title: Is there a tool for generating C headers from Rust modules?
body: <p>If you write a Rust library and you want to call it from C, you have to mark all the export functions with extern C and make sure everything uses the C ABI. But then you also have to write a header file by hand to include in your C code, and manually ensure that it is consistent with the Rust definitions, or Bad Things will happen. This seems both dangerous and tedious.</p>
  
  <p>Is there a tool for generating C headers from Rust code? I've seen bindings that go the other way, for using C from Rust, and that's actually a harder problem!</p>