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RE: [PATCH 2/4] gdb: remove use of iterate_over_inferiors in mi/mi-interp.c
- From: "Aktemur, Tankut Baris" <tankut dot baris dot aktemur at intel dot com>
- To: Simon Marchi <simark at simark dot ca>, Simon Marchi <simon dot marchi at efficios dot com>, "gdb-patches at sourceware dot org" <gdb-patches at sourceware dot org>
- Date: Fri, 17 Jan 2020 07:24:47 +0000
- Subject: RE: [PATCH 2/4] gdb: remove use of iterate_over_inferiors in mi/mi-interp.c
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- References: <20200115191222.28208-1-simon.marchi@efficios.com> <20200115191222.28208-3-simon.marchi@efficios.com> <BYAPR11MB303040C052014A5EFB2F87A1C4360@BYAPR11MB3030.namprd11.prod.outlook.com> <80e26b82-476e-f898-3b97-4d923c2eb6e7@simark.ca>
On Thursday, January 16, 2020 4:24 PM, Simon Marchi wrote:
> On 2020-01-16 4:01 a.m., Aktemur, Tankut Baris wrote:
> >> @@ -140,8 +138,22 @@ mi_interp::init (bool top_level)
> >> /* The initial inferior is created before this function is
> >> called, so we need to report it explicitly. Use iteration in
> >> case future version of GDB creates more than one inferior
> >> - up-front. */
> >> - iterate_over_inferiors (report_initial_inferior, mi);
> >> + up-front.
> >> +
> >> + This function is called from mi_interpreter_init, and since
> >
> > There is an 8-spaces/tab issue above. And also, the comment piece "This
> > function is called from mi_interpreter_init, and" seems obsolete now.
>
> Thanks for spotting these.
>
> That made me realize there are many issues with that comment.
>
> - The part about not being able to use mi_inferior_added because top_level_interpreter_data
> is not set is stale. That was true before the interps were made into C++ classes. Back
> then, the mi_interpreter_init function would return the pointer to be used as interpreter
> data, which the caller (the interp_set function) would assign to interp->data. So it was
> indeed not possible to call mi_inferior_added, because it required interp->data to be set.
>
> - It is still not possible today to use mi_inferior_added, because it iterates over all MI UIs
> and to print the event on all of them. So if you do:
>
> 1. Start GDB with `-i mi`
> 2. Add some inferiors
> 3. Create a new MI UI, with `new-ui mi /dev/pts/X`
>
> When initializing the new MI UI, it will print the inferior-added events on both MI UIs.
>
> - It is necessary to use iteration, not only in case GDB creates more than one inferior
> up front, but also because there might be multiple inferiors when initializing a secondary
> MI UI, as shown above.
>
> I don't know if it is by design, that the =inferior-added events are sent to a new MI UI added
> with new-ui, but in any case I don't want to change the behavior with this patch.
>
> Also, when testing this, I realized it was wrong to put the gdb_flush out of the loop. It's not
> a simple flush as in "make sure the data is all sent to the underlying device", it's also what
> adds the final \n! So with the gdb_flush outside the loop, all the events were printed on the same
> line. I've put the terminal setting calls and the gdb_flush back into the loop, to minimize the
> changes.
>
> The patch would now look like this:
Thank you for the detailed explanation. I think the revised patch is very clear.
-Baris
>
> From cb845a4f28d1761feb463914c13b0a45c97d9974 Mon Sep 17 00:00:00 2001
> From: Simon Marchi <simon.marchi@efficios.com>
> Date: Wed, 15 Jan 2020 14:12:20 -0500
> Subject: [PATCH] gdb: remove use of iterate_over_inferiors in mi/mi-interp.c
>
> Replace it with a range-based for. I've updated the comment in
> mi_interp::init, which was a bit stale.
>
> gdb/ChangeLog:
>
> * mi/mi-interp.c (report_initial_inferior): Remove.
> (mi_interp::init): Use range-based for to iterate over inferiors.
> ---
> gdb/mi/mi-interp.c | 49 ++++++++++++++++++++--------------------------
> 1 file changed, 21 insertions(+), 28 deletions(-)
>
> diff --git a/gdb/mi/mi-interp.c b/gdb/mi/mi-interp.c
> index 2ac4c119961c..e77093cfa282 100644
> --- a/gdb/mi/mi-interp.c
> +++ b/gdb/mi/mi-interp.c
> @@ -91,8 +91,6 @@ static void mi_memory_changed (struct inferior *inf, CORE_ADDR memaddr,
> ssize_t len, const bfd_byte *myaddr);
> static void mi_on_sync_execution_done (void);
>
> -static int report_initial_inferior (struct inferior *inf, void *closure);
> -
> /* Display the MI prompt. */
>
> static void
> @@ -137,12 +135,27 @@ mi_interp::init (bool top_level)
>
> if (top_level)
> {
> - /* The initial inferior is created before this function is
> - called, so we need to report it explicitly. Use iteration in
> - case future version of GDB creates more than one inferior
> - up-front. */
> - iterate_over_inferiors (report_initial_inferior, mi);
> - }
> + /* The initial inferior is created before this function is called, so we
> + need to report it explicitly when initializing the top-level MI
> + interpreter.
> +
> + This is also called when additional MI interpreters are added (using
> + the new-ui command), when multiple inferiors possibly exist, so we need
> + to use iteration to report all the inferiors. mi_inferior_added can't
> + be used, because it would print the event on all the other MI UIs. */
> +
> + for (inferior *inf : all_inferiors ())
> + {
> + target_terminal::scoped_restore_terminal_state term_state;
> + target_terminal::ours_for_output ();
> +
> + fprintf_unfiltered (mi->event_channel,
> + "thread-group-added,id=\"i%d\"",
> + inf->num);
> +
> + gdb_flush (mi->event_channel);
> + }
> + }
> }
>
> void
> @@ -1253,26 +1266,6 @@ mi_user_selected_context_changed (user_selected_what selection)
> }
> }
>
> -static int
> -report_initial_inferior (struct inferior *inf, void *closure)
> -{
> - /* This function is called from mi_interpreter_init, and since
> - mi_inferior_added assumes that inferior is fully initialized
> - and top_level_interpreter_data is set, we cannot call
> - it here. */
> - struct mi_interp *mi = (struct mi_interp *) closure;
> -
> - target_terminal::scoped_restore_terminal_state term_state;
> - target_terminal::ours_for_output ();
> -
> - fprintf_unfiltered (mi->event_channel,
> - "thread-group-added,id=\"i%d\"",
> - inf->num);
> - gdb_flush (mi->event_channel);
> -
> - return 0;
> -}
> -
> ui_out *
> mi_interp::interp_ui_out ()
> {
> --
> 2.24.1
>
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