fix(Logger): disable channels instead of destroying the map on shutdo…

Foundation/include/Poco/Logger.h

@@ -434,8 +434,15 @@ class Foundation_API Logger: public Channel
 		/// become invalid.
 
 	static void shutdown();
-		/// Shuts down the logging framework and releases all
-		/// Loggers.
+		/// Shuts down the logging framework: detaches and releases the
+		/// channels of all existing Loggers, so that channel resources
+		/// (open files, sockets, ...) are freed. The Logger instances
+		/// themselves remain alive, so any cached Logger references held
+		/// by singletons stay valid; logging through them becomes a
+		/// silent no-op.
+		///
+		/// Intended to be called once, as the last logging-related action
+		/// before the process exits.
 
 	static void names(std::vector<std::string>& names);
 		/// Fills the given vector with the names

Foundation/src/Logger.cpp

@@ -345,7 +345,18 @@ void Logger::shutdown()
 {
 	Mutex::ScopedLock lock(_mapMtx);
 
-	_pLoggerMap.reset();
+	// Detach channels from all loggers instead of destroying the logger
+	// objects. Singletons and other components may still hold Logger
+	// references obtained via Logger::get() during their lifetime.
+	// Destroying the loggers would leave those references dangling,
+	// causing use-after-free during static destruction.
+	if (_pLoggerMap)
+	{
+		for (auto& [name, pLogger] : *_pLoggerMap)
+		{
+			if (pLogger) pLogger->setChannel(nullptr);
+		}
+	}
 }
 
 

Foundation/testsuite/src/LoggerTest.cpp

@@ -385,6 +385,32 @@ void LoggerTest::testFormatStdThreadName()
 #endif
 }
 
+void LoggerTest::testLoggerRefSurvivesShutdown()
+{
+	// Simulate a singleton caching a Logger& obtained before shutdown.
+	Logger& cached = Logger::get("TestLogger.Cached");
+	AutoPtr<TestChannel> pChannel = new TestChannel;
+	cached.setChannel(pChannel);
+	cached.setLevel(Message::PRIO_INFORMATION);
+	cached.information("before shutdown");
+	assertTrue (pChannel->list().size() == 1);
+
+	Logger::shutdown();
+
+	// The cached reference must still be valid; logging through it
+	// must be a safe no-op (channel detached).
+	cached.information("post-shutdown message");
+	cached.log(Message("x", "y", Message::PRIO_ERROR));
+	assertTrue (cached.getChannel().isNull());
+	assertTrue (pChannel->list().size() == 1);
+
+	// get() with the same name returns the same (muted) instance.
+	Logger& again = Logger::get("TestLogger.Cached");
+	assertTrue (&again == &cached);
+	assertTrue (again.getChannel().isNull());
+}
+
+
 void LoggerTest::setUp()
 {
 	Logger::shutdown();
@@ -406,6 +432,7 @@ CppUnit::Test* LoggerTest::suite()
 	CppUnit_addTest(pSuite, LoggerTest, testDump);
 	CppUnit_addTest(pSuite, LoggerTest, testFormatThreadName);
 	CppUnit_addTest(pSuite, LoggerTest, testFormatStdThreadName);
+	CppUnit_addTest(pSuite, LoggerTest, testLoggerRefSurvivesShutdown);
 
 	return pSuite;
 }

Foundation/testsuite/src/LoggerTest.h

@@ -30,6 +30,7 @@ class LoggerTest: public CppUnit::TestCase
 	void testDump();
 	void testFormatThreadName();
 	void testFormatStdThreadName();
+	void testLoggerRefSurvivesShutdown();
 
 	void setUp();
 	void tearDown();