gdb: Fix crash on stop emulation if gdb stub is enabled with app running

src/ARMeilleure/Instructions/NativeInterface.cs

@@ -3,7 +3,6 @@ using ARMeilleure.State;
 using ARMeilleure.Translation;
 using System;
 using System.Runtime.InteropServices;
-using System.Threading;
 using ExecutionContext = ARMeilleure.State.ExecutionContext;
 
 namespace ARMeilleure.Instructions

src/ARMeilleure/State/ExecutionContext.cs

@@ -1,6 +1,4 @@
 using ARMeilleure.Memory;
-using System.Collections.Concurrent;
-using System.Diagnostics;
 using System.Threading;
 
 namespace ARMeilleure.State

src/Ryujinx.Cpu/Jit/JitExecutionContext.cs

@@ -1,6 +1,5 @@
 using ARMeilleure.Memory;
 using ARMeilleure.State;
-using System.Threading;
 using ExecutionContext = ARMeilleure.State.ExecutionContext;
 
 namespace Ryujinx.Cpu.Jit

src/Ryujinx.HLE/Debugger/Debugger.cs

@@ -47,7 +47,7 @@ namespace Ryujinx.HLE.Debugger
             MessageHandlerThread.Start();
         }
 
-        private IDebuggableProcess DebugProcess => Device.System.DebugGetApplicationProcess();
+        private IDebuggableProcess DebugProcess => Device.System?.DebugGetApplicationProcess();
         private KThread[] GetThreads() => DebugProcess.GetThreadUids().Select(x => DebugProcess.GetThread(x)).ToArray();
         private bool IsProcessAarch32 => DebugProcess.GetThread(gThread.Value).Context.IsAarch32;
         private KernelContext KernelContext => Device.System.KernelContext;
@@ -238,7 +238,6 @@ namespace Ryujinx.HLE.Debugger
 
         private void ProcessCommand(string cmd)
         {
-            Logger.Debug?.Print(LogClass.GdbStub, $"Receive: {cmd}");
             StringStream ss = new StringStream(cmd);
 
             switch (ss.ReadChar())
@@ -762,6 +761,20 @@ namespace Ryujinx.HLE.Debugger
                 {
                     return;
                 }
+
+                // If the user connects before the application is running, wait for the application to start.
+                int retries = 10;
+                while (DebugProcess == null && retries-- > 0)
+                {
+                    Thread.Sleep(200);
+                }
+                if (DebugProcess == null)
+                {
+                    Logger.Warning?.Print(LogClass.GdbStub, "Application is not running, cannot accept GDB client connection");
+                    ClientSocket.Close();
+                    continue;
+                }
+
                 ClientSocket.NoDelay = true;
                 ReadStream = new NetworkStream(ClientSocket, System.IO.FileAccess.Read);
                 WriteStream = new NetworkStream(ClientSocket, System.IO.FileAccess.Write);

src/Ryujinx.HLE/HOS/Kernel/Process/KProcess.cs

@@ -689,6 +689,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Process
                 {
                     mainThread.Suspend(ThreadSchedState.ThreadPauseFlag);
                     debugState = (int)DebugState.Stopped;
+                    Logger.Notice.Print(LogClass.Kernel, $"Application is suspended on start for debugging.");
                 }
 
                 result = mainThread.Start();
@@ -742,7 +743,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Process
             ExceptionCallback breakCallback = null;
             ExceptionCallbackNoArgs stepCallback = null;
 
-            if (KernelContext.Device.Configuration.EnableGdbStub)
+            if (KernelContext.Device.Configuration.EnableGdbStub && KernelContext.Device.Debugger != null)
             {
                 breakCallback = KernelContext.Device.Debugger.BreakHandler;
                 stepCallback = KernelContext.Device.Debugger.StepHandler;

src/Ryujinx.HLE/Switch.cs

@@ -176,7 +176,7 @@ namespace Ryujinx.HLE
                 AudioDeviceDriver.Dispose();
                 FileSystem.Dispose();
                 Memory.Dispose();
-                Debugger.Dispose();
+                Debugger?.Dispose();
 
                 TitleIDs.CurrentApplication.Value = null;
                 Shared = null;