Rust modules inside RIOT

Currently, I am trying to figure out how to implement a network protocol module in Rust on RIOT, but I still can’t know how I can put the Rust code into the C application code. Specifically, my current setup is like this:

  • I have a rcoap.h header file in the sys/include that defines:
void hello(void);
  • The module sys/rcoap:
    • Makefile:
include $(RIOTBASE)/Makefile.base

include $(RIOTMAKE)/

USEMODULE += rust_riotmodules

# No need to set the Cargo features enabled through the general pseudomodules:
# They're added to the crate in no matter whether it's
# building the rust_riotmodules_standalone top level crate or an application
# crate.

include $(RIOTMAKE)/
  • Code:

pub extern "C" fn hello() {
    riot_wrappers::println!("Hello world");
  • And a C application examples/hello-rcoap like this:
#include <stdio.h>
#include "rcoap.h"

int main(void)

    return 0;
  • I try to compile the application, but I still get the errors:
/usr/bin/ld: /media/duich1605/extras/projects/iot/rcoap/RIOT/examples/hello-rcoap/bin/native/application_hello-world/main.o: in function `main':
/media/duich1605/extras/projects/iot/rcoap/RIOT/examples/hello-rcoap/main.c:27: undefined reference to `hello'
collect2: error: ld returned 1 exit status

I have read rust modules inside the RIOT directory, but still can’t figure how I can link the header file and the rust source code together? Is there any specific configuration that allows me to do this?