I hope one does not need to write the signatures manually and tweak the cxx generator, for detecting flags, types and the like just to get it properly working. If that's the case, then that would be tons of maintenance and more trouble than its worth for a more complex C++ codebase.

Best to make that a first party feature built into the language compiler and have it do the majority of the work automatically rather than manually define the C++ types, functions, etc using a third party library.