How do I prevent and or handle a StackOverflowException

Question

I would like to either prevent or handle a StackOverflowException that I am getting from a call to the XslCompiledTransform Transform method within an Xsl Editor I am writing  The problem seems to be that the user can write an Xsl script that is infinitely recursive  and it just blows up on the call to the Transform method    That is  the problem is not just the typical programmatic error  which is usually the cause of such an exception    Is there a way to detect and or limit how many recursions are allowed   Or any other ideas to keep this code from just blowing up on me

User · Answer

WilliamJockusch  if I understood correctly your concern  it s not possible  from a mathematical point of view  to always identify an infinite recursion as it would mean to solve the Halting problem  To solve it you d need a Super-recursive algorithm  like Trial-and-error predicates for example  or a machine that can hypercompute  an example is explained in the following section - available as preview - of this book    From a practical point of view  you d have to know    How much stack memory you have left at the given time How much stack memory your recursive method will need at the given time for the specific output    Keep in mind that  with the current machines  this data is extremely mutable due to multitasking and I haven t heard of a software that does the task   Let me know if something is unclear

User · Answer

From Microsoft      Starting with the  NET Framework   version 2 0  a StackOverflowException   object cannot be caught by a try-catch   block and the corresponding process is   terminated by default  Consequently    users are advised to write their code   to detect and prevent a stack   overflow  For example  if your   application depends on recursion  use   a counter or a state condition to   terminate the recursive loop    I m assuming the exception is happening within an internal  NET method  and not in your code   You can do a couple things    Write code that checks the xsl for infinite recursion and notifies the user prior to applying a transform  Ugh   Load the XslTransform code into a separate process  Hacky  but less work     You can use the Process class to load the assembly that will apply the transform into a separate process  and alert the user of the failure if it dies  without killing your main app   EDIT  I just tested  here is how to do it   MainProcess      This is just an example  obviously you ll want to pass args to this  Process p1   new Process    p1 StartInfo FileName    ApplyTransform exe   p1 StartInfo UseShellExecute   false  p1 StartInfo WindowStyle   ProcessWindowStyle Hidden   p1 Start    p1 WaitForExit     if  p1 ExitCode    1         Console WriteLine  StackOverflow was thrown      ApplyTransform Process   class Program       static void Main string   args                AppDomain CurrentDomain UnhandledException    new UnhandledExceptionEventHandler CurrentDomain UnhandledException           throw new StackOverflowException                  We trap this  we can t save the process          but we can prevent the  ILLEGAL OPERATION  window      static void CurrentDomain UnhandledException object sender  UnhandledExceptionEventArgs e                if  e IsTerminating                        Environment Exit 1

User · Answer

I had a stackoverflow today and i read some of your posts and decided to help out the Garbage Collecter    I used to have a near infinite loop like this       class Foo               public Foo                         Go                       public void Go                         for  float i   float MinValue  i  lt  float MaxValue  i   0 000000000000001f                                byte   b   new byte 1      Causes stackoverflow                                 Instead let the resource run out of scope like this   class Foo       public Foo                 GoHelper               public void GoHelper                 for  float i   float MinValue  i  lt  float MaxValue  i   0 000000000000001f                        Go                         public void Go                 byte   b   new byte 1      Will get cleaned by GC            right now     It worked for me  hope it helps someone

User · Answer

You can read up this property every few calls  Environment StackTrace   and if the stacktrace exceded a specific threshold that you preset  you can return the function   You should also try to replace some recursive functions with loops

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If you application depends on 3d-party code  in Xsl-scripts  then you have to decide first do you want to defend from bugs in them or not  If you really want to defend then I think you should execute your logic which prone to external errors in separate AppDomains  Catching StackOverflowException is not good   Check also this question

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I would suggest creating a wrapper around XmlWriter object  so it would count amount of calls to WriteStartElement WriteEndElement  and if you limit amount of tags to some number  f e  100   you would be able to throw a different exception  for example - InvalidOperation   That should solve the problem in the majority of the cases  public class LimitedDepthXmlWriter   XmlWriter       private readonly XmlWriter  innerWriter      private readonly int  maxDepth      private int  depth       public LimitedDepthXmlWriter XmlWriter innerWriter   this innerWriter  100                   public LimitedDepthXmlWriter XmlWriter innerWriter  int maxDepth                 maxDepth   maxDepth           innerWriter   innerWriter             public override void Close                  innerWriter Close               public override void Flush                  innerWriter Flush               public override string LookupPrefix string ns                return  innerWriter LookupPrefix ns              public override void WriteBase64 byte   buffer  int index  int count                 innerWriter WriteBase64 buffer  index  count              public override void WriteCData string text                 innerWriter WriteCData text              public override void WriteCharEntity char ch                 innerWriter WriteCharEntity ch              public override void WriteChars char   buffer  int index  int count                 innerWriter WriteChars buffer  index  count              public override void WriteComment string text                 innerWriter WriteComment text              public override void WriteDocType string name  string pubid  string sysid  string subset                 innerWriter WriteDocType name  pubid  sysid  subset              public override void WriteEndAttribute                  innerWriter WriteEndAttribute               public override void WriteEndDocument                  innerWriter WriteEndDocument               public override void WriteEndElement                  depth--            innerWriter WriteEndElement               public override void WriteEntityRef string name                 innerWriter WriteEntityRef name              public override void WriteFullEndElement                  innerWriter WriteFullEndElement               public override void WriteProcessingInstruction string name  string text                 innerWriter WriteProcessingInstruction name  text              public override void WriteRaw string data                 innerWriter WriteRaw data              public override void WriteRaw char   buffer  int index  int count                 innerWriter WriteRaw buffer  index  count              public override void WriteStartAttribute string prefix  string localName  string ns                 innerWriter WriteStartAttribute prefix  localName  ns              public override void WriteStartDocument bool standalone                 innerWriter WriteStartDocument standalone              public override void WriteStartDocument                  innerWriter WriteStartDocument               public override void WriteStartElement string prefix  string localName  string ns                if   depth    gt   maxDepth  ThrowException              innerWriter WriteStartElement prefix  localName  ns              public override WriteState WriteState               get   return  innerWriter WriteState               public override void WriteString string text                 innerWriter WriteString text              public override void WriteSurrogateCharEntity char lowChar  char highChar                 innerWriter WriteSurrogateCharEntity lowChar  highChar              public override void WriteWhitespace string ws                 innerWriter WriteWhitespace ws              private void ThrowException                 throw new InvalidOperationException string Format  Result xml has more than  0  nested tags  It is possible that xslt transformation contains an endless recursive call     maxDepth

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From Microsoft      Starting with the  NET Framework   version 2 0  a StackOverflowException   object cannot be caught by a try-catch   block and the corresponding process is   terminated by default  Consequently    users are advised to write their code   to detect and prevent a stack   overflow  For example  if your   application depends on recursion  use   a counter or a state condition to   terminate the recursive loop    I m assuming the exception is happening within an internal  NET method  and not in your code   You can do a couple things    Write code that checks the xsl for infinite recursion and notifies the user prior to applying a transform  Ugh   Load the XslTransform code into a separate process  Hacky  but less work     You can use the Process class to load the assembly that will apply the transform into a separate process  and alert the user of the failure if it dies  without killing your main app   EDIT  I just tested  here is how to do it   MainProcess      This is just an example  obviously you ll want to pass args to this  Process p1   new Process    p1 StartInfo FileName    ApplyTransform exe   p1 StartInfo UseShellExecute   false  p1 StartInfo WindowStyle   ProcessWindowStyle Hidden   p1 Start    p1 WaitForExit     if  p1 ExitCode    1         Console WriteLine  StackOverflow was thrown      ApplyTransform Process   class Program       static void Main string   args                AppDomain CurrentDomain UnhandledException    new UnhandledExceptionEventHandler CurrentDomain UnhandledException           throw new StackOverflowException                  We trap this  we can t save the process          but we can prevent the  ILLEGAL OPERATION  window      static void CurrentDomain UnhandledException object sender  UnhandledExceptionEventArgs e                if  e IsTerminating                        Environment Exit 1

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With  NET 4 0 You can add the HandleProcessCorruptedStateExceptions attribute from System Runtime ExceptionServices to the method containing the try catch block  This really worked  Maybe not recommended but works   using System  using System Reflection  using System Runtime InteropServices  using System Runtime ExceptionServices   namespace ExceptionCatching       public class Test               public void StackOverflow                         StackOverflow                       public void CustomException                         throw new Exception                       public unsafe void AccessViolation                         byte b     byte   8762765876                        class Program                HandleProcessCorruptedStateExceptions          static void Main string   args                        Test test   new Test                try                     test StackOverflow                    test AccessViolation                      test CustomException                              catch                               Console WriteLine  Caught                                Console WriteLine  End of program

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With  NET 4 0 You can add the HandleProcessCorruptedStateExceptions attribute from System Runtime ExceptionServices to the method containing the try catch block  This really worked  Maybe not recommended but works   using System  using System Reflection  using System Runtime InteropServices  using System Runtime ExceptionServices   namespace ExceptionCatching       public class Test               public void StackOverflow                         StackOverflow                       public void CustomException                         throw new Exception                       public unsafe void AccessViolation                         byte b     byte   8762765876                        class Program                HandleProcessCorruptedStateExceptions          static void Main string   args                        Test test   new Test                try                     test StackOverflow                    test AccessViolation                      test CustomException                              catch                               Console WriteLine  Caught                                Console WriteLine  End of program

User · Answer

You can read up this property every few calls  Environment StackTrace   and if the stacktrace exceded a specific threshold that you preset  you can return the function   You should also try to replace some recursive functions with loops

User · Answer

From Microsoft      Starting with the  NET Framework   version 2 0  a StackOverflowException   object cannot be caught by a try-catch   block and the corresponding process is   terminated by default  Consequently    users are advised to write their code   to detect and prevent a stack   overflow  For example  if your   application depends on recursion  use   a counter or a state condition to   terminate the recursive loop    I m assuming the exception is happening within an internal  NET method  and not in your code   You can do a couple things    Write code that checks the xsl for infinite recursion and notifies the user prior to applying a transform  Ugh   Load the XslTransform code into a separate process  Hacky  but less work     You can use the Process class to load the assembly that will apply the transform into a separate process  and alert the user of the failure if it dies  without killing your main app   EDIT  I just tested  here is how to do it   MainProcess      This is just an example  obviously you ll want to pass args to this  Process p1   new Process    p1 StartInfo FileName    ApplyTransform exe   p1 StartInfo UseShellExecute   false  p1 StartInfo WindowStyle   ProcessWindowStyle Hidden   p1 Start    p1 WaitForExit     if  p1 ExitCode    1         Console WriteLine  StackOverflow was thrown      ApplyTransform Process   class Program       static void Main string   args                AppDomain CurrentDomain UnhandledException    new UnhandledExceptionEventHandler CurrentDomain UnhandledException           throw new StackOverflowException                  We trap this  we can t save the process          but we can prevent the  ILLEGAL OPERATION  window      static void CurrentDomain UnhandledException object sender  UnhandledExceptionEventArgs e                if  e IsTerminating                        Environment Exit 1

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NOTE The question in the bounty by  WilliamJockusch and the original question are different       This answer is about StackOverflow s in the general case of third-party libraries and what you can can t do with them  If you re looking about the special case with XslTransform  see the accepted answer      Stack overflows happen because the data on the stack exceeds a certain limit  in bytes   The details of how this detection works can be found here      I m wondering if there is a general way to track down StackOverflowExceptions  In other words  suppose I have infinite recursion somewhere in my code  but I have no idea where  I want to track it down by some means that is easier than stepping through code all over the place until I see it happening  I don t care how hackish it is    As I mentioned in the link  detecting a stack overflow from static code analysis would require solving the halting problem which is undecidable  Now that we ve established that there is no silver bullet  I can show you a few tricks that I think helps track down the problem   I think this question can be interpreted in different ways  and since I m a bit bored  -   I ll break it down into different variations    Detecting a stack overflow in a test environment  Basically the problem here is that you have a  limited  test environment and want to detect a stack overflow in an  expanded  production environment    Instead of detecting the SO itself  I solve this by exploiting the fact that the stack depth can be set  The debugger will give you all the information you need  Most languages allow you to specify the stack size or the max recursion depth    Basically I try to force a SO by making the stack depth as small as possible  If it doesn t overflow  I can always make it bigger   in this case  safer  for the production environment  The moment you get a stack overflow  you can manually decide if it s a  valid  one or not    To do this  pass the stack size  in our case  a small value  to a Thread parameter  and see what happens  The default stack size in  NET is 1 MB  we re going to use a way smaller value   class StackOverflowDetector       static int Recur                 int variable   1          return variable   Recur               static void Start                 int depth   1   Recur               static void Main string   args                Thread t   new Thread Start  1           t Start            t Join            Console WriteLine            Console ReadLine              Note  we re going to use this code below as well   Once it overflows  you can set it to a bigger value until you get a SO that makes sense    Creating exceptions before you SO  The StackOverflowException is not catchable  This means there s not much you can do when it has happened  So  if you believe something is bound to go wrong in your code  you can make your own exception in some cases  The only thing you need for this is the current stack depth  there s no need for a counter  you can use the real values from  NET   class StackOverflowDetector       static void CheckStackDepth                 if  new StackTrace   FrameCount  gt  10     some arbitrary limit                       throw new StackOverflowException  Bad thread                          static int Recur                 CheckStackDepth            int variable   1          return variable   Recur               static void Main string   args                try                       int depth   1   Recur                      catch  ThreadAbortException e                        Console WriteLine  We ve been a  0    e ExceptionState                     Console WriteLine            Console ReadLine              Note that this approach also works if you are dealing with third-party components that use a callback mechanism  The only thing required is that you can intercept some calls in the stack trace   Detection in a separate thread  You explicitly suggested this  so here goes this one   You can try detecting a SO in a separate thread   but it probably won t do you any good  A stack overflow can happen fast  even before you get a context switch  This means that this mechanism isn t reliable at all    I wouldn t recommend actually using it  It was fun to build though  so here s the code  -   class StackOverflowDetector       static int Recur                 Thread Sleep 1      simulate that we re actually doing something  -          int variable   1          return variable   Recur               static void Start                 try                       int depth   1   Recur                      catch  ThreadAbortException e                        Console WriteLine  We ve been a  0    e ExceptionState                        static void Main string   args                   Prepare the execution thread         Thread t   new Thread Start           t Priority   ThreadPriority Lowest              Create the watch thread         Thread watcher   new Thread Watcher           watcher Priority   ThreadPriority Highest          watcher Start t               Start the execution thread         t Start            t Join             watcher Abort            Console WriteLine            Console ReadLine               private static void Watcher object o                Thread towatch    Thread o           while  true                        if  towatch ThreadState    System Threading ThreadState Running                                towatch Suspend                    var frames   new System Diagnostics StackTrace towatch  false                   if  frames FrameCount  gt  20                                        towatch Resume                        towatch Abort  Bad bad thread                                       else                                       towatch Resume                                                        Run this in the debugger and have fun of what happens   Using the characteristics of a stack overflow  Another interpretation of your question is   Where are the pieces of code that could potentially cause a stack overflow exception    Obviously the answer of this is  all code with recursion  For each piece of code  you can then do some manual analysis   It s also possible to determine this using static code analysis  What you need to do for that is to decompile all methods and figure out if they contain an infinite recursion  Here s some code that does that for you      A simple decompiler that extracts all method tokens  that is  call  callvirt  newobj in IL  internal class Decompiler       private Decompiler            static Decompiler                 singleByteOpcodes   new OpCode 0x100           multiByteOpcodes   new OpCode 0x100           FieldInfo   infoArray1   typeof OpCodes  GetFields            for  int num1   0  num1  lt  infoArray1 Length  num1                          FieldInfo info1   infoArray1 num1               if  info1 FieldType    typeof OpCode                                 OpCode code1    OpCode info1 GetValue null                   ushort num2    ushort code1 Value                  if  num2  lt  0x100                                        singleByteOpcodes  int num2    code1                                    else                                       if   num2  amp  0xff00     0xfe00                                                throw new Exception  Invalid opcode      num2 ToString                                               multiByteOpcodes num2  amp  0xff    code1                                                       private static OpCode   singleByteOpcodes      private static OpCode   multiByteOpcodes       public static MethodBase   Decompile MethodBase mi  byte   ildata                HashSet lt MethodBase gt  result   new HashSet lt MethodBase gt              Module module   mi Module           int position   0          while  position  lt  ildata Length                        OpCode code   OpCodes Nop               ushort b   ildata position                 if  b    0xfe                                code   singleByteOpcodes b                             else                               b   ildata position                     code   multiByteOpcodes b                   b     ushort  0xfe00                              switch  code OperandType                                case OperandType InlineNone                      break                  case OperandType ShortInlineBrTarget                  case OperandType ShortInlineI                  case OperandType ShortInlineVar                      position    1                      break                  case OperandType InlineVar                      position    2                      break                  case OperandType InlineBrTarget                  case OperandType InlineField                  case OperandType InlineI                  case OperandType InlineSig                  case OperandType InlineString                  case OperandType InlineTok                  case OperandType InlineType                  case OperandType ShortInlineR                      position    4                      break                  case OperandType InlineR                  case OperandType InlineI8                      position    8                      break                  case OperandType InlineSwitch                      int count   BitConverter ToInt32 ildata  position                       position    count   4   4                      break                   case OperandType InlineMethod                      int methodId   BitConverter ToInt32 ildata  position                       position    4                      try                                               if  mi is ConstructorInfo                                                        result Add  MethodBase module ResolveMember methodId  mi DeclaringType GetGenericArguments    Type EmptyTypes                                                      else                                                       result Add  MethodBase module ResolveMember methodId  mi DeclaringType GetGenericArguments    mi GetGenericArguments                                                                          catch                          break                    default                      throw new Exception  Unknown instruction operand  cannot continue  Operand type      code OperandType                                   return result ToArray             class StackOverflowDetector          This method will be found      static int Recur                 CheckStackDepth            int variable   1          return variable   Recur               static void Main string   args                RecursionDetector            Console WriteLine            Console ReadLine               static void RecursionDetector                    First decompile all methods in the assembly          Dictionary lt MethodBase  MethodBase   gt  calling   new Dictionary lt MethodBase  MethodBase   gt             var assembly   typeof StackOverflowDetector  Assembly           foreach  var type in assembly GetTypes                          foreach  var member in type GetMembers BindingFlags Public   BindingFlags NonPublic   BindingFlags Static   BindingFlags Instance  OfType lt MethodBase gt                                   var body   member GetMethodBody                    if  body  null                                        var bytes   body GetILAsByteArray                        if  bytes    null                                                   Store all the calls of this method                          var calls   Decompiler Decompile member  bytes                           calling member    calls                                                                              Check every method          foreach  var method in calling Keys                           If method A - gt      - gt  method A  we have a possible infinite recursion             CheckRecursion method  calling  new HashSet lt MethodBase gt                        Now  the fact that a method cycle contains recursion  is by no means a guarantee that a stack overflow will happen - it s just the most likely precondition for your stack overflow exception  In short  this means that this code will determine the pieces of code where a stack overflow can occur  which should narrow down most code considerably   Yet other approaches  There are some other approaches you can try that I haven t described here    Handling the stack overflow by hosting the CLR process and handling it  Note that you still cannot  catch  it  Changing all IL code  building another DLL  adding checks on recursion  Yes  that s quite possible  I ve implemented it in the past  -   it s just difficult and involves a lot of code to get it right  Use the  NET profiling API to capture all method calls and use that to figure out stack overflows  For example  you can implement checks that if you encounter the same method X times in your call tree  you give a signal  There s a project here that will give you a head start

User · Answer

From Microsoft      Starting with the  NET Framework   version 2 0  a StackOverflowException   object cannot be caught by a try-catch   block and the corresponding process is   terminated by default  Consequently    users are advised to write their code   to detect and prevent a stack   overflow  For example  if your   application depends on recursion  use   a counter or a state condition to   terminate the recursive loop    I m assuming the exception is happening within an internal  NET method  and not in your code   You can do a couple things    Write code that checks the xsl for infinite recursion and notifies the user prior to applying a transform  Ugh   Load the XslTransform code into a separate process  Hacky  but less work     You can use the Process class to load the assembly that will apply the transform into a separate process  and alert the user of the failure if it dies  without killing your main app   EDIT  I just tested  here is how to do it   MainProcess      This is just an example  obviously you ll want to pass args to this  Process p1   new Process    p1 StartInfo FileName    ApplyTransform exe   p1 StartInfo UseShellExecute   false  p1 StartInfo WindowStyle   ProcessWindowStyle Hidden   p1 Start    p1 WaitForExit     if  p1 ExitCode    1         Console WriteLine  StackOverflow was thrown      ApplyTransform Process   class Program       static void Main string   args                AppDomain CurrentDomain UnhandledException    new UnhandledExceptionEventHandler CurrentDomain UnhandledException           throw new StackOverflowException                  We trap this  we can t save the process          but we can prevent the  ILLEGAL OPERATION  window      static void CurrentDomain UnhandledException object sender  UnhandledExceptionEventArgs e                if  e IsTerminating                        Environment Exit 1

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I had a stackoverflow today and i read some of your posts and decided to help out the Garbage Collecter    I used to have a near infinite loop like this       class Foo               public Foo                         Go                       public void Go                         for  float i   float MinValue  i  lt  float MaxValue  i   0 000000000000001f                                byte   b   new byte 1      Causes stackoverflow                                 Instead let the resource run out of scope like this   class Foo       public Foo                 GoHelper               public void GoHelper                 for  float i   float MinValue  i  lt  float MaxValue  i   0 000000000000001f                        Go                         public void Go                 byte   b   new byte 1      Will get cleaned by GC            right now     It worked for me  hope it helps someone

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This answer is for  WilliamJockusch      I m wondering if there is a general way to track down   StackOverflowExceptions  In other words  suppose I have infinite   recursion somewhere in my code  but I have no idea where  I want to   track it down by some means that is easier than stepping through code   all over the place until I see it happening  I don t care how hackish   it is  For example  It would be great to have a module I could   activate  perhaps even from another thread  that polled the stack   depth and complained if it got to a level I considered  too high   For   example  I might set  too high  to 600 frames  figuring that if the   stack were too deep  that has to be a problem  Is something like that   possible  Another example would be to log every 1000th method call   within my code to the debug output  The chances this would get some   evidence of the overlow would be pretty good  and it likely would not   blow up the output too badly  The key is that it cannot involve   writing a check wherever the overflow is happening  Because the entire   problem is that I don t know where that is  Preferrably the solution   should not depend on what my development environment looks like  i e    it should not assumet that I am using C  via a specific toolset  e g    VS     It sounds like you re keen to hear some debugging techniques to catch this StackOverflow so I thought I would share a couple for you to try   1  Memory Dumps   Pro s  Memory Dumps are a sure fire way to work out the cause of a Stack Overflow  A C  MVP  amp  I worked together troubleshooting a SO and he went on to blog about it here   This method is the fastest way to track down the problem   This method wont require you to reproduce problems by following steps seen in logs   Con s  Memory Dumps are very large and you have to attach AdPlus procdump the process   2  Aspect Orientated Programming   Pro s  This is probably the easiest way for you to implement code that checks the size of the call stack from any method without writing code in every method of your application  There are a bunch of AOP Frameworks that allow you to Intercept before and after calls   Will tell you the methods that are causing the Stack Overflow   Allows you to check the StackTrace   FrameCount at the entry and exit of all methods in your application   Con s  It will have a performance impact - the hooks are embedded into the IL for every method and you cant really  de-activate  it out   It somewhat depends on your development environment tool set   3  Logging User Activity   A week ago I was trying to hunt down several hard to reproduce problems  I posted this QA User Activity Logging  Telemetry  and Variables in Global Exception Handlers    The conclusion I came to was a really simple user-actions-logger to see how to reproduce problems in a debugger when any unhandled exception occurs   Pro s  You can turn it on  or off at will  ie subscribing to events     Tracking the user actions doesn t require intercepting every method   You can count the number of events methods are subscribed too far more simply than with AOP    The log files are relatively small and focus on what actions you need to perform to reproduce the problem   It can help you to understand how users are using your application   Con s  Isn t suited to a Windows Service and I m sure there are better tools like this for web apps   Doesn t necessarily tell you the methods that cause the Stack Overflow   Requires you to step through logs manually reproducing problems rather than a Memory Dump where you can get it and debug it straight away    nbsp       Maybe you might try all techniques I mention above and some that  atlaste posted and tell us which one s you found were the easiest quickest dirtiest most acceptable to run in a PROD environment etc    Anyway good luck tracking down this SO

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WilliamJockusch  if I understood correctly your concern  it s not possible  from a mathematical point of view  to always identify an infinite recursion as it would mean to solve the Halting problem  To solve it you d need a Super-recursive algorithm  like Trial-and-error predicates for example  or a machine that can hypercompute  an example is explained in the following section - available as preview - of this book    From a practical point of view  you d have to know    How much stack memory you have left at the given time How much stack memory your recursive method will need at the given time for the specific output    Keep in mind that  with the current machines  this data is extremely mutable due to multitasking and I haven t heard of a software that does the task   Let me know if something is unclear

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NOTE The question in the bounty by  WilliamJockusch and the original question are different       This answer is about StackOverflow s in the general case of third-party libraries and what you can can t do with them  If you re looking about the special case with XslTransform  see the accepted answer      Stack overflows happen because the data on the stack exceeds a certain limit  in bytes   The details of how this detection works can be found here      I m wondering if there is a general way to track down StackOverflowExceptions  In other words  suppose I have infinite recursion somewhere in my code  but I have no idea where  I want to track it down by some means that is easier than stepping through code all over the place until I see it happening  I don t care how hackish it is    As I mentioned in the link  detecting a stack overflow from static code analysis would require solving the halting problem which is undecidable  Now that we ve established that there is no silver bullet  I can show you a few tricks that I think helps track down the problem   I think this question can be interpreted in different ways  and since I m a bit bored  -   I ll break it down into different variations    Detecting a stack overflow in a test environment  Basically the problem here is that you have a  limited  test environment and want to detect a stack overflow in an  expanded  production environment    Instead of detecting the SO itself  I solve this by exploiting the fact that the stack depth can be set  The debugger will give you all the information you need  Most languages allow you to specify the stack size or the max recursion depth    Basically I try to force a SO by making the stack depth as small as possible  If it doesn t overflow  I can always make it bigger   in this case  safer  for the production environment  The moment you get a stack overflow  you can manually decide if it s a  valid  one or not    To do this  pass the stack size  in our case  a small value  to a Thread parameter  and see what happens  The default stack size in  NET is 1 MB  we re going to use a way smaller value   class StackOverflowDetector       static int Recur                 int variable   1          return variable   Recur               static void Start                 int depth   1   Recur               static void Main string   args                Thread t   new Thread Start  1           t Start            t Join            Console WriteLine            Console ReadLine              Note  we re going to use this code below as well   Once it overflows  you can set it to a bigger value until you get a SO that makes sense    Creating exceptions before you SO  The StackOverflowException is not catchable  This means there s not much you can do when it has happened  So  if you believe something is bound to go wrong in your code  you can make your own exception in some cases  The only thing you need for this is the current stack depth  there s no need for a counter  you can use the real values from  NET   class StackOverflowDetector       static void CheckStackDepth                 if  new StackTrace   FrameCount  gt  10     some arbitrary limit                       throw new StackOverflowException  Bad thread                          static int Recur                 CheckStackDepth            int variable   1          return variable   Recur               static void Main string   args                try                       int depth   1   Recur                      catch  ThreadAbortException e                        Console WriteLine  We ve been a  0    e ExceptionState                     Console WriteLine            Console ReadLine              Note that this approach also works if you are dealing with third-party components that use a callback mechanism  The only thing required is that you can intercept some calls in the stack trace   Detection in a separate thread  You explicitly suggested this  so here goes this one   You can try detecting a SO in a separate thread   but it probably won t do you any good  A stack overflow can happen fast  even before you get a context switch  This means that this mechanism isn t reliable at all    I wouldn t recommend actually using it  It was fun to build though  so here s the code  -   class StackOverflowDetector       static int Recur                 Thread Sleep 1      simulate that we re actually doing something  -          int variable   1          return variable   Recur               static void Start                 try                       int depth   1   Recur                      catch  ThreadAbortException e                        Console WriteLine  We ve been a  0    e ExceptionState                        static void Main string   args                   Prepare the execution thread         Thread t   new Thread Start           t Priority   ThreadPriority Lowest              Create the watch thread         Thread watcher   new Thread Watcher           watcher Priority   ThreadPriority Highest          watcher Start t               Start the execution thread         t Start            t Join             watcher Abort            Console WriteLine            Console ReadLine               private static void Watcher object o                Thread towatch    Thread o           while  true                        if  towatch ThreadState    System Threading ThreadState Running                                towatch Suspend                    var frames   new System Diagnostics StackTrace towatch  false                   if  frames FrameCount  gt  20                                        towatch Resume                        towatch Abort  Bad bad thread                                       else                                       towatch Resume                                                        Run this in the debugger and have fun of what happens   Using the characteristics of a stack overflow  Another interpretation of your question is   Where are the pieces of code that could potentially cause a stack overflow exception    Obviously the answer of this is  all code with recursion  For each piece of code  you can then do some manual analysis   It s also possible to determine this using static code analysis  What you need to do for that is to decompile all methods and figure out if they contain an infinite recursion  Here s some code that does that for you      A simple decompiler that extracts all method tokens  that is  call  callvirt  newobj in IL  internal class Decompiler       private Decompiler            static Decompiler                 singleByteOpcodes   new OpCode 0x100           multiByteOpcodes   new OpCode 0x100           FieldInfo   infoArray1   typeof OpCodes  GetFields            for  int num1   0  num1  lt  infoArray1 Length  num1                          FieldInfo info1   infoArray1 num1               if  info1 FieldType    typeof OpCode                                 OpCode code1    OpCode info1 GetValue null                   ushort num2    ushort code1 Value                  if  num2  lt  0x100                                        singleByteOpcodes  int num2    code1                                    else                                       if   num2  amp  0xff00     0xfe00                                                throw new Exception  Invalid opcode      num2 ToString                                               multiByteOpcodes num2  amp  0xff    code1                                                       private static OpCode   singleByteOpcodes      private static OpCode   multiByteOpcodes       public static MethodBase   Decompile MethodBase mi  byte   ildata                HashSet lt MethodBase gt  result   new HashSet lt MethodBase gt              Module module   mi Module           int position   0          while  position  lt  ildata Length                        OpCode code   OpCodes Nop               ushort b   ildata position                 if  b    0xfe                                code   singleByteOpcodes b                             else                               b   ildata position                     code   multiByteOpcodes b                   b     ushort  0xfe00                              switch  code OperandType                                case OperandType InlineNone                      break                  case OperandType ShortInlineBrTarget                  case OperandType ShortInlineI                  case OperandType ShortInlineVar                      position    1                      break                  case OperandType InlineVar                      position    2                      break                  case OperandType InlineBrTarget                  case OperandType InlineField                  case OperandType InlineI                  case OperandType InlineSig                  case OperandType InlineString                  case OperandType InlineTok                  case OperandType InlineType                  case OperandType ShortInlineR                      position    4                      break                  case OperandType InlineR                  case OperandType InlineI8                      position    8                      break                  case OperandType InlineSwitch                      int count   BitConverter ToInt32 ildata  position                       position    count   4   4                      break                   case OperandType InlineMethod                      int methodId   BitConverter ToInt32 ildata  position                       position    4                      try                                               if  mi is ConstructorInfo                                                        result Add  MethodBase module ResolveMember methodId  mi DeclaringType GetGenericArguments    Type EmptyTypes                                                      else                                                       result Add  MethodBase module ResolveMember methodId  mi DeclaringType GetGenericArguments    mi GetGenericArguments                                                                          catch                          break                    default                      throw new Exception  Unknown instruction operand  cannot continue  Operand type      code OperandType                                   return result ToArray             class StackOverflowDetector          This method will be found      static int Recur                 CheckStackDepth            int variable   1          return variable   Recur               static void Main string   args                RecursionDetector            Console WriteLine            Console ReadLine               static void RecursionDetector                    First decompile all methods in the assembly          Dictionary lt MethodBase  MethodBase   gt  calling   new Dictionary lt MethodBase  MethodBase   gt             var assembly   typeof StackOverflowDetector  Assembly           foreach  var type in assembly GetTypes                          foreach  var member in type GetMembers BindingFlags Public   BindingFlags NonPublic   BindingFlags Static   BindingFlags Instance  OfType lt MethodBase gt                                   var body   member GetMethodBody                    if  body  null                                        var bytes   body GetILAsByteArray                        if  bytes    null                                                   Store all the calls of this method                          var calls   Decompiler Decompile member  bytes                           calling member    calls                                                                              Check every method          foreach  var method in calling Keys                           If method A - gt      - gt  method A  we have a possible infinite recursion             CheckRecursion method  calling  new HashSet lt MethodBase gt                        Now  the fact that a method cycle contains recursion  is by no means a guarantee that a stack overflow will happen - it s just the most likely precondition for your stack overflow exception  In short  this means that this code will determine the pieces of code where a stack overflow can occur  which should narrow down most code considerably   Yet other approaches  There are some other approaches you can try that I haven t described here    Handling the stack overflow by hosting the CLR process and handling it  Note that you still cannot  catch  it  Changing all IL code  building another DLL  adding checks on recursion  Yes  that s quite possible  I ve implemented it in the past  -   it s just difficult and involves a lot of code to get it right  Use the  NET profiling API to capture all method calls and use that to figure out stack overflows  For example  you can implement checks that if you encounter the same method X times in your call tree  you give a signal  There s a project here that will give you a head start

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If you application depends on 3d-party code  in Xsl-scripts  then you have to decide first do you want to defend from bugs in them or not  If you really want to defend then I think you should execute your logic which prone to external errors in separate AppDomains  Catching StackOverflowException is not good   Check also this question

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By the looks of it  apart from starting another process  there doesn t seem to be any way of handling a StackOverflowException  Before anyone else asks  I tried using AppDomain  but that didn t work   using System  using System Collections Generic  using System Linq  using System Reflection  using System Text  using System Threading   namespace StackOverflowExceptionAppDomainTest       class Program               static void recrusiveAlgorithm                         recrusiveAlgorithm                      static void Main string   args                        if args Length gt 0 amp  amp args 0    --child                                 recrusiveAlgorithm                              else                               var domain   AppDomain CreateDomain  Child domain to test StackOverflowException in                     domain ExecuteAssembly Assembly GetEntryAssembly   CodeBase  new      --child                      domain UnhandledException     object sender  UnhandledExceptionEventArgs e    gt                                        Console WriteLine  Detected unhandled exception      e ExceptionObject ToString                                        while  true                                        Console WriteLine                           Thread Sleep 1000                                                       If you do end up using the separate-process solution  however  I would recommend using Process Exited and Process StandardOutput and handle the errors yourself  to give your users a better experience

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I would suggest creating a wrapper around XmlWriter object  so it would count amount of calls to WriteStartElement WriteEndElement  and if you limit amount of tags to some number  f e  100   you would be able to throw a different exception  for example - InvalidOperation   That should solve the problem in the majority of the cases  public class LimitedDepthXmlWriter   XmlWriter       private readonly XmlWriter  innerWriter      private readonly int  maxDepth      private int  depth       public LimitedDepthXmlWriter XmlWriter innerWriter   this innerWriter  100                   public LimitedDepthXmlWriter XmlWriter innerWriter  int maxDepth                 maxDepth   maxDepth           innerWriter   innerWriter             public override void Close                  innerWriter Close               public override void Flush                  innerWriter Flush               public override string LookupPrefix string ns                return  innerWriter LookupPrefix ns              public override void WriteBase64 byte   buffer  int index  int count                 innerWriter WriteBase64 buffer  index  count              public override void WriteCData string text                 innerWriter WriteCData text              public override void WriteCharEntity char ch                 innerWriter WriteCharEntity ch              public override void WriteChars char   buffer  int index  int count                 innerWriter WriteChars buffer  index  count              public override void WriteComment string text                 innerWriter WriteComment text              public override void WriteDocType string name  string pubid  string sysid  string subset                 innerWriter WriteDocType name  pubid  sysid  subset              public override void WriteEndAttribute                  innerWriter WriteEndAttribute               public override void WriteEndDocument                  innerWriter WriteEndDocument               public override void WriteEndElement                  depth--            innerWriter WriteEndElement               public override void WriteEntityRef string name                 innerWriter WriteEntityRef name              public override void WriteFullEndElement                  innerWriter WriteFullEndElement               public override void WriteProcessingInstruction string name  string text                 innerWriter WriteProcessingInstruction name  text              public override void WriteRaw string data                 innerWriter WriteRaw data              public override void WriteRaw char   buffer  int index  int count                 innerWriter WriteRaw buffer  index  count              public override void WriteStartAttribute string prefix  string localName  string ns                 innerWriter WriteStartAttribute prefix  localName  ns              public override void WriteStartDocument bool standalone                 innerWriter WriteStartDocument standalone              public override void WriteStartDocument                  innerWriter WriteStartDocument               public override void WriteStartElement string prefix  string localName  string ns                if   depth    gt   maxDepth  ThrowException              innerWriter WriteStartElement prefix  localName  ns              public override WriteState WriteState               get   return  innerWriter WriteState               public override void WriteString string text                 innerWriter WriteString text              public override void WriteSurrogateCharEntity char lowChar  char highChar                 innerWriter WriteSurrogateCharEntity lowChar  highChar              public override void WriteWhitespace string ws                 innerWriter WriteWhitespace ws              private void ThrowException                 throw new InvalidOperationException string Format  Result xml has more than  0  nested tags  It is possible that xslt transformation contains an endless recursive call     maxDepth

User · Answer

This answer is for  WilliamJockusch      I m wondering if there is a general way to track down   StackOverflowExceptions  In other words  suppose I have infinite   recursion somewhere in my code  but I have no idea where  I want to   track it down by some means that is easier than stepping through code   all over the place until I see it happening  I don t care how hackish   it is  For example  It would be great to have a module I could   activate  perhaps even from another thread  that polled the stack   depth and complained if it got to a level I considered  too high   For   example  I might set  too high  to 600 frames  figuring that if the   stack were too deep  that has to be a problem  Is something like that   possible  Another example would be to log every 1000th method call   within my code to the debug output  The chances this would get some   evidence of the overlow would be pretty good  and it likely would not   blow up the output too badly  The key is that it cannot involve   writing a check wherever the overflow is happening  Because the entire   problem is that I don t know where that is  Preferrably the solution   should not depend on what my development environment looks like  i e    it should not assumet that I am using C  via a specific toolset  e g    VS     It sounds like you re keen to hear some debugging techniques to catch this StackOverflow so I thought I would share a couple for you to try   1  Memory Dumps   Pro s  Memory Dumps are a sure fire way to work out the cause of a Stack Overflow  A C  MVP  amp  I worked together troubleshooting a SO and he went on to blog about it here   This method is the fastest way to track down the problem   This method wont require you to reproduce problems by following steps seen in logs   Con s  Memory Dumps are very large and you have to attach AdPlus procdump the process   2  Aspect Orientated Programming   Pro s  This is probably the easiest way for you to implement code that checks the size of the call stack from any method without writing code in every method of your application  There are a bunch of AOP Frameworks that allow you to Intercept before and after calls   Will tell you the methods that are causing the Stack Overflow   Allows you to check the StackTrace   FrameCount at the entry and exit of all methods in your application   Con s  It will have a performance impact - the hooks are embedded into the IL for every method and you cant really  de-activate  it out   It somewhat depends on your development environment tool set   3  Logging User Activity   A week ago I was trying to hunt down several hard to reproduce problems  I posted this QA User Activity Logging  Telemetry  and Variables in Global Exception Handlers    The conclusion I came to was a really simple user-actions-logger to see how to reproduce problems in a debugger when any unhandled exception occurs   Pro s  You can turn it on  or off at will  ie subscribing to events     Tracking the user actions doesn t require intercepting every method   You can count the number of events methods are subscribed too far more simply than with AOP    The log files are relatively small and focus on what actions you need to perform to reproduce the problem   It can help you to understand how users are using your application   Con s  Isn t suited to a Windows Service and I m sure there are better tools like this for web apps   Doesn t necessarily tell you the methods that cause the Stack Overflow   Requires you to step through logs manually reproducing problems rather than a Memory Dump where you can get it and debug it straight away    nbsp       Maybe you might try all techniques I mention above and some that  atlaste posted and tell us which one s you found were the easiest quickest dirtiest most acceptable to run in a PROD environment etc    Anyway good luck tracking down this SO

User · Answer

By the looks of it  apart from starting another process  there doesn t seem to be any way of handling a StackOverflowException  Before anyone else asks  I tried using AppDomain  but that didn t work   using System  using System Collections Generic  using System Linq  using System Reflection  using System Text  using System Threading   namespace StackOverflowExceptionAppDomainTest       class Program               static void recrusiveAlgorithm                         recrusiveAlgorithm                      static void Main string   args                        if args Length gt 0 amp  amp args 0    --child                                 recrusiveAlgorithm                              else                               var domain   AppDomain CreateDomain  Child domain to test StackOverflowException in                     domain ExecuteAssembly Assembly GetEntryAssembly   CodeBase  new      --child                      domain UnhandledException     object sender  UnhandledExceptionEventArgs e    gt                                        Console WriteLine  Detected unhandled exception      e ExceptionObject ToString                                        while  true                                        Console WriteLine                           Thread Sleep 1000                                                       If you do end up using the separate-process solution  however  I would recommend using Process Exited and Process StandardOutput and handle the errors yourself  to give your users a better experience

[c#] How do I prevent and/or handle a StackOverflowException?

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