From ec0d74690d45d0bc8c4be2d914755b4ce8c487d8 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Alexander=20K=C3=B6plinger?= <alex.koeplinger@outlook.com>
Date: Wed, 18 Jan 2017 16:48:07 +0100
Subject: [PATCH] [pdb2mdb] Detect portable PDB and fail gracefully instead of
 crashing (#4261)

Before when trying to convert an assembly that had a portable PDB
instead of a native PDB alongside it we'd just crash in the
Microsoft.Cci pdb reader.

We now check whether the symbol file is a portable PDB and exit
gracefully with an error message and exit code 2 from the app.

Users which access the Converter class (like e.g. Xamarin Android [1])
directly can now catch the PortablePdbNotSupportedException to
do custom logic.

[1] https://github.com/xamarin/xamarin-android/blob/15f7547fa673e02256a75910c60c5e13eb158d2b/src/Xamarin.Android.Build.Tasks/Tasks/ConvertDebuggingFiles.cs#L28
---
 mcs/tools/pdb2mdb/Driver.cs | 49 +++++++++++++++++++++++++++++----------------
 1 file changed, 32 insertions(+), 17 deletions(-)

diff --git a/mcs/tools/pdb2mdb/Driver.cs b/mcs/tools/pdb2mdb/Driver.cs
index 93d9e8a4544..5aa1fcf0b5b 100644
--- a/mcs/tools/pdb2mdb/Driver.cs
+++ b/mcs/tools/pdb2mdb/Driver.cs
@@ -33,12 +33,31 @@ namespace Pdb2Mdb {
 			var pdb = asm.Name.Name + ".pdb";
 			pdb = Path.Combine (Path.GetDirectoryName (filename), pdb);
 
+			if (!File.Exists (pdb))
+				throw new FileNotFoundException ("PDB file doesn't exist: " + pdb);
+
 			using (var stream = File.OpenRead (pdb)) {
+				if (IsPortablePdb (stream))
+					throw new PortablePdbNotSupportedException ();
+
 				var funcs = PdbFile.LoadFunctions (stream, true);
 				Converter.Convert (asm, funcs, new MonoSymbolWriter (filename));
 			}
 		}
 
+		static bool IsPortablePdb (FileStream stream)
+		{
+			const uint ppdb_signature = 0x424a5342;
+
+			var position = stream.Position;
+			try {
+				var reader = new BinaryReader (stream);
+				return reader.ReadUInt32 () == ppdb_signature;
+			} finally {
+				stream.Position = position;
+			}
+		}
+
 		internal Converter (MonoSymbolWriter mdb)
 		{
 			this.mdb = mdb;
@@ -158,6 +177,9 @@ namespace Pdb2Mdb {
 		}
 	}
 
+	public class PortablePdbNotSupportedException : Exception {
+	}
+
 	class Driver {
 
 		static void Main (string [] args)
@@ -170,25 +192,16 @@ namespace Pdb2Mdb {
 			if (!File.Exists (asm))
 				Usage ();
 
-			var assembly = AssemblyDefinition.ReadAssembly (asm);
-
-			var pdb = assembly.Name.Name + ".pdb";
-			pdb = Path.Combine (Path.GetDirectoryName (asm), pdb);
-
-			if (!File.Exists (pdb))
+			try {
+				Converter.Convert (asm);
+			} catch (FileNotFoundException ex) {
 				Usage ();
-
-			using (var stream = File.OpenRead (pdb)) {
-				Convert (assembly, stream, new MonoSymbolWriter (asm));
+			} catch (PortablePdbNotSupportedException) {
+				Console.WriteLine ("Error: A portable PDB can't be converted to mdb.");
+				Environment.Exit (2);
 			}
-		}
-
-		static void Convert (AssemblyDefinition assembly, Stream pdb, MonoSymbolWriter mdb)
-		{
-			try {
-				Converter.Convert (assembly, PdbFile.LoadFunctions (pdb, true), mdb);
-			} catch (Exception e) {
-				Error (e);
+			catch (Exception ex) {
+				Error (ex);
 			}
 		}
 
@@ -204,6 +217,8 @@ namespace Pdb2Mdb {
 		{
 			Console.WriteLine ("Fatal error:");
 			Console.WriteLine (e);
+
+			Environment.Exit (1);
 		}
 	}
 }
-- 
2.11.4.GIT