C++ interop , how to use fltk c++ library

[devosalain]

A small working c++ interop at,
https://gitlab.com/alaindevos/other_lang/-/tree/main/5_carbon/e?ref_type=heads

But now I want to make a carbon-lang GUI program using fltk library.
No idea where to start ?
In c++ it's easy just do a g++ "-lfltk" and include header file.
So i don't want to import all fltk library cpp files but just import the header file and then link explicitly

[devosalain]

ok, after hours of trying it works.
See,
https://gitlab.com/alaindevos/other_lang/-/tree/main/5_carbon/e?ref_type=heads

Only on exit,
free(): invalid pointer
./build: regel 9: 198131 Afgebroken (geheugendump gemaakt) ./main