout << "A" << endl;
    else
        cout << "B" << endl;
    return 0;
}

When compiled in VS 2010 SP1 in 32bit, this code does not produce the same result in debug and release mode: In debug "A" is displayed, in release "B" is displayed.

Now if I display s at the end of the function like this:

int _tmain(int argc, _TCHAR* argv[])
{
    char c = 0xC3;
    char* pc = &c;
    unsigned short s = *pc;
    if(s > 0xFF)
        cout << "A" << endl;
    else
        cout << "B" << endl;
    cout << s << endl;
    return 0;
}

The behaviour in release mode is changed and "A" is displayed.

It this a bug of the optimiser?

Ben