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Re: [RFC] Don't show "display"s twice in MI
- From: Pedro Alves <palves at redhat dot com>
- To: Tom Tromey <tromey at adacore dot com>, gdb-patches at sourceware dot org
- Date: Wed, 13 Mar 2019 15:04:23 +0000
- Subject: Re: [RFC] Don't show "display"s twice in MI
- References: <20190312190320.19645-1-tromey@adacore.com>
On 03/12/2019 07:03 PM, Tom Tromey wrote:
> If you run "gdb -i=mi2" and set a "display", then when "next"ing the
> displays will be shown twice:
>
> ~"1: x = 23\n"
> ~"7\t printf(\"%d\\n\", x);\n"
> ~"1: x = 23\n"
> *stopped,reason="end-stepping-range",frame={addr="0x0000000000400565",func="main",args=[],file="q.c",fullname="/tmp/q.c",line="7"},thread-id="1",stopped-threads="all",core="1"
>
> The immediate cause of this is this code in mi_on_normal_stop_1:
>
> print_stop_event (mi_uiout);
>
> console_interp = interp_lookup (current_ui, INTERP_CONSOLE);
> if (should_print_stop_to_console (console_interp, tp))
> print_stop_event (mi->cli_uiout);
>
> ... which obviously prints the stop twice.
>
> However, I think the first call to print_stop_event is intended just
> to emit the MI *stopped notification, which explains why the source
> line does not show up two times.
>
> This patch fixes the bug by changing print_stop_event to only call
> do_displays for non-MI-like ui-outs.
Yeah, this was previously discussed here:
https://sourceware.org/ml/gdb/2018-06/msg00006.html
See my comment there:
> Fixing this probably needs to take in consideration whether
> we print the displays on the CLI uiout even if the stop
> isn't printed there according to should_print_stop_to_console.
> I.e., what makes more sense for a user that enabled some display,
> but then stepped with the frontend's "step" buttons instead of
> typing "next" or "step". Probably we shouldn't print the
> displays in that case, just to keep things simple, respecting
> should_print_stop_to_console, but not 100% sure.
So your patch makes GDB not do the displays in the
-exec-step/-exec-next case, which is the solution I was
leaning to above too, even though I'm not 100% sure about it.
I think that change should be covered by the testcase too, though.
I.e., check that displays aren't printed in the -exec-step/-exec-next
cases (they are without your patch), and that they are in the
-exec-continue case (I believe they are with your patch).
>
> Tested on x86-64 Fedora 29.
>
> gdb/ChangeLog
> 2019-03-12 Tom Tromey <tromey@adacore.com>
>
> * infrun.c (print_stop_event): Don't call do_displays for MI-like
> ui-outs.
>
> gdb/testsuite/ChangeLog
> 2019-03-12 Tom Tromey <tromey@adacore.com>
>
> * gdb.mi/mi2-cli-display.c: New file.
> * gdb.mi/mi2-cli-display.exp: New file.
> ---
> gdb/ChangeLog | 5 ++
> gdb/infrun.c | 3 +-
> gdb/testsuite/ChangeLog | 5 ++
> gdb/testsuite/gdb.mi/mi2-cli-display.c | 30 ++++++++++++
> gdb/testsuite/gdb.mi/mi2-cli-display.exp | 62 ++++++++++++++++++++++++
> 5 files changed, 104 insertions(+), 1 deletion(-)
> create mode 100644 gdb/testsuite/gdb.mi/mi2-cli-display.c
> create mode 100644 gdb/testsuite/gdb.mi/mi2-cli-display.exp
>
> diff --git a/gdb/infrun.c b/gdb/infrun.c
> index 33e5d434b35..9261588db32 100644
> --- a/gdb/infrun.c
> +++ b/gdb/infrun.c
> @@ -7867,7 +7867,8 @@ print_stop_event (struct ui_out *uiout)
> print_stop_location (&last);
>
> /* Display the auto-display expressions. */
> - do_displays ();
> + if (!uiout->is_mi_like_p ())
> + do_displays ();
> }
>
> tp = inferior_thread ();
> diff --git a/gdb/testsuite/gdb.mi/mi2-cli-display.c b/gdb/testsuite/gdb.mi/mi2-cli-display.c
> new file mode 100644
> index 00000000000..813fda47cfc
> --- /dev/null
> +++ b/gdb/testsuite/gdb.mi/mi2-cli-display.c
> @@ -0,0 +1,30 @@
> +/* Copyright 2019 Free Software Foundation, Inc.
> +
> + This file is part of GDB.
> +
> + 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/>. */
> +
> +int do_tests (int x)
Like break after return type?
> +{
> + ++x;
> + ++x;
> + ++x;
> + ++x;
> + return x;
> +}
> +
> +int main (void)
Ditto.
> +{
> + return do_tests (23);
> +}
> diff --git a/gdb/testsuite/gdb.mi/mi2-cli-display.exp b/gdb/testsuite/gdb.mi/mi2-cli-display.exp
> new file mode 100644
> index 00000000000..b11306a51cd
> --- /dev/null
> +++ b/gdb/testsuite/gdb.mi/mi2-cli-display.exp
> @@ -0,0 +1,62 @@
> +# Copyright 2019 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/>.
> +
> +# Ensure that CLI "display"s aren't double-emitted in MI mode.
> +
> +load_lib mi-support.exp
> +set MIFLAGS "-i=mi2"
> +
> +if {[mi_gdb_start]} {
> + continue
> +}
> +
> +standard_testfile
> +
> +if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
> + untested "failed to compile"
> + return -1
> +}
> +
> +mi_delete_breakpoints
> +mi_gdb_reinitialize_dir $srcdir/$subdir
> +mi_gdb_load ${binfile}
> +
> +mi_runto do_tests
> +
> +mi_gdb_test "display x" \
> + "&\"display x\\\\n\"\r\n~\"1: x = 23\\\\n\"\r\n\\^done" \
> + "display x"
> +
> +mi_send_resuming_command "interpreter-exec console next" next
> +
> +# Now check for the display and the source line. Note we don't check
> +# the source line too closely, since it's not really important here.
> +gdb_expect {
> + -re "~\"1: x = 24\\\\n\"\r\n~\"\[0-9\]+.*\\\\n\"\r\n~\"1: x = 24\\\\n\"\r\n" {
> + # This case is the bug: the display is shown twice.
> + fail "check display and source line"
> + }
> + -re "~\"\[0-9\]+.*\\\\n\"\r\n~\"1: x = 24\\\\n\"\r\n" {
> + pass "check display and source line"
Hard to tell, but just to double-check -- is the pass regex a
subset of the fail regex case above? I'm just wondering whether
this could issue a false pass if expect consumes just the right amount
of the bad case's output. A comment indicating otherwise here would
be good, IMO.
> + }
> + -re ".*\r\n$mi_gdb_prompt$" {
> + fail "check display and source line"
> + }
> + timeout {
> + fail "check display and source line"
Add " (timeout)" ?
> + }
> +}
> +
> +mi_expect_stop end-stepping-range {.*} {.*} {.*} {.*} {.*} "stop for next"
>
Thanks,
Pedro Alves