Debugged program stops when adding breakpoint

1. Create a new Qt GUI Application project.
2. In main.cpp, replace the last line:

       return a.exec();
   

   by:

       int r = a.exec();
       return r;
   

3. Run the project in gdb debugger.
4. While the project is running, set a breakpoint in the line containing the return statement.
   Execution of the the project will stop.

The execution of a debugged program should not stop until a breakpoint is actually being hit.