Fix handling of empty string constants (#776)

Author: jbevain

Mono.Cecil/AssemblyReader.cs

@@ -3005,7 +3005,9 @@ ConstantDebugInformation ReadLocalConstant (uint rid)
 
 			object value;
 			if (type.etype == ElementType.String) {
-				if (signature.CanReadMore () && signature.buffer [signature.position] != 0xff) {
+				if (!signature.CanReadMore ())
+					value = "";
+				else if (signature.buffer [signature.position] != 0xff) {
 					var bytes = signature.ReadBytes ((int) (signature.sig_length - (signature.position - signature.start)));
 					value = Encoding.Unicode.GetString (bytes, 0, bytes.Length);
 				} else

Test/Mono.Cecil.Tests/PortablePdbTests.cs

@@ -474,6 +474,23 @@ public void GenericInstConstantRecord ()
 			}
 		}
 
+		[Test]
+		public void EmptyStringLocalConstant ()
+		{
+			TestModule ("empty-str-const.exe", module => {
+				var type = module.GetType ("<Program>$");
+				var method = type.GetMethod ("<Main>$");
+				var symbol = method.DebugInformation;
+
+				Assert.IsNotNull (symbol);
+				Assert.AreEqual (1, symbol.Scope.Constants.Count);
+
+				var a = symbol.Scope.Constants [0];
+				Assert.AreEqual ("value", a.Name);
+				Assert.AreEqual ("", a.Value);
+			}, symbolReaderProvider: typeof (PortablePdbReaderProvider), symbolWriterProvider: typeof (PortablePdbWriterProvider));
+		}
+
 		[Test]
 		public void SourceLink ()
 		{