Yes, it is possible to do it by just avoiding the runtime, e.g. the following works fine: #![crate_id="example_c"] #![crate_type="dylib"] #[no

Yes, it is possible to do it by just avoiding the runtime, e.g. the following works fine: #![crate_id="example_c"] #![crate_type="dylib"] #[no_mangle] pub extern fn my_rust_function(x: i32, y: i32) -> i32 { x + y } Then compiling that gives a libexample_c....so file, which can be linked against the following C: #include<stdio.h> extern int my_rust_function(int, int); int main() { printf("%d", my_rust_function(1, 2)); return 0; } printing 3. (There's no interaction with a runtime here at all.) In fact, it's even possible to "manually" start a runtime[1] inside another process (and if it's started on its own thread then I think it will work flawlessly, if not, then it might break in some corner cases). [1]: http://static.rust-lang.org/doc/master/guide-runtime.html http://static.rust-lang.org/doc/master/guide-runtime.html