"Merging" your replies I have been able to solve the problem :-).
Sergey: Yes, you are right. My mistake. However the problem was still present.
Jeremy: Enabling the newlib-nano with floating support (and enabling some heap!! Probably this is the core of the problem) solved the issue! Thank you.
As a side question, how did you see the heap usage?
Karol: I had 1k of stack in the dummy project. But thank you for the "main stack" reducton trick!