From 5c61f7618f4e2b52b55f33c0e64afb40f2a950ff Mon Sep 17 00:00:00 2001
From: de4dot <de4dot@gmail.com>
Date: Wed, 11 Apr 2012 02:00:44 +0200
Subject: [PATCH] Support invalid try handlers where start == end

---
 blocks/CodeGenerator.cs         | 20 ++++++++++++++------
 blocks/InstructionListParser.cs |  3 +++
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/blocks/CodeGenerator.cs b/blocks/CodeGenerator.cs
index 4546072a..1db3d945 100644
--- a/blocks/CodeGenerator.cs
+++ b/blocks/CodeGenerator.cs
@@ -50,7 +50,7 @@ namespace de4dot.blocks {
 			public ExceptionInfo(int tryStart, int tryEnd, int filterStart,
 				int handlerStart, int handlerEnd, TypeReference catchType,
 				ExceptionHandlerType handlerType) {
-				if (tryStart > tryEnd || filterStart > handlerStart || handlerStart > handlerEnd ||
+				if (tryStart > tryEnd || filterStart > handlerStart ||
 					tryStart < 0 || tryEnd < 0 || filterStart < 0 || handlerStart < 0 || handlerEnd < 0)
 					throw new ApplicationException("Invalid start/end/filter/handler indexes");
 				this.tryStart = tryStart;
@@ -196,11 +196,11 @@ namespace de4dot.blocks {
 			}
 
 			foreach (var ex in exceptions) {
-				var tryStart = blockInfos[ex.tryStart].start;
-				var tryEnd = blockInfos[ex.tryEnd].end;
-				var filterStart = ex.filterStart == -1 ? -1 : blockInfos[ex.filterStart].start;
-				var handlerStart = blockInfos[ex.handlerStart].start;
-				var handlerEnd = blockInfos[ex.handlerEnd].end;
+				var tryStart = getBlockInfo(blockInfos, ex.tryStart).start;
+				var tryEnd = getBlockInfo(blockInfos, ex.tryEnd).end;
+				var filterStart = ex.filterStart == -1 ? -1 : getBlockInfo(blockInfos, ex.filterStart).start;
+				var handlerStart = getBlockInfo(blockInfos, ex.handlerStart).start;
+				var handlerEnd = getBlockInfo(blockInfos, ex.handlerEnd).end;
 
 				var eh = new ExceptionHandler(ex.handlerType);
 				eh.CatchType = ex.catchType;
@@ -214,6 +214,14 @@ namespace de4dot.blocks {
 			}
 		}
 
+		static BlockInfo getBlockInfo(List<BlockInfo> blockInfos, int index) {
+			if (index >= blockInfos.Count)
+				index = blockInfos.Count - 1;
+			if (index < 0)
+				index = 0;
+			return blockInfos[index];
+		}
+
 		static Instruction getInstruction(IList<Instruction> allInstructions, int i) {
 			if (i < allInstructions.Count)
 				return allInstructions[i];
diff --git a/blocks/InstructionListParser.cs b/blocks/InstructionListParser.cs
index f7b3b83d..33288f03 100644
--- a/blocks/InstructionListParser.cs
+++ b/blocks/InstructionListParser.cs
@@ -289,6 +289,9 @@ namespace de4dot.blocks {
 
 			// Replace the BaseBlocks with a new BaseBlock, returning the old ones.
 			public List<BaseBlock> replace(int startInstr, int endInstr, ScopeBlock bb) {
+				if (endInstr < startInstr)
+					return new List<BaseBlock>();
+
 				int startIndex, endIndex;
 				var rv = getBlocks(startInstr, endInstr, out startIndex, out endIndex);
 				updateParent(rv, bb);