From: Andrew Burgess <aburgess@redhat.com>
To: Jan Vrany <jan.vrany@labware.com>
Cc: GDB Patches <gdb-patches@sourceware.org>
Subject: Re: [PATCH v3 1/1] gdb/mi: PR20684, preserve user selected thread and frame when invoking MI commands
Date: Wed, 02 Mar 2022 10:00:17 +0000 [thread overview]
Message-ID: <87a6e8znbi.fsf@redhat.com> (raw)
In-Reply-To: <4c975d42f6a2a165328ff0132f7be3feccae4828.camel@labware.com>
Jan Vrany via Gdb-patches <gdb-patches@sourceware.org> writes:
> On Thu, 2022-02-17 at 22:24 +0000, Andrew Burgess wrote:
>> * Jan Vrany via Gdb-patches <gdb-patches@sourceware.org> [2022-01-27 14:50:11 +0000]:
>>
>> > When invoking MI commands with --thread and/or --frame, user selected
>> > thread and frame was not preserved:
>> >
>> > (gdb)
>> > info thread
>> > &"info thread\n"
>> > ~" Id Target Id Frame \n"
>> > ~"* 1 Thread 0x7ffff7c30740 (LWP 19302) \"user-selected-c\" main () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:60\n"
>> > ~" 2 Thread 0x7ffff7c2f700 (LWP 19306) \"user-selected-c\" child_sub_function () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30\n"
>> > ~" 3 Thread 0x7ffff742e700 (LWP 19307) \"user-selected-c\" child_sub_function () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30\n"
>> > ^done
>> > (gdb)
>> > info frame
>> > &"info frame\n"
>> > ~"Stack level 0, frame at 0x7fffffffdf90:\n"
>> > ~" rip = 0x555555555207 in main (/home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:60); saved rip = 0x7ffff7c5709b\n"
>> > ~" source language c.\n"
>> > ~" Arglist at 0x7fffffffdf80, args: \n"
>> > ~" Locals at 0x7fffffffdf80, Previous frame's sp is 0x7fffffffdf90\n"
>> > ~" Saved registers:\n "
>> > ~" rbp at 0x7fffffffdf80, rip at 0x7fffffffdf88\n"
>> > ^done
>> > (gdb)
>> > -stack-info-depth --thread 3
>> > ^done,depth="4"
>> > (gdb)
>> > info thread
>> > &"info thread\n"
>> > ~" Id Target Id Frame \n"
>> > ~" 1 Thread 0x7ffff7c30740 (LWP 19302) \"user-selected-c\" main () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:60\n"
>> > ~" 2 Thread 0x7ffff7c2f700 (LWP 19306) \"user-selected-c\" child_sub_function () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30\n"
>> > ~"* 3 Thread 0x7ffff742e700 (LWP 19307) \"user-selected-c\" child_sub_function () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30\n"
>> > ^done
>> > (gdb)
>> > info frame
>> > &"info frame\n"
>> > ~"Stack level 0, frame at 0x7ffff742dee0:\n"
>> > ~" rip = 0x555555555169 in child_sub_function (/home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30); saved rip = 0x555555555188\n"
>> > ~" called by frame at 0x7ffff742df00\n"
>> > ~" source language c.\n"
>> > ~" Arglist at 0x7ffff742ded0, args: \n"
>> > ~" Locals at 0x7ffff742ded0, Previous frame's sp is 0x7ffff742dee0\n"
>> > ~" Saved registers:\n "
>> > ~" rbp at 0x7ffff742ded0, rip at 0x7ffff742ded8\n"
>> > ^done
>> > (gdb)
>> >
>> > This was problematic for frontends that provide access to CLI because UI
>> > may silently change the context for CLI commands (as demonstrated above).
>> >
>> > Bug: https://urldefense.proofpoint.com/v2/url?u=https-3A__sourceware.org_bugzilla_show-5Fbug.cgi-3Fid-3D20684&d=DwIBAg&c=sPZ6DeHLiehUHQWKIrsNwWp3t7snrE-az24ztT0w7Jc&r=WpFFGgYa98Yp-c29WHTCwU1wAGFBvszA6a4RzgpMSqc&m=soXzjKh4zT-FpxAe1wtdv7ka2r_jXNbrkEUR4XdUcOY&s=QkEM5YHXj7mpWI1y1z1AxRbosKxMhhfvfsMXmRnFoQc&e=
>> > ---
>> > gdb/mi/mi-cmds.h | 12 ++
>> > gdb/mi/mi-main.c | 54 ++++---
>> > gdb/testsuite/gdb.mi/mi-cmd-user-context.exp | 155 +++++++++++++++++++
>> > 3 files changed, 198 insertions(+), 23 deletions(-)
>> > create mode 100644 gdb/testsuite/gdb.mi/mi-cmd-user-context.exp
>> >
>> > diff --git a/gdb/mi/mi-cmds.h b/gdb/mi/mi-cmds.h
>> > index 2a93a9f5476..785652ee1c9 100644
>> > --- a/gdb/mi/mi-cmds.h
>> > +++ b/gdb/mi/mi-cmds.h
>> > @@ -23,6 +23,7 @@
>> > #define MI_MI_CMDS_H
>> >
>> > #include "gdbsupport/gdb_optional.h"
>> > +#include "mi/mi-main.h"
>> >
>> > enum print_values {
>> > PRINT_NO_VALUES,
>> > @@ -163,6 +164,17 @@ struct mi_command
>> > wrong. */
>> > void invoke (struct mi_parse *parse) const;
>> >
>> > + /* Return whether this command preserves user selected context (thread
>> > + and frame). */
>> > + bool preserve_user_selected_context () const
>> > + {
>> > + /* Here we exploit the fact that if MI command is supposed to change
>> > + user context, then it should not emit change notifications. Therefore if
>> > + command does not suppress user context change notifications, then it should
>> > + preserve the context. */
>> > + return m_suppress_notification != &mi_suppress_notification.user_selected_context;
>> > + }
>> > +
>> > protected:
>> >
>> > /* The core of command invocation, this needs to be overridden in each
>> > diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
>> > index 4860da7536a..e112707e4d1 100644
>> > --- a/gdb/mi/mi-main.c
>> > +++ b/gdb/mi/mi-main.c
>> > @@ -1907,6 +1907,16 @@ command_notifies_uscc_observer (struct mi_parse *command)
>> > }
>> > }
>> >
>> > +/* Determine whether the thread has changed. */
>> > +
>> > +static bool
>> > +command_changed_user_selected_thread (ptid_t previous_ptid, ptid_t current_ptid)
>> > +{
>> > + return previous_ptid != null_ptid
>> > + && current_ptid != previous_ptid
>> > + && current_ptid != null_ptid;
>>
>> You need to wrap multi-line conditions like this inside parenthesis.
>>
>
> Thanks!
>
>> > +}
>> > +
>> > void
>> > mi_execute_command (const char *cmd, int from_tty)
>> > {
>> > @@ -1971,28 +1981,17 @@ mi_execute_command (const char *cmd, int from_tty)
>> > && any_thread_p ()
>> > /* If the command already reports the thread change, no need to do it
>> > again. */
>> > - && !command_notifies_uscc_observer (command.get ()))
>> > + && !command_notifies_uscc_observer (command.get ())
>> > + /* Don't report anything if --thread was specified -- the user selected
>> > + thread is preserved by mi_execute_command and therefore cannot
>> > + change. */
>> > + && command->thread == -1
>>
>> I think including this check is a bug. Not a bug of your making I
>> think, as I believe the bug already existed. I'll explain...
>>
>> If I start GDB, and then spawn a new-ui for the mi interpreter. Start
>> a multi-threaded inferior, and then stop at a gdb prompt.
>>
>> Assuming thread 1 is selected, then, from the mi terminal I do:
>>
>> -thread-select 2
>>
>> I will get the '^done,new-thread-id="2"....' result on the mi
>> terminal, but on the cli terminal I'll also get some output telling me
>> that the thread changed. I think this is what you'd want, right? The
>> cli thread _did_ just change.
>>
>> However, now that thread 2 is selected, if I do this from the mi
>> terminal:
>>
>> -thread-select --thread 1 1
>>
>> then I get nothing on the cli terminal. This feels like a bug to me,
>
> Yes, this looks like a bug indeed. And I think we just opened
> can of worms...
>
>> and it's caused by the 'command->thread == -1' check above.
>
> I do not think so. When the command is -thread-select, then
> command_notifies_uscc_observer() return 1, therefore the whole
> condition won't hold anyway, right?
>
>>
>> I think that check should just be dropped completely. Your scoped
>> thread/frame restore that you've added will ensure that, when
>> appropriate, the thread doesn't change. If it does change, then you
>> want to notify I think, regardless of whether --thread or --frame was
>> used.
>
> If I do just drop "&& command->thread == -1" from the condition, it breaks
> existing test "--stack-select-frame 3" in mi-cmd-user-context.exp since it
> produces change notification the test does not expect. Clearly it should not
> produce MI notification, whether it should "Switching to..." CLI output over MI
> channel I'm not sure.
>
> But:
>
> Now I think we can get rid of the whole "if" and with that command_notifies_uscc_observer()
> and command_changed_user_selected_thread(). There are only two MI commands
> that can change context are -thread-select and -stack-select-frame, right?
> -thread-select implementation ( in mi_cmd_thread_select () ) does notify observers
> on its own and if we add similar logic to -stack-select-frame implementation
> ( in mi_cmd_stack_select_frame () ) we're fine. Makes sense?
>
> I tried that (see the first patch below) and it seems to pass all MI tests
> and the code seems to me much simpler.
>
> Still, this change itself does not solve your original bug. That's because
> thread is already switched when we enter mi_cmd_thread_select() so the
> condition "inferior_ptid != previous_ptid" won't hold and so no notification
> is printed.
>
> I went ahead and tried to address this by lifting the logic up to mi_cmd_execute ()
> where --thread option is handled - see the second patch below. With that patch,
> all gdb.mi tests pass and your bug seems to be fixed. Still, the patch needs more
> work (test + check it works with -stack-frame-select).
>
> That being said, I'd be cautious. It took me quite a bit to make heads and tails
> of this and still not sure I got it. My preference would be to fix the original
> problem *WITHOUT* fixing "your" bug and once done, submit another patch fixing
> "your" bug.
>
> So, if you agree and the first part of my response about dropping the
> whole "if" makes any sense, I'll properly resubmit it as v4.
>
> Makes sense?
Sorry for missing this reply.
Yes, what you said makes sense. If you follow up with a v4 based on
your original patch plus minor fixes I suggested that will probably be
fine I think.
Thanks,
Andrew
>
>>
>> It would be great if we could have a test for this added too. You'll
>> need to start gdb with a separate mi tty. You can look at
>> gdb.mi/mi-exec-run.exp for an example, look for passing the
>> 'separate-mi-tty' string to mi_gdb_start, and then later for using
>> switch_gdb_spawn_id to switch between the main cli tty and the extra
>> mi tty. If you have any problem, I'll be happy to help.
>>
>> You still have some white space bugs (tabs vs spaces at the start of
>> lines), I have this in my .gitconfig:
>>
>> [core]
>> whitespace = space-before-tab,indent-with-non-tab,trailing-space
>>
>> which will have git highlight anywhere I've failed to indent with a
>> tab when I should have done.
>>
>> Additionally, some of your lines are over 80 characters, so need to be
>> wrapped.
>>
>> Thanks,
>> Andrew
>>
>>
>> > + /* Don't report anything if the selected thread actually did not change
>> > + (compared to selected thread before execution the command). */
>> > + && command_changed_user_selected_thread (previous_ptid, inferior_ptid))
>> > {
>> > - int report_change = 0;
>> > -
>> > - if (command->thread == -1)
>> > - {
>> > - report_change = (previous_ptid != null_ptid
>> > - && inferior_ptid != previous_ptid
>> > - && inferior_ptid != null_ptid);
>> > - }
>> > - else if (inferior_ptid != null_ptid)
>> > - {
>> > - struct thread_info *ti = inferior_thread ();
>> > -
>> > - report_change = (ti->global_num != command->thread);
>> > - }
>> > -
>> > - if (report_change)
>> > - {
>> > - gdb::observers::user_selected_context_changed.notify
>> > - (USER_SELECTED_THREAD | USER_SELECTED_FRAME);
>> > - }
>> > + gdb::observers::user_selected_context_changed.notify
>> > + (USER_SELECTED_THREAD | USER_SELECTED_FRAME);
>> > }
>> > }
>> > }
>> > @@ -2037,6 +2036,7 @@ mi_cmd_execute (struct mi_parse *parse)
>> > set_current_program_space (inf->pspace);
>> > }
>> >
>> > + gdb::optional<scoped_restore_current_thread> thread_saver;
>> > if (parse->thread != -1)
>> > {
>> > thread_info *tp = find_thread_global_id (parse->thread);
>> > @@ -2047,9 +2047,13 @@ mi_cmd_execute (struct mi_parse *parse)
>> > if (tp->state == THREAD_EXITED)
>> > error (_("Thread id: %d has terminated"), parse->thread);
>> >
>> > + if (parse->cmd->preserve_user_selected_context ())
>> > + thread_saver.emplace ();
>> > +
>> > switch_to_thread (tp);
>> > }
>> >
>> > + gdb::optional<scoped_restore_selected_frame> frame_saver;
>> > if (parse->frame != -1)
>> > {
>> > struct frame_info *fid;
>> > @@ -2057,8 +2061,12 @@ mi_cmd_execute (struct mi_parse *parse)
>> >
>> > fid = find_relative_frame (get_current_frame (), &frame);
>> > if (frame == 0)
>> > - /* find_relative_frame was successful */
>> > - select_frame (fid);
>> > + {
>> > + if (parse->cmd->preserve_user_selected_context ())
>> > + frame_saver.emplace ();
>> > +
>> > + select_frame (fid);
>> > + }
>> > else
>> > error (_("Invalid frame id: %d"), frame);
>> > }
>> > diff --git a/gdb/testsuite/gdb.mi/mi-cmd-user-context.exp b/gdb/testsuite/gdb.mi/mi-cmd-user-context.exp
>> > new file mode 100644
>> > index 00000000000..a373dd3a4b0
>> > --- /dev/null
>> > +++ b/gdb/testsuite/gdb.mi/mi-cmd-user-context.exp
>> > @@ -0,0 +1,155 @@
>> > +# Copyright 2022 Free Software Foundation, Inc.
>> > +
>> > +# This program is free software; you can redistribute it and/or modify
>> > +# it under the terms of the GNU General Public License as published by
>> > +# the Free Software Foundation; either version 3 of the License, or
>> > +# (at your option) any later version.
>> > +#
>> > +# This program is distributed in the hope that it will be useful,
>> > +# but WITHOUT ANY WARRANTY; without even the implied warranty of
>> > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>> > +# GNU General Public License for more details.
>> > +#
>> > +# You should have received a copy of the GNU General Public License
>> > +# along with this program. If not, see <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.gnu.org_licenses_&d=DwIBAg&c=sPZ6DeHLiehUHQWKIrsNwWp3t7snrE-az24ztT0w7Jc&r=WpFFGgYa98Yp-c29WHTCwU1wAGFBvszA6a4RzgpMSqc&m=soXzjKh4zT-FpxAe1wtdv7ka2r_jXNbrkEUR4XdUcOY&s=q6IZFROyYXzF9keb4NCS6EL93YiTxbx2HkwQEtqDr8k&e= >.
>> > +
>> > +# Test that GDB/MI commands preserve user selected context when
>> > +# passed --thread and/or --frame.
>> > +
>> > +load_lib mi-support.exp
>> > +
>> > +standard_testfile user-selected-context-sync.c
>> > +
>> > +if {[build_executable $testfile.exp $testfile ${srcfile} "debug pthreads"] == -1} {
>> > + untested "failed to compile"
>> > + return -1
>> > +}
>> > +
>> > +set main_break_line [gdb_get_line_number "main break line"]
>> > +
>> > +set any "\[^\r\n\]*"
>> > +set nl "\[\r\n\]"
>> > +
>> > +mi_clean_restart $binfile
>> > +mi_create_breakpoint "$srcfile:$main_break_line" "set breakpoint in main"
>> > +mi_run_cmd
>> > +mi_expect_stop "breakpoint-hit" "main" "" $srcfile $main_break_line \
>> > + { "" "disp=\"keep\"" } "run to breakpoint in main"
>> > +
>> > +mi_gdb_test "thread" \
>> > + ".*Current thread is 1.*" \
>> > + "info thread 1"
>> > +
>> > +#=========================
>> > +
>> > +mi_gdb_test "-stack-info-depth --thread 3" \
>> > + "\\^done,depth=.*" \
>> > + "-stack-info-depth --thread 3"
>> > +
>> > +mi_gdb_test "thread" \
>> > + ".*Current thread is 1.*" \
>> > + "info thread 2"
>> > +
>> > +#=========================
>> > +
>> > +mi_gdb_test "-thread-select 3" \
>> > + "\\^done,.*" \
>> > + "-thread-select 3"
>> > +
>> > +mi_gdb_test "thread" \
>> > + ".*Current thread is 3.*" \
>> > + "info thread 3"
>> > +
>> > +#=========================
>> > +
>> > +mi_gdb_test "-thread-select --thread 2 1" \
>> > + "\\^done,.*" \
>> > + "-thread-select --thread 2 1"
>> > +
>> > +mi_gdb_test "thread" \
>> > + ".*Current thread is 1.*" \
>> > + "info thread 4"
>> > +
>> > +#=========================
>> > +
>> > +mi_gdb_test "-thread-select --thread 2 2" \
>> > + "\\^done,.*" \
>> > + "-thread-select --thread 2 2"
>> > +
>> > +mi_gdb_test "thread" \
>> > + ".*Current thread is 2.*" \
>> > + "info thread 5"
>> > +
>> > +#=========================
>> > +
>> > +mi_gdb_test "frame" \
>> > + ".*#0 0x.*" \
>> > + "frame 1"
>> > +
>> > +mi_gdb_test "-stack-info-frame --thread 2 --frame 1" \
>> > + "\\^done,frame=\{level=\"1\".*" \
>> > + "-stack-info-frame 1"
>> > +
>> > +mi_gdb_test "thread" \
>> > + ".*Current thread is 2.*" \
>> > + "info thread 6"
>> > +
>> > +mi_gdb_test "frame" \
>> > + ".*#0 0x.*" \
>> > + "frame 2"
>> > +
>> > +#=========================
>> > +
>> > +mi_gdb_test "-stack-info-frame --thread 3 --frame 1" \
>> > + "\\^done,frame=\{level=\"1\".*" \
>> > + "-stack-info-frame 2"
>> > +
>> > +mi_gdb_test "thread" \
>> > + ".*Current thread is 2.*" \
>> > + "info thread 7"
>> > +
>> > +mi_gdb_test "frame" \
>> > + ".*#0 0x.*" \
>> > + "frame 3"
>> > +
>> > +#=========================
>> > +
>> > +mi_gdb_test "-stack-select-frame --thread 2 --frame 0 1" \
>> > + "\\^done" \
>> > + "--stack-select-frame 1"
>> > +
>> > +mi_gdb_test "thread" \
>> > + ".*Current thread is 2.*" \
>> > + "info thread 8"
>> > +
>> > +mi_gdb_test "frame" \
>> > + ".*#1 0x.*" \
>> > + "frame 4"
>> > +
>> > +#=========================
>> > +
>> > +mi_gdb_test "-stack-select-frame --thread 2 --frame 2 2" \
>> > + "\\^done" \
>> > + "--stack-select-frame 2"
>> > +
>> > +mi_gdb_test "thread" \
>> > + ".*Current thread is 2.*" \
>> > + "info thread 9"
>> > +
>> > +mi_gdb_test "frame" \
>> > + ".*#2 0x.*" \
>> > + "frame 5"
>> > +
>> > +#=========================
>> > +
>> > +mi_gdb_test "-stack-select-frame --thread 1 --frame 0 0" \
>> > + "\\^done" \
>> > + "--stack-select-frame 3"
>> > +
>> > +mi_gdb_test "thread" \
>> > + ".*Current thread is 1.*" \
>> > + "info thread 10"
>> > +
>> > +mi_gdb_test "frame" \
>> > + ".*#0 main.*" \
>> > + "frame 6"
>> > --
>> > 2.30.2
>> >
>>
>
> From db229be447707d57980e4c21f394cdba1ec86b4c Mon Sep 17 00:00:00 2001
> From: Jan Vrany <jan.vrany@labware.com>
> Date: Thu, 27 Jan 2022 13:45:09 +0000
> Subject: [PATCH 1/2] gdb/mi: PR20684, preserve user selected thread and frame
> when invoking MI commands
>
> When invoking MI commands with --thread and/or --frame, user selected
> thread and frame was not preserved:
>
> (gdb)
> info thread
> &"info thread\n"
> ~" Id Target Id Frame \n"
> ~"* 1 Thread 0x7ffff7c30740 (LWP 19302) \"user-selected-c\" main () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:60\n"
> ~" 2 Thread 0x7ffff7c2f700 (LWP 19306) \"user-selected-c\" child_sub_function () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30\n"
> ~" 3 Thread 0x7ffff742e700 (LWP 19307) \"user-selected-c\" child_sub_function () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30\n"
> ^done
> (gdb)
> info frame
> &"info frame\n"
> ~"Stack level 0, frame at 0x7fffffffdf90:\n"
> ~" rip = 0x555555555207 in main (/home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:60); saved rip = 0x7ffff7c5709b\n"
> ~" source language c.\n"
> ~" Arglist at 0x7fffffffdf80, args: \n"
> ~" Locals at 0x7fffffffdf80, Previous frame's sp is 0x7fffffffdf90\n"
> ~" Saved registers:\n "
> ~" rbp at 0x7fffffffdf80, rip at 0x7fffffffdf88\n"
> ^done
> (gdb)
> -stack-info-depth --thread 3
> ^done,depth="4"
> (gdb)
> info thread
> &"info thread\n"
> ~" Id Target Id Frame \n"
> ~" 1 Thread 0x7ffff7c30740 (LWP 19302) \"user-selected-c\" main () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:60\n"
> ~" 2 Thread 0x7ffff7c2f700 (LWP 19306) \"user-selected-c\" child_sub_function () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30\n"
> ~"* 3 Thread 0x7ffff742e700 (LWP 19307) \"user-selected-c\" child_sub_function () at /home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30\n"
> ^done
> (gdb)
> info frame
> &"info frame\n"
> ~"Stack level 0, frame at 0x7ffff742dee0:\n"
> ~" rip = 0x555555555169 in child_sub_function (/home/uuu/gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:30); saved rip = 0x555555555188\n"
> ~" called by frame at 0x7ffff742df00\n"
> ~" source language c.\n"
> ~" Arglist at 0x7ffff742ded0, args: \n"
> ~" Locals at 0x7ffff742ded0, Previous frame's sp is 0x7ffff742dee0\n"
> ~" Saved registers:\n "
> ~" rbp at 0x7ffff742ded0, rip at 0x7ffff742ded8\n"
> ^done
> (gdb)
>
> This was problematic for frontends that provide access to CLI because UI
> may silently change the context for CLI commands (as demonstrated above).
>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=20684
> ---
> gdb/mi/mi-cmd-stack.c | 11 ++
> gdb/mi/mi-cmds.h | 12 ++
> gdb/mi/mi-main.c | 74 ++-------
> gdb/testsuite/gdb.mi/mi-cmd-user-context.exp | 155 +++++++++++++++++++
> 4 files changed, 189 insertions(+), 63 deletions(-)
> create mode 100644 gdb/testsuite/gdb.mi/mi-cmd-user-context.exp
>
> diff --git a/gdb/mi/mi-cmd-stack.c b/gdb/mi/mi-cmd-stack.c
> index e63f1706149..1be8aa81c3d 100644
> --- a/gdb/mi/mi-cmd-stack.c
> +++ b/gdb/mi/mi-cmd-stack.c
> @@ -36,6 +36,8 @@
> #include "mi-parse.h"
> #include "gdbsupport/gdb_optional.h"
> #include "safe-ctype.h"
> +#include "inferior.h"
> +#include "observable.h"
>
> enum what_to_list { locals, arguments, all };
>
> @@ -756,7 +758,16 @@ mi_cmd_stack_select_frame (const char *command, char **argv, int argc)
> if (argc == 0 || argc > 1)
> error (_("-stack-select-frame: Usage: FRAME_SPEC"));
>
> + ptid_t previous_ptid = inferior_ptid;
> +
> select_frame_for_mi (parse_frame_specification (argv[0]));
> +
> + /* Notify if the thread has effectively changed. */
> + if (inferior_ptid != previous_ptid)
> + {
> + gdb::observers::user_selected_context_changed.notify
> + (USER_SELECTED_THREAD | USER_SELECTED_FRAME);
> + }
> }
>
> void
> diff --git a/gdb/mi/mi-cmds.h b/gdb/mi/mi-cmds.h
> index 2a93a9f5476..785652ee1c9 100644
> --- a/gdb/mi/mi-cmds.h
> +++ b/gdb/mi/mi-cmds.h
> @@ -23,6 +23,7 @@
> #define MI_MI_CMDS_H
>
> #include "gdbsupport/gdb_optional.h"
> +#include "mi/mi-main.h"
>
> enum print_values {
> PRINT_NO_VALUES,
> @@ -163,6 +164,17 @@ struct mi_command
> wrong. */
> void invoke (struct mi_parse *parse) const;
>
> + /* Return whether this command preserves user selected context (thread
> + and frame). */
> + bool preserve_user_selected_context () const
> + {
> + /* Here we exploit the fact that if MI command is supposed to change
> + user context, then it should not emit change notifications. Therefore if
> + command does not suppress user context change notifications, then it should
> + preserve the context. */
> + return m_suppress_notification != &mi_suppress_notification.user_selected_context;
> + }
> +
> protected:
>
> /* The core of command invocation, this needs to be overridden in each
> diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
> index 4860da7536a..23e2373dcec 100644
> --- a/gdb/mi/mi-main.c
> +++ b/gdb/mi/mi-main.c
> @@ -1879,34 +1879,6 @@ mi_print_exception (const char *token, const struct gdb_exception &exception)
> fputs_unfiltered ("\n", mi->raw_stdout);
> }
>
> -/* Determine whether the parsed command already notifies the
> - user_selected_context_changed observer. */
> -
> -static int
> -command_notifies_uscc_observer (struct mi_parse *command)
> -{
> - if (command->op == CLI_COMMAND)
> - {
> - /* CLI commands "thread" and "inferior" already send it. */
> - return (startswith (command->command, "thread ")
> - || startswith (command->command, "inferior "));
> - }
> - else /* MI_COMMAND */
> - {
> - if (strcmp (command->command, "interpreter-exec") == 0
> - && command->argc > 1)
> - {
> - /* "thread" and "inferior" again, but through -interpreter-exec. */
> - return (startswith (command->argv[1], "thread ")
> - || startswith (command->argv[1], "inferior "));
> - }
> -
> - else
> - /* -thread-select already sends it. */
> - return strcmp (command->command, "thread-select") == 0;
> - }
> -}
> -
> void
> mi_execute_command (const char *cmd, int from_tty)
> {
> @@ -1932,8 +1904,6 @@ mi_execute_command (const char *cmd, int from_tty)
>
> if (command != NULL)
> {
> - ptid_t previous_ptid = inferior_ptid;
> -
> command->token = token;
>
> if (do_timings)
> @@ -1963,37 +1933,6 @@ mi_execute_command (const char *cmd, int from_tty)
>
> bpstat_do_actions ();
>
> - if (/* The notifications are only output when the top-level
> - interpreter (specified on the command line) is MI. */
> - top_level_interpreter ()->interp_ui_out ()->is_mi_like_p ()
> - /* Don't try report anything if there are no threads --
> - the program is dead. */
> - && any_thread_p ()
> - /* If the command already reports the thread change, no need to do it
> - again. */
> - && !command_notifies_uscc_observer (command.get ()))
> - {
> - int report_change = 0;
> -
> - if (command->thread == -1)
> - {
> - report_change = (previous_ptid != null_ptid
> - && inferior_ptid != previous_ptid
> - && inferior_ptid != null_ptid);
> - }
> - else if (inferior_ptid != null_ptid)
> - {
> - struct thread_info *ti = inferior_thread ();
> -
> - report_change = (ti->global_num != command->thread);
> - }
> -
> - if (report_change)
> - {
> - gdb::observers::user_selected_context_changed.notify
> - (USER_SELECTED_THREAD | USER_SELECTED_FRAME);
> - }
> - }
> }
> }
>
> @@ -2037,6 +1976,7 @@ mi_cmd_execute (struct mi_parse *parse)
> set_current_program_space (inf->pspace);
> }
>
> + gdb::optional<scoped_restore_current_thread> thread_saver;
> if (parse->thread != -1)
> {
> thread_info *tp = find_thread_global_id (parse->thread);
> @@ -2047,9 +1987,13 @@ mi_cmd_execute (struct mi_parse *parse)
> if (tp->state == THREAD_EXITED)
> error (_("Thread id: %d has terminated"), parse->thread);
>
> + if (parse->cmd->preserve_user_selected_context ())
> + thread_saver.emplace ();
> +
> switch_to_thread (tp);
> }
>
> + gdb::optional<scoped_restore_selected_frame> frame_saver;
> if (parse->frame != -1)
> {
> struct frame_info *fid;
> @@ -2057,8 +2001,12 @@ mi_cmd_execute (struct mi_parse *parse)
>
> fid = find_relative_frame (get_current_frame (), &frame);
> if (frame == 0)
> - /* find_relative_frame was successful */
> - select_frame (fid);
> + {
> + if (parse->cmd->preserve_user_selected_context ())
> + frame_saver.emplace ();
> +
> + select_frame (fid);
> + }
> else
> error (_("Invalid frame id: %d"), frame);
> }
> diff --git a/gdb/testsuite/gdb.mi/mi-cmd-user-context.exp b/gdb/testsuite/gdb.mi/mi-cmd-user-context.exp
> new file mode 100644
> index 00000000000..a373dd3a4b0
> --- /dev/null
> +++ b/gdb/testsuite/gdb.mi/mi-cmd-user-context.exp
> @@ -0,0 +1,155 @@
> +# Copyright 2022 Free Software Foundation, Inc.
> +
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program. If not, see <http://www.gnu.org/licenses/>.
> +
> +# Test that GDB/MI commands preserve user selected context when
> +# passed --thread and/or --frame.
> +
> +load_lib mi-support.exp
> +
> +standard_testfile user-selected-context-sync.c
> +
> +if {[build_executable $testfile.exp $testfile ${srcfile} "debug pthreads"] == -1} {
> + untested "failed to compile"
> + return -1
> +}
> +
> +set main_break_line [gdb_get_line_number "main break line"]
> +
> +set any "\[^\r\n\]*"
> +set nl "\[\r\n\]"
> +
> +mi_clean_restart $binfile
> +mi_create_breakpoint "$srcfile:$main_break_line" "set breakpoint in main"
> +mi_run_cmd
> +mi_expect_stop "breakpoint-hit" "main" "" $srcfile $main_break_line \
> + { "" "disp=\"keep\"" } "run to breakpoint in main"
> +
> +mi_gdb_test "thread" \
> + ".*Current thread is 1.*" \
> + "info thread 1"
> +
> +#=========================
> +
> +mi_gdb_test "-stack-info-depth --thread 3" \
> + "\\^done,depth=.*" \
> + "-stack-info-depth --thread 3"
> +
> +mi_gdb_test "thread" \
> + ".*Current thread is 1.*" \
> + "info thread 2"
> +
> +#=========================
> +
> +mi_gdb_test "-thread-select 3" \
> + "\\^done,.*" \
> + "-thread-select 3"
> +
> +mi_gdb_test "thread" \
> + ".*Current thread is 3.*" \
> + "info thread 3"
> +
> +#=========================
> +
> +mi_gdb_test "-thread-select --thread 2 1" \
> + "\\^done,.*" \
> + "-thread-select --thread 2 1"
> +
> +mi_gdb_test "thread" \
> + ".*Current thread is 1.*" \
> + "info thread 4"
> +
> +#=========================
> +
> +mi_gdb_test "-thread-select --thread 2 2" \
> + "\\^done,.*" \
> + "-thread-select --thread 2 2"
> +
> +mi_gdb_test "thread" \
> + ".*Current thread is 2.*" \
> + "info thread 5"
> +
> +#=========================
> +
> +mi_gdb_test "frame" \
> + ".*#0 0x.*" \
> + "frame 1"
> +
> +mi_gdb_test "-stack-info-frame --thread 2 --frame 1" \
> + "\\^done,frame=\{level=\"1\".*" \
> + "-stack-info-frame 1"
> +
> +mi_gdb_test "thread" \
> + ".*Current thread is 2.*" \
> + "info thread 6"
> +
> +mi_gdb_test "frame" \
> + ".*#0 0x.*" \
> + "frame 2"
> +
> +#=========================
> +
> +mi_gdb_test "-stack-info-frame --thread 3 --frame 1" \
> + "\\^done,frame=\{level=\"1\".*" \
> + "-stack-info-frame 2"
> +
> +mi_gdb_test "thread" \
> + ".*Current thread is 2.*" \
> + "info thread 7"
> +
> +mi_gdb_test "frame" \
> + ".*#0 0x.*" \
> + "frame 3"
> +
> +#=========================
> +
> +mi_gdb_test "-stack-select-frame --thread 2 --frame 0 1" \
> + "\\^done" \
> + "--stack-select-frame 1"
> +
> +mi_gdb_test "thread" \
> + ".*Current thread is 2.*" \
> + "info thread 8"
> +
> +mi_gdb_test "frame" \
> + ".*#1 0x.*" \
> + "frame 4"
> +
> +#=========================
> +
> +mi_gdb_test "-stack-select-frame --thread 2 --frame 2 2" \
> + "\\^done" \
> + "--stack-select-frame 2"
> +
> +mi_gdb_test "thread" \
> + ".*Current thread is 2.*" \
> + "info thread 9"
> +
> +mi_gdb_test "frame" \
> + ".*#2 0x.*" \
> + "frame 5"
> +
> +#=========================
> +
> +mi_gdb_test "-stack-select-frame --thread 1 --frame 0 0" \
> + "\\^done" \
> + "--stack-select-frame 3"
> +
> +mi_gdb_test "thread" \
> + ".*Current thread is 1.*" \
> + "info thread 10"
> +
> +mi_gdb_test "frame" \
> + ".*#0 main.*" \
> + "frame 6"
> --
> 2.34.1
>
>
> From 18d8dc95fe1a834ecbde319dd6e5960fd4d82a3f Mon Sep 17 00:00:00 2001
> From: Jan Vrany <jan.vrany@labware.com>
> Date: Fri, 18 Feb 2022 17:04:13 +0000
> Subject: [PATCH 2/2] [WIP] gdb/mi: properly notify user when GDB/MI client
> uses -thread-select
>
> If we start GDB, and then spawn a new-ui for the mi interpreter. Start
> a multi-threaded inferior, and then stop at a gdb prompt.
>
> Assuming thread 1 is selected, then, from the mi terminal I do:
>
> -thread-select 2
>
> We will get the '^done,new-thread-id="2"....' result on the mi
> terminal, but on the cli terminal I'll also get some output telling me
> that the thread changed.
>
> However, now that thread 2 is selected, if I do this from the mi
> terminal:
>
> -thread-select --thread 1 1
>
> then I get nothing on the CLI terminal. This seems to be a bug.
>
> The problem was that when `-thread-select --thread 1 1` then thread
> is switched to thread 1 before mi_cmd_thread_select () is called,
> therefore the condition "inferior_ptid != previous_ptid" there does
> not hold.
>
> To address this problem, we have to move this logic up to
> mi_cmd_execute () where --thread option is processed and notify
> user selected contents observers there if context changes.
>
> However, this in itself breaks GDB/MI because it would cause context
> notification to be sent on MI channel. This is because by the time
> we notify, MI notification suppression is already restored (done in
> mi_command::invoke(). Therefore we had to lift notification suppression
> logic also up to mi_cmd_execute ().
>
> With this change, all gdb.mi tests pass, tested on x86_64-linux.
>
> TODO:
> * add test
> ---
> gdb/mi/mi-cmd-stack.c | 10 ----------
> gdb/mi/mi-cmds.c | 2 --
> gdb/mi/mi-cmds.h | 16 ++++++++--------
> gdb/mi/mi-main.c | 32 +++++++++++++++++++++++---------
> 4 files changed, 31 insertions(+), 29 deletions(-)
>
> diff --git a/gdb/mi/mi-cmd-stack.c b/gdb/mi/mi-cmd-stack.c
> index 1be8aa81c3d..afe584b7fca 100644
> --- a/gdb/mi/mi-cmd-stack.c
> +++ b/gdb/mi/mi-cmd-stack.c
> @@ -757,17 +757,7 @@ mi_cmd_stack_select_frame (const char *command, char **argv, int argc)
> {
> if (argc == 0 || argc > 1)
> error (_("-stack-select-frame: Usage: FRAME_SPEC"));
> -
> - ptid_t previous_ptid = inferior_ptid;
> -
> select_frame_for_mi (parse_frame_specification (argv[0]));
> -
> - /* Notify if the thread has effectively changed. */
> - if (inferior_ptid != previous_ptid)
> - {
> - gdb::observers::user_selected_context_changed.notify
> - (USER_SELECTED_THREAD | USER_SELECTED_FRAME);
> - }
> }
>
> void
> diff --git a/gdb/mi/mi-cmds.c b/gdb/mi/mi-cmds.c
> index cd7cabdda9b..957dfb4e03d 100644
> --- a/gdb/mi/mi-cmds.c
> +++ b/gdb/mi/mi-cmds.c
> @@ -171,8 +171,6 @@ mi_command::mi_command (const char *name, int *suppress_notification)
> void
> mi_command::invoke (struct mi_parse *parse) const
> {
> - gdb::optional<scoped_restore_tmpl<int>> restore
> - = do_suppress_notification ();
> this->do_invoke (parse);
> }
>
> diff --git a/gdb/mi/mi-cmds.h b/gdb/mi/mi-cmds.h
> index 785652ee1c9..da1598a3f32 100644
> --- a/gdb/mi/mi-cmds.h
> +++ b/gdb/mi/mi-cmds.h
> @@ -175,14 +175,6 @@ struct mi_command
> return m_suppress_notification != &mi_suppress_notification.user_selected_context;
> }
>
> -protected:
> -
> - /* The core of command invocation, this needs to be overridden in each
> - base class. PARSE is the parsed command line from the user. */
> - virtual void do_invoke (struct mi_parse *parse) const = 0;
> -
> -private:
> -
> /* If this command was created with a suppress notifications pointer,
> then this function will set the suppress flag and return a
> gdb::optional with its value set to an object that will restore the
> @@ -192,6 +184,14 @@ struct mi_command
> then this function returns an empty gdb::optional. */
> gdb::optional<scoped_restore_tmpl<int>> do_suppress_notification () const;
>
> +protected:
> +
> + /* The core of command invocation, this needs to be overridden in each
> + base class. PARSE is the parsed command line from the user. */
> + virtual void do_invoke (struct mi_parse *parse) const = 0;
> +
> +private:
> +
> /* The name of the command. */
> const char *m_name;
>
> diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
> index 23e2373dcec..608b226f496 100644
> --- a/gdb/mi/mi-main.c
> +++ b/gdb/mi/mi-main.c
> @@ -556,19 +556,10 @@ mi_cmd_thread_select (const char *command, char **argv, int argc)
> if (thr == NULL)
> error (_("Thread ID %d not known."), num);
>
> - ptid_t previous_ptid = inferior_ptid;
> -
> thread_select (argv[0], thr);
>
> print_selected_thread_frame (current_uiout,
> USER_SELECTED_THREAD | USER_SELECTED_FRAME);
> -
> - /* Notify if the thread has effectively changed. */
> - if (inferior_ptid != previous_ptid)
> - {
> - gdb::observers::user_selected_context_changed.notify
> - (USER_SELECTED_THREAD | USER_SELECTED_FRAME);
> - }
> }
>
> void
> @@ -1936,6 +1927,16 @@ mi_execute_command (const char *cmd, int from_tty)
> }
> }
>
> +/* Determine whether the thread has changed. */
> +
> +static bool
> +command_changed_user_selected_thread (ptid_t previous_ptid, ptid_t current_ptid)
> +{
> + return (previous_ptid != null_ptid
> + && current_ptid != previous_ptid
> + && current_ptid != null_ptid);
> +}
> +
> static void
> mi_cmd_execute (struct mi_parse *parse)
> {
> @@ -1976,6 +1977,8 @@ mi_cmd_execute (struct mi_parse *parse)
> set_current_program_space (inf->pspace);
> }
>
> + ptid_t previous_ptid = inferior_ptid;
> +
> gdb::optional<scoped_restore_current_thread> thread_saver;
> if (parse->thread != -1)
> {
> @@ -2021,7 +2024,18 @@ mi_cmd_execute (struct mi_parse *parse)
> current_context = parse;
>
> gdb_assert (parse->cmd != nullptr);
> +
> + gdb::optional<scoped_restore_tmpl<int>> restore_suppress_notification
> + = parse->cmd->do_suppress_notification ();
> +
> parse->cmd->invoke (parse);
> +
> + if (!parse->cmd->preserve_user_selected_context ()
> + && command_changed_user_selected_thread (previous_ptid, inferior_ptid))
> + {
> + gdb::observers::user_selected_context_changed.notify
> + (USER_SELECTED_THREAD | USER_SELECTED_FRAME);
> + }
> }
>
> /* See mi-main.h. */
> --
> 2.34.1
next prev parent reply other threads:[~2022-03-02 10:00 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-25 14:51 [PATCH 0/1] PR20684, preserve user selected context " Jan Vrany
2022-01-25 14:51 ` [PATCH 1/1] gdb/mi: PR20684, preserve user selected thread and frame " Jan Vrany
2022-01-25 18:59 ` Simon Marchi
2022-01-26 13:21 ` [PATCH v2 0/1] PR20684, preserve user selected context " Jan Vrany
2022-01-26 13:21 ` [PATCH v2 1/1] gdb/mi: PR20684, preserve user selected thread and frame " Jan Vrany
2022-01-26 15:01 ` Simon Marchi
2022-01-26 17:08 ` Jan Vrany
2022-01-27 14:50 ` [PATCH v3 0/1] PR20684, preserve user selected context " Jan Vrany
2022-02-07 11:56 ` Jan Vrany
2022-02-17 16:07 ` [PING] " Jan Vrany
2022-01-27 14:50 ` [PATCH v3 1/1] gdb/mi: PR20684, preserve user selected thread and frame " Jan Vrany
2022-02-17 22:24 ` Andrew Burgess
2022-02-18 17:45 ` Jan Vrany
2022-03-01 11:59 ` [PING] " Jan Vrany
2022-03-02 10:00 ` Andrew Burgess [this message]
2022-03-02 13:23 ` [PATCH v4] " Jan Vrany
2022-03-08 16:58 ` Andrew Burgess
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