Rust如何将struct传回C？

#[repr(C)]
pub struct MyStruct {
    field1: i32,
    field2: f64,
}

#[no_mangle]
pub extern "C" fn create_struct() -> *mut MyStruct {
    let my_struct = Box::new(MyStruct {
        field1: 42,
        field2: 3.14,
    });

    Box::into_raw(my_struct)
}

#[no_mangle]
pub extern "C" fn free_struct(ptr: *mut MyStruct) {
    unsafe {
        Box::from_raw(ptr);
    }
}

#include <stdio.h>

struct MyStruct {
    int field1;
    double field2;
};

struct MyStruct* create_struct();
void free_struct(struct MyStruct* ptr);

int main() {
    struct MyStruct* my_struct = create_struct();
    printf("Field 1: %d\n", my_struct->field1);
    printf("Field 2: %f\n", my_struct->field2);
    free_struct(my_struct);
    
    return 0;
}