1 /* Definitions used by the GDB event loop.
2 Copyright 1999 Free Software Foundation, Inc.
3 Written by Elena Zannoni <ezannoni@cygnus.com> of Cygnus Solutions.
5 This file is part of GDB.
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 2 of the License, or
10 (at your option) any later version.
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.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
21 /* An event loop listens for events from multiple event sources. When
22 an event arrives, it is queued and processed by calling the
23 appropriate event handler. The event loop then continues to listen
24 for more events. An event loop completes when there are no event
25 sources to listen on. External event sources can be plugged into
28 There are 3 main components:
29 - a list of file descriptors to be monitored, GDB_NOTIFIER.
30 - a list of events that have occurred, EVENT_QUEUE.
31 - a list of signal handling functions, SIGHANDLER_LIST.
33 GDB_NOTIFIER keeps track of the event sources. Event sources for
34 gdb are currently the UI and the target. Gdb communicates with the
35 command line user interface via the readline library and usually
36 communicates with remote targets via a serial port. Serial ports
37 are represented in GDB as file descriptors and select/poll calls.
38 For native targets instead, the communication consists of calls to
39 ptrace and waits (via signals) or calls to poll/select (via file
40 descriptors). In the current gdb, the code handling events related
41 to the target resides in the wait_for_inferior function and in
42 various target specific files (*-tdep.c).
44 EVENT_QUEUE keeps track of the events that have happened during the
45 last iteration of the event loop, and need to be processed. An
46 event is represented by a procedure to be invoked in order to
47 process the event. The queue is scanned head to tail. If the
48 event of interest is a change of state in a file descriptor, then a
49 call to poll or select will be made to detect it.
51 If the events generate signals, they are also queued by special
52 functions that are invoked through traditional signal handlers.
53 The actions to be taken is response to such events will be executed
54 when the SIGHANDLER_LIST is scanned, the next time through the
57 Corollary tasks are the creation and deletion of event sources. */
59 typedef PTR gdb_client_data;
60 typedef struct gdb_event gdb_event;
62 typedef void (file_handler_func) PARAMS ((gdb_client_data, int mask));
63 typedef void (async_handler_func) PARAMS ((gdb_client_data));
64 typedef void (event_handler_func) PARAMS ((int));
66 /* Event for the GDB event system. Events are queued by calling
67 async_queue_event and serviced later on by gdb_do_one_event. An
68 event can be, for instance, a file descriptor becoming ready to be
69 read. Servicing an event simply means that the procedure PROC will
70 be called. We have 2 queues, one for file handlers that we listen
71 to in the event loop, and one for the file handlers+events that are
72 ready. The procedure PROC associated with each event is always the
73 same (handle_file_event). Its duty is to invoke the handler
74 associated with the file descriptor whose state change generated
75 the event, plus doing other cleanups adn such. */
79 event_handler_func *proc; /* Procedure to call to service this event. */
80 int fd; /* File descriptor that is ready. */
81 struct gdb_event *next_event; /* Next in list of events or NULL. */
84 /* Information about each file descriptor we register with the event
87 typedef struct file_handler
89 int fd; /* File descriptor. */
90 int mask; /* Events we want to monitor: POLLIN, etc. */
91 int ready_mask; /* Events that have been seen since
93 file_handler_func *proc; /* Procedure to call when fd is ready. */
94 gdb_client_data client_data; /* Argument to pass to proc. */
95 struct file_handler *next_file; /* Next registered file descriptor. */
99 /* PROC is a function to be invoked when the READY flag is set. This
100 happens when there has been a signal and the corresponding signal
101 handler has 'triggered' this async_signal_handler for
102 execution. The actual work to be done in response to a signal will
103 be carried out by PROC at a later time, within process_event. This
104 provides a deferred execution of signal handlers.
105 Async_init_signals takes care of setting up such an
106 asyn_signal_handler for each interesting signal. */
108 typedef struct async_signal_handler
110 int ready; /* If ready, call this handler from the main event loop,
111 using invoke_async_handler. */
112 struct async_signal_handler *next_handler; /* Ptr to next handler */
113 async_handler_func *proc; /* Function to call to do the work */
114 gdb_client_data client_data; /* Argument to async_handler_func */
116 async_signal_handler;
118 /* Where to add an event onto the event queue, by queue_event. */
121 /* Add at tail of queue. It will be processed in first in first
124 /* Add at head of queue. It will be processed in last in first out
130 /* Tell create_file_handler what events we are interested in.
131 This is used by the select version of the event loop. */
133 #define GDB_READABLE (1<<1)
134 #define GDB_WRITABLE (1<<2)
135 #define GDB_EXCEPTION (1<<3)
137 /* Type of the mask arguments to select. */
140 #define SELECT_MASK fd_set
143 typedef long fd_mask;
146 #define SELECT_MASK void
148 #define SELECT_MASK int
152 /* Define "NBBY" (number of bits per byte) if it's not already defined. */
159 /* Define the number of fd_masks in an fd_set */
163 #define FD_SETSIZE OPEN_MAX
165 #define FD_SETSIZE 256
168 #if !defined(howmany)
169 #define howmany(x, y) (((x)+((y)-1))/(y))
172 #define NFDBITS NBBY*sizeof(fd_mask)
174 #define MASK_SIZE howmany(FD_SETSIZE, NFDBITS)
177 /* Stack for prompts. Each prompt is composed as a prefix, a prompt
178 and a suffix. The prompt to be displayed at any given time is the
179 one on top of the stack. A stack is necessary because of cases in
180 which the execution of a gdb command requires further input from
181 the user, like for instance 'commands' for breakpoints and
182 'actions' for tracepoints. In these cases, the prompt is '>' and
183 gdb should process input using the asynchronous readline interface
184 and the event loop. In order to achieve this, we need to save
185 somewhere the state of GDB, i.e. that it is processing user input
186 as part of a command and not as part of the top level command loop.
187 The prompt stack represents part of the saved state. Another part
188 would be the function that readline would invoke after a whole line
189 of input has ben entered. This second piece would be something
190 like, for instance, where to return within the code for the actions
191 commands after a line has been read. This latter portion has not
192 beeen implemented yet. The need for a 3-part prompt arises from
193 the annotation level. When this is set to 2, the prompt is actually
194 composed of a prefix, the prompt itself and a suffix. */
196 /* At any particular time there will be always at least one prompt on
197 the stack, the one being currently displayed by gdb. If gdb is
198 using annotation level equal 2, there will be 2 prompts on the
199 stack: the usual one, w/o prefix and suffix (at top - 1), and the
200 'composite' one with prefix and suffix added (at top). At this
201 time, this is the only use of the prompt stack. Resetting annotate
202 to 0 or 1, pops the top of the stack, resetting its size to one
203 element. The MAXPROMPTS limit is safe, for now. Once other cases
204 are dealt with (like the different prompts used for 'commands' or
205 'actions') this array implementation of the prompt stack may have
208 #define MAXPROMPTS 10
217 prompt_stack[MAXPROMPTS];
221 #define PROMPT(X) the_prompts.prompt_stack[the_prompts.top + X].prompt
222 #define PREFIX(X) the_prompts.prompt_stack[the_prompts.top + X].prefix
223 #define SUFFIX(X) the_prompts.prompt_stack[the_prompts.top + X].suffix
225 /* Exported functions from event-loop.c */
227 extern void start_event_loop PARAMS ((void));
228 extern void delete_file_handler PARAMS ((int));
229 extern void add_file_handler PARAMS ((int, file_handler_func, gdb_client_data));
230 extern void mark_async_signal_handler PARAMS ((async_signal_handler *));
231 extern async_signal_handler *
232 create_async_signal_handler PARAMS ((async_handler_func *, gdb_client_data));
233 extern void delete_async_signal_handler PARAMS ((async_signal_handler *async_handler_ptr));
235 /* Exported functions from event-top.c.
236 FIXME: these should really go into top.h. */
238 extern void display_gdb_prompt PARAMS ((char*));
239 extern void async_init_signals PARAMS ((void));
240 extern void set_async_editing_command PARAMS ((char *, int, struct cmd_list_element *));
241 extern void set_async_annotation_level PARAMS ((char *, int, struct cmd_list_element *));
242 extern void set_async_prompt PARAMS ((char *, int, struct cmd_list_element *));
243 extern void handle_stop_sig PARAMS ((int));
244 extern void gdb_readline2 PARAMS ((void));
246 /* Exported variables from event-top.c.
247 FIXME: these should really go into top.h. */
249 extern int async_command_editing_p;
250 extern char *async_annotation_suffix;
251 extern char *new_async_prompt;
252 extern struct prompts the_prompts;
253 extern void (*call_readline) PARAMS ((void));
254 extern void (*input_handler) PARAMS ((char *));