hello.c

#include <stdio.h>
#include "pants.h"

int
main() {
    printf("Hello World\n");
    pants();
}

hello.rs

extern {
    fn pants();
}

fn main() {
    println!("Hello World");
    unsafe { pants(); }
}

pants.c

#include <stdio.h>
#include "pants.h"
#include "shirt.h"
#include "socks.h"

inline void
pants() {
    printf("Hello Pants\n");
    shirt();
    socks();
}

pants.h

//__attribute__((always_inline))
void pants();

shirt.h

#include <stdio.h>

//__attribute__((always_inline))
static inline void shirt() {
   printf("Hello Shirt\n");
}

socks.c

#include <stdio.h>
#include "socks.h"

inline void
socks() {
    printf("Hello Socks\n");
}

socks.h

//__attribute__((always_inline))
void socks();