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Debugging the World Starting with the CLR Corneliu I. Tusnea Senior Consultant, Readify. It works on my machine!. Agenda. (Improving) Visual Studio Debugging Production Debugging Tips & Tools Resources. Visual Studio Debugging. Attributes Debug support DebuggerStepThroughAttribute
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Debugging the World Starting with the CLR Corneliu I. Tusnea Senior Consultant, Readify It works on my machine! Discover, Master, Influence
Agenda • (Improving) Visual Studio Debugging • Production Debugging • Tips & Tools • Resources Discover, Master, Influence
Visual Studio Debugging • Attributes • Debug support • DebuggerStepThroughAttribute • DebuggerNonUserCodeAttribute • Debug enhancement • DebuggerDisplayAttribute • DebuggerTypeProxyAttribute • DebuggerBrowsableAttribute • DebuggerVisualizerAttribute Discover, Master, Influence
Visual Studio DebuggingDemo Attributes Discover, Master, Influence
Sample Source Code [DebuggerDisplayAttribute( "Id={id} Name={firstName, nq} {lastName, nq}")] public class Customer { [DebuggerBrowsable(DebuggerBrowsableState.Never)] private int id; [DebuggerBrowsable(DebuggerBrowsableState.Never)] private string firstName; [DebuggerBrowsable(DebuggerBrowsableState.Never)] private string lastName; Discover, Master, Influence
Improving Visual Studio Debugging • Object Ids • Custom breakpoints • Trace points • Breakpoint Conditions Discover, Master, Influence
Visual Studio DebuggingDemo Object Ids, Breakpoints and Trace points Discover, Master, Influence
Production Debugging • Memory dumps • Full memory dump • Mini memory dump • Process crashes • Start-up crashes • Recovering code • Full memory dump • Mini memory dump Discover, Master, Influence
Production DebuggingDemo Taking memory dumps of processes Discover, Master, Influence
Demo Walkthrough Vista/W2k8: - Task Manager - Right-click process - “Create Dump File” Memory dump on crash/exception: - adplus –crash –quiet –pn w3wp.exe Memory dump now: - adplus –hang –quiet –pn w3wp.exe Discover, Master, Influence
Production Debugging • Process crashes • Crash • Start-up crashes • Hang (deadlock) • Sudden death (unexpected exit) • Exceptions • First chance exceptions • Second chance exceptions Discover, Master, Influence
Production DebuggingDemo Finding the cause of a crashing process Discover, Master, Influence
Demo walkthrough Windbg <load memory dump or attach to process> .loadbysosmscorwks – load sosextentions !threads – check running threads ~xs – switch to thread id (x = thread id) !pe – print thread exception !dso – dump stack objects !do – dump object with address Discover, Master, Influence
Production DebuggingDemo Recovering the code from a memory dump Discover, Master, Influence
Recovering Assemblies start end Module: 01250000 01256000ACorns_Debugging_StartupCrashTest Method Table -> lmv m*<name>* 800135c0 public class MyClass { Method Desc -> !dumpmt 80013570 private void MyFunction(stringsomeParameter) { ... 8015026f if (String.IsNullOrEmpty( someParameter )) IP -> !ip2md 801502c3 throw new ApplicationException(); ... 801504d1 } 80014290 private void MyOtherFunction() {...} } Use RetAddress from Call Stack (!clrstack) Use IP from Exception (!pe) Discover, Master, Influence
Demo walkthrough !ip2md <IP> - map instruction to method !dumpmt <method table> - show the method table lmv m*<module name>* - show details of module !savemodule <addr> <dll> - save the module Discover, Master, Influence
Production DebuggingDemo Finding crashes on start-up Discover, Master, Influence
Start-up Crashes • Start-up Crashes in Windows Services • Gflags.exe • Service has to be able to interact with desktop • Set Debugger for your ImageFile to windbg.exe • Image file is the executable name • This will modify the following registry key: • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT \ CurrentVersion\Image File Execution Options\<name of the exe>\Debugger • For processes set this value to allow long wait from SCM on start-up • HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Control \ ServicesPipeTimeout (30000000) Discover, Master, Influence
GFlags • gflags.exe Discover, Master, Influence
WinDbg • Good to know tips: • sxeav break on access violation • sxeclr break on all clr exceptions • SRV*c:\..* http://msdl.microsoft.com/download/symbols • bpnative breakpoint • bpntdll!zwterminateprocess breakpoint when process is terminated • sxe -c "!pe;!clrstack;gc" clr stop, display exception, dump stack, go • !dumpheap -type CompilerError asp.net compilation errors • !dumpobject0xxxxxxx • !dumpobjecterrorMessageText • !dumpheap -stat -min 85000 Large Object Heap Objects • !dumpdomain -stat • AdPlus (Memory dumps) • Adplus.vbs –crash –pnprocessname| –p processid • Adplus.vbs –hang –p|-pn Discover, Master, Influence
Tools and Resources • ACorns.Debugging Tools • FindDeadlock • FindStartupException • SOS Assist • SOS Extensions • http://www.stevestechspot.com/SOSEXANewDebuggingExtensionForManagedCode.aspx • DbgHelp (trigger memory dumps from .net code) • http://msdn.microsoft.com/en-us/library/ms679294(VS.85).aspx • Hawkeye • www.acorns.com.au/projects/hawkeye/ • www.codeplex.com/hawkeye/ • Good references • http://www.microsoft.com/whdc/ddk/debugging/ • http://dotnetdebug.net/category/windbg/ • http://blogs.msdn.com/tess/pages/net-debugging-demos-information-and-setup-instructions.aspx • http://www.codeproject.com/KB/debug/windbg_part1.aspx Discover, Master, Influence
A Readify Developer Network session By Corneliu I. Tusnea, Senior Consultant, Readify Email Address: corneliu.tusnea@readify.net RDN Website: www.readify.net/rdn Blog: http://www.acorns.com.au Discover, Master, Influence