What other language would you use for an open-source project, if you wanted C-level performance and the maximum number of contributors? I think choosing D or Ru

What other language would you use for an open-source project, if you wanted C-level performance and the maximum number of contributors? I think choosing D or Rust (or Go, but with it we'd already be a bit further from C-lever performance already) would seriously reduce the number of potential contributors. It's not a rhetoric question, I'd really want an answer as I'm contemplating the choice of language for and open-source project. And C++ is out because everybody has their own way of writing code in it and it's just too much work to police people into following a strong-handed style guide... ...so what would be left for an open source projects that has the goal of being able to squeeze the maximum performance without having to drop into a lower level language for the most performance sensitive parts?