创建一个rust共享库,该库将函数指针的结构返回给c主程序

我想在没有太多运气的情况下把锈粘在NBDKIT上。我要做一个 .so 文件,这很简单。这个 所以 文件必须有一个名为 plugin_init ,也很简单。但是,此函数必须返回指向c兼容的指针 struct 包含字符串和函数指针的混合(C主程序稍后将调用)。

API是: https://github.com/libguestfs/nbdkit/blob/409ce4c9238a84ede6688423b20d5f706067834b/include/nbdkit-plugin.h#L53

我想到了:

#[repr(C)]
pub struct NBDKitPlugin {
    _struct_size: uint64_t,
    _api_version: c_int,
    _thread_model: c_int,

    name: *const c_char,
    longname: Option<*const c_char>,
    version: Option<*const c_char>,
    description: Option<*const c_char>,

    load: Option<extern fn ()>,
    unload: Option<extern fn ()>,

    config: Option<extern fn ()>, // XXX
    config_complete: Option<extern fn () -> c_int>,
    config_help: Option<*const c_char>,

    open: extern fn (c_int) -> *mut c_void,
    close: Option<extern fn (*mut c_void)>,
}

和A 小精灵 功能:

extern fn hello_load () {
    println! ("hello this is the load method");
}

struct MyHandle {
}

extern fn hello_open (readonly: c_int) -> *mut c_void {
    println! ("hello, this is the open method");
    let mut h = MyHandle {};
    let vp: *mut c_void = &mut h as *mut _ as *mut c_void;
    return vp;
}

#[no_mangle]
pub extern fn plugin_init () -> *const NBDKitPlugin {
    println! ("hello from the plugin");

    let plugin = Box::new (NBDKitPlugin {
        _struct_size: mem::size_of::<NBDKitPlugin>() as uint64_t,
        _api_version: 2,
        _thread_model: 3,
        name: CString::new("hello").unwrap().into_raw(),
        longname: None,
        version: None,
        description: None,
        load: Some (hello_load),
        unload: None,
        config: None,
        config_complete: None,
        config_help: Some (CString::new("my config_help here").unwrap().into_raw()),
        open: hello_open,
        close: None,
    });

    return Box::into_raw(plugin);
}

除了泄漏内存,这部分工作。整数和字符串是从c ok中看到的。但是函数指针根本不起作用。它们完全是假的,似乎比原始指针占用更多的空间,所以我想我暴露了一个“胖”锈指针。

关于这个主题,我几乎找不到什么文档。帮助。