关于dll动态调用的问题，求救各位大虾 ( 积分: 100 )

小弟在调用xdll.DLL（exports OpenCom,SendByte,CloseCom三个函数）时老是提示错误，不只是什么原因，求教各位大虾，急！！！

源码如下：
type
TOpenCom = function(const port:dword):boolean;
TCloseCom = function():boolean;
TSendByte = function(const SendBchar;const SLen:dword):boolean;

procedure TForm1.Button1Click(Sender: TObject);
Var
LibHandle: Thandle;
OpenCom: TOpenCom;
CloseCom: TCloseCom;
SendByte: TSendByte;
Begin
LibHandle := LoadLibrary('xdll.dll');
try
if LibHandle = 0 then
raise exception.create('找不到动态库xdll.dll');

@OpenCom := GetProcAddress(LibHandle,'OpenCom');
@CloseCom := GetProcAddress(LibHandle,'CloseCom');
@SendByte := GetProcAddress(LibHandle,'SendByte')


if @SendByte=nil then exit;
begin
OpenCom(ComboBox1.itemindex+1);
SendByte(pchar('abcd'),4)
{运行到此会出错Project xxx.exe faulted with message:'access violation at 0x024acefc:read of address 0x00464000'.}
CloseCom();
end;
finally
FreeLibrary(LibHandle);
end;
end;

小弟在调用xdll.DLL（exports OpenCom,SendByte,CloseCom三个函数）时老是提示错误，不只是什么原因，求教各位大虾，急！！！

源码如下：
type
TOpenCom = function(const port:dword):boolean;
TCloseCom = function():boolean;
TSendByte = function(const SendBchar;const SLen:dword):boolean;

procedure TForm1.Button1Click(Sender: TObject);
Var
LibHandle: Thandle;
OpenCom: TOpenCom;
CloseCom: TCloseCom;
SendByte: TSendByte;
Begin
LibHandle := LoadLibrary('xdll.dll');
try
if LibHandle = 0 then
raise exception.create('找不到动态库xdll.dll');

@OpenCom := GetProcAddress(LibHandle,'OpenCom');
@CloseCom := GetProcAddress(LibHandle,'CloseCom');
@SendByte := GetProcAddress(LibHandle,'SendByte')


if @SendByte=nil then exit;
begin
OpenCom(ComboBox1.itemindex+1);
SendByte(pchar('abcd'),4)
{运行到此会出错Project xxx.exe faulted with message:'access violation at 0x024acefc:read of address 0x00464000'.}
CloseCom();
end;
finally
FreeLibrary(LibHandle);
end;
end;

没人回答么

c := 'abcd';
SendByte(c, 4);

改了也不行啊，应该不是这个问题。
谢谢xianguo

TSendByte = function(const SendBchar;const SLen:dword):boolean

－－>
TSendByte = function(SendBchar;const SLen:dword):boolean;

var
buf:array[0..255] of char;
....
buf:='abcd';
SendByte(buf,4);

TOpenCom = function(const port:dword):boolean;stdcall;
TCloseCom = function():boolean;stdcall;
TSendByte = function(const SendBchar;const SLen:dword):boolean;stdcall;

谢谢wqyzsh

问题如wqyzsh所言，已解决