数组的下标越界是怎么回事？

2008-10-16 05:02:05 252 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

数组下标越界原理：因为c语言不会检测数组下标，所以如果我们给数组一个超出它大小的下标，就会照成数组越界。如果是想数组中写入数据的话，就会造成数据写入到不属于数组的地方，或者说如果读取数据的话，就会读取到别的地方的数据。因为数组地址是自低往高增长，而栈的地址是自高向下降低，所以如果我们将数组下标根据栈内的空间的分布，设置为特定的值，就可以修改或者是查看我们想要查看的地址的值。比如将返回地址设置成我们想要调用函数... 阅读详情



If Read(LBound(Read)) = &HAA And Read(UBound(Read)) = &H55 Then

      For i = 1 To 9

          CRC = CRC + Read(i + 1)

      Next i

      CRC_B = CRC Mod 256

      If Not Read(11) = CRC_B Then

         Exit Sub

      End If

      Select Case Read(1)

         Case &H51

             If Read(3) > 128 Then

                weitht_value = 0

             Else

                 weight_value = Format((Read(3) * 256 + Read(4)) / 1000, "0.00")

             End If

             Text1.Text = weight_value

             sngTemp(0, X) = weight_value

             scale_value = (Read(5) * 256 + Read(6)) / 10

             Text2.Text = scale_value

             sngTemp(1, X) = scale_value

             height_value = (Read(7) * 256 + Read(8)) / 10

             Text3.Text = height_value

             sngTemp(2, X) = height_value

             rotate_value = Read(9) * 256 + Read(10)

             'If (rotate_value Mod 360) >= 0 Then  '需要考虑一下这里的情况说明了什么

                sngTemp(3, X) = rotate_value 'Mod 360

             'Else

                'sngTemp(3, x) = (rotate_value Mod 360) + 360

             'End If

             Text4.Text = rotate_value

             torque_value = (weight_value * 1000 + car_weight) * scale_value / 1000

             Text5.Text = Format(torque_value, "0.00")

             sngTemp(4, X) = Format(torque_value, "0.00")

             If color_flag = True Then

           num = num + 1

           If num >= 5 Then

            Shape1.BackColor = &HFF&

          End If

      Else

      num = 0

      Shape1.BackColor = &HFF00&

   End If

...全文

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hengkongshi

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切换为时间正序

hengkongshi 2008-10-17

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谢谢上面的朋友了。我试试……

fvflove 2008-10-16

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Dim Read() As Byte

   Dim CRC As Integer

   Dim CRC_B As Byte

   Dim w1, w2, w3, w4, w5 As Double

   Dim fault_times As Integer

   Dim temp As String

   Sleep 30



'建议在此处增加语句

'ReDim Read(0) As Byte



   With MSComm1

      Select Case .CommEvent

         Case comEvReceive

           ReDim Read(.InBufferCount) As Byte '如果条件不满足,不会执行这句.

           Read = .Input

           .InBufferCount = 0

         Case comEvSend

      End Select

   End With

   

'这儿有问题:

'如果上面我注释的那句没有执行,则 Read 数组是空.以下就有问题了.



   If Read(LBound(Read)) = &HAA And Read(UBound(Read)) = &H55 Then

      For i = 1 To 9

          CRC = CRC + Read(i + 1)

      Next i

      CRC_B = CRC Mod 256

      If Not Read(11) = CRC_B Then

         Exit Sub

      End If

      Select Case Read(1)

         Case &H51

             If Read(3) > 128 Then

                weitht_value = 0

             Else

                 weight_value = Format((Read(3) * 256 + Read(4)) / 1000, "0.00")

             End If

             Text1.Text = weight_value

             sngTemp(0, X) = weight_value

             scale_value = (Read(5) * 256 + Read(6)) / 10

             Text2.Text = scale_value

             sngTemp(1, X) = scale_value

             height_value = (Read(7) * 256 + Read(8)) / 10

             Text3.Text = height_value

             sngTemp(2, X) = height_value

             rotate_value = Read(9) * 256 + Read(10)

             'If (rotate_value Mod 360) >= 0 Then  '需要考虑一下这里的情况说明了什么

                sngTemp(3, X) = rotate_value 'Mod 360

             'Else

                'sngTemp(3, x) = (rotate_value Mod 360) + 360

             'End If

             Text4.Text = rotate_value

             torque_value = (weight_value * 1000 + car_weight) * scale_value / 1000

             Text5.Text = Format(torque_value, "0.00")

             sngTemp(4, X) = Format(torque_value, "0.00")

             If color_flag = True Then

           num = num + 1

           If num >= 5 Then

            Shape1.BackColor = &HFF&

          End If

      Else

      num = 0

      Shape1.BackColor = &HFF00&

   End If

   color_flag = True

  

             Picture1.Cls

             X = X + 1

       

             Open App.Path & "\备份\temp.txt" For Append As #1

                 If pre_time = str(Now) Then

                    fdsk = fdsk + 1

                 Else

                    fdsk = 1

                    

                 End If

                 pre_time = Now

                 temp = str(Now) & "#" & Trim(str(fdsk))

               

                 Write #1, temp, weight_value, scale_value, height_value, rotate_value, torque_value

             Close #1

           ' Timer3.Enabled = True

           'Timer3.Interval = 3000

           savecurr_data

         Case &H40

             MSComm1.Output = Read

         Case Else

             Exit Sub

      End Select

        If Check1.Value = 1 Then

           Call Plot(spa_weight, 0)

        End If

        If Check2.Value = 1 Then

           Call Plot(spa_scale, 1)

        End If

        If Check3.Value = 1 Then

           Call Plot(spa_height, 2)

        End If

        If Check4.Value = 1 Then

           Call Plot(spa_rotate, 3)

        End If

        If Check5.Value = 1 Then

           Call Plot(spa_torque, 4)

        End If

        Picture2.Cls

        w1 = Picture2.Width * weight_value / spa_weight

       

        Picture2.Line (0, 0)-(w1, Picture2.Height), vbBlack, BF

         Picture2.ToolTipText = "比例值为" & Format(Val(w1 / Picture2.Width), "0.00")

        Picture3.Cls

        w2 = Picture3.Width * scale_value / spa_scale

         Picture3.ToolTipText = "比例值为" & Format(Val(w2 / Picture3.Width), "0.00")

        Picture3.Line (0, 0)-(w2, Picture3.Height), vbRed, BF

        Picture4.Cls

        w3 = Picture4.Width * height_value / spa_height

         Picture4.ToolTipText = "比例值为" & Format(Val(w3 / Picture4.Width), "0.00")

        Picture4.Line (0, 0)-(w3, Picture4.Height), vbGreen, BF

        Picture5.Cls

        w4 = Picture5.Width * rotate_value / spa_rotate

         Picture5.ToolTipText = "比例值为" & Format(Val(w4 / Picture5.Width), "0.00")

        Picture5.Line (0, 0)-(w4, Picture5.Height), vbYellow, BF

        Picture6.Cls

        w5 = Picture6.Width * torque_value / spa_torque

         Picture6.ToolTipText = "比例值为" & Format(Val(w5 / Picture6.Width), "0.00")

        Picture6.Line (0, 0)-(w5, Picture6.Height), vbBlue, BF

    End If

    

    If data_flag = 4 Then

       If fault_flag = False Then

          

          data_flag = 0

       End If

    End If

    data_flag = data_flag + 1

    color_flag = Not color_flag

   

End Sub

hengkongshi 2008-10-16

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重新沾一下代码：



   Dim Read() As Byte

   Dim CRC As Integer

   Dim CRC_B As Byte

   Dim w1, w2, w3, w4, w5 As Double

   Dim fault_times As Integer

   Dim temp As String

   Sleep 30

   With MSComm1

      Select Case .CommEvent

         Case comEvReceive

           ReDim Read(.InBufferCount) As Byte

           Read = .Input

           .InBufferCount = 0

         Case comEvSend

      End Select

   End With

   

   If Read(LBound(Read)) = &HAA And Read(UBound(Read)) = &H55 Then

      For i = 1 To 9

          CRC = CRC + Read(i + 1)

      Next i

      CRC_B = CRC Mod 256

      If Not Read(11) = CRC_B Then

         Exit Sub

      End If

      Select Case Read(1)

         Case &H51

             If Read(3) > 128 Then

                weitht_value = 0

             Else

                 weight_value = Format((Read(3) * 256 + Read(4)) / 1000, "0.00")

             End If

             Text1.Text = weight_value

             sngTemp(0, X) = weight_value

             scale_value = (Read(5) * 256 + Read(6)) / 10

             Text2.Text = scale_value

             sngTemp(1, X) = scale_value

             height_value = (Read(7) * 256 + Read(8)) / 10

             Text3.Text = height_value

             sngTemp(2, X) = height_value

             rotate_value = Read(9) * 256 + Read(10)

             'If (rotate_value Mod 360) >= 0 Then  '需要考虑一下这里的情况说明了什么

                sngTemp(3, X) = rotate_value 'Mod 360

             'Else

                'sngTemp(3, x) = (rotate_value Mod 360) + 360

             'End If

             Text4.Text = rotate_value

             torque_value = (weight_value * 1000 + car_weight) * scale_value / 1000

             Text5.Text = Format(torque_value, "0.00")

             sngTemp(4, X) = Format(torque_value, "0.00")

             If color_flag = True Then

           num = num + 1

           If num >= 5 Then

            Shape1.BackColor = &HFF&

          End If

      Else

      num = 0

      Shape1.BackColor = &HFF00&

   End If

   color_flag = True

  

             Picture1.Cls

             X = X + 1

       

             Open App.Path & "\备份\temp.txt" For Append As #1

                 If pre_time = str(Now) Then

                    fdsk = fdsk + 1

                 Else

                    fdsk = 1

                    

                 End If

                 pre_time = Now

                 temp = str(Now) & "#" & Trim(str(fdsk))

               

                 Write #1, temp, weight_value, scale_value, height_value, rotate_value, torque_value

             Close #1

           ' Timer3.Enabled = True

           'Timer3.Interval = 3000

           savecurr_data

         Case &H40

             MSComm1.Output = Read

         Case Else

             Exit Sub

      End Select

        If Check1.Value = 1 Then

           Call Plot(spa_weight, 0)

        End If

        If Check2.Value = 1 Then

           Call Plot(spa_scale, 1)

        End If

        If Check3.Value = 1 Then

           Call Plot(spa_height, 2)

        End If

        If Check4.Value = 1 Then

           Call Plot(spa_rotate, 3)

        End If

        If Check5.Value = 1 Then

           Call Plot(spa_torque, 4)

        End If

        Picture2.Cls

        w1 = Picture2.Width * weight_value / spa_weight

       

        Picture2.Line (0, 0)-(w1, Picture2.Height), vbBlack, BF

         Picture2.ToolTipText = "比例值为" & Format(Val(w1 / Picture2.Width), "0.00")

        Picture3.Cls

        w2 = Picture3.Width * scale_value / spa_scale

         Picture3.ToolTipText = "比例值为" & Format(Val(w2 / Picture3.Width), "0.00")

        Picture3.Line (0, 0)-(w2, Picture3.Height), vbRed, BF

        Picture4.Cls

        w3 = Picture4.Width * height_value / spa_height

         Picture4.ToolTipText = "比例值为" & Format(Val(w3 / Picture4.Width), "0.00")

        Picture4.Line (0, 0)-(w3, Picture4.Height), vbGreen, BF

        Picture5.Cls

        w4 = Picture5.Width * rotate_value / spa_rotate

         Picture5.ToolTipText = "比例值为" & Format(Val(w4 / Picture5.Width), "0.00")

        Picture5.Line (0, 0)-(w4, Picture5.Height), vbYellow, BF

        Picture6.Cls

        w5 = Picture6.Width * torque_value / spa_torque

         Picture6.ToolTipText = "比例值为" & Format(Val(w5 / Picture6.Width), "0.00")

        Picture6.Line (0, 0)-(w5, Picture6.Height), vbBlue, BF

    End If

    

    If data_flag = 4 Then

       If fault_flag = False Then

          

          data_flag = 0

       End If

    End If

    data_flag = data_flag + 1

    color_flag = Not color_flag

   

End Sub

dlmeijianyu 2008-10-16

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lz的代码好像不全，if与endif不对称。还有，没有select case结束的地方。

数组的下标越界是怎么回事？

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