Arduino is almost all plain C, not C++. It is written C++ style., but it is usually plain C.
C++ is way too heavy to use at all.
The base wiring library is plain C, but most other libraries seem like C++ (except if
class X : public Y is a valid C construct). I'm no expert in C/C++, let alone the differences between the two, but I did spot use of inheritance and using-declaration (I had to search for that definition):
class TwoWire : public Stream
{
...
using Print::write;
};
I only want to point out that the question to get access to available functionality in Arduino is reasonable, I just think it will be a lot more difficult that linking to a plain C library.