GNU Profiler Blank Profile

I'm trying to learn profiling with GNU gprof and I just tried to get the same results as in this tutorial using exactly the same code and applying the same steps: http://www.ibm.com/developerworks/library/ l-gnuprof.html

However, when I try to achieve a flat profile gprof example1 gmon.out -p

, I don't see anything. It says:

Each sample is considered equal to 0.01 seconds. time does not accumulate

and I see an empty flat profile. And when I try to get the call graph I get

gprof: call-graph data missing in gmon.out file

I am using Ubuntu in a virtual machine. Could a reason for using VirtualBox?