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With this patch, when an inferior, thread or frame is explicitly
selected by the user, notifications will appear on all CLI and MI UIs.
When a GDB console is integrated in a front-end, this allows the
front-end to follow a selection made by the user ont he CLI, and it
informs the user about selection changes made behind the scenes by the
front-end.
This patch addresses PR gdb/20487.
In order to communicate frame changes to the front-end, this patch adds
a new field to the =thread-selected event for the selected frame. The
idea is that since inferior/thread/frame can be seen as a composition,
it makes sense to send them together in the same event. The vision
would be to eventually send the inferior information as well, if we find
that it's needed, although the "=thread-selected" event would be
ill-named for that job.
Front-ends need to handle this new field if they want to follow the
frame selection changes that originate from the console. The format of
the frame attribute is the same as what is found in the *stopped events.
Here's a detailed example for each command and the events they generate:
thread
------
1. CLI command:
thread 1.3
MI event:
=thread-selected,id="3",frame={...}
2. MI command:
-thread-select 3
CLI event:
[Switching to thread 1.3 ...]
3. MI command (CLI-in-MI):
thread 1.3
MI event/reply:
&"thread 1.3\n"
~"#0 child_sub_function () ...
=thread-selected,id="3",frame={level="0",...}
^done
frame
-----
1. CLI command:
frame 1
MI event:
=thread-selected,id="3",frame={level="1",...}
2. MI command:
-stack-select-frame 1
CLI event:
#1 0x00000000004007f0 in child_function...
3. MI command (CLI-in-MI):
frame 1
MI event/reply:
&"frame 1\n"
~"#1 0x00000000004007f9 in ..."
=thread-selected,id="3",frame={level="1"...}
^done
inferior
--------
Inferior selection events only go from the console to MI, since there's
no way to select the inferior in pure MI.
1. CLI command:
inferior 2
MI event:
=thread-selected,id="3"
Note that if the user selects an inferior that is not started or exited,
the MI doesn't receive a notification. Since there is no threads to
select, the =thread-selected event does not apply...
2. MI command (CLI-in-MI):
inferior 2
MI event/reply:
&"inferior 2\n"
~"[Switching to inferior 2 ...]"
=thread-selected,id="4",frame={level="0"...}
^done
Internal implementation detail: this patch makes it possible to suppress
notifications caused by a CLI command, like what is done in mi-interp.c.
This means that it's now possible to use the
add_com_suppress_notification function to register a command with some
event suppressed. It is used to implement the select-frame command in
this patch.
The function command_notifies_uscc_observer was added to extract
the rather complicated logical expression from the if statement. It is
also now clearer what that logic does: if the command used by the user
already notifies the user_selected_context_changed observer, there is
not need to notify it again. It therefore protects again emitting the
event twice.
No regressions, tested on ubuntu 14.04 x86 with target boards unix and
native-extended-gdbserver.
gdb/ChangeLog:
YYYY-MM-DD Antoine Tremblay <antoine.tremblay@ericsson.com>
YYYY-MM-DD Simon Marchi <simon.marchi@ericsson.com>
PR gdb/20487
* NEWS: Mention new frame field of =thread-selected event.
* cli/cli-decode.c (add_cmd): Initialize c->suppress_notification.
(add_com_suppress_notification): New function definition.
(cmd_func): Set and restore the suppress_notification flag.
* cli/cli-deicode.h (struct cmd_list_element)
<suppress_notification>: New field.
* cli/cli-interp.c (cli_suppress_notification): New global variable.
(cli_on_user_selected_context_changed): New function.
(_initialize_cli_interp): Attach to user_selected_context_changed
observer.
* command.h (struct cli_suppress_notification): New structure.
(cli_suppress_notification): New global variable declaration.
(add_com_suppress_notification): New function declaration.
* defs.h (enum user_selected_what_flag): New enum.
(user_selected_what): New enum flag type.
* frame.h (print_stack_frame_to_uiout): New function declaration.
* gdbthread.h (print_selected_thread_frame): New function declaration.
* inferior.c (print_selected_inferior): New function definition.
(inferior_command): Remove printing of inferior/thread/frame switch
notifications, notify user_selected_context_changed observer.
* inferior.h (print_selected_inferior): New function declaration.
* mi/mi-cmds.c (struct mi_cmd): Add user_selected_context
suppression to stack-select-frame and thread-select commands.
* mi/mi-interp.c (struct mi_suppress_notification)
<user_selected_context>: Initialize.
(mi_user_selected_context_changed): New function definition.
(_initialize_mi_interp): Attach to user_selected_context_changed.
* mi/mi-main.c (mi_cmd_thread_select): Print thread selection reply.
(mi_execute_command): Handle notification suppression. Notify
user_selected_context_changed observer on thread change instead of printing
event directly. Don't send it if command already sends the notification.
(command_notifies_uscc_observer): New function.
(mi_cmd_execute): Don't handle notification suppression.
* mi/mi-main.h (struct mi_suppress_notification)
<user_selected_context>: New field.
* stack.c (print_stack_frame_to_uiout): New function definition.
(select_frame_command): Notify user_selected_context_changed
observer.
(frame_command): Call print_selected_thread_frame if there's no frame
change or notify user_selected_context_changed observer if there is.
(up_command): Notify user_selected_context_changed observer.
(down_command): Likewise.
(_initialize_stack): Suppress user_selected_context notification for
command select-frame.
* thread.c (thread_command): Notify
user_selected_context_changed if the thread has changed, print
thread info directly if it hasn't.
(do_captured_thread_select): Do not print thread switch event.
(print_selected_thread_frame): New function definition.
* tui/tui-interp.c (tui_on_user_selected_context_changed):
New function definition.
(_initialize_tui_interp): Attach to user_selected_context_changed
observer.
gdb/doc/ChangeLog:
PR gdb/20487
* gdb.texinfo (Context management): Update mention of frame
change notifications.
(gdb/mi Async Records): Document frame field in
=thread-select event.
* observer.texi (GDB Observers): New user_selected_context_changed
observer.
gdb/testsuite/ChangeLog:
PR gdb/20487
* gdb.mi/mi-pthreads.exp (check_mi_thread_command_set): Adapt
=thread-select-event check.
314 lines
12 KiB
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314 lines
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Plaintext
@c -*-texinfo-*-
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@c This file is part of the GDB manual.
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@c
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@c Copyright (C) 2003-2016 Free Software Foundation, Inc.
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@c
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@c See the file gdbint.texinfo for copying conditions.
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@c
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@c Also, the @deftypefun lines from this file are processed into a
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@c header file during the GDB build process. Permission is granted
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@c to redistribute and/or modify those lines under the terms of the
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@c GNU General Public License as published by the Free Software
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@c Foundation; either version 3 of the License, or (at your option)
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@c any later version.
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@node GDB Observers
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@appendix @value{GDBN} Currently available observers
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@section Implementation rationale
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@cindex observers implementation rationale
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An @dfn{observer} is an entity which is interested in being notified
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when GDB reaches certain states, or certain events occur in GDB.
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The entity being observed is called the @dfn{subject}. To receive
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notifications, the observer attaches a callback to the subject.
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One subject can have several observers.
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@file{observer.c} implements an internal generic low-level event
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notification mechanism. This generic event notification mechanism is
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then re-used to implement the exported high-level notification
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management routines for all possible notifications.
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The current implementation of the generic observer provides support
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for contextual data. This contextual data is given to the subject
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when attaching the callback. In return, the subject will provide
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this contextual data back to the observer as a parameter of the
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callback.
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Note that the current support for the contextual data is only partial,
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as it lacks a mechanism that would deallocate this data when the
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callback is detached. This is not a problem so far, as this contextual
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data is only used internally to hold a function pointer. Later on, if
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a certain observer needs to provide support for user-level contextual
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data, then the generic notification mechanism will need to be
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enhanced to allow the observer to provide a routine to deallocate the
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data when attaching the callback.
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The observer implementation is also currently not reentrant.
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In particular, it is therefore not possible to call the attach
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or detach routines during a notification.
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@section Debugging
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Observer notifications can be traced using the command @samp{set debug
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observer 1} (@pxref{Debugging Output, , Optional messages about
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internal happenings, gdb, Debugging with @var{GDBN}}).
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@section @code{normal_stop} Notifications
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@cindex @code{normal_stop} observer
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@cindex notification about inferior execution stop
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@value{GDBN} notifies all @code{normal_stop} observers when the
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inferior execution has just stopped, the associated messages and
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annotations have been printed, and the control is about to be returned
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to the user.
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Note that the @code{normal_stop} notification is not emitted when
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the execution stops due to a breakpoint, and this breakpoint has
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a condition that is not met. If the breakpoint has any associated
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commands list, the commands are executed after the notification
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is emitted.
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The following interfaces are available to manage observers:
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@deftypefun extern struct observer *observer_attach_@var{event} (observer_@var{event}_ftype *@var{f})
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Using the function @var{f}, create an observer that is notified when
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ever @var{event} occurs, return the observer.
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@end deftypefun
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@deftypefun extern void observer_detach_@var{event} (struct observer *@var{observer});
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Remove @var{observer} from the list of observers to be notified when
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@var{event} occurs.
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@end deftypefun
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@deftypefun extern void observer_notify_@var{event} (void);
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Send a notification to all @var{event} observers.
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@end deftypefun
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The following observable events are defined:
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@deftypefun void normal_stop (struct bpstats *@var{bs}, int @var{print_frame})
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The inferior has stopped for real. The @var{bs} argument describes
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the breakpoints were are stopped at, if any. Second argument
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@var{print_frame} non-zero means display the location where the
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inferior has stopped.
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@end deftypefun
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@deftypefun void signal_received (enum gdb_signal @var{siggnal})
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The inferior was stopped by a signal.
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@end deftypefun
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@deftypefun void end_stepping_range (void)
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We are done with a step/next/si/ni command.
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@end deftypefun
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@deftypefun void signal_exited (enum gdb_signal @var{siggnal})
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The inferior was terminated by a signal.
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@end deftypefun
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@deftypefun void exited (int @var{exitstatus})
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The inferior program is finished.
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@end deftypefun
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@deftypefun void no_history (void)
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Reverse execution: target ran out of history info.
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@end deftypefun
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@deftypefun void sync_execution_done (void)
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A synchronous command finished.
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@end deftypefun
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@deftypefun void command_error (void)
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An error was caught while executing a command.
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@end deftypefun
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@deftypefun void target_changed (struct target_ops *@var{target})
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The target's register contents have changed.
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@end deftypefun
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@deftypefun void executable_changed (void)
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The executable being debugged by GDB has changed: The user decided
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to debug a different program, or the program he was debugging has
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been modified since being loaded by the debugger (by being recompiled,
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for instance).
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@end deftypefun
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@deftypefun void inferior_created (struct target_ops *@var{objfile}, int @var{from_tty})
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@value{GDBN} has just connected to an inferior. For @samp{run},
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@value{GDBN} calls this observer while the inferior is still stopped
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at the entry-point instruction. For @samp{attach} and @samp{core},
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@value{GDBN} calls this observer immediately after connecting to the
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inferior, and before any information on the inferior has been printed.
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@end deftypefun
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@deftypefun void record_changed (struct inferior *@var{inferior}, int @var{started}, const char *@var{method}, const char *@var{format})
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The status of process record for inferior @var{inferior} in
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@value{GDBN} has changed. The process record is started if
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@var{started} is true, and the process record is stopped if
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@var{started} is false.
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When @var{started} is true, @var{method} indicates the short name of the method
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used for recording. If the method supports multiple formats, @var{format}
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indicates which one is being used, otherwise it is NULL. When @var{started} is
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false, they are both NULL.
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@end deftypefun
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@deftypefun void solib_loaded (struct so_list *@var{solib})
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The shared library specified by @var{solib} has been loaded. Note that
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when @value{GDBN} calls this observer, the library's symbols probably
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haven't been loaded yet.
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@end deftypefun
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@deftypefun void solib_unloaded (struct so_list *@var{solib})
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The shared library specified by @var{solib} has been unloaded.
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Note that when @value{GDBN} calls this observer, the library's
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symbols have not been unloaded yet, and thus are still available.
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@end deftypefun
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@deftypefun void new_objfile (struct objfile *@var{objfile})
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The symbol file specified by @var{objfile} has been loaded.
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Called with @var{objfile} equal to @code{NULL} to indicate
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previously loaded symbol table data has now been invalidated.
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@end deftypefun
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@deftypefun void free_objfile (struct objfile *@var{objfile})
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The object file specified by @var{objfile} is about to be freed.
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@end deftypefun
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@deftypefun void new_thread (struct thread_info *@var{t})
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The thread specified by @var{t} has been created.
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@end deftypefun
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@deftypefun void thread_exit (struct thread_info *@var{t}, int @var{silent})
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The thread specified by @var{t} has exited. The @var{silent} argument
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indicates that @value{GDBN} is removing the thread from its tables
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without wanting to notify the user about it.
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@end deftypefun
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@deftypefun void thread_stop_requested (ptid_t @var{ptid})
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An explicit stop request was issued to @var{ptid}. If @var{ptid}
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equals @var{minus_one_ptid}, the request applied to all threads. If
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@code{ptid_is_pid(ptid)} returns true, the request applied to all
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threads of the process pointed at by @var{ptid}. Otherwise, the
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request applied to the single thread pointed at by @var{ptid}.
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@end deftypefun
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@deftypefun void target_resumed (ptid_t @var{ptid})
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The target was resumed. The @var{ptid} parameter specifies which
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thread was resume, and may be RESUME_ALL if all threads are resumed.
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@end deftypefun
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@deftypefun void about_to_proceed (void)
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The target is about to be proceeded.
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@end deftypefun
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@deftypefun void breakpoint_created (struct breakpoint *@var{b})
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A new breakpoint @var{b} has been created.
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@end deftypefun
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@deftypefun void breakpoint_deleted (struct breakpoint *@var{b})
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A breakpoint has been destroyed. The argument @var{b} is the
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pointer to the destroyed breakpoint.
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@end deftypefun
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@deftypefun void breakpoint_modified (struct breakpoint *@var{b})
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A breakpoint has been modified in some way. The argument @var{b}
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is the modified breakpoint.
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@end deftypefun
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@deftypefun void traceframe_changed (int @var{tfnum}, int @var{tpnum})
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The trace frame is changed to @var{tfnum} (e.g., by using the
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@code{tfind} command). If @var{tfnum} is negative, it means
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@value{GDBN} resumes live debugging. The number of the tracepoint
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associated with this traceframe is @var{tpnum}.
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@end deftypefun
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@deftypefun void architecture_changed (struct gdbarch *@var{newarch})
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The current architecture has changed. The argument @var{newarch} is
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a pointer to the new architecture.
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@end deftypefun
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@deftypefun void thread_ptid_changed (ptid_t @var{old_ptid}, ptid_t @var{new_ptid})
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The thread's ptid has changed. The @var{old_ptid} parameter specifies
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the old value, and @var{new_ptid} specifies the new value.
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@end deftypefun
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@deftypefun void inferior_added (struct inferior *@var{inf})
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The inferior @var{inf} has been added to the list of inferiors. At
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this point, it might not be associated with any process.
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@end deftypefun
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@deftypefun void inferior_appeared (struct inferior *@var{inf})
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The inferior identified by @var{inf} has been attached to a process.
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@end deftypefun
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@deftypefun void inferior_exit (struct inferior *@var{inf})
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Either the inferior associated with @var{inf} has been detached from the
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process, or the process has exited.
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@end deftypefun
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@deftypefun void inferior_removed (struct inferior *@var{inf})
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The inferior @var{inf} has been removed from the list of inferiors.
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This method is called immediately before freeing @var{inf}.
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@end deftypefun
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@deftypefun void memory_changed (struct inferior *@var{inferior}, CORE_ADDR @var{addr}, ssize_t @var{len}, const bfd_byte *@var{data})
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Bytes from @var{data} to @var{data} + @var{len} have been written
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to the @var{inferior} at @var{addr}.
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@end deftypefun
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@deftypefun void before_prompt (const char *@var{current_prompt})
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Called before a top-level prompt is displayed. @var{current_prompt} is
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the current top-level prompt.
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@end deftypefun
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@deftypefun void gdb_datadir_changed (void)
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Variable gdb_datadir has been set. The value may not necessarily change.
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@end deftypefun
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@deftypefun void command_param_changed (const char *@var{param}, const char *@var{value})
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The parameter of some @code{set} commands in console are changed. This
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method is called after a command @code{set @var{param} @var{value}}.
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@var{param} is the parameter of @code{set} command, and @var{value}
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is the value of changed parameter.
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@end deftypefun
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@deftypefun void tsv_created (const struct trace_state_variable *@var{tsv})
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The new trace state variable @var{tsv} is created.
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@end deftypefun
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@deftypefun void tsv_deleted (const struct trace_state_variable *@var{tsv})
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The trace state variable @var{tsv} is deleted. If @var{tsv} is
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@code{NULL}, all trace state variables are deleted.
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@end deftypefun
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@deftypefun void tsv_modified (const struct trace_state_variable *@var{tsv})
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The trace state value @var{tsv} is modified.
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@end deftypefun
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@deftypefun void inferior_call_pre (ptid_t @var{thread}, CORE_ADDR @var{address})
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An inferior function at @var{address} is about to be called in thread
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@var{thread}.
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@end deftypefun
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@deftypefun void inferior_call_post (ptid_t @var{thread}, CORE_ADDR @var{address})
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The inferior function at @var{address} has just been called. This observer
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is called even if the inferior exits during the call. @var{thread} is the
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thread in which the function was called, which may be different from the
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current thread.
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@end deftypefun
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@deftypefun void register_changed (struct frame_info *@var{frame}, int @var{regnum})
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A register in the inferior has been modified by the @value{GDBN} user.
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@end deftypefun
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@deftypefun void test_notification (int @var{somearg})
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This observer is used for internal testing. Do not use.
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See testsuite/gdb.gdb/observer.exp.
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@end deftypefun
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@deftypefun void user_selected_context_changed (user_selected_what @var{selection})
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The user-selected inferior, thread and/or frame has changed. The user_select_what
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flag specifies if the inferior, thread and/or frame has changed.
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@end deftypefun
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