Seems like the conversion glitch could be happening at several places.

Maybe the initial assignment of float foo needs a cast. MSVC warns about loss of precision in such cases -- maybe it's serious. :)

float foo = (float)nv;
[download]

As a workaround, perhaps you could truncate the initial assignment of the double:

double nv = (float)(2.0 / 3);
[download]

Lastly, maybe something is awry in the conversions that are being done during the comparison -- like it's ignoring your cast. It's a stab in the dark, but maybe a hack like this would get it to pay attention:

static __inline int
compare_truncated_double_to_float(double d, float f)
{
    float truncted_double = (float)d;
    if (f == truncated_double) { return 1; }
    else                       { return 0; }
}
[download]

PS: This is relevant to the work I do ensuring Windows compatibility for my XS distros.