ffi.c

#include <assert.h>
#include <stdint.h>
#include <stdio.h>

struct CXCursor {
    unsigned kind;
    int xdata;
    void *data[3];
};

struct CXCursor mk_cxcursor(void) {
    struct CXCursor x = {1, 2, {(void*)3, (void*)4, (void*)5}};
    return x;
}

typedef unsigned (*Visitor)(struct CXCursor c1, struct CXCursor c2, void *data);

unsigned visit_children(struct CXCursor c, Visitor f, void *data) {
    assert(c.kind == 6);
    assert(c.xdata == 7);
    assert((uintptr_t)c.data[0] == 8);
    assert((uintptr_t)c.data[1] == 9);
    assert((uintptr_t)c.data[2] == 10);
    assert((uintptr_t)data == 0x12345678);

    struct CXCursor a = {11, 12, {(void*)13, (void*)14, (void*)15}};
    struct CXCursor b = {16, 17, {(void*)18, (void*)19, (void*)20}};
    unsigned r = f(a, b, (void*)0x90abcdef);
    assert(r == 0x11111111);
    return 0xffffffff;
}

Makefile

RUSTC = rustc
CC = gcc
AR = ar

test: test.rs ffi.o
	$(RUSTC) $< -L . -o $@

ffi.o: ffi.c
	$(CC) -fPIC -c $< -o $@

clean:
	$(RM) -f test ffi.o

.PHONY: clean

test.rs

use std::libc::*;

pub struct CXCursor {
    kind: c_uint,
    xdata: c_int,
    data: [*c_void, ..3u],
}

type Visitor = extern "C" fn(a: CXCursor, b: CXCursor, x: *c_void) -> c_uint;

#[link_args="ffi.o"]
extern "C" {
    pub fn mk_cxcursor() -> CXCursor;
    pub fn visit_children(c: CXCursor, f: Visitor, x: *c_void) -> c_uint;
}

extern fn cb(a: CXCursor, b: CXCursor, x: *c_void) -> c_uint {
    assert!(a.kind == 11);
    assert!(a.xdata == 12);
    assert!(a.data[0] as c_uint == 13);
    assert!(a.data[1] as c_uint == 14);
    assert!(a.data[2] as c_uint == 15);

    assert!(b.kind == 16);
    assert!(b.xdata == 17);
    assert!(b.data[0] as c_uint == 18);
    assert!(b.data[1] as c_uint == 19);
    assert!(b.data[2] as c_uint == 20);
    
    assert!(x as c_uint == 0x90abcdef);

    return 0x11111111;
}

#[fixed_stack_segment]
fn main() {
    unsafe {
        let c = mk_cxcursor();
        assert!(c.kind == 1);
        assert!(c.xdata == 2);
        assert!(c.data[0] as c_uint == 3);
        assert!(c.data[1] as c_uint == 4);
        assert!(c.data[2] as c_uint == 5);

        let c = CXCursor {
            kind: 6,
            xdata: 7,
            data: [8 as *c_void, 9 as *c_void, 10 as *c_void]
        };
        let r = visit_children(c, cb, 0x12345678 as *c_void);
        assert!(r == 0xffffffff);
    }
}