I believe I found a bug in Semantic, when 2 namespaces are nested like this in a header file :
namespace animals
   namespace cats
        // some classes

and then used in a cpp file like this :
using namespace animals;
using namespace cats;

Semantic doesn't understand that namespace cats is actually animals::cats, and it doesn't find any of the objects defined there.

After browsing Semantic's source code I found function semantic-calculate-scope, which doesn't fill the classes of cats in the :fullscope slot.

I tried overriding this function and adding the classes myself ; then semantic-ia-fast-jump and semantic-complete-symbol started to work on those.

Is there a configuration of Semantic I missed out or is it a real bug ?