rust调用DLL，编译没有问题，执行时报错，感觉是内存问题，但不知道哪里错了，请高手指教，谢谢！

dll中函数原型： long iReadCardBas(int iType, char* pOutInfo)

调用方法：

extern crate libc;
extern crate libloading;

use libc::*;
use libloading::{Library, Symbol};

type IReadCardBas = unsafe fn(i32, *mut u8) -> i32;

pub fn readcardinfo(itype: i32) -> String {
    let lib = Library::new("./SSCardDriver.dll").unwrap();
    unsafe {
        let mut outinfo = [0u8; 1024];
        let poutinfo = outinfo.as_mut_ptr();
        let func: Symbol<IReadCardBas> = lib.get(b"iReadCardBas").unwrap();
        let i = func(itype, poutinfo);
        if i == 0 {
            let sv = &outinfo[0..strlen(outinfo.as_ptr() as *const i8)];
            String::from_utf8_unchecked(sv.to_vec())
        } else {
            i.to_string()
        }
    }
}

错误信息：

    Finished test [unoptimized + debuginfo] target(s) in 0.01s
     Running target\i686-pc-windows-msvc\debug\deps\sbkdriver-34fc5f2476b98ac9.exe

running 1 test
error: test failed, to rerun pass '--lib'

Caused by:
  process didn't exit successfully: `D:\Codes\rust\sbkdriver\target\i686-pc-windows-msvc\debug\deps\sbkdriver-34fc5f2476b98ac9.exe` (exit code: 0xc0000005, STATUS_ACCESS_VIOLATION)