Hi! I have created a sample code to show my "-nan" problem. It is not the cleanest code :-), but I do not want to delete a lot from the problematic files.
I realized, that the problem appears only when the compiler "Optimize" flag is enabled. I use Derelict and Codeblocks. You can also download the code here: http://compaq.iit.uni-miskolc.hu/d/SampleBug.zip Thanks for reply.
