Refer to empty/null accounts as nano::account{nullptr} (#3388)

* Introduce null accounts as nano::account{nullptr}

* Fix formatting

* Default nano::account constructor to nano::account{0}

* Fix formatting

* Introduce nano::public_key::null() method instead of std::nullptr_t constructor

* Fix formatting

* Address code review #3

* Last code review addressing

* Fix formatting

* Address code review #4

nano/core_test/active_transactions.cpp

@@ -50,7 +50,7 @@ TEST (active_transactions, confirm_active)
 		nano::lock_guard<nano::mutex> guard (node2.rep_crawler.probable_reps_mutex);
 		node2.rep_crawler.probable_reps.emplace (nano::dev::genesis_key.pub, nano::dev::constants.genesis_amount, *peers.begin ());
 	}
-	ASSERT_TIMELY (5s, election->votes ().size () != 1); // Votes were inserted (except for not_an_account)
+	ASSERT_TIMELY (5s, election->votes ().size () != 1); // Votes were inserted (except for the null account)
 	auto confirm_req_count (election->confirmation_request_count.load ());
 	// At least one confirmation request
 	ASSERT_GT (confirm_req_count, 0u);
@@ -62,7 +62,7 @@ TEST (active_transactions, confirm_active)
 	ASSERT_TIMELY (10s, node2.ledger.cache.cemented_count == 2 && node2.active.empty ());
 	// At least one more confirmation request
 	ASSERT_GT (election->confirmation_request_count, confirm_req_count);
-	// Blocks were cleared (except for not_an_account)
+	// Blocks were cleared (except for the null account)
 	ASSERT_EQ (1, election->blocks ().size ());
 }
 }

nano/core_test/block_store.cpp

@@ -523,7 +523,7 @@ TEST (block_store, frontier_retrieval)
 	nano::logger_mt logger;
 	auto store = nano::make_store (logger, nano::unique_path (), nano::dev::constants);
 	ASSERT_TRUE (!store->init_error ());
-	nano::account account1 (0);
+	nano::account account1{};
 	nano::account_info info1 (0, 0, 0, 0, 0, 0, nano::epoch::epoch_0);
 	auto transaction (store->tx_begin_write ());
 	store->confirmation_height.put (transaction, account1, { 0, nano::block_hash (0) });
@@ -538,7 +538,7 @@ TEST (block_store, one_account)
 	nano::logger_mt logger;
 	auto store = nano::make_store (logger, nano::unique_path (), nano::dev::constants);
 	ASSERT_TRUE (!store->init_error ());
-	nano::account account (0);
+	nano::account account{};
 	nano::block_hash hash (0);
 	auto transaction (store->tx_begin_write ());
 	store->confirmation_height.put (transaction, account, { 20, nano::block_hash (15) });
@@ -783,7 +783,7 @@ TEST (block_store, large_iteration)
 		store->account.put (transaction, account, nano::account_info ());
 	}
 	std::unordered_set<nano::account> accounts2;
-	nano::account previous (0);
+	nano::account previous{};
 	auto transaction (store->tx_begin_read ());
 	for (auto i (store->account.begin (transaction, 0)), n (store->account.end ()); i != n; ++i)
 	{
@@ -1874,9 +1874,9 @@ TEST (block_store, confirmation_height)
 	nano::logger_mt logger;
 	auto store = nano::make_store (logger, path, nano::dev::constants);
 
-	nano::account account1 (0);
-	nano::account account2 (1);
-	nano::account account3 (2);
+	nano::account account1{};
+	nano::account account2{ 1 };
+	nano::account account3{ 2 };
 	nano::block_hash cemented_frontier1 (3);
 	nano::block_hash cemented_frontier2 (4);
 	nano::block_hash cemented_frontier3 (5);

nano/core_test/ledger.cpp

@@ -1525,13 +1525,13 @@ TEST (ledger, block_destination_source)
 	ASSERT_TRUE (ledger.block_source (transaction, block1).is_zero ());
 	ASSERT_EQ (nano::dev::genesis->account (), ledger.block_destination (transaction, block2));
 	ASSERT_TRUE (ledger.block_source (transaction, block2).is_zero ());
-	ASSERT_TRUE (ledger.block_destination (transaction, block3).is_zero ());
+	ASSERT_TRUE (ledger.block_destination (transaction, block3) == nullptr);
 	ASSERT_EQ (block2.hash (), ledger.block_source (transaction, block3));
 	ASSERT_EQ (dest.pub, ledger.block_destination (transaction, block4));
 	ASSERT_TRUE (ledger.block_source (transaction, block4).is_zero ());
 	ASSERT_EQ (nano::dev::genesis->account (), ledger.block_destination (transaction, block5));
 	ASSERT_TRUE (ledger.block_source (transaction, block5).is_zero ());
-	ASSERT_TRUE (ledger.block_destination (transaction, block6).is_zero ());
+	ASSERT_TRUE (ledger.block_destination (transaction, block6) == nullptr);
 	ASSERT_EQ (block5.hash (), ledger.block_source (transaction, block6));
 }
 
@@ -2411,7 +2411,7 @@ TEST (ledger, epoch_blocks_fork)
 	store->initialize (transaction, ledger.cache);
 	nano::work_pool pool{ nano::dev::network_params.network, std::numeric_limits<unsigned>::max () };
 	nano::keypair destination;
-	nano::send_block send1 (nano::dev::genesis->hash (), nano::account (0), nano::dev::constants.genesis_amount, nano::dev::genesis_key.prv, nano::dev::genesis_key.pub, *pool.generate (nano::dev::genesis->hash ()));
+	nano::send_block send1 (nano::dev::genesis->hash (), nano::account{}, nano::dev::constants.genesis_amount, nano::dev::genesis_key.prv, nano::dev::genesis_key.pub, *pool.generate (nano::dev::genesis->hash ()));
 	ASSERT_EQ (nano::process_result::progress, ledger.process (transaction, send1).code);
 	nano::state_block epoch1 (nano::dev::genesis->account (), nano::dev::genesis->hash (), nano::dev::genesis->account (), nano::dev::constants.genesis_amount, ledger.epoch_link (nano::epoch::epoch_1), nano::dev::genesis_key.prv, nano::dev::genesis_key.pub, *pool.generate (nano::dev::genesis->hash ()));
 	ASSERT_EQ (nano::process_result::fork, ledger.process (transaction, epoch1).code);

nano/core_test/network.cpp

@@ -797,7 +797,7 @@ TEST (tcp_listener, tcp_node_id_handshake)
 
 	ASSERT_TIMELY (5s, write_done);
 
-	boost::optional<std::pair<nano::account, nano::signature>> response_zero (std::make_pair (nano::account (0), nano::signature (0)));
+	boost::optional<std::pair<nano::account, nano::signature>> response_zero (std::make_pair (nano::account{}, nano::signature (0)));
 	nano::node_id_handshake node_id_handshake_response{ nano::dev::network_params.network, boost::none, response_zero };
 	auto output (node_id_handshake_response.to_bytes ());
 	std::atomic<bool> done (false);

nano/core_test/node.cpp

@@ -20,6 +20,17 @@ namespace
 void add_required_children_node_config_tree (nano::jsonconfig & tree);
 }
 
+TEST (node, null_account)
+{
+	const auto & null_account = nano::account::null ();
+	ASSERT_TRUE (null_account == nullptr);
+	ASSERT_FALSE (null_account != nullptr);
+
+	nano::account default_account{};
+	ASSERT_FALSE (default_account == nullptr);
+	ASSERT_TRUE (default_account != nullptr);
+}
+
 TEST (node, stop)
 {
 	nano::system system (1);

nano/core_test/system.cpp

@@ -106,7 +106,7 @@ TEST (system, DISABLED_generate_send_new)
 	// This indirectly waits for online weight to stabilize, required to prevent intermittent failures
 	ASSERT_TIMELY (5s, node1.wallets.reps ().voting > 0);
 	system.generate_send_new (node1, accounts);
-	nano::account new_account (0);
+	nano::account new_account{};
 	{
 		auto transaction (node1.wallets.tx_begin_read ());
 		auto iterator2 (system.wallet (0)->store.begin (transaction));

nano/core_test/wallet.cpp

@@ -335,7 +335,7 @@ TEST (wallet, rekey)
 
 TEST (account, encode_zero)
 {
-	nano::account number0 (0);
+	nano::account number0{};
 	std::string str0;
 	number0.encode_account (str0);
 
@@ -367,7 +367,7 @@ TEST (account, encode_all)
 
 TEST (account, encode_fail)
 {
-	nano::account number0 (0);
+	nano::account number0{};
 	std::string str0;
 	number0.encode_account (str0);
 	str0[16] ^= 1;

nano/lib/blocks.cpp

@@ -3,6 +3,7 @@
 #include <nano/lib/memory.hpp>
 #include <nano/lib/numbers.hpp>
 #include <nano/lib/threading.hpp>
+#include <nano/secure/common.hpp>
 
 #include <crypto/cryptopp/words.h>
 
@@ -151,8 +152,8 @@ bool nano::block::has_sideband () const
 
 nano::account const & nano::block::representative () const
 {
-	static nano::account rep{ 0 };
-	return rep;
+	static nano::account representative{};
+	return representative;
 }
 
 nano::block_hash const & nano::block::source () const
@@ -163,7 +164,7 @@ nano::block_hash const & nano::block::source () const
 
 nano::account const & nano::block::destination () const
 {
-	static nano::account destination{ 0 };
+	static nano::account destination{};
 	return destination;
 }
 
@@ -175,7 +176,7 @@ nano::link const & nano::block::link () const
 
 nano::account const & nano::block::account () const
 {
-	static nano::account account{ 0 };
+	static nano::account account{};
 	return account;
 }
 
@@ -363,6 +364,8 @@ nano::send_block::send_block (nano::block_hash const & previous_a, nano::account
 	signature (nano::sign_message (prv_a, pub_a, hash ())),
 	work (work_a)
 {
+	debug_assert (destination_a != nullptr);
+	debug_assert (pub_a != nullptr);
 }
 
 nano::send_block::send_block (bool & error_a, nano::stream & stream_a) :
@@ -524,13 +527,18 @@ nano::open_block::open_block (nano::block_hash const & source_a, nano::account c
 	signature (nano::sign_message (prv_a, pub_a, hash ())),
 	work (work_a)
 {
-	debug_assert (!representative_a.is_zero ());
+	debug_assert (representative_a != nullptr);
+	debug_assert (account_a != nullptr);
+	debug_assert (pub_a != nullptr);
 }
 
 nano::open_block::open_block (nano::block_hash const & source_a, nano::account const & representative_a, nano::account const & account_a, std::nullptr_t) :
 	hashables (source_a, representative_a, account_a),
 	work (0)
 {
+	debug_assert (representative_a != nullptr);
+	debug_assert (account_a != nullptr);
+
 	signature.clear ();
 }
 
@@ -787,6 +795,8 @@ nano::change_block::change_block (nano::block_hash const & previous_a, nano::acc
 	signature (nano::sign_message (prv_a, pub_a, hash ())),
 	work (work_a)
 {
+	debug_assert (representative_a != nullptr);
+	debug_assert (pub_a != nullptr);
 }
 
 nano::change_block::change_block (bool & error_a, nano::stream & stream_a) :
@@ -1060,6 +1070,10 @@ nano::state_block::state_block (nano::account const & account_a, nano::block_has
 	signature (nano::sign_message (prv_a, pub_a, hash ())),
 	work (work_a)
 {
+	debug_assert (account_a != nullptr);
+	debug_assert (representative_a != nullptr);
+	debug_assert (link_a.as_account () != nullptr);
+	debug_assert (pub_a != nullptr);
 }
 
 nano::state_block::state_block (bool & error_a, nano::stream & stream_a) :
@@ -1505,6 +1519,7 @@ nano::receive_block::receive_block (nano::block_hash const & previous_a, nano::b
 	signature (nano::sign_message (prv_a, pub_a, hash ())),
 	work (work_a)
 {
+	debug_assert (pub_a != nullptr);
 }
 
 nano::receive_block::receive_block (bool & error_a, nano::stream & stream_a) :

nano/lib/blocks.hpp

@@ -64,7 +64,7 @@ class block_sideband final
 	bool deserialize (nano::stream &, nano::block_type);
 	static size_t size (nano::block_type);
 	nano::block_hash successor{ 0 };
-	nano::account account{ 0 };
+	nano::account account{};
 	nano::amount balance{ 0 };
 	uint64_t height{ 0 };
 	uint64_t timestamp{ 0 };

nano/lib/numbers.cpp

@@ -3,6 +3,7 @@
 #include <nano/crypto_lib/secure_memory.hpp>
 #include <nano/lib/numbers.hpp>
 #include <nano/lib/utility.hpp>
+#include <nano/secure/common.hpp>
 
 #include <crypto/cryptopp/aes.h>
 #include <crypto/cryptopp/modes.h>
@@ -61,6 +62,16 @@ std::string nano::public_key::to_account () const
 	return result;
 }
 
+nano::public_key::public_key () :
+	uint256_union{ 0 }
+{
+}
+
+const nano::public_key & nano::public_key::null ()
+{
+	return nano::hardened_constants::get ().not_an_account;
+}
+
 std::string nano::public_key::to_node_id () const
 {
 	return to_account ().replace (0, 4, "node");
@@ -781,6 +792,11 @@ std::string nano::uint128_union::to_string_dec () const
 	return result;
 }
 
+nano::hash_or_account::hash_or_account () :
+	account{}
+{
+}
+
 nano::hash_or_account::hash_or_account (uint64_t value_a) :
 	raw (value_a)
 {
@@ -939,6 +955,16 @@ nano::public_key::operator nano::hash_or_account const & () const
 	return reinterpret_cast<nano::hash_or_account const &> (*this);
 }
 
+bool nano::public_key::operator== (std::nullptr_t) const
+{
+	return bytes == null ().bytes;
+}
+
+bool nano::public_key::operator!= (std::nullptr_t) const
+{
+	return !(*this == nullptr);
+}
+
 nano::block_hash::operator nano::link const & () const
 {
 	return reinterpret_cast<nano::link const &> (*this);

nano/lib/numbers.hpp

@@ -115,6 +115,10 @@ class public_key final : public uint256_union
 public:
 	using uint256_union::uint256_union;
 
+	public_key ();
+
+	static const public_key & null ();
+
 	std::string to_node_id () const;
 	bool decode_node_id (std::string const & source_a);
 	void encode_account (std::string &) const;
@@ -124,6 +128,10 @@ class public_key final : public uint256_union
 	operator nano::link const & () const;
 	operator nano::root const & () const;
 	operator nano::hash_or_account const & () const;
+	bool operator== (std::nullptr_t) const;
+	bool operator!= (std::nullptr_t) const;
+	using uint256_union::operator==;
+	using uint256_union::operator!=;
 };
 
 class wallet_id : public uint256_union
@@ -137,7 +145,7 @@ using account = public_key;
 class hash_or_account
 {
 public:
-	hash_or_account () = default;
+	hash_or_account ();
 	hash_or_account (uint64_t value_a);
 
 	bool is_zero () const;

nano/lib/walletconfig.hpp

@@ -19,6 +19,6 @@ class wallet_config final
 	nano::error serialize_toml (nano::tomlconfig & toml_a) const;
 	nano::error deserialize_toml (nano::tomlconfig & toml_a);
 	nano::wallet_id wallet;
-	nano::account account{ 0 };
+	nano::account account{};
 };
 }

nano/nano_node/entry.cpp

@@ -1459,7 +1459,7 @@ int main (int argc, char * const * argv)
 					}
 				}
 				uint64_t previous_timestamp (0);
-				nano::account calculated_representative (0);
+				nano::account calculated_representative{};
 				while (!hash.is_zero () && block != nullptr)
 				{
 					++block_count;
@@ -1704,7 +1704,7 @@ int main (int argc, char * const * argv)
 				else
 				{
 					// Check if pending destination is correct
-					nano::account destination (0);
+					nano::account destination{};
 					bool previous_pruned = node->ledger.pruning && node->store.pruned.exists (transaction, block->previous ());
 					if (previous_pruned)
 					{

nano/node/active_transactions.cpp

@@ -180,11 +180,11 @@ void nano::active_transactions::block_cemented_callback (std::shared_ptr<nano::b
 	{
 		if (election_status_type == nano::election_status_type::inactive_confirmation_height)
 		{
-			nano::account account (0);
+			nano::account account{};
 			nano::uint128_t amount (0);
 			bool is_state_send (false);
 			bool is_state_epoch (false);
-			nano::account pending_account (0);
+			nano::account pending_account{};
 			node.process_confirmed_data (transaction, block_a, block_a->hash (), account, amount, is_state_send, is_state_epoch, pending_account);
 			node.observers.blocks.notify (nano::election_status{ block_a, 0, 0, std::chrono::duration_cast<std::chrono::milliseconds> (std::chrono::system_clock::now ().time_since_epoch ()), std::chrono::duration_values<std::chrono::milliseconds>::zero (), 0, 1, 0, nano::election_status_type::inactive_confirmation_height }, {}, account, amount, is_state_send, is_state_epoch);
 		}
@@ -206,11 +206,11 @@ void nano::active_transactions::block_cemented_callback (std::shared_ptr<nano::b
 					add_recently_cemented (status_l);
 					auto destination (block_a->link ().is_zero () ? block_a->destination () : block_a->link ().as_account ());
 					node.receive_confirmed (transaction, hash, destination);
-					nano::account account (0);
+					nano::account account{};
 					nano::uint128_t amount (0);
 					bool is_state_send (false);
 					bool is_state_epoch (false);
-					nano::account pending_account (0);
+					nano::account pending_account{};
 					node.process_confirmed_data (transaction, block_a, hash, account, amount, is_state_send, is_state_epoch, pending_account);
 					election_lk.lock ();
 					election->status.type = *election_status_type;

nano/node/active_transactions.hpp

@@ -279,7 +279,7 @@ class active_transactions final
 	void confirm_expired_frontiers_pessimistically (nano::transaction const &, uint64_t, uint64_t &);
 	void frontiers_confirmation (nano::unique_lock<nano::mutex> &);
 	bool insert_election_from_frontiers_confirmation (std::shared_ptr<nano::block> const &, nano::account const &, nano::uint128_t, nano::election_behavior);
-	nano::account next_frontier_account{ 0 };
+	nano::account next_frontier_account{};
 	std::chrono::steady_clock::time_point next_frontier_check{ std::chrono::steady_clock::now () };
 	constexpr static size_t max_active_elections_frontier_insertion{ 1000 };
 	prioritize_num_uncemented priority_wallet_cementable_frontiers;

nano/node/bootstrap/bootstrap.hpp

@@ -82,7 +82,7 @@ class bootstrap_initiator final
 	explicit bootstrap_initiator (nano::node &);
 	~bootstrap_initiator ();
 	void bootstrap (nano::endpoint const &, bool add_to_peers = true, std::string id_a = "");
-	void bootstrap (bool force = false, std::string id_a = "", uint32_t const frontiers_age_a = std::numeric_limits<uint32_t>::max (), nano::account const & start_account_a = nano::account (0));
+	void bootstrap (bool force = false, std::string id_a = "", uint32_t const frontiers_age_a = std::numeric_limits<uint32_t>::max (), nano::account const & start_account_a = nano::account{});
 	bool bootstrap_lazy (nano::hash_or_account const &, bool force = false, bool confirmed = true, std::string id_a = "");
 	void bootstrap_wallet (std::deque<nano::account> &);
 	void run_bootstrap ();