148 lines
5.7 KiB
C++
148 lines
5.7 KiB
C++
/* Definitions used by the GDB event loop.
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Copyright (C) 1999-2022 Free Software Foundation, Inc.
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Written by Elena Zannoni <ezannoni@cygnus.com> of Cygnus Solutions.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef EVENT_LOOP_H
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#define EVENT_LOOP_H
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/* An event loop listens for events from multiple event sources. When
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an event arrives, it is queued and processed by calling the
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appropriate event handler. The event loop then continues to listen
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for more events. An event loop completes when there are no event
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sources to listen on. External event sources can be plugged into
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the loop.
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There are 4 main components:
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- a list of file descriptors to be monitored, GDB_NOTIFIER.
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- a list of asynchronous event sources to be monitored,
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ASYNC_EVENT_HANDLER_LIST.
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- a list of events that have occurred, EVENT_QUEUE.
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- a list of signal handling functions, SIGHANDLER_LIST.
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GDB_NOTIFIER keeps track of the file descriptor based event
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sources. ASYNC_EVENT_HANDLER_LIST keeps track of asynchronous
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event sources that are signalled by some component of gdb, usually
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a target_ops instance. Event sources for gdb are currently the UI
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and the target. Gdb communicates with the command line user
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interface via the readline library and usually communicates with
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remote targets via a serial port. Serial ports are represented in
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GDB as file descriptors and select/poll calls. For native targets
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instead, the communication varies across operating system debug
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APIs, but usually consists of calls to ptrace and waits (via
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signals) or calls to poll/select (via file descriptors). In the
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current gdb, the code handling events related to the target resides
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in wait_for_inferior for synchronous targets; or, for asynchronous
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capable targets, by having the target register either a target
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controlled file descriptor and/or an asynchronous event source in
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the event loop, with the fetch_inferior_event function as the event
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callback. In both the synchronous and asynchronous cases, usually
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the target event is collected through the target_wait interface.
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The target is free to install other event sources in the event loop
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if it so requires.
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EVENT_QUEUE keeps track of the events that have happened during the
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last iteration of the event loop, and need to be processed. An
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event is represented by a procedure to be invoked in order to
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process the event. The queue is scanned head to tail. If the
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event of interest is a change of state in a file descriptor, then a
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call to poll or select will be made to detect it.
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If the events generate signals, they are also queued by special
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functions that are invoked through traditional signal handlers.
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The actions to be taken is response to such events will be executed
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when the SIGHANDLER_LIST is scanned, the next time through the
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infinite loop.
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Corollary tasks are the creation and deletion of event sources. */
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typedef void *gdb_client_data;
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typedef void (handler_func) (int, gdb_client_data);
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typedef void (timer_handler_func) (gdb_client_data);
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/* Exported functions from event-loop.c */
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extern int gdb_do_one_event (void);
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extern void delete_file_handler (int fd);
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/* Add a file handler/descriptor to the list of descriptors we are
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interested in.
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FD is the file descriptor for the file/stream to be listened to.
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NAME is a user-friendly name for the handler.
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If IS_UI is set, this file descriptor is used for a user interface. */
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extern void add_file_handler (int fd, handler_func *proc,
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gdb_client_data client_data,
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std::string &&name, bool is_ui = false);
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extern int create_timer (int milliseconds,
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timer_handler_func *proc,
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gdb_client_data client_data);
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extern void delete_timer (int id);
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/* Must be defined by client. */
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extern void handle_event_loop_exception (const gdb_exception &);
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/* Must be defined by client. Returns true if any signal handler was
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ready. */
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extern int invoke_async_signal_handlers ();
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/* Must be defined by client. Returns true if any event handler was
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ready. */
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extern int check_async_event_handlers ();
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enum class debug_event_loop_kind
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{
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OFF,
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/* Print all event-loop related messages, except events from user-interface
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event sources. */
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ALL_EXCEPT_UI,
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/* Print all event-loop related messages. */
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ALL,
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};
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/* True if we are printing event loop debug statements. */
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extern debug_event_loop_kind debug_event_loop;
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/* Print an "event loop" debug statement. */
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#define event_loop_debug_printf(fmt, ...) \
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debug_prefixed_printf_cond (debug_event_loop != debug_event_loop_kind::OFF, \
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"event-loop", fmt, ##__VA_ARGS__)
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/* Print an "event loop" debug statement that is know to come from a UI-related
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event (e.g. calling the event handler for the fd of the CLI). */
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#define event_loop_ui_debug_printf(is_ui, fmt, ...) \
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do \
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{ \
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if (debug_event_loop == debug_event_loop_kind::ALL \
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|| (debug_event_loop == debug_event_loop_kind::ALL_EXCEPT_UI \
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&& !is_ui)) \
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debug_prefixed_printf ("event-loop", __func__, fmt, ##__VA_ARGS__); \
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} \
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while (0)
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#endif /* EVENT_LOOP_H */
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