consume COM library from C# to rust

Question




I want to rewrite my project from C# to rust.
But I stuck in Segmentation Fault situation.
I think I misunderstood something, or meet crate limitation, hope for some help.


Rust Code






* find interface UUID
regedit capture

* find CLSID
regedit capture

* other id (I'm not sure shall we need it)
regedit capture



use windows::core::{GUID, HRESULT, IUnknown, IUnknown_Vtbl, interface};
use windows::Win32::System::Com::{
COINIT_APARTMENTTHREADED,
CLSCTX_ALL,
CoInitializeEx,
CoCreateInstance};

// define interface
#[interface("288EFDEC-3CF0-4F6C-8473-4E4CD47A93C7")]
unsafe trait Inhicshisx: IUnknown {
fn VPNGetRandomX(&self) -> HRESULT;
}

fn run() -> Result {
unsafe {
// 2F5AECD5-B5CD-41E1-8265-E2F6AA4548CB
const CLSID: GUID = GUID {
data1: 0x2F5AECD5,
data2: 0xB5CD,
data3: 0x41E1,
data4: [0x82, 0x65, 0xE2, 0xF6, 0xAA, 0x45, 0x48, 0xCB],
};

// initialize runtime
CoInitializeEx(Some(ptr::null_mut() as *mut c_void), COINIT_APARTMENTTHREADED)?;

// create COM object
let hisx: Inhicshisx = CoCreateInstance(&CLSID, None, CLSCTX_ALL)?;

// call object function
let value = hisx.VPNGetRandomX();
}

Ok(())
}



C# Part






* add a reference
regedit capture
* call function




using CSHISXLib;
string MyStr0;
CSHISXLib.Inhicshisx CSHISXLibObj = new CSHISXLib.nhicshisx();
MyStr0 = CSHISXLibObj.VPNGetRandomX();
Console.WriteLine(MyStr0);




* It works.






Update information




According to @IInspectable help, I can generate interface by oleview.exe tool.



* generated interface




[
odl,
uuid(288EFDEC-3CF0-4F6C-8473-4E4CD47A93C7),
helpstring("Inhicshisx Interface"),
dual,
oleautomation
]
interface Inhicshisx : IDispatch {
[id(0x00000001), helpstring("method VPNGetRandomX")]
HRESULT VPNGetRandomX([out, retval] BSTR* strRandom);
[id(0x00000002), helpstring("method VPNH_SignX")]
HRESULT VPNH_SignX(
[in] BSTR strRandom,
[in, optional, defaultvalue("")] BSTR strCardType,
[in, optional, defaultvalue("")] BSTR strServiceType,
[out, retval] BSTR* strRet);
}




* Rust code change




use windows::core::BSTR;

#[interface("288EFDEC-3CF0-4F6C-8473-4E4CD47A93C7")]
unsafe trait Inhicshisx: IDispatch {
fn VPNGetRandomX(&self) -> BSTR;
fn VPNH_SignX(&self, *mut BSTR, *mut BSTR, *mut BSTR) -> BSTR;
}



But it still cause Segmentation Fault, hope some advice 🙏