Set ErrorInfo in Marshal.GetHRForException

Marshal.GetHRForException had a MonoTODO because it needs to set the errorinfo object so that exceptions get properly passed to unmanaged code. Since not all managed exceptions have a corresponding HR value but we might need to get to the original thrown exception we implement a ManagedErrorInfo helper class that implements the IErrorInfo interface but also stores the exception. In GetExceptionForHR we check if the errorinfo we get is a ManagedErrorInfo. If it is we return the exception stored in there (if it converts to the same error code), otherwise we construct a new exception. Change-Id: Ib400636ee3caa54c9db8f41dbd40f15710024a63
mono · Jan 19, 2012 · c442c61 · c442c61
1 parent aa39994
commit c442c61
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Showing 3 changed files with 98 additions and 20 deletions.
diff --git a/mcs/class/corlib/System.Runtime.InteropServices/ManagedErrorInfo.cs b/mcs/class/corlib/System.Runtime.InteropServices/ManagedErrorInfo.cs
@@ -0,0 +1,63 @@
+// ManagedErrorInfo class
+//
+// Eberhard Beilharz (eb1@sil.org)
+//
+// Copyright (C) 2012 SIL International
+using System;
+using System.Runtime.CompilerServices;
+using System.Security;
+
+namespace System.Runtime.InteropServices
+{
+	/// <summary>
+	/// Helper class that allows to pass an exception as an IErrorInfo object. This is useful
+	/// when we get an exception in managed code that is called from unmanaged code that is called
+	/// from managed code and we want to get to the exception in the outer managed code.
+	/// </summary>
+	internal class ManagedErrorInfo: IErrorInfo
+	{
+		private Exception m_Exception;
+		public ManagedErrorInfo (Exception e)
+		{
+			m_Exception = e;
+		}
+
+		public Exception Exception {
+			get { return m_Exception; }
+		}
+
+		#region IErrorInfo
+		public int GetGUID (out Guid guid)
+		{
+			// not supported
+			guid = Guid.Empty;
+			return 0;
+		}
+
+		public int GetSource (out string source)
+		{
+			source = m_Exception.Source;
+			return 0;
+		}
+
+		public int GetDescription (out string description)
+		{
+			description = m_Exception.Message;
+			return 0;
+		}
+
+		public int GetHelpFile (out string helpFile)
+		{
+			helpFile = m_Exception.HelpLink;
+			return 0;
+		}
+
+		public int GetHelpContext(out uint helpContext)
+		{
+			// not supported
+			helpContext = 0;
+			return 0;
+		}
+		#endregion
+	}
+}
diff --git a/mcs/class/corlib/System.Runtime.InteropServices/Marshal.cs b/mcs/class/corlib/System.Runtime.InteropServices/Marshal.cs
@@ -363,9 +363,16 @@ public static IntPtr GetHINSTANCE (Module m)
 		}
 #endif // !NET_2_1
 
-		[MonoTODO ("SetErrorInfo")]
 		public static int GetHRForException (Exception e)
 		{
+			try {
+				var errorInfo = new ManagedErrorInfo(e);
+				SetErrorInfo (0, errorInfo);
+			} catch (Exception ee) {
+				// ignore any exception - probably there's no suitable SetErrorInfo
+				// method available.
+			}
+
 			return e.hresult;
 		}
 
@@ -1242,6 +1249,10 @@ private static Exception ConvertHrToException (int errorCode)
 			return null;
 		}
 
+		[DllImport ("oleaut32.dll", CharSet=CharSet.Unicode)]
+		internal static extern int SetErrorInfo (int dwReserved,
+			[MarshalAs(UnmanagedType.Interface)] IErrorInfo pIErrorInfo);
+
 		[DllImport ("oleaut32.dll", CharSet=CharSet.Unicode)]
 		internal static extern int GetErrorInfo (int dwReserved,
 			[MarshalAs(UnmanagedType.Interface)] out IErrorInfo ppIErrorInfo);
@@ -1253,10 +1264,8 @@ public static Exception GetExceptionForHR (int errorCode)
 
 		public static Exception GetExceptionForHR (int errorCode, IntPtr errorInfoPtr)
 		{
-			Exception e = ConvertHrToException (errorCode);
-
-			if (errorInfoPtr != (IntPtr)(-1) && e != null) {
-				IErrorInfo errorInfo = null;
+			IErrorInfo errorInfo = null;
+			if (errorInfoPtr != (IntPtr)(-1)) {
 				if (errorInfoPtr == IntPtr.Zero) {
 					try {
 						if (GetErrorInfo (0, out errorInfo) != 0) {
@@ -1270,22 +1279,27 @@ public static Exception GetExceptionForHR (int errorCode, IntPtr errorInfoPtr)
 				} else {
 					errorInfo = Marshal.GetObjectForIUnknown (errorInfoPtr) as IErrorInfo;
 				}
+			}
 
-				if (errorInfo != null) {
-					uint helpContext;
-					errorInfo.GetHelpContext (out helpContext);
-					string str;
-					errorInfo.GetSource (out str);
-					e.Source = str;
-					errorInfo.GetDescription (out str);
-					e.SetMessage (str);
-					errorInfo.GetHelpFile (out str);
-
-					if (helpContext == 0) {
-						e.HelpLink = str;
-					} else {
-						e.HelpLink = string.Format ("{0}#{1}", str, helpContext);
-					}
+			if (errorInfo is ManagedErrorInfo && ((ManagedErrorInfo)errorInfo).Exception.hresult == errorCode) {
+				return ((ManagedErrorInfo)errorInfo).Exception;
+			}
+
+			Exception e = ConvertHrToException (errorCode);
+			if (errorInfo != null && e != null) {
+				uint helpContext;
+				errorInfo.GetHelpContext (out helpContext);
+				string str;
+				errorInfo.GetSource (out str);
+				e.Source = str;
+				errorInfo.GetDescription (out str);
+				e.SetMessage (str);
+				errorInfo.GetHelpFile (out str);
+
+				if (helpContext == 0) {
+					e.HelpLink = str;
+				} else {
+					e.HelpLink = string.Format ("{0}#{1}", str, helpContext);
 				}
 			}
 			return e;

diff --git a/mcs/class/corlib/corlib.dll.sources b/mcs/class/corlib/corlib.dll.sources
@@ -774,6 +774,7 @@ System.Runtime.InteropServices/InvalidOleVariantTypeException.cs
 System.Runtime.InteropServices/LCIDConversionAttribute.cs
 System.Runtime.InteropServices/LIBFLAGS.cs
 System.Runtime.InteropServices/LayoutKind.cs
+System.Runtime.InteropServices/ManagedErrorInfo.cs
 System.Runtime.InteropServices/Marshal.cs
 System.Runtime.InteropServices/MarshalAsAttribute.cs
 System.Runtime.InteropServices/MarshalDirectiveException.cs