For 1. I'd still recommend using C++ (or D or Rust) and wrapping it in a C interface because these languages are just better at handling complexity compared to

For 1. I'd still recommend using C++ (or D or Rust) and wrapping it in a C interface because these languages are just better at handling complexity compared to C. Usually one has some idea what the target platforms are, and writing C code that runs everywhere is pretty hard anyway.