Thank you Eric for your help!

adding the marked line in the project definition (in ~/.emacs file) did the trick:

(setq test-project
      (ede-cpp-root-project "test"
                            :file "/projects/test/test.cpp"
                            :include-path '("/")
                        :spp-table '( ("PROTO" . "1") )
                            ))

I am sure I have tried this before posting here but it only worked after deleting the ~/.semanticdb directory.
Maybe it was created before adding the :spp-table customization and no longer took into consideration my modified project?

Having a global ".semanticdb" directory (shared probably for multiple projects) can cause any problems like the one I described earlier?
Is it possible to have separate ".semanticdb" directories for each project defined?
Can one project share many ".semanticdb" dirs?

Where can I find more documentation about how this "database" can be configured?

Thank you again!
Bogdan Graur