activeX DLL 的编译有关问题

activeX DLL 的编译问题
问题描述:
我在一个activeX dll中定义了一个类,将这个类作为其他各个dll与客户程序标志变量的公共载体,全局变量
在类中定义了一个timer 类型的变量g_timer2,以及一个control类型的变量g_MSCOMM,它作为一个对客户程序mscomm控件的引用,在其他dll中以及客户程序中都对该类在主程序中的对象进行了引用.在调试过程中,没有出现问题.
现在对该类进行编译,第一次在编译时选择no compatibility选项,生成gf.dll,二次编译选择binary compatibility选项,这时弹出'g_MSCOMM' in the 'Globalflags'class module has arguments and/or a return type that is incompatible with a similar declaration in the version compatible component.

Original definition:
Public g_MSCOMM As Object

Current definition:
Public g_MSCOMM As Control

Original definition:
Property Set g_MSCOMM(ByVal RHS As Object)

Current definition:
Public g_MSCOMM As Control

然后有两个选项 break compatibility 和 preserve compatibility

g_timer2也会出现同样的提示

我不明白究竟是哪里出了问题,这个向后兼容性究竟应该注意什么?我前后两次程序并没改动什么,g_MSCOMM,g_timer2的定义有问题吗?

VB code

 
 Option Explicit 
 Public Offline As Boolean 
 Public SendingMsg As Boolean 
 Public SendAll As Boolean 
 Public langflag As Integer 
 Public FinishULData As Boolean 
 Public Iniflag As Boolean 
 Public FinishFlag As Boolean 
 Public PressStop As Boolean 
  
 Public Almshow As Boolean 
 Public SendFile As Boolean 
 Public AllowMoni As Boolean 
 Public FinishMoni As Boolean 
 Public SendPara As Boolean 
 Public Addr As Integer 
 Public addrStr1 As String 
 Public addrRecieve As String 
 Public ParaTabShow As Boolean 
  
 Public TestStyle As Integer 
 Public SparaExist As Boolean 
 Public reqTest As Boolean 
 Public DatAddr03 As String 
  
 Public coderight As Boolean 
 Public coderight1 As Boolean 
 Public ResumeFlag As Boolean 
 Public fftFlag As Boolean 
  
 Public message As String 
 Public AdjFlag As Integer 
 Public ServoType As String 
 Public TimerCount As Integer 
  
 [color=#FF0000]Public g_MSCOMM As Control 
 Public g_Timer2 As Timer[/color] 
  
 Public MDIhwnd As Long 
 Public SpecialShow As Boolean 
 Public PhaseShow As Boolean 
 Public OperationShow As Boolean 
 Public LoadingShow As Boolean 
 Public JOGShow As Boolean 
 Public InertiaShow As Boolean 
 Public HandShow As Boolean 
 Public DMShow As Boolean 
 Public IMShow As Boolean 
 Public ScopeShow As Boolean 
  
 Public fftCmdShow As Boolean 
 Public fftGraphicShow As Boolean 
 Public testCmdShow As Boolean 
 Public testGraphicShow As Boolean 
 Public testParaShow As Boolean 
  
 Public Cn As ADODB.Connection 
  
 Public Function ProcessContinue(ByVal hwnd As Long) As Boolean 
    If Not FinishULData Then 
       If Not PressStop Then 
          ProcessContinue = False 
          MessageBoxEx hwnd, "UpLoad Plot Data", , MB_OK Or MB_ICONINFORMATION, LANG_ENGLISH 
          Exit Function 
       End If 
    End If 
     
    If SendPara Then 
       ProcessContinue = False 
       MessageBoxEx hwnd, "SendPara", ,MB_OK Or MB_ICONINFORMATION, LANG_ENGLISH 
       Exit Function 
    End If 
     
    If fftFlag Then 
       ProcessContinue = False 
       MessageBoxEx hwnd, "fftFlag", , MB_OK Or MB_ICONINFORMATION, LANG_ENGLISH 
       Exit Function 
    End If 
     
     
    ProcessContinue = True 
     
 End Function 
  
 Public Sub SendingMessage(ByVal msg As String) 
  
    Dim Out1() As Byte   
    Dim Lrc As Long 
    Dim a As Integer 
    Dim L As Integer 
      
 
    SendingMsg = True 
     
    msg = addrStr1 & msg 
    L = Len(msg) 
    Dim i As Integer 
    Lrc = 0 
     
    For i = 0 To L / 2 - 1 
      a = Val("&H" & Mid(msg, 2 * i + 1, 2)) 
      Lrc = a + Lrc 
    Next 
     
    Lrc = Lrc Mod 256 
    Lrc = 256 - Lrc 
     
    If Lrc = 256 Then 
      Lrc = 0 
    End If 
     
    ReDim Out1(L + 4) As Byte 
    For i = 1 To L 
      Out1(i) = Asc(Mid(msg, i, 1)) 
    Next i 
     
    If Lrc  &lt; 16 Then 
      Out1(L + 1) = Asc(Mid("0" & Hex(Lrc), 1, 1)) 
      Out1(L + 2) = Asc(Mid("0" & Hex(Lrc), 2, 1)) 
    Else 
      Out1(L + 1) = Asc(Mid(Hex(Lrc), 1, 1)) 
      Out1(L + 2) = Asc(Mid(Hex(Lrc), 2, 1)) 
    End If 
     
    Out1(0) = Asc(":") 
    Out1(L + 3) = &HD 
    Out1(L + 4) = &HA 
     
    If g_MSCOMM.PortOpen = True Then 
       g_MSCOMM.OutBufferCount = 0 
       g_MSCOMM.Output = Out1   &#39; 
    End If 
     
 End Sub

[解决办法]
编译时选择二进制兼容模式。还有，你那些这是定义，如果不是供外部引用，就改成private。
[解决办法]
VB.Control 其实是 VB 内部的一个特殊类，它自动对控件进行封装让它们具有一定的共性。
比如用 MSComm 控件调用下面的函数可以正常工作，但是在其它编程环境中就不会有 .Parent 属性。

VB code

Private Sub f(ByVal c As Control) Debug.Print c.Parent.Name Debug.Print c.CommPortEnd Sub
[解决办法]
在 COM 标准中没有公共变量，一个属性通过 {get_XXX, set_XXX, let_XXX} 等方法表示。
VB 自动将公共变量翻译为属性，所以接口中就有 Property Set g_MSCOMM(...)。

具体细节可用 Visual Studio 的工具 OLE View 打开 dll 查看。

activeX DLL 的编译有关问题

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