215 lines
8.6 KiB
Text
215 lines
8.6 KiB
Text
@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, 2004, 2005, 2006, 2008
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@c 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 2 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 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 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 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 (int @var{bpnum})
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A new breakpoint has been created. The argument @var{bpnum} is the
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number of the newly-created breakpoint.
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@end deftypefun
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@deftypefun void breakpoint_deleted (int @var{bpnum})
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A breakpoint has been destroyed. The argument @var{bpnum} is the
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number of the newly-destroyed breakpoint.
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@end deftypefun
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@deftypefun void breakpoint_modified (int @var{bpnum})
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A breakpoint has been modified in some way. The argument @var{bpnum}
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is the number of the modified breakpoint.
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@end deftypefun
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@deftypefun void tracepoint_created (int @var{tpnum})
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A new tracepoint has been created. The argument @var{tpnum} is the
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number of the newly-created tracepoint.
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@end deftypefun
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@deftypefun void tracepoint_deleted (int @var{tpnum})
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A tracepoint has been destroyed. The argument @var{tpnum} is the
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number of the newly-destroyed tracepoint.
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@end deftypefun
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@deftypefun void tracepoint_modified (int @var{tpnum})
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A tracepoint has been modified in some way. The argument @var{tpnum}
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is the number of the modified tracepoint.
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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 new_inferior (int @var{pid})
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@value{GDBN} has attached to a new inferior identified by @var{pid}.
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@end deftypefun
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@deftypefun void inferior_exit (int @var{pid})
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Either @value{GDBN} detached from the inferior, or the inferior
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exited. The argument @var{pid} identifies the inferior.
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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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