Fix #9388: thread unsafe use of NetworkAdminConsole/IConsolePrint

(cherry picked from commit d7a0e80fc18b689455eaca09883fccbcc722d7e3)

# Conflicts:
#	src/debug.cpp
#	src/debug.h
#	src/table/settings/gui_settings.ini

See: https://github.com/OpenTTD/OpenTTD/pull/9456

src/debug.cpp

@@ -15,7 +15,9 @@
 #include "fileio_func.h"
 #include "settings_type.h"
 #include "date_func.h"
+#include "thread.h"
 #include <array>
+#include <mutex>
 
 #if defined(_WIN32)
 #include "os/windows/win32.h"
@@ -32,6 +34,16 @@ SOCKET _debug_socket = INVALID_SOCKET;
 
 #include "safeguards.h"
 
+/** Element in the queue of debug messages that have to be passed to either NetworkAdminConsole or IConsolePrint.*/
+struct QueuedDebugItem {
+	std::string level;   ///< The used debug level.
+	std::string message; ///< The actual formatted message.
+};
+std::atomic<bool> _debug_remote_console; ///< Whether we need to send data to either NetworkAdminConsole or IConsolePrint.
+std::mutex _debug_remote_console_mutex; ///< Mutex to guard the queue of debug messages for either NetworkAdminConsole or IConsolePrint.
+std::vector<QueuedDebugItem> _debug_remote_console_queue; ///< Queue for debug messages to be passed to NetworkAdminConsole or IConsolePrint.
+std::vector<QueuedDebugItem> _debug_remote_console_queue_spare; ///< Spare queue to swap with _debug_remote_console_queue.
+
 int _debug_driver_level;
 int _debug_grf_level;
 int _debug_map_level;
@@ -130,6 +142,11 @@ static void debug_print(const char *dbg, const char *buf)
 		char buf2[1024 + 32];
 
 		seprintf(buf2, lastof(buf2), "%sdbg: [%s] %s\n", GetLogPrefix(), dbg, buf);
+
+		/* Prevent sending a message concurrently, as that might cause interleaved messages. */
+		static std::mutex _debug_socket_mutex;
+		std::lock_guard<std::mutex> lock(_debug_socket_mutex);
+
 		/* Sending out an error when this fails would be nice, however... the error
 		 * would have to be send over this failing socket which won't work. */
 		send(_debug_socket, buf2, (int)strlen(buf2), 0);
@@ -192,8 +209,16 @@ static void debug_print(const char *dbg, const char *buf)
 	fputs(buffer, stderr);
 #endif
 
-	NetworkAdminConsole(dbg, buf);
-	IConsoleDebug(dbg, buf);
+	if (_debug_remote_console.load()) {
+		/* Only add to the queue when there is at least one consumer of the data. */
+		if (IsNonGameThread()) {
+			std::lock_guard<std::mutex> lock(_debug_remote_console_mutex);
+			_debug_remote_console_queue.push_back({ dbg, buf });
+		} else {
+			NetworkAdminConsole(dbg, buf);
+			if (_settings_client.gui.developer >= 2) IConsolePrintF(CC_DEBUG, "dbg: [%s] %s", dbg, buf);
+		}
+	}
 }
 
 /**
@@ -403,3 +428,50 @@ void LogRemoteDesyncMsg(Date date, DateFract date_fract, uint8 tick_skip_counter
 	entry.src_id = src_id;
 	_remote_desync_msg_log.LogMsg(std::move(entry));
 }
+
+/**
+ * Send the queued Debug messages to either NetworkAdminConsole or IConsolePrint from the
+ * GameLoop thread to prevent concurrent accesses to both the NetworkAdmin's packet queue
+ * as well as IConsolePrint's buffers.
+ *
+ * This is to be called from the GameLoop thread.
+ */
+void DebugSendRemoteMessages()
+{
+	if (!_debug_remote_console.load()) return;
+
+	{
+		std::lock_guard<std::mutex> lock(_debug_remote_console_mutex);
+		std::swap(_debug_remote_console_queue, _debug_remote_console_queue_spare);
+	}
+
+	for (auto &item : _debug_remote_console_queue_spare) {
+		NetworkAdminConsole(item.level.c_str(), item.message.c_str());
+		if (_settings_client.gui.developer >= 2) IConsolePrintF(CC_DEBUG, "dbg: [%s] %s", item.level.c_str(), item.message.c_str());
+	}
+
+	_debug_remote_console_queue_spare.clear();
+}
+
+/**
+ * Reconsider whether we need to send debug messages to either NetworkAdminConsole
+ * or IConsolePrint. The former is when they have enabled console handling whereas
+ * the latter depends on the gui.developer setting's value.
+ *
+ * This is to be called from the GameLoop thread.
+ */
+void DebugReconsiderSendRemoteMessages()
+{
+	bool enable = _settings_client.gui.developer >= 2;
+
+	if (!enable) {
+		for (ServerNetworkAdminSocketHandler *as : ServerNetworkAdminSocketHandler::IterateActive()) {
+			if (as->update_frequency[ADMIN_UPDATE_CONSOLE] & ADMIN_FREQUENCY_AUTOMATIC) {
+				enable = true;
+				break;
+			}
+		}
+	}
+
+	_debug_remote_console.store(enable);
+}