but pybind11 makes interop so much more trivial between C++ and python. passing std::vector, std::string, custom types, etc... it all just works and with much less errors possible than the C Python API. Why would you subject yourself to it ?

Pybind11 is for "C++11" -- I assume there's no special magic in later revisions that would cause anything to silently fail (i.e. fail at runtime)?

Works just fine here with c++20. it even automatically converts std::variant and std::optional

    extern "C" {
       // my C++ code

    }

Big deal.

Problem is, not many C++ libraries would care to do this in the first place.

The point was writing a library specially to be called from Python via the C ABI.

By the way, clang and Visual C runtime libraries are actually implemented in C++ with extern "C".