I am trying to compile my rust code into staticlib and I try to write function for use in C# programming langue. This is first time I try it.

I think I only need to export one function for C# code to use my lib, so I wrote this funtion

type Callback = extern "C" fn(u64);

#[no_mangle]
pub extern "C" fn laz2xyz(config_name: *const u8, length: usize, callback: Callback) {
    let config_name = unsafe { std::slice::from_raw_parts(config_name, length) };
    let config_name = String::from_utf8_lossy(config_name).to_string();
    let config_name = std::path::PathBuf::from(config_name);
    let xyz = ToXYZ::build(config_name).expect("Failed to initialize ToXYZ");

    xyz.run(move |progress| {
        callback(progress);
    })
    .expect("Failed to process files");
}

This function needs to get path to file and callback function. Callback function will report progress of execution to caller.

But I get this error

|
5 | #[no_mangle]
| ^^^^^^^^^ usage of unsafe attribute
|
help: wrap the attribute in unsafe(...)
|
5 | #[unsafe(no_mangle)]
| +++++++ +

But I don't understand why. I never seen #[unsafe(no_mangle)]. All code on internet I seen was using #[no_mangle]

If I change as sugested I get diffirent error

error: this public function might dereference a raw pointer but is not marked unsafe
--> src\exports\laz2xyz.rs:7:59
|
7 | let config_name = unsafe { std::slice::from_raw_parts(config_name, length) };
|

But this function is inside unsafe block? config_name is marked as problem

But code does compile. I am using Visual Studio Code
Can this error be false positive?

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