1 /* Definitions used by the GDB event loop. 2 Copyright (C) 1999-2024 Free Software Foundation, Inc. 3 Written by Elena Zannoni <ezannoni (at) cygnus.com> of Cygnus Solutions. 4 5 This file is part of GDB. 6 7 This program is free software; you can redistribute it and/or modify 8 it under the terms of the GNU General Public License as published by 9 the Free Software Foundation; either version 3 of the License, or 10 (at your option) any later version. 11 12 This program is distributed in the hope that it will be useful, 13 but WITHOUT ANY WARRANTY; without even the implied warranty of 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 GNU General Public License for more details. 16 17 You should have received a copy of the GNU General Public License 18 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 19 20 #ifndef EVENT_LOOP_H 21 #define EVENT_LOOP_H 22 23 /* An event loop listens for events from multiple event sources. When 24 an event arrives, it is queued and processed by calling the 25 appropriate event handler. The event loop then continues to listen 26 for more events. An event loop completes when there are no event 27 sources to listen on. External event sources can be plugged into 28 the loop. 29 30 There are 4 main components: 31 - a list of file descriptors to be monitored, GDB_NOTIFIER. 32 - a list of asynchronous event sources to be monitored, 33 ASYNC_EVENT_HANDLER_LIST. 34 - a list of events that have occurred, EVENT_QUEUE. 35 - a list of signal handling functions, SIGHANDLER_LIST. 36 37 GDB_NOTIFIER keeps track of the file descriptor based event 38 sources. ASYNC_EVENT_HANDLER_LIST keeps track of asynchronous 39 event sources that are signalled by some component of gdb, usually 40 a target_ops instance. Event sources for gdb are currently the UI 41 and the target. Gdb communicates with the command line user 42 interface via the readline library and usually communicates with 43 remote targets via a serial port. Serial ports are represented in 44 GDB as file descriptors and select/poll calls. For native targets 45 instead, the communication varies across operating system debug 46 APIs, but usually consists of calls to ptrace and waits (via 47 signals) or calls to poll/select (via file descriptors). In the 48 current gdb, the code handling events related to the target resides 49 in wait_for_inferior for synchronous targets; or, for asynchronous 50 capable targets, by having the target register either a target 51 controlled file descriptor and/or an asynchronous event source in 52 the event loop, with the fetch_inferior_event function as the event 53 callback. In both the synchronous and asynchronous cases, usually 54 the target event is collected through the target_wait interface. 55 The target is free to install other event sources in the event loop 56 if it so requires. 57 58 EVENT_QUEUE keeps track of the events that have happened during the 59 last iteration of the event loop, and need to be processed. An 60 event is represented by a procedure to be invoked in order to 61 process the event. The queue is scanned head to tail. If the 62 event of interest is a change of state in a file descriptor, then a 63 call to poll or select will be made to detect it. 64 65 If the events generate signals, they are also queued by special 66 functions that are invoked through traditional signal handlers. 67 The actions to be taken is response to such events will be executed 68 when the SIGHANDLER_LIST is scanned, the next time through the 69 infinite loop. 70 71 Corollary tasks are the creation and deletion of event sources. */ 72 73 typedef void *gdb_client_data; 74 typedef void (handler_func) (int, gdb_client_data); 75 typedef void (timer_handler_func) (gdb_client_data); 76 77 /* Exported functions from event-loop.c */ 78 79 extern int gdb_do_one_event (int mstimeout = -1); 80 extern void delete_file_handler (int fd); 81 82 /* Add a file handler/descriptor to the list of descriptors we are 83 interested in. 84 85 FD is the file descriptor for the file/stream to be listened to. 86 87 NAME is a user-friendly name for the handler. 88 89 If IS_UI is set, this file descriptor is used for a user interface. */ 90 91 extern void add_file_handler (int fd, handler_func *proc, 92 gdb_client_data client_data, 93 std::string &&name, bool is_ui = false); 94 95 extern int create_timer (int milliseconds, 96 timer_handler_func *proc, 97 gdb_client_data client_data); 98 extern void delete_timer (int id); 99 100 /* Must be defined by client. */ 101 102 extern void handle_event_loop_exception (const gdb_exception &); 103 104 /* Must be defined by client. Returns true if any signal handler was 105 ready. */ 106 107 extern int invoke_async_signal_handlers (); 108 109 /* Must be defined by client. Returns true if any event handler was 110 ready. */ 111 112 extern int check_async_event_handlers (); 113 114 enum class debug_event_loop_kind 115 { 116 OFF, 117 118 /* Print all event-loop related messages, except events from user-interface 119 event sources. */ 120 ALL_EXCEPT_UI, 121 122 /* Print all event-loop related messages. */ 123 ALL, 124 }; 125 126 /* True if we are printing event loop debug statements. */ 127 extern debug_event_loop_kind debug_event_loop; 128 129 /* Print an "event loop" debug statement. */ 130 131 #define event_loop_debug_printf(fmt, ...) \ 132 debug_prefixed_printf_cond (debug_event_loop != debug_event_loop_kind::OFF, \ 133 "event-loop", fmt, ##__VA_ARGS__) 134 135 /* Print an "event loop" debug statement that is know to come from a UI-related 136 event (e.g. calling the event handler for the fd of the CLI). */ 137 138 #define event_loop_ui_debug_printf(is_ui, fmt, ...) \ 139 do \ 140 { \ 141 if (debug_event_loop == debug_event_loop_kind::ALL \ 142 || (debug_event_loop == debug_event_loop_kind::ALL_EXCEPT_UI \ 143 && !is_ui)) \ 144 debug_prefixed_printf ("event-loop", __func__, fmt, ##__VA_ARGS__); \ 145 } \ 146 while (0) 147 148 #endif /* EVENT_LOOP_H */ 149
Indexes created Sun Mar 01 05:31:48 UTC 2026