关于Delphi的指针，@这些操作我实在搞不懂了

Question

typedef struct _COM_WAIT_STATUS { 
    ULONG       COMTag; 
    ULONG       COMout; 
    ULONG       COMState; 
 
} COM_WAIT_STATUS, *PCOM_WAIT_STATUS; 
typedef struct _COM_STATUS { 
    ULONG       COMState; 
    ULONG       COMCAP; 
} COM_STATUS, *PCOM_STATUS; COM_WAIT_STATUS bws;
COM_STATUS bs;
DWORD rbytes;
memset(&bws,0,sizeof(bws));
BOOL r = DeviceIoControl(
m_COM,
IOCTL_COM_QUERY_STATUS,
&bws,
sizeof(bws),
&bs,
sizeof(bs),
&rbytes,
NULL);///////////////////////////////
上面DeviceIoControl函数中的m_COM,
IOCTL_COM_QUERY_STATUS,
这两个是const的常量，暂时不用管
以上我在VC中实验是正确的，返回true
//////////////////////////////////我转为delphi如下
typeCOM_STATUS = ^PCOM_STATUS ;
PCOM_STATUS = packed record
 COMState:ulong;
 COMCAP:ulong;end;COM_WAIT_STATUS =  ^PCOM_WAIT_STATUS ;
 PCOM_WAIT_STATUS  = packed record
 COMTag:ulong;
 COMout:ulong; 
 COMState:ulong;end;
var
bws:COM_WAIT_STATUS ;
bs:COM_STATUS;
begin
 bws:= AllocMem(sizeof(@bws));
 DeviceIoControl(m_COM,IOCTL_COM_QUERY_STATUS,@bws,sizeof(bws),bws,sizeof(bs),rbytes,nil);DeviceIoControl总是返回false
结果用GetLastError查询提示--》提供给请求操作的用户缓冲区无效请问我哪里写错了吗？对于Delphi的指针不是太了解

Answer 1

bws:= AllocMem(sizeof(@bws));
其中bws是指针吧去掉@或改成
bws:= AllocMem(sizeof(PCOM_WAIT_STATUS));看看

Answer 2

DeviceIoControl(
 hDevice: THandle; 
 dwIoControlCode: DWORD; 
 lpInBuffer: Pointer;
 nInBufferSize: DWORD;
 lpOutBuffer: Pointer; 
 nOutBufferSize: DWORD;
 var lpBytesReturned: DWORD; 
lpOverlapped: POverlapped): DeviceIoControl(
    HANDLE hDevice,
    DWORD dwIoControlCode,
    LPVOID lpInBuffer,
    DWORD nInBufferSize,
    LPVOID lpOutBuffer,
    DWORD nOutBufferSize,
    LPDWORD lpBytesReturned,
    LPOVERLAPPED lpOverlapped
    );我居然发现vc和Delphi定义这个函数的参数类型不一样，注意倒数第二个参数，VC里是指针，delphi里成了dword，怪不得，不知道是不是这个原因