Method make_nt

include/wasm.hh:155–159

  }

  static auto make_nt(std::string s) -> vec<char> {
    auto v = vec(s.length() + 1);
    if (v) std::strcpy(v.get(), s.data());
    return v;
  }

  // TODO(mvsc): MVSC requires this special case:
  static auto make() -> vec {