MessageLayoutRenderer - Handle Exception ToString can throw with AOT

snakefoot · snakefoot · commit 09b9ec395b95 · 2025-09-07T11:55:20.000+02:00
diff --git a/src/NLog/LayoutRenderers/ExceptionLayoutRenderer.cs b/src/NLog/LayoutRenderers/ExceptionLayoutRenderer.cs
@@ -440,8 +440,8 @@ protected virtual void AppendToString(StringBuilder sb, Exception ex)
 
             try
             {
-                exceptionMessage = ex.Message;
                 innerException = ex.InnerException;
+                exceptionMessage = ex.Message;
                 sb.Append(ex.ToString());
             }
             catch (Exception exception)
diff --git a/src/NLog/LayoutRenderers/MessageLayoutRenderer.cs b/src/NLog/LayoutRenderers/MessageLayoutRenderer.cs
@@ -35,6 +35,7 @@ namespace NLog.LayoutRenderers
 {
     using System;
     using System.Text;
+    using NLog.Common;
     using NLog.Config;
     using NLog.Internal;
 
@@ -96,7 +97,31 @@ protected override void Append(StringBuilder builder, LogEventInfo logEvent)
                 Exception primaryException = GetPrimaryException(logEvent.Exception);
                 if (!exceptionOnly)
                     builder.Append(ExceptionSeparator);
-                builder.Append(primaryException.ToString());
+
+                AppendExceptionToString(builder, primaryException);
+            }
+        }
+
+        private static void AppendExceptionToString(StringBuilder builder, Exception exception)
+        {
+            string exceptionMessage = string.Empty;
+            Exception? innerException = null;
+
+            try
+            {
+                innerException = exception.InnerException;
+                exceptionMessage = exception.Message;
+                builder.Append(exception.ToString());
+            }
+            catch (Exception ex)
+            {
+                InternalLogger.Warn(ex, "Message-LayoutRenderer Could not output ToString for Exception: {0}", exception.GetType());
+                builder.Append($"{exception.GetType()}: {exceptionMessage}");
+                if (innerException != null)
+                {
+                    builder.AppendLine();
+                    AppendExceptionToString(builder, innerException);
+                }
             }
         }
 

Original file line number	Diff line number	Diff line change
`@@ -440,8 +440,8 @@ protected virtual void AppendToString(StringBuilder sb, Exception ex)`
`440`	`440`
`441`	`441`	`try`
`442`	`442`	`{`
`443`		`- exceptionMessage = ex.Message;`
`444`	`443`	`innerException = ex.InnerException;`
	`444`	`+ exceptionMessage = ex.Message;`
`445`	`445`	`sb.Append(ex.ToString());`
`446`	`446`	`}`
`447`	`447`	`catch (Exception exception)`