#1024: Make PDB Support in ILSpy more robust.

ICSharpCode.Decompiler/DebugInfo/PortablePdbWriter.cs

@@ -6,6 +6,7 @@ using System.IO;
 using System.Linq;
 using System.Reflection.Metadata;
 using System.Reflection.Metadata.Ecma335;
+using System.Reflection.PortableExecutable;
 using System.Security.Cryptography;
 using System.Text;
 using ICSharpCode.Decompiler.CSharp;
@@ -29,6 +30,10 @@ namespace ICSharpCode.Decompiler.DebugInfo
 		public static readonly Guid HashAlgorithmSHA256 = new Guid("8829d00f-11b8-4213-878b-770e8597ac16");
 		static readonly FileVersionInfo decompilerVersion = FileVersionInfo.GetVersionInfo(typeof(CSharpDecompiler).Assembly.Location);
 
+		public static bool HasCodeViewDebugDirectoryEntry(PEFile file)
+		{
+			return file.Reader.ReadDebugDirectory().Any(entry => entry.Type == DebugDirectoryEntryType.CodeView);
+		}
 
 		public static void WritePdb(PEFile file, CSharpDecompiler decompiler, DecompilerSettings settings, Stream targetStream)
 		{
@@ -101,7 +106,8 @@ namespace ICSharpCode.Decompiler.DebugInfo
 					metadata.AddImportScope(default, default);
 				}
 			}
-			var debugDir = file.Reader.ReadDebugDirectory().FirstOrDefault(dir => dir.IsPortableCodeView);
+
+			var debugDir = file.Reader.ReadDebugDirectory().FirstOrDefault(dir => dir.Type == DebugDirectoryEntryType.CodeView);
 			var portable = file.Reader.ReadCodeViewDebugDirectoryData(debugDir);
 			var contentId = new BlobContentId(portable.Guid, debugDir.Stamp);
 			PortablePdbBuilder serializer = new PortablePdbBuilder(metadata, GetRowCounts(reader), entrypointHandle, blobs => contentId);

ILSpy/Commands/GeneratePdbContextMenuEntry.cs

@@ -21,6 +21,7 @@ using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
+using System.Windows;
 using ICSharpCode.Decompiler;
 using ICSharpCode.Decompiler.CSharp;
 using ICSharpCode.Decompiler.DebugInfo;
@@ -51,6 +52,11 @@ namespace ICSharpCode.ILSpy
 
 		internal static void GeneratePdbForAssembly(LoadedAssembly assembly)
 		{
+			var file = assembly.GetPEFileOrNull();
+			if (!PortablePdbWriter.HasCodeViewDebugDirectoryEntry(file)) {
+				MessageBox.Show($"Cannot create PDB file for {Path.GetFileName(assembly.FileName)}, because it does not contain a PE Debug Directory Entry of type 'CodeView'.");
+				return;
+			}
 			SaveFileDialog dlg = new SaveFileDialog();
 			dlg.FileName = DecompilerTextView.CleanUpName(assembly.ShortName) + ".pdb";
 			dlg.Filter = "Portable PDB|*.pdb|All files|*.*";
@@ -62,7 +68,6 @@ namespace ICSharpCode.ILSpy
 				Stopwatch stopwatch = Stopwatch.StartNew();
 				using (FileStream stream = new FileStream(fileName, FileMode.OpenOrCreate, FileAccess.Write)) {
 					try {
-						var file = assembly.GetPEFileOrNull();
 						var decompiler = new CSharpDecompiler(file, assembly.GetAssemblyResolver(), options.DecompilerSettings);
 						PortablePdbWriter.WritePdb(file, decompiler, options.DecompilerSettings, stream);
 					} catch (OperationCanceledException) {

ILSpy/LoadedAssembly.cs

@@ -22,6 +22,7 @@ using System.IO;
 using System.Reflection.Metadata;
 using System.Reflection.PortableExecutable;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 using System.Threading;
 using System.Threading.Tasks;
 using ICSharpCode.Decompiler;
@@ -174,12 +175,12 @@ namespace ICSharpCode.ILSpy
 			return module;
 		}
 		
-		private void LoadSymbols(PEFile module)
+		void LoadSymbols(PEFile module)
 		{
 			try {
 				var reader = module.Reader;
 				// try to open portable pdb file/embedded pdb info:
-				if (reader.TryOpenAssociatedPortablePdb(fileName, OpenStream, out var provider, out var pdbFileName)) {
+				if (TryOpenPortablePdb(module, out var provider, out var pdbFileName)) {
 					debugInfoProvider = new PortableDebugInfoProvider(pdbFileName, provider);
 				} else {
 					// search for pdb in same directory as dll
@@ -192,9 +193,40 @@ namespace ICSharpCode.ILSpy
 
 					// TODO: use symbol cache, get symbols from microsoft
 				}
-			} catch (BadImageFormatException) {
+			} catch (Exception ex) when (ex is BadImageFormatException || ex is COMException) {
 				// Ignore PDB load errors
 			}
+		}
+
+		const string LegacyPDBPrefix = "Microsoft C/C++ MSF 7.00";
+		byte[] buffer = new byte[LegacyPDBPrefix.Length];
+
+		bool TryOpenPortablePdb(PEFile module, out MetadataReaderProvider provider, out string pdbFileName)
+		{
+			provider = null;
+			pdbFileName = null;
+			var reader = module.Reader;
+			foreach (var entry in reader.ReadDebugDirectory()) {
+				if (entry.IsPortableCodeView) {
+					return reader.TryOpenAssociatedPortablePdb(fileName, OpenStream, out provider, out pdbFileName);
+				}
+				if (entry.Type == DebugDirectoryEntryType.CodeView) {
+					string pdbDirectory = Path.GetDirectoryName(fileName);
+					pdbFileName = Path.Combine(pdbDirectory, Path.GetFileNameWithoutExtension(fileName) + ".pdb");
+					if (File.Exists(pdbFileName)) {
+						Stream stream = OpenStream(pdbFileName);
+						if (stream.Read(buffer, 0, buffer.Length) == LegacyPDBPrefix.Length
+							&& System.Text.Encoding.ASCII.GetString(buffer) == LegacyPDBPrefix) {
+							return false;
+						}
+						stream.Position = 0;
+						provider = MetadataReaderProvider.FromPortablePdbStream(stream);
+						return true;
+					}
+				}
+			}
+			return false;
+		}
 
 		Stream OpenStream(string fileName)
 		{
@@ -206,7 +238,6 @@ namespace ICSharpCode.ILSpy
 			memory.Position = 0;
 			return memory;
 		}
-		}
 
 		[ThreadStatic]
 		static int assemblyLoadDisableCount;