Re: [PING] Re: [PATCH] MI: PR20684, preserve user selected thread and frame when invoking MI commands

[Jonah Graham <jonah@kichwacoders.com>]

Hi Jan,

I am not a GDB maintainer, so not sure how much I can help here (I was
cc'ed in the original patch email).

How does this change interact with -thread-select? Eclipse CDT
expects -thread-select issued on the MI channel to affect the thread in the
CLI channel. In fact this use was added in CDT when the new-ui was
introduced, while the referenced bug 20684 is actually concerning "old ui"
use case.

Jonah




On Tue, 2 Mar 2021 at 05:36, Jan Vrany via Gdb-patches <
gdb-patches@sourceware.org> wrote:

> Polite ping.
>
> On Tue, 2021-02-23 at 11:20 +0000, Jan Vrany wrote:
> > Polite ping.
> >
> > On Tue, 2021-02-09 at 10:08 +0000, Jan Vrany wrote:
> > > 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).
> > >
> > > gdb/Changelog
> > >
> > >         PR 20684
> > >         * gdb/mi/mi-main.c (mi_cmd_execute): Preserve user selected
> > > thread
> > >         and frame when invoking MI commands.
> > > ---
> > >  gdb/ChangeLog    |  6 ++++++
> > >  gdb/mi/mi-main.c | 36 +++++++++++++++---------------------
> > >  2 files changed, 21 insertions(+), 21 deletions(-)
> > >
> > > diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> > > index e67668d315c..ea232ff1b3f 100644
> > > --- a/gdb/ChangeLog
> > > +++ b/gdb/ChangeLog
> > > @@ -1,3 +1,9 @@
> > > +2021-02-09  Jan Vrany  <jan.vrany@labware.com>
> > > +
> > > +       PR 20684
> > > +       * gdb/mi/mi-main.c (mi_cmd_execute): Preserve user selected
> > > thread
> > > +       and frame when invoking MI commands.
> > > +
> > >  2021-02-08  Shahab Vahedi  <shahab@synopsys.com>
> > >
> > >         PR tdep/27369
> > > diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
> > > index 9a14d78e1e2..c5103800314 100644
> > > --- a/gdb/mi/mi-main.c
> > > +++ b/gdb/mi/mi-main.c
> > > @@ -1971,25 +1971,13 @@ mi_execute_command (const char *cmd, int
> > > from_tty)
> > >              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);
> > > +         if (command->thread == -1
> > > +             && previous_ptid != null_ptid
> > > +             && inferior_ptid != previous_ptid
> > > +             && inferior_ptid != null_ptid)
> > > +            {
> > > +              gdb::observers::user_selected_context_changed.notify
> > > +                      (USER_SELECTED_THREAD |
> > > USER_SELECTED_FRAME);
> > >             }
> > >         }
> > >      }
> > > @@ -2035,6 +2023,7 @@ 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);
> > > @@ -2045,9 +2034,11 @@ mi_cmd_execute (struct mi_parse *parse)
> > >        if (tp->state == THREAD_EXITED)
> > >         error (_("Thread id: %d has terminated"), parse->thread);
> > >
> > > +      thread_saver.emplace ();
> > >        switch_to_thread (tp);
> > >      }
> > >
> > > +  gdb::optional<scoped_restore_selected_frame> frame_saver;
> > >    if (parse->frame != -1)
> > >      {
> > >        struct frame_info *fid;
> > > @@ -2055,8 +2046,11 @@ 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);
> > > +        {
> > > +          /* find_relative_frame was successful */
> > > +          frame_saver.emplace ();
> > > +          select_frame (fid);
> > > +        }
> > >        else
> > >         error (_("Invalid frame id: %d"), frame);
> > >      }
> >
>
>
>