Unable to execute func-eval using Mdbg due to exception "code optimized"

Question

We use MdbgCore.dll to evaluate the property with the parameter in the freeze frame of the stream.

To do this, we run func-eval.

Unfortunately, all our attempts to execute func-eval fail with CORDBG_E_ILLEGAL_IN_OPTIMIZED_CODE, which is apparently due to the fact that the stream is used to prevent func-eval from being in the GC security point.

This is described here: http://blogs.msdn.com/b/jmstall/archive/2005/11/15/funceval-rules.aspx .

We tried to check all the threads in the process to find the thread that is in the GC security point, but they all seem to have a UserState marked USER_UNSAFE_POINT.

There is very little documentation on this, and we are pulling our hair trying to figure out if there is a way to get the thread at the GC security point so that we can execute func-eval. We will look at everything that allows us to break into a process deterministically using a thread to perform func-eval with.

Disclaimer: we are trying to evaluate a method for a class that is in an optimized assembly, so we are not sure if this could also cause a problem.

The following is sample code:

if (argument.TypeName.EndsWith( "WorkerRequest", StringComparison.OrdinalIgnoreCase) && !argument.IsNull) { try { // Invoke the "GetUriPath()" function to obtain the URI string functionName = "System.Web.HttpWorkerRequest.GetUriPath"; MDbgFunction func = debugger.Processes.Active.ResolveFunctionNameFromScope( functionName, thread.CorThread.AppDomain ); if (null == func) { throw new InvalidOperationException( String.Format("Could not resolve {0}", functionName)); } // Setup the eval CorEval eval = threadForFuncEvals.CorThread.CreateEval(); // Setup the function parameters List<CorValue> values = new List<CorValue>(); // Add the worker request "this" pointer values.Add( argument.CorValue ); // resume the thread being used to do the func-eval threadForFuncEvals.CorThread.DebugState = CorDebugThreadState.THREAD_RUN; // Queue the function for execution // EXCEPTION THROWN BELOW // EXCEPTION THROWN BELOW // EXCEPTION THROWN BELOW eval.CallFunction(func.CorFunction, values.ToArray()); // BUGBUG: Should we pause all other threads to prevent them from moving? // Continue the process to execute the function if (!proc.Go().WaitOne(settings.BreakTimeout)) { throw new InvalidOperationException("Timeout while evaluating function"); } // get the returned string var result = eval.Result; if (result != null) { MDbgValue mv = new MDbgValue(proc, result); string returnedValue = mv.GetStringValue(false); threadInfo.Url = returnedValue; } } catch (Exception e) { // BUGBUG: Ignoring exception } finally { // suspend the thread again if (threadForFuncEvals != null) { threadForFuncEvals.CorThread.DebugState = CorDebugThreadState.THREAD_SUSPEND; } } 

}

Microsoft / Mdbg team, can you help?

Best, Mike

Answer 1

Does this have anything to do with JIT optimization? JIT optimization is disabled in my program (for technical reasons, I think you can only do this using CreateProcess () and not use Attach ()).

  proc = m_Debugger.CreateProcess(ProcessName, ProcessArgs, DebugModeFlag.Default, DebugEngineUtils.GetAssemblyRuntimeVersion(ProcessName,DefaultNetVersion)); if (proc!=null) proc.CorProcess.OnCreateProcess += new Microsoft.Samples.Debugging.CorDebug.CorProcessEventHandler(CorProcess_OnCreateProcess); if (proc!=null) proc.CorProcess.OnModuleLoad += new Microsoft.Samples.Debugging.CorDebug.CorModuleEventHandler(CorProcess_OnModuleLoad); void CorProcess_OnModuleLoad(object sender, Microsoft.Samples.Debugging.CorDebug.CorModuleEventArgs e) { e.Module.JITCompilerFlags = Microsoft.Samples.Debugging.CorDebug.CorDebugJITCompilerFlags.CORDEBUG_JIT_DISABLE_OPTIMIZATION; } void CorProcess_OnCreateProcess(object sender, Microsoft.Samples.Debugging.CorDebug.CorProcessEventArgs e) { //try to disable optimization ((Microsoft.Samples.Debugging.CorDebug.CorProcess)sender).DesiredNGENCompilerFlags = Microsoft.Samples.Debugging.CorDebug.CorDebugJITCompilerFlags.CORDEBUG_JIT_DISABLE_OPTIMIZATION; }