Fix negative-wraparound issue when converting size_t to ptrdiff_t whi…

…ch is used by std::views::take.

This issue was flagged by VisualStudio debug asserts

nano/node/active_elections.cpp

@@ -268,7 +268,7 @@ void nano::active_elections::request_confirm (nano::unique_lock<nano::mutex> & l
 	lock_a.unlock ();
 
 	nano::confirmation_solicitor solicitor (node.network, node.config);
-	solicitor.prepare (node.rep_crawler.principal_representatives (std::numeric_limits<std::size_t>::max ()));
+	solicitor.prepare (node.rep_crawler.principal_representatives (std::numeric_limits<std::ptrdiff_t>::max ()));
 
 	std::size_t unconfirmed_count_l (0);
 	nano::timer<std::chrono::milliseconds> elapsed (nano::timer_state::started);
@@ -652,4 +652,4 @@ nano::stat::type nano::to_stat_type (nano::election_state state)
 nano::stat::detail nano::to_stat_detail (nano::election_status_type type)
 {
 	return nano::enum_util::cast<nano::stat::detail> (type);
-}
+}

nano/node/repcrawler.cpp

@@ -435,8 +435,9 @@ nano::uint128_t nano::rep_crawler::total_weight () const
 	return result;
 }
 
-std::vector<nano::representative> nano::rep_crawler::representatives (std::size_t count, nano::uint128_t const minimum_weight, std::optional<decltype (nano::network_constants::protocol_version)> const & minimum_protocol_version)
+std::vector<nano::representative> nano::rep_crawler::representatives (std::ptrdiff_t count, nano::uint128_t const minimum_weight, std::optional<decltype (nano::network_constants::protocol_version)> const & minimum_protocol_version)
 {
+	debug_assert (count >= 0);
 	auto const version_min = minimum_protocol_version.value_or (node.network_params.network.protocol_version_min);
 
 	nano::lock_guard<nano::mutex> lock{ mutex };
@@ -452,15 +453,16 @@ std::vector<nano::representative> nano::rep_crawler::representatives (std::size_
 	}
 
 	std::vector<nano::representative> result;
-	for (auto const & [weight, rep] : ordered | std::views::take (count))
+	for (auto const & [weight, rep] : ordered | std::views::take (/* Signed type*/count))
 	{
 		result.push_back ({ rep.account, rep.channel });
 	}
 	return result;
 }
 
-std::vector<nano::representative> nano::rep_crawler::principal_representatives (std::size_t count, std::optional<decltype (nano::network_constants::protocol_version)> const & minimum_protocol_version)
+std::vector<nano::representative> nano::rep_crawler::principal_representatives (std::ptrdiff_t count, std::optional<decltype (nano::network_constants::protocol_version)> const & minimum_protocol_version)
 {
+	debug_assert (count >= 0);
 	return representatives (count, node.minimum_principal_weight (), minimum_protocol_version);
 }
 

nano/node/repcrawler.hpp

@@ -76,11 +76,11 @@ class rep_crawler final
 
 	/** Request a list of the top \p count known representatives in descending order of weight, with at least \p weight_a voting weight, and optionally with a minimum version \p minimum_protocol_version
 	 */
-	std::vector<representative> representatives (std::size_t count = std::numeric_limits<std::size_t>::max (), nano::uint128_t minimum_weight = 0, std::optional<decltype (nano::network_constants::protocol_version)> const & minimum_protocol_version = {});
+	std::vector<representative> representatives (std::ptrdiff_t count = std::numeric_limits<std::ptrdiff_t>::max (), nano::uint128_t minimum_weight = 0, std::optional<decltype (nano::network_constants::protocol_version)> const & minimum_protocol_version = {});
 
 	/** Request a list of the top \p count known principal representatives in descending order of weight, optionally with a minimum version \p minimum_protocol_version
 	 */
-	std::vector<representative> principal_representatives (std::size_t count = std::numeric_limits<std::size_t>::max (), std::optional<decltype (nano::network_constants::protocol_version)> const & minimum_protocol_version = {});
+	std::vector<representative> principal_representatives (std::ptrdiff_t count = std::numeric_limits<std::ptrdiff_t>::max (), std::optional<decltype (nano::network_constants::protocol_version)> const & minimum_protocol_version = {});
 
 	/** Total number of representatives */
 	std::size_t representative_count ();