Triangle
        { 0.0,  1.0, 0.0},
        {-1.0, -1.0, 0.0},
        { 1.0, -1.0, 0.0}
Point
        { 0.0, 1.0 + 5e-12, 0.0}

This point lies in the plane of the triangle, therefore d == 0 and sign is set to 1.e10 by the original code. This results in the distance being calculated as 0.05 (1e10 * 5e-12). This is clearly wrong.