OnixS C++ FIX Engine  4.4.0
API Documentation
Using QuickFIX Data Dictionary

FIX Engine supports dictionaries in the QuickFIX xml format, so you can use it as it is. However, there are some details:

EngineSettings settings;
settings.dictionaryFile("QuickFixDictionary.xml");
Engine::init(settings);
Dictionary quickFixDictionary("QuickFixDictionary");
Session sessionWithQuickFixDictionary("Sender", "Target", quickFixDictionary, &listener);