Inline functions can't be called with FFI

Hello,
I am trying to use Pipewire from Rust via its Foreign Function Interface.
Unfortunately, there are some functions like pw_core_get_registry that I can not call because they are in the header and therefore not in the .so to link to.
As they also use a lot of deeply nested macros, they seem pretty annoying to reimplement in another language.
Is there a reason these functions are marked inline and in the header, or would you consider moving them into a source file?