From 7b17adba08b53d6c82f2defd15261faa663c0d9b Mon Sep 17 00:00:00 2001
From: Christoph Jentzsch <jentzsch.software@gmail.com>
Date: Tue, 30 Sep 2014 06:51:20 +0200
Subject: [PATCH] Exemplar alteration to show effect of using boost::exception

---
 alethzero/MainWin.cpp    |  8 +++++++-
 libdevcore/Exceptions.h  | 17 ++++++++++++++---
 libdevcore/RLP.cpp       |  8 ++++----
 libethcore/BlockInfo.cpp | 13 +++++++++++++
 4 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/alethzero/MainWin.cpp b/alethzero/MainWin.cpp
index b4bbb8ca7..76a2f9077 100644
--- a/alethzero/MainWin.cpp
+++ b/alethzero/MainWin.cpp
@@ -776,7 +776,13 @@ static bool blockMatch(string const& _f, dev::eth::BlockDetails const& _b, h256
 		if (_f.size() > 1 && _f.size() < 10 && _f[0] == '#' && stoul(_f.substr(1)) == _b.number)
 			return true;
 	}
-	catch (...) {}
+	catch (...)
+	{
+		std::cerr << "Unhandled exception!" << std::endl <<
+			boost::current_exception_diagnostic_information();
+		// possible output would include: function name, __FILE__, __LINE__ (at throw) and all added information,
+		// such has the block header info added in BlockInfo.cpp line 101-102.
+	}
 	if (toHex(_h.ref()).find(_f) != string::npos)
 		return true;
 	BlockInfo bi(_bc.block(_h));
diff --git a/libdevcore/Exceptions.h b/libdevcore/Exceptions.h
index 15ef2019f..c1d65badc 100644
--- a/libdevcore/Exceptions.h
+++ b/libdevcore/Exceptions.h
@@ -22,6 +22,8 @@
 #pragma once
 
 #include <exception>
+#include <boost/exception/all.hpp>
+#include <boost/throw_exception.hpp>
 #include "CommonIO.h"
 #include "CommonData.h"
 #include "FixedHash.h"
@@ -36,11 +38,20 @@ public:
 	virtual char const* what() const noexcept { return typeid(*this).name(); }
 };
 
-class BadHexCharacter: public Exception {};
+// As an exemplar case I only restructure BadRLP, if I would restrucutre everything the above Exception class
+// can be replaced completely.
+
+struct BException: virtual boost::exception, virtual std::exception {};
+
+// there is no need to derive from any other class then BException just to add more information.
+// This can be done dynamically during runtime.
 
-class RLPException: public Exception {};
+struct BadRLP: virtual BException {};
+
+
+class BadHexCharacter: public Exception {};
+class RLPException: public BException {};
 class BadCast: public RLPException {};
-class BadRLP: public RLPException {};
 class NoNetworking: public Exception {};
 class NoUPnPDevice: public Exception {};
 class RootNotFound: public Exception {};
diff --git a/libdevcore/RLP.cpp b/libdevcore/RLP.cpp
index 68ae02065..79f586fa1 100644
--- a/libdevcore/RLP.cpp
+++ b/libdevcore/RLP.cpp
@@ -104,13 +104,13 @@ bool RLP::isInt() const
 	else if (n <= c_rlpDataIndLenZero)
 	{
 		if (m_data.size() <= 1)
-			throw BadRLP();
+			BOOST_THROW_EXCEPTION(BadRLP());
 		return m_data[1] != 0;
 	}
 	else if (n < c_rlpListStart)
 	{
 		if ((int)m_data.size() <= 1 + n - c_rlpDataIndLenZero)
-			throw BadRLP();
+			BOOST_THROW_EXCEPTION(BadRLP());
 		return m_data[1 + n - c_rlpDataIndLenZero] != 0;
 	}
 	else
@@ -131,7 +131,7 @@ unsigned RLP::length() const
 	else if (n < c_rlpListStart)
 	{
 		if ((int)m_data.size() <= n - c_rlpDataIndLenZero)
-			throw BadRLP();
+			BOOST_THROW_EXCEPTION(BadRLP());
 		for (int i = 0; i < n - c_rlpDataIndLenZero; ++i)
 			ret = (ret << 8) | m_data[i + 1];
 	}
@@ -140,7 +140,7 @@ unsigned RLP::length() const
 	else
 	{
 		if ((int)m_data.size() <= n - c_rlpListIndLenZero)
-			throw BadRLP();
+			BOOST_THROW_EXCEPTION(BadRLP());
 		for (int i = 0; i < n - c_rlpListIndLenZero; ++i)
 			ret = (ret << 8) | m_data[i + 1];
 	}
diff --git a/libethcore/BlockInfo.cpp b/libethcore/BlockInfo.cpp
index 9ceb4c708..0ea2ff5f7 100644
--- a/libethcore/BlockInfo.cpp
+++ b/libethcore/BlockInfo.cpp
@@ -91,6 +91,19 @@ void BlockInfo::populateFromHeader(RLP const& _header, bool _checkNonce)
 		extraData = _header[field = 11].toBytes();
 		nonce = _header[field = 12].toHash<h256>();
 	}
+	catch (BException const& e)
+	{
+		// define error information to be added to the exception
+		typedef boost::error_info<struct field_info,int> InvalidBlockHeaderFormat_field;
+		typedef boost::error_info<struct header_field_data,string> InvalidBlockHeaderFormat_header_field_data;
+
+		// instead of using a new exception type, we add information to the existing exception
+		e << InvalidBlockHeaderFormat_field(field);
+		e << InvalidBlockHeaderFormat_header_field_data(toHex(_header[field].data().toBytes()));
+
+		throw;
+	}
+	// this block would be replaced
 	catch (RLPException const&)
 	{
 		throw InvalidBlockHeaderFormat(field, _header[field].data());