StringBuilder causing access violation

[holisticdeveloper]

It seems that use of the StringBuilder class is causing an access violation in my application when it shuts down. This is very reproducible in my app, but I can't get it to reproduce in a standalone application.

I have a function in a class library that executes the following code:

Dim QueryString As StringBuilder
Set QueryString = New StringBuilder
   
QueryString.Append "sgMaximumWalkingDistanceGetFromClientIdTripdate @ClientId = "
QueryString.Append ClientID
I have left out the rest of the code from this function because the access violation will occur even if the rest of the code is commented out.

A particular execution path through my app calls this function, and then if the user exits the application immediately afterword, the application throws an access violation.

Interestingly, if I change the last line to the following, the crash does not occur:
QueryString.Append CStr(ClientID)
(note that the ClientID variable is a long)

Any thoughts on why this might be happening?

[Kelly Ethridge]

I can't reproduce this error with the following code:

Option Explicit
Public sb As New StringBuilder
Public l As Long

Public Sub Main()
   l = 1234
   
   sb.Append "words: "
   sb.Append l
   Console.WriteLine sb.ToString
   Console.ReadKey
End Sub

Can you provide a complete example that reproduces this error?

Thank You,
Kelly

[holisticdeveloper]

It seems to be some odd interaction with the WebBrowser control from Microsoft. Here is some code to reproduce the problem (note that I can only get this to crash when running as a compiled app on Windows XP).

With this code, doing the following will repro:

• Start compiled app.
  
• Wait for webrowser control to load Google
  
• Click the StringBuilder button.
  
• Close the app.
  

After that, the access violation occurs as the app is shutting down.

Project1.vbp:Type=Exe
Reference=*\G{00020430-0000-0000-C000-000000000046}#2.0#0#..\..\Windows\SysWOW64\stdole2.tlb#OLE Automation
Object={EAB22AC0-30C1-11CF-A7EB-0000C05BAE0B}#1.1#0; ieframe.dll
Reference=*\G{14CF02DE-3978-4CCB-9114-674233159946}#2.1#0#..\ADEPT-NYCT\dev\ITP\lib\VBCorLib.dll#VB.EXT: VBCorLib 2.3
Form=Form1.frm
IconForm="Form1"
Startup="Form1"
HelpFile=""
Title="StringBuilderCrash"
ExeName32="StringBuilderCrash.exe"
Command32=""
Name="StringBuilderCrash"
HelpContextID="0"
CompatibleMode="0"
MajorVer=1
MinorVer=0
RevisionVer=0
AutoIncrementVer=0
ServerSupportFiles=0
VersionCompanyName=""
CompilationType=0
OptimizationType=0
FavorPentiumPro(tm)=0
CodeViewDebugInfo=0
NoAliasing=0
BoundsCheck=0
OverflowCheck=0
FlPointCheck=0
FDIVCheck=0
UnroundedFP=0
StartMode=0
Unattended=0
Retained=0
ThreadPerObject=0
MaxNumberOfThreads=1
DebugStartupOption=0

Form1.frm:VERSION 5.00
Object = "{EAB22AC0-30C1-11CF-A7EB-0000C05BAE0B}#1.1#0"; "ieframe.dll"
Begin VB.Form Form1
  Caption         =   "Form1"
  ClientHeight    =   6675
  ClientLeft      =   120
  ClientTop       =   420
  ClientWidth     =   11385
  LinkTopic       =   "Form1"
  ScaleHeight     =   6675
  ScaleWidth      =   11385
  StartUpPosition =   3  'Windows Default
  Begin VB.CommandButton stringBuilderButton
     Caption         =   "String Builder"
     Height          =   495
     Left            =   480
     TabIndex        =   1
     Top             =   5160
     Width           =   1815
  End
  Begin SHDocVwCtl.WebBrowser WebBrowser1
     Height          =   4215
     Left            =   480
     TabIndex        =   0
     Top             =   360
     Width           =   10335
     ExtentX         =   18230
     ExtentY         =   7435
     ViewMode        =   0
     Offline         =   0
     Silent          =   0
     RegisterAsBrowser=   0
     RegisterAsDropTarget=   1
     AutoArrange     =   0   'False
     NoClientEdge    =   0   'False
     AlignLeft       =   0   'False
     NoWebView       =   0   'False
     HideFileNames   =   0   'False
     SingleClick     =   0   'False
     SingleSelection =   0   'False
     NoFolders       =   0   'False
     Transparent     =   0   'False
     ViewID          =   "{0057D0E0-3573-11CF-AE69-08002B2E1262}"
     Location        =   ""
  End
End
Attribute VB_Name = "Form1"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Option Explicit

Private Sub Form_Load()
   WebBrowser1.Navigate "http://www.google.com/"
End Sub

Private Sub stringBuilderButton_Click()
   Dim clientID As Long
   clientID = 628507

   Dim QueryString As StringBuilder
   Set QueryString = New StringBuilder
   
   QueryString.Append "sgMaximumWalkingDistanceGetFromClientIdTripdate @ClientId = "
   QueryString.Append clientID
   
End Sub

[Kelly Ethridge]

Ok, here is a link to an updated version (2.3.1) www.kellyethridge.com/vbcorlib/VBCorLib.dll. It should resolve the issure you're seeing. This is the only compile of this updated version.

[holisticdeveloper]

Hooray! This version does seem to fix the issue, both in my sample and in my actual application.

However, I did notice that the .dll is not binarily compatible with the 2.3.0.0 version. Several IIDs have new GUIDs:

• ArrayListStatic
  
• BigInteger
  
• BigIntegerStatic
  
• CDateTimeStatic
  
• Constructors
  
• StaticClasses
  
• TimeSpanStatic
  

Would it be possible to get an official release, or to see the changes to the source that I could compile myself?

Thanks so much!

[Kelly Ethridge]

I've recompiled the dll. Could you try it again for binary compatibility?
www.kellyethridge.com/vbcorlib/VBCorLib.dll

If that still doesn't work, then you can replace the CultureTable.cls with www.kellyethridge.com/vbcorlib/CultureTable.cls and recompile on your machine.

[holisticdeveloper]

The binary compatibility seems to be perfect on this one! Thanks so much for your help!