upgrade asio from 1.29.0 to 1.38.0 (#827)

Migrate removed deprecated APIs:
- io_service -> io_context
- io_service::work -> executor_work_guard
- resolver::query/iterator -> resolver::resolve() with results_type
- address::from_string() -> make_address()

---

Breaking Changes (1.33.0)
  - deferred as default completion token — can omit token in coroutines: co_await socket.async_read_some(buf)
  - cancel_after / cancel_at — timeout any async operation: co_await sock.async_read_some(buf, cancel_after(5s))
  - Partial completion token adapters — as_tuple, redirect_error, bind_executor etc. composable via pipe: co_await (async_write(sock, buf) | as_tuple | cancel_after(10s))
  - composed — simpler alternative to async_compose for stateful operation implementations
  - co_composed moved out of experimental

  1.35.0 — Allocator & Resolver
  - Allocator constructors for io_context and thread_pool — control memory allocation for services, I/O objects, strands
  - Configurable resolver thread pool ("resolver"/"threads")
  - Timer heap pre-allocation ("timer"/"heap_reserve")

  1.37.0 — Inline Executors & Reactor Tuning
  - inline_executor — always executes inline (useful as completion executor)
  - inline_or_executor<> — tries inline first, falls back to wrapped executor
  - New dispatch/post/defer overloads that run a function on one executor and deliver result to a handler on another
  - redirect_disposition — captures disposition into a variable (like redirect_error but generic)
  - Reactor config: reset_edge_on_partial_read, use_eventfd, use_timerfd

  Notable Fixes

  - Resource leak in awaitable move assignment (1.37.0)
  - Memory leak in SSL stream move assignment (1.37.0)
  - Thread sanitizer issue in kqueue reactor (1.37.0)
  - co_spawn non-reentrant completion handler fix (1.36.0)
  - Windows file append mode fix (1.32.0)
  - SSL engine move assignment leak (1.33.0)

6 files changed, 40 insertions, 41 deletions

diff --git a/src/zenhttp/clients/httpwsclient.cpp b/src/zenhttp/clients/httpwsclient.cpp
index 792848a6b..2d566ae86 100644
--- a/src/zenhttp/clients/httpwsclient.cpp
+++ b/src/zenhttp/clients/httpwsclient.cpp
@@ -125,8 +125,8 @@ struct HttpWsClient::Impl
 	{
 		if (m_OwnedIoContext)
 		{
-			m_WorkGuard = std::make_unique<asio::io_context::work>(m_IoContext);
-			m_IoThread	= std::thread([this] { m_IoContext.run(); });
+			m_WorkGuard.emplace(m_IoContext.get_executor());
+			m_IoThread = std::thread([this] { m_IoContext.run(); });
 		}
 
 #if defined(ASIO_HAS_LOCAL_SOCKETS)
@@ -564,10 +564,10 @@ struct HttpWsClient::Impl
 	std::string m_Path;
 
 	// io_context: owned (standalone) or external (shared)
-	std::unique_ptr<asio::io_context>		m_OwnedIoContext;
-	asio::io_context&						m_IoContext;
-	std::unique_ptr<asio::io_context::work> m_WorkGuard;
-	std::thread								m_IoThread;
+	std::unique_ptr<asio::io_context>										  m_OwnedIoContext;
+	asio::io_context&														  m_IoContext;
+	std::optional<asio::executor_work_guard<asio::io_context::executor_type>> m_WorkGuard;
+	std::thread																  m_IoThread;
 
 	// Connection state
 	std::unique_ptr<asio::ip::tcp::resolver> m_Resolver;
diff --git a/src/zenhttp/servers/httpasio.cpp b/src/zenhttp/servers/httpasio.cpp
index ee8e71256..e8b27da70 100644
--- a/src/zenhttp/servers/httpasio.cpp
+++ b/src/zenhttp/servers/httpasio.cpp
@@ -530,9 +530,9 @@ public:
 
 	int GetEffectiveHttpsPort() const;
 
-	asio::io_service						 m_IoService;
-	asio::io_service::work					 m_Work{m_IoService};
-	std::unique_ptr<asio_http::HttpAcceptor> m_Acceptor;
+	asio::io_context										   m_IoService;
+	asio::executor_work_guard<asio::io_context::executor_type> m_Work{m_IoService.get_executor()};
+	std::unique_ptr<asio_http::HttpAcceptor>				   m_Acceptor;
 #if defined(ASIO_HAS_LOCAL_SOCKETS)
 	std::unique_ptr<asio_http::UnixAcceptor> m_UnixAcceptor;
 #endif
@@ -1507,7 +1507,7 @@ HttpServerConnectionT<SocketType>::HandleRequest()
 struct TcpAcceptorBase
 {
 	TcpAcceptorBase(HttpAsioServerImpl& Server,
-					asio::io_service&	IoService,
+					asio::io_context&	IoService,
 					uint16_t			BasePort,
 					bool				ForceLoopback,
 					bool				AllowPortProbing,
@@ -1580,7 +1580,7 @@ protected:
 	virtual void OnAccept(std::unique_ptr<asio::ip::tcp::socket> Socket) = 0;
 
 	HttpAsioServerImpl& m_Server;
-	asio::io_service&	m_IoService;
+	asio::io_context&	m_IoService;
 
 private:
 	template<typename AddressType>
@@ -1785,7 +1785,7 @@ private:
 
 struct HttpAcceptor final : TcpAcceptorBase
 {
-	HttpAcceptor(HttpAsioServerImpl& Server, asio::io_service& IoService, uint16_t BasePort, bool ForceLoopback, bool AllowPortProbing)
+	HttpAcceptor(HttpAsioServerImpl& Server, asio::io_context& IoService, uint16_t BasePort, bool ForceLoopback, bool AllowPortProbing)
 	: TcpAcceptorBase(Server, IoService, BasePort, ForceLoopback, AllowPortProbing, "HTTP")
 	{
 	}
@@ -1810,7 +1810,7 @@ protected:
 
 struct UnixAcceptor
 {
-	UnixAcceptor(HttpAsioServerImpl& Server, asio::io_service& IoService, const std::string& SocketPath)
+	UnixAcceptor(HttpAsioServerImpl& Server, asio::io_context& IoService, const std::string& SocketPath)
 	: m_Server(Server)
 	, m_IoService(IoService)
 	, m_Acceptor(m_IoService)
@@ -1897,7 +1897,7 @@ private:
 	}
 
 	HttpAsioServerImpl&					   m_Server;
-	asio::io_service&					   m_IoService;
+	asio::io_context&					   m_IoService;
 	asio::local::stream_protocol::acceptor m_Acceptor;
 	std::string							   m_SocketPath;
 	bool								   m_IsValid{false};
@@ -1913,7 +1913,7 @@ private:
 struct HttpsAcceptor final : TcpAcceptorBase
 {
 	HttpsAcceptor(HttpAsioServerImpl& Server,
-				  asio::io_service&	  IoService,
+				  asio::io_context&	  IoService,
 				  asio::ssl::context& SslContext,
 				  uint16_t			  Port,
 				  bool				  ForceLoopback,
@@ -2284,7 +2284,7 @@ HttpAsioServerImpl::Stop()
 
 	// Drain remaining handlers (e.g. cancellation callbacks from active WebSocket
 	// connections) so that their captured Ref<> pointers are released while the
-	// io_service and its epoll reactor are still alive.  Without this, sockets
+	// io_context and its epoll reactor are still alive.  Without this, sockets
 	// held by external code (e.g. IWebSocketHandler connection lists) can outlive
 	// the reactor and crash during deregistration.
 	m_IoService.restart();
@@ -2486,9 +2486,9 @@ HttpAsioServer::OnGetExternalHost() const
 	// causes the OS to select the appropriate local interface without sending any data.
 	try
 	{
-		asio::io_service	  IoService;
+		asio::io_context	  IoService;
 		asio::ip::udp::socket Sock(IoService, asio::ip::udp::v4());
-		Sock.connect(asio::ip::udp::endpoint(asio::ip::address::from_string("8.8.8.8"), 80));
+		Sock.connect(asio::ip::udp::endpoint(asio::ip::make_address("8.8.8.8"), 80));
 		return Sock.local_endpoint().address().to_string();
 	}
 	catch (const std::exception&)
diff --git a/src/zenhttp/servers/httpsys.cpp b/src/zenhttp/servers/httpsys.cpp
index 83b98013e..4d6a53696 100644
--- a/src/zenhttp/servers/httpsys.cpp
+++ b/src/zenhttp/servers/httpsys.cpp
@@ -2758,9 +2758,9 @@ HttpSysServer::OnGetExternalHost() const
 	// causes the OS to select the appropriate local interface without sending any data.
 	try
 	{
-		asio::io_service	  IoService;
+		asio::io_context	  IoService;
 		asio::ip::udp::socket Sock(IoService, asio::ip::udp::v4());
-		Sock.connect(asio::ip::udp::endpoint(asio::ip::address::from_string("8.8.8.8"), 80));
+		Sock.connect(asio::ip::udp::endpoint(asio::ip::make_address("8.8.8.8"), 80));
 		return Sock.local_endpoint().address().to_string();
 	}
 	catch (const std::exception&)
diff --git a/src/zenhttp/servers/wstest.cpp b/src/zenhttp/servers/wstest.cpp
index 042afd8ff..59c46a418 100644
--- a/src/zenhttp/servers/wstest.cpp
+++ b/src/zenhttp/servers/wstest.cpp
@@ -508,7 +508,7 @@ TEST_CASE("websocket.integration")
 	{
 		asio::io_context	  IoCtx;
 		asio::ip::tcp::socket Sock(IoCtx);
-		Sock.connect(asio::ip::tcp::endpoint(asio::ip::address::from_string("127.0.0.1"), static_cast<uint16_t>(Port)));
+		Sock.connect(asio::ip::tcp::endpoint(asio::ip::make_address("127.0.0.1"), static_cast<uint16_t>(Port)));
 
 		bool Ok = DoWebSocketHandshake(Sock, "/wstest/ws", Port);
 		CHECK(Ok);
@@ -523,7 +523,7 @@ TEST_CASE("websocket.integration")
 	{
 		asio::io_context	  IoCtx;
 		asio::ip::tcp::socket Sock(IoCtx);
-		Sock.connect(asio::ip::tcp::endpoint(asio::ip::address::from_string("127.0.0.1"), static_cast<uint16_t>(Port)));
+		Sock.connect(asio::ip::tcp::endpoint(asio::ip::make_address("127.0.0.1"), static_cast<uint16_t>(Port)));
 
 		// Send a normal HTTP GET (not upgrade)
 		std::string HttpReq = fmt::format(
@@ -547,7 +547,7 @@ TEST_CASE("websocket.integration")
 	{
 		asio::io_context	  IoCtx;
 		asio::ip::tcp::socket Sock(IoCtx);
-		Sock.connect(asio::ip::tcp::endpoint(asio::ip::address::from_string("127.0.0.1"), static_cast<uint16_t>(Port)));
+		Sock.connect(asio::ip::tcp::endpoint(asio::ip::make_address("127.0.0.1"), static_cast<uint16_t>(Port)));
 
 		bool Ok = DoWebSocketHandshake(Sock, "/wstest/ws", Port);
 		REQUIRE(Ok);
@@ -573,7 +573,7 @@ TEST_CASE("websocket.integration")
 	{
 		asio::io_context	  IoCtx;
 		asio::ip::tcp::socket Sock(IoCtx);
-		Sock.connect(asio::ip::tcp::endpoint(asio::ip::address::from_string("127.0.0.1"), static_cast<uint16_t>(Port)));
+		Sock.connect(asio::ip::tcp::endpoint(asio::ip::make_address("127.0.0.1"), static_cast<uint16_t>(Port)));
 
 		bool Ok = DoWebSocketHandshake(Sock, "/wstest/ws", Port);
 		REQUIRE(Ok);
@@ -595,7 +595,7 @@ TEST_CASE("websocket.integration")
 	{
 		asio::io_context	  IoCtx;
 		asio::ip::tcp::socket Sock(IoCtx);
-		Sock.connect(asio::ip::tcp::endpoint(asio::ip::address::from_string("127.0.0.1"), static_cast<uint16_t>(Port)));
+		Sock.connect(asio::ip::tcp::endpoint(asio::ip::make_address("127.0.0.1"), static_cast<uint16_t>(Port)));
 
 		bool Ok = DoWebSocketHandshake(Sock, "/wstest/ws", Port);
 		REQUIRE(Ok);
@@ -627,7 +627,7 @@ TEST_CASE("websocket.integration")
 		for (int i = 0; i < NumClients; ++i)
 		{
 			Sockets.emplace_back(IoCtx);
-			Sockets.back().connect(asio::ip::tcp::endpoint(asio::ip::address::from_string("127.0.0.1"), static_cast<uint16_t>(Port)));
+			Sockets.back().connect(asio::ip::tcp::endpoint(asio::ip::make_address("127.0.0.1"), static_cast<uint16_t>(Port)));
 
 			bool Ok = DoWebSocketHandshake(Sockets.back(), "/wstest/ws", Port);
 			REQUIRE(Ok);
@@ -672,7 +672,7 @@ TEST_CASE("websocket.integration")
 
 		asio::io_context	  IoCtx;
 		asio::ip::tcp::socket Sock(IoCtx);
-		Sock.connect(asio::ip::tcp::endpoint(asio::ip::address::from_string("127.0.0.1"), static_cast<uint16_t>(Port)));
+		Sock.connect(asio::ip::tcp::endpoint(asio::ip::make_address("127.0.0.1"), static_cast<uint16_t>(Port)));
 
 		// Attempt WebSocket upgrade on the plain service
 		ExtendableStringBuilder<512> Request;
@@ -702,7 +702,7 @@ TEST_CASE("websocket.integration")
 	{
 		asio::io_context	  IoCtx;
 		asio::ip::tcp::socket Sock(IoCtx);
-		Sock.connect(asio::ip::tcp::endpoint(asio::ip::address::from_string("127.0.0.1"), static_cast<uint16_t>(Port)));
+		Sock.connect(asio::ip::tcp::endpoint(asio::ip::make_address("127.0.0.1"), static_cast<uint16_t>(Port)));
 
 		bool Ok = DoWebSocketHandshake(Sock, "/wstest/ws", Port);
 		REQUIRE(Ok);
@@ -729,7 +729,7 @@ TEST_CASE("websocket.integration")
 	{
 		asio::io_context	  IoCtx;
 		asio::ip::tcp::socket Sock(IoCtx);
-		Sock.connect(asio::ip::tcp::endpoint(asio::ip::address::from_string("127.0.0.1"), static_cast<uint16_t>(Port)));
+		Sock.connect(asio::ip::tcp::endpoint(asio::ip::make_address("127.0.0.1"), static_cast<uint16_t>(Port)));
 
 		bool Ok = DoWebSocketHandshake(Sock, "/wstest/ws", Port);
 		REQUIRE(Ok);
diff --git a/src/zenhttp/transports/asiotransport.cpp b/src/zenhttp/transports/asiotransport.cpp
index 23ac1bc8b..d5413b9af 100644
--- a/src/zenhttp/transports/asiotransport.cpp
+++ b/src/zenhttp/transports/asiotransport.cpp
@@ -47,10 +47,10 @@ private:
 	uint16_t m_BasePort	   = 8558;
 	int		 m_ThreadCount = 0;
 
-	asio::io_service					   m_IoService;
-	asio::io_service::work				   m_Work{m_IoService};
-	std::unique_ptr<AsioTransportAcceptor> m_Acceptor;
-	std::vector<std::thread>			   m_ThreadPool;
+	asio::io_context										   m_IoService;
+	asio::executor_work_guard<asio::io_context::executor_type> m_Work{m_IoService.get_executor()};
+	std::unique_ptr<AsioTransportAcceptor>					   m_Acceptor;
+	std::vector<std::thread>								   m_ThreadPool;
 };
 
 struct AsioTransportConnection : public TransportConnection, std::enable_shared_from_this<AsioTransportConnection>
@@ -85,7 +85,7 @@ private:
 
 struct AsioTransportAcceptor
 {
-	AsioTransportAcceptor(TransportServer* ServerInterface, asio::io_service& IoService, uint16_t BasePort);
+	AsioTransportAcceptor(TransportServer* ServerInterface, asio::io_context& IoService, uint16_t BasePort);
 	~AsioTransportAcceptor();
 
 	void Start();
@@ -95,7 +95,7 @@ struct AsioTransportAcceptor
 
 private:
 	TransportServer*		m_ServerInterface = nullptr;
-	asio::io_service&		m_IoService;
+	asio::io_context&		m_IoService;
 	asio::ip::tcp::acceptor m_Acceptor;
 	std::atomic<bool>		m_IsStopped{false};
 
@@ -104,7 +104,7 @@ private:
 
 //////////////////////////////////////////////////////////////////////////
 
-AsioTransportAcceptor::AsioTransportAcceptor(TransportServer* ServerInterface, asio::io_service& IoService, uint16_t BasePort)
+AsioTransportAcceptor::AsioTransportAcceptor(TransportServer* ServerInterface, asio::io_context& IoService, uint16_t BasePort)
 : m_ServerInterface(ServerInterface)
 , m_IoService(IoService)
 , m_Acceptor(m_IoService, asio::ip::tcp::v6())
diff --git a/src/zennet/statsdclient.cpp b/src/zennet/statsdclient.cpp
index 8afa2e835..9a8aae348 100644
--- a/src/zennet/statsdclient.cpp
+++ b/src/zennet/statsdclient.cpp
@@ -43,7 +43,7 @@ public:
 	}
 
 private:
-	asio::io_service m_IoService;
+	asio::io_context m_IoService;
 	std::string		 m_TargetHost;
 	uint16_t		 m_TargetPort;
 
@@ -68,9 +68,8 @@ StatsdUdpClient::InitializeSocket()
 		return m_Socket.reset();
 	}
 
-	udp::resolver			DnsResolver(m_IoService);
-	udp::resolver::query	DnsQuery(udp::v4(), m_TargetHost, fmt::format("{}", m_TargetPort));
-	udp::resolver::iterator It = DnsResolver.resolve(DnsQuery, Ec);
+	udp::resolver				DnsResolver(m_IoService);
+	udp::resolver::results_type Results = DnsResolver.resolve(udp::v4(), m_TargetHost, fmt::format("{}", m_TargetPort), Ec);
 
 	if (Ec)
 	{
@@ -79,7 +78,7 @@ StatsdUdpClient::InitializeSocket()
 		return m_Socket.reset();
 	}
 
-	m_ServerAddr = *It;
+	m_ServerAddr = *Results.begin();
 }
 
 void