waterbox: When compiled in debug mode, forcibly evict self at every opportunity. This can be used to catch bugs using pointers past their valid time. Catch and fix two such bugs in the libsnes wrapper.

BizHawk.Common/Win32Hacks.cs

@@ -458,6 +458,14 @@ namespace BizHawk.Common
 		{
 			DeleteFileW(path + ":Zone.Identifier");
 		}
+
+		[DllImport("kernel32.dll")]
+		static extern bool IsDebuggerPresent();
+		
+		public static bool IsDebuggerReallyPresent()
+		{
+			return IsDebuggerPresent();
+		}
 	}
 
 }

BizHawk.Emulation.Cores/Consoles/Nintendo/SNES/LibsnesApi.cs

@@ -62,10 +62,12 @@ namespace BizHawk.Emulation.Cores.Nintendo.SNES
 				PlainHeapSizeKB = 2 * 1024, // TODO: wasn't there more in here?
 				SealedHeapSizeKB = 128 * 1024
 			});
-
+			using (_exe.EnterExit())
+			{
 				_core = BizInvoker.GetInvoker<CoreImpl>(_exe, _exe);
 				_comm = (CommStruct*)_core.DllInit().ToPointer();
 			}
+		}
 
 		public void Dispose()
 		{

BizHawk.Emulation.Cores/Consoles/Nintendo/SNES/LibsnesCore.ISaveRam.cs

@@ -2,6 +2,7 @@
 using System.Runtime.InteropServices;
 
 using BizHawk.Emulation.Common;
+using BizHawk.Common;
 
 namespace BizHawk.Emulation.Cores.Nintendo.SNES
 {
@@ -12,6 +13,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.SNES
 			|| Api.QUERY_get_memory_size(LibsnesApi.SNES_MEMORY.SGB_CARTRAM) != 0;
 
 		public byte[] CloneSaveRam()
+		{
+			using (Api.EnterExit())
 			{
 				byte* buf = Api.QUERY_get_memory_data(LibsnesApi.SNES_MEMORY.CARTRIDGE_RAM);
 				var size = Api.QUERY_get_memory_size(LibsnesApi.SNES_MEMORY.CARTRIDGE_RAM);
@@ -25,8 +28,11 @@ namespace BizHawk.Emulation.Cores.Nintendo.SNES
 				Marshal.Copy((IntPtr)buf, ret, 0, size);
 				return ret;
 			}
+		}
 
 		public void StoreSaveRam(byte[] data)
+		{
+			using (Api.EnterExit())
 			{
 				byte* buf = Api.QUERY_get_memory_data(LibsnesApi.SNES_MEMORY.CARTRIDGE_RAM);
 				var size = Api.QUERY_get_memory_size(LibsnesApi.SNES_MEMORY.CARTRIDGE_RAM);
@@ -50,3 +56,4 @@ namespace BizHawk.Emulation.Cores.Nintendo.SNES
 			}
 		}
 	}
+}

BizHawk.Emulation.Cores/Waterbox/PeRunner.cs

@@ -734,8 +734,10 @@ namespace BizHawk.Emulation.Cores.Waterbox
 				_syscalls.Init();
 
 				Console.WriteLine("About to enter unmanaged code");
-				if (System.Diagnostics.Debugger.IsAttached)
+				if (Win32Hacks.IsDebuggerReallyPresent() && !System.Diagnostics.Debugger.IsAttached)
 				{
+					// this means that GDB or another unconventional debugger is attached.
+					// if that's the case, and it's observing this core, it probably wants a break
 					System.Diagnostics.Debugger.Break();
 				}
 

BizHawk.Emulation.Cores/Waterbox/Swappable.cs

@@ -54,6 +54,12 @@ namespace BizHawk.Emulation.Cores.Waterbox
 		{
 			public object Sync;
 			private WeakReference LoadedRef = new WeakReference(null);
+#if DEBUG
+			/// <summary>
+			/// recursive lock count
+			/// </summary>
+			public int LockCount;
+#endif
 			public Swappable Loaded
 			{
 				get
@@ -78,6 +84,10 @@ namespace BizHawk.Emulation.Cores.Waterbox
 		public void Enter()
 		{
 			Monitor.Enter(_currentLockInfo.Sync);
+#if DEBUG
+			if (_currentLockInfo.LockCount++ != 0 && _currentLockInfo.Loaded != this)
+				throw new InvalidOperationException("Woops!");
+#endif
 			if (_currentLockInfo.Loaded != this)
 			{
 				if (_currentLockInfo.Loaded != null)
@@ -93,6 +103,16 @@ namespace BizHawk.Emulation.Cores.Waterbox
 		/// </summary>
 		public void Exit()
 		{
+#if DEBUG
+			// when debugging, if we're releasing the lock then deactivate
+			if (_currentLockInfo.LockCount-- == 1)
+			{
+				if (_currentLockInfo.Loaded != this)
+					throw new InvalidOperationException("Woops!");
+				DeactivateInternal();
+				_currentLockInfo.Loaded = null;
+			}
+#endif
 			Monitor.Exit(_currentLockInfo.Sync);
 		}