/* Definitions used by the GDB event loop. Copyright (C) 1999-2024 Free Software Foundation, Inc. Written by Elena Zannoni <ezannoni@cygnus.com> of Cygnus Solutions. This file is part of GDB. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. */ #ifndef EVENT_LOOP_H #define EVENT_LOOP_H /* An event loop listens for events from multiple event sources. When an event arrives, it is queued and processed by calling the appropriate event handler. The event loop then continues to listen for more events. An event loop completes when there are no event sources to listen on. External event sources can be plugged into the loop. There are 4 main components: - a list of file descriptors to be monitored, GDB_NOTIFIER. - a list of asynchronous event sources to be monitored, ASYNC_EVENT_HANDLER_LIST. - a list of events that have occurred, EVENT_QUEUE. - a list of signal handling functions, SIGHANDLER_LIST. GDB_NOTIFIER keeps track of the file descriptor based event sources. ASYNC_EVENT_HANDLER_LIST keeps track of asynchronous event sources that are signalled by some component of gdb, usually a target_ops instance. Event sources for gdb are currently the UI and the target. Gdb communicates with the command line user interface via the readline library and usually communicates with remote targets via a serial port. Serial ports are represented in GDB as file descriptors and select/poll calls. For native targets instead, the communication varies across operating system debug APIs, but usually consists of calls to ptrace and waits (via signals) or calls to poll/select (via file descriptors). In the current gdb, the code handling events related to the target resides in wait_for_inferior for synchronous targets; or, for asynchronous capable targets, by having the target register either a target controlled file descriptor and/or an asynchronous event source in the event loop, with the fetch_inferior_event function as the event callback. In both the synchronous and asynchronous cases, usually the target event is collected through the target_wait interface. The target is free to install other event sources in the event loop if it so requires. EVENT_QUEUE keeps track of the events that have happened during the last iteration of the event loop, and need to be processed. An event is represented by a procedure to be invoked in order to process the event. The queue is scanned head to tail. If the event of interest is a change of state in a file descriptor, then a call to poll or select will be made to detect it. If the events generate signals, they are also queued by special functions that are invoked through traditional signal handlers. The actions to be taken is response to such events will be executed when the SIGHANDLER_LIST is scanned, the next time through the infinite loop. Corollary tasks are the creation and deletion of event sources. */ typedef void *gdb_client_data; typedef void (handler_func) (int, gdb_client_data); typedef void (timer_handler_func) (gdb_client_data); /* Exported functions from event-loop.c */ extern int gdb_do_one_event (int mstimeout = -1); extern void delete_file_handler (int fd); /* Add a file handler/descriptor to the list of descriptors we are interested in. FD is the file descriptor for the file/stream to be listened to. NAME is a user-friendly name for the handler. If IS_UI is set, this file descriptor is used for a user interface. */ extern void add_file_handler (int fd, handler_func *proc, gdb_client_data client_data, std::string &&name, bool is_ui = false); extern int create_timer (int milliseconds, timer_handler_func *proc, gdb_client_data client_data); extern void delete_timer (int id); /* Must be defined by client. */ extern void handle_event_loop_exception (const gdb_exception &); /* Must be defined by client. Returns true if any signal handler was ready. */ extern int invoke_async_signal_handlers (); /* Must be defined by client. Returns true if any event handler was ready. */ extern int check_async_event_handlers (); enum class debug_event_loop_kind { OFF, /* Print all event-loop related messages, except events from user-interface event sources. */ ALL_EXCEPT_UI, /* Print all event-loop related messages. */ ALL, }; /* True if we are printing event loop debug statements. */ extern debug_event_loop_kind debug_event_loop; /* Print an "event loop" debug statement. */ #define event_loop_debug_printf(fmt, ...) \ debug_prefixed_printf_cond (debug_event_loop != debug_event_loop_kind::OFF, \ "event-loop", fmt, ##__VA_ARGS__) /* Print an "event loop" debug statement that is know to come from a UI-related event (e.g. calling the event handler for the fd of the CLI). */ #define event_loop_ui_debug_printf(is_ui, fmt, ...) \ do \ { \ if (debug_event_loop == debug_event_loop_kind::ALL \ || (debug_event_loop == debug_event_loop_kind::ALL_EXCEPT_UI \ && !is_ui)) \ debug_prefixed_printf ("event-loop", __func__, fmt, ##__VA_ARGS__); \ } \ while (0) #endif /* EVENT_LOOP_H */