omp_get_num_procs() doesn't returns all processor

Hi, I have an application in c++ that is using Qt libraries.

When I call omp_get_num_procs() from any part of the program, doesn't return the maximum number of processors that my machine has, so all the threads are distributed in the available processors.

But, If I call  omp_get_num_procs() from main.cpp, before to QApplication constructor, I obtain all processor and the thread are distributed in all processors that the machine has.

I've tried to find out what exactly does  omp_get_num_procs() that is changing the available processors fro the application.

Best Regards,

Leonardo