how to call C++ apt methods in C gui

Hi, the gui is done in "plain" C, so how do I "call" the methods from C++ apt (list, update, upgrade ...)

doing some searchs I found:
https://stackoverflow.com/questions/2744181/how-to-call-c-function-from-c
Tried "The C++ code of class AAA - Pure C++, I don't modify it:" (2nd answer) and seems to work, but don't know if I'm doing the hard way.
So if you can help somehow I'll be glad.

Here is my test: https://github.com/javierdlr/apt-os4/commit/26eb4b7694716f98e130e07b7118af943f6ec9b1

I found too this one, but haven't read it yet:
https://isocpp.org/wiki/faq/mixing-c-and-cpp#call-cpp