Negative NaN is not a NaN?

Question

While writing some test cases, and some of the tests check for the result of a NaN.

I tried using std::isnan but the assert failes:

Asse         


        

Answer 1

This is based off the wikipedia article posted in the comments. Note that it's entirely untested -- it should give you an idea of something you can do though.

bool reallyIsNan(float x)
{
    //Assumes sizeof(float) == sizeof(int)
    int intIzedX = *(reinterpret_cast(&x));
    int clearAllNonNanBits = intIzedX & 0x7F800000;
    return clearAllNonNanBits == 0x7F800000;
}

EDIT: I really think you should consider filing a bug with the GLibc guys on that one though.