Question

我正在用C创建一个优先级队列结构。

结构：

void Initialize(PriorityQueue *PQ)
{
    PQ->Count=0;
}

初始化函数：

int main (void) {
  PriorityQueue* PQ;
  Initialize(PQ);

  Insert(2, PQ);
  Insert(3, PQ);
  Insert(5, PQ);
  Insert(1, PQ);
  Insert(12, PQ);
  Insert(6, PQ);
  Insert(10, PQ);

  printPQ(PQ);

  return 0;
}

主要：

int

问题是，当我运行它时，我遇到了分段错误。使用gdb，我发现它被抛出了初始化函数。令我感到困惑的是，Public Function SendEmailViaGmail(SendTo As String, Optional Subject As String = "", Optional TextBody As String = "", Optional ReplyTo As String = "", Optional AttachedFiles As Variant = "") As String On Error GoTo send_emailErr Dim ErrNum As Long Dim ErrDes As String SendEmailViaGmail = "" ErrNum = 0 Set cdomsg = CreateObject("CDO.message") With cdomsg.Configuration.Fields .Item("http://schemas.microsoft.com/cdo/configuration/sendusing") = 2 'NTLM method .Item("http://schemas.microsoft.com/cdo/configuration/smtpserver") = "smtp.gmail.com" .Item("http://schemas.microsoft.com/cdo/configuration/smptserverport") = 587 .Item("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate") = 1 .Item("http://schemas.microsoft.com/cdo/configuration/smtpusessl") = True .Item("http://schemas.microsoft.com/cdo/configuration/smtpconnectiontimeout") = 60 .Item("http://schemas.microsoft.com/cdo/configuration/sendusername") = sendusername ' .Item("http://schemas.microsoft.com/cdo/configuration/sendpassword") = sendpassword .Update End With ' build email parts With cdomsg .To = SendTo .FROM = sendusername .Subject = Subject .TextBody = TextBody & vbCrLf & vbCrLf & vbCrLf & "--" & vbCrLf & "Sent using Marlan Data-Systems" If IsArray(AttachedFiles) Then For Each AttachedFile In AttachedFiles If Len(AttachedFile) > 3 Then .AddAttachment AttachedFile Next Else If Len(AttachedFiles) > 3 Then .AddAttachment AttachedFiles End If .send End With SendEmailViaGmail = "Done!" send_emailExit: Set cdomsg = Nothing Exit Function send_emailErr: ErrNum = Err.Number ErrDes = Err.Description Select Case Err.Number Case -2147220977 'Likely cause, Incorrectly Formatted Email Address, server rejected the Email Format SendEmailViaGmail = "Please Format the Email Address Correctly." Case -2147220980 'Likely cause, No Recipient Provided (No Email Address) SendEmailViaGmail = "Please Provide an Email Address" Case -2147220960 'Likely cause, SendUsing Configuration Error SendEmailViaGmail = "SendUsing Configuration Error" Case -2147220973 'Likely cause, No Internet Connection SendEmailViaGmail = "Please Check Internet Connection" Case -2147220975 'Likely cause, Incorrect Password SendEmailViaGmail = "Please Check Password" Case Else 'Report Other Errors SendEmailViaGmail = "" End Select SendEmailViaGmail = SendEmailViaGmail & " Error number: " & Err.Number & " Description: " & Err.Description 'If ErrNum = -2147220975 Then ' cdomsg.Configuration.Fields.Item("http://schemas.microsoft.com/cdo/configuration/smptserverport") = 465 ' Resume 'End If Resume send_emailExit End Function的简单赋值如何引发分段错误。

Answer 1

令我感到困惑的是int的简单分配如何引发分段错误。

那么，看看之前!!!

在Initialize()功能中，当您尝试访问PQ时，未分配有效内存。在解除反射之前，您需要为PQ分配适当的内存。否则，尝试访问无效内存会调用undefined behavior。

Answer 2

声明：

PriorityQueue* PQ;

声明一个变量（它的类型和名称，以及它在内存中的间接位置），但不初始化它。所以当你用

传递值时

Initialize(PQ);

被调用的函数使用随机值作为内存的地址 - 赋值

PQ->Count=0;

将零置于任意内存位置，很高兴您进入无效/禁止位置。

Answer 3

改为编写PriorityQueue PQ;（即删除指针类型），并在&PQ中的每个其他实例中使用main。在这种情况下，使用自动变量作为优先级队列就足够了。

否则你需要分配内存（使用malloc＆amp; c。），将该内存的位置分配给PQ，并记得呼叫{{1}当你完成时。

Answer 4

PriorityQueue变量PQ没有为其分配任何内存空间，分段错误的原因是您试图将变量存储在未分配的空间（或您无权访问的内存位置）。要获取变量PQ的内存空间，请使用malloc（）函数。

PQ = (PriorityQueue*) malloc(sizeof(PriorityQueue));

简单分配中的分段错误

4 个答案: