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Re: [PATCH] gdb: Restore selected frame in print_frame_local_vars
Simon,
Thanks for your feedback. I've addressed most of your feedback in
this revision, there's a couple of points I've replied too inline.
* Simon Marchi <simark@simark.ca> [2018-05-20 23:00:13 -0400]:
> On 2018-05-19 06:08 PM, Andrew Burgess wrote:
> > PR gdb/23203 reports 'bt full' causing the currently selected frame to
> > change, this issue is fixed in this commit.
> >
> > Add a new class scoped_restore_selected_frame that saves and restores
> > the selected frame. Make use of this in print_frame_local_vars to
> > restore the selected frame on exit.
>
> Hi Andrew,
>
> Thanks for the patch. I noted some comments and questions below, but
> overall this looks great, thanks for taking the time to do this.
>
> > gdb/ChangeLog:
> >
> > PR gdb/23203
> > * frame.c
> > (scoped_restore_selected_frame::scoped_restore_selected_frame):
> > Define.
> > (scoped_restore_selected_frame::~scoped_restore_selected_frame):
> > Define.
> > * frame.h (class scoped_restore_selected_frame): New class.
> > * stack.c (print_frame_local_vars): Remove catching and rethrowing
> > of any exception, use scoped_restore_selected_frame to restore the
> > frame instead.
> >
> > gdb/testsuite/ChangeLog:
> >
> > PR gdb/23203
> > * gdb.base/bt-full.c: New file.
> > * gdb.base/bt-full.exp: New file.
> > ---
> > gdb/ChangeLog | 13 +++++++++
> > gdb/frame.c | 16 ++++++++++
> > gdb/frame.h | 16 ++++++++++
> > gdb/stack.c | 24 +++------------
> > gdb/testsuite/ChangeLog | 6 ++++
> > gdb/testsuite/gdb.base/bt-full.c | 35 ++++++++++++++++++++++
> > gdb/testsuite/gdb.base/bt-full.exp | 60 ++++++++++++++++++++++++++++++++++++++
> > 7 files changed, 150 insertions(+), 20 deletions(-)
> > create mode 100644 gdb/testsuite/gdb.base/bt-full.c
> > create mode 100644 gdb/testsuite/gdb.base/bt-full.exp
> >
> > diff --git a/gdb/frame.c b/gdb/frame.c
> > index 07fa2bc77d6..3e42aa82398 100644
> > --- a/gdb/frame.c
> > +++ b/gdb/frame.c
> > @@ -269,6 +269,22 @@ frame_stash_invalidate (void)
> > htab_empty (frame_stash);
> > }
> >
> > +/* Save the currently selected frame. */
>
> Please put the doc in the header file, and put /* See frame.h. */ here.
>
> > +scoped_restore_selected_frame::scoped_restore_selected_frame ()
> > +{
> > + m_fid = get_frame_id (get_selected_frame (NULL));
> > +}
> > +
> > +/* Restore the currently selected frame. */
>
> Here too.
>
> > +scoped_restore_selected_frame::~scoped_restore_selected_frame ()
> > +{
> > + frame_info *frame = frame_find_by_id (m_fid);
> > + if (frame == NULL)
> > + warning (_("Unable to restore previously selected frame."));
> > + else
> > + select_frame (frame);
> > +}
> > +
> > /* Flag to control debugging. */
> >
> > unsigned int frame_debug;
> > diff --git a/gdb/frame.h b/gdb/frame.h
> > index d5800b78c25..2c8f815a4ae 100644
> > --- a/gdb/frame.h
> > +++ b/gdb/frame.h
> > @@ -164,6 +164,22 @@ struct frame_id
> > int artificial_depth;
> > };
> >
> > +/* Save and restore the currently selected frame. */
> > +
> > +class scoped_restore_selected_frame
> > +{
> > +public:
> > + scoped_restore_selected_frame ();
> > + ~scoped_restore_selected_frame ();
> > +
> > + DISABLE_COPY_AND_ASSIGN (scoped_restore_selected_frame);
> > +
> > +private:
> > +
> > + /* The ID of the previously selected frame. */
> > + struct frame_id m_fid;
> > +};
> > +
> > /* Methods for constructing and comparing Frame IDs. */
> >
> > /* For convenience. All fields are zero. This means "there is no frame". */
> > diff --git a/gdb/stack.c b/gdb/stack.c
> > index ecf1ee83793..7e377764865 100644
> > --- a/gdb/stack.c
> > +++ b/gdb/stack.c
> > @@ -2019,7 +2019,6 @@ print_frame_local_vars (struct frame_info *frame, int num_tabs,
> > struct print_variable_and_value_data cb_data;
> > const struct block *block;
> > CORE_ADDR pc;
> > - struct gdb_exception except = exception_none;
> >
> > if (!get_frame_pc_if_available (frame, &pc))
> > {
> > @@ -2043,27 +2042,12 @@ print_frame_local_vars (struct frame_info *frame, int num_tabs,
> > /* Temporarily change the selected frame to the given FRAME.
> > This allows routines that rely on the selected frame instead
> > of being given a frame as parameter to use the correct frame. */
> > + scoped_restore_selected_frame restore_selected_frame;
>
> Should we instead put this scoped_restore in the caller, so we only save/restore the
> frame once during the execution of "bt full"?
I'm inclined not to, so that print_frame_local_vars doesn't end up
changing the frame. However, I'm not that fussed, so if you'd really
prefer it done differently then I'm happy to make that change.
>
> > select_frame (frame);
> >
> > - TRY
> > - {
> > - iterate_over_block_local_vars (block,
> > - do_print_variable_and_value,
> > - &cb_data);
> > - }
> > - CATCH (ex, RETURN_MASK_ALL)
> > - {
> > - except = ex;
> > - }
> > - END_CATCH
> > -
> > - /* Restore the selected frame, and then rethrow if there was a problem. */
> > - select_frame (frame_find_by_id (cb_data.frame_id));
> > - if (except.reason < 0)
> > - throw_exception (except);
> > -
> > - /* do_print_variable_and_value invalidates FRAME. */
> > - frame = NULL;
> > + iterate_over_block_local_vars (block,
> > + do_print_variable_and_value,
> > + &cb_data);
> >
> > if (!cb_data.values_printed)
> > fprintf_filtered (stream, _("No locals.\n"));
> > diff --git a/gdb/testsuite/gdb.base/bt-full.c b/gdb/testsuite/gdb.base/bt-full.c
> > new file mode 100644
> > index 00000000000..708dc69b250
> > --- /dev/null
> > +++ b/gdb/testsuite/gdb.base/bt-full.c
> > @@ -0,0 +1,35 @@
> > +/* This testcase is part of GDB, the GNU debugger.
> > +
> > + Copyright 2018 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/>. */
> > +
> > +void
> > +breakpt ()
> > +{
> > + asm ("" ::: "memory");
> > +}
> > +
> > +void
> > +func ()
> > +{
> > + breakpt ();
> > +}
> > +
> > +int
> > +main ()
> > +{
> > + func ();
> > + return 0;
> > +}
> > diff --git a/gdb/testsuite/gdb.base/bt-full.exp b/gdb/testsuite/gdb.base/bt-full.exp
> > new file mode 100644
> > index 00000000000..7b64293dcfb
> > --- /dev/null
> > +++ b/gdb/testsuite/gdb.base/bt-full.exp
> > @@ -0,0 +1,60 @@
> > +# Copyright 2018 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/>.
> > +
> > +standard_testfile
> > +
> > +if { [prepare_for_testing "failed to prepare" $testfile $srcfile debug] } {
> > + return -1
> > +}
> > +
> > +if ![runto_main] then {
> > + fail "can't run to main"
> > + return 0
> > +}
> > +
> > +gdb_breakpoint "breakpt"
> > +gdb_continue_to_breakpoint "breakpt"
> > +
> > +# Return the frame number for the currently selected frame
> > +proc get_current_frame_number {{test_name ""}} {
> > + global gdb_prompt
> > +
> > + if { $test_name == "" } {
> > + set test_name "get current frame number"
> > + }
> > + set frame_num -1
> > + gdb_test_multiple "frame" $test_name {
> > + -re "#(\[0-9\]+) .*$gdb_prompt $" {
> > + set frame_num $expect_out(1,string)
> > + }
> > + }
> > + return $frame_num
> > +}
>
> This could go in lib/gdb.exp I suppose.
>
> > +
> > +# Visit each frame in the stack and ensure that 'bt full' doesn't
> > +# change the selected stack frame.
> > +for {set i 0} {$i < 3} {incr i} {
>
> I have a personal preference for this style:
>
> foreach_with_prefix frame {1 2 3} {
> ...
> }
>
> I think it expresses the intent better than a simple for loop, and it automatically
> scopes the test messages (with frame=X), so you don't need to put $i in every test
> message.
>
> > + if { $i == 0 } {
> > + gdb_assert {[get_current_frame_number] == $i} "check frame $i is selected"
> > + } else {
> > + gdb_test "frame $i" "#$i .*" "select frame $i"
> > + }
>
> Is there a particular reason for this if? Could we not do both "frame $i" and check
> the current frame at every iteration?
I'd prefer to keep things as they are. The code as it currently is
checks that we are in frame 0 when we stop at the breakpoint. Sure
this is checked many times elsewhere, but it doesn't hurt to check it
again.
We could move the gdb_assert outside the if/then/else, but we already
check that the frame number changes after the 'frame <N>' in the
regexp, so I don't think moving the gdb_assert adds anything.
Again, I'm not that fussed, so if you feel strongly, let me know and
I'll change it as you suggested.
>
> > +
> > + gdb_test "bt full" "#0 \[^\n\r\]+\[\n\r\]+No locals\.\[\n\r\]+#1 \[^\n\r\]+\[\n\r\]+No locals\.\[\n\r\]+#2 \[^\n\r\]+\[\n\r\]+No locals\.\[\n\r\]+" \
> > + "perform 'bt full' in frame $i"
>
> Did you try using the multi_line proc? It might help make this more readable.
>
> > +
> > + gdb_assert {[get_current_frame_number] == $i} "check frame $i is still selected"
> > +}
> > +
> >
>
> Is there already a test that does the equivalent of this, but for "bt" not-full? It might
> not be really necessary, but I thought it would be a low-hanging fruit to test with both
> "bt" and "bt-fulL" at this point. Obviously, the test wouldn't be
> named bt-full.exp then :).
I renamed the test, and extended it to cover 'bt' as well as 'bt full'.
Thanks,
Andrew
---
gdb: Restore selected frame in print_frame_local_vars
PR gdb/23203 reports 'bt full' causing the currently selected frame to
change, this issue is fixed in this commit.
Add a new class scoped_restore_selected_frame that saves and restores
the selected frame. Make use of this in print_frame_local_vars to
restore the selected frame on exit.
gdb/ChangeLog:
PR gdb/23203
* frame.c
(scoped_restore_selected_frame::scoped_restore_selected_frame):
Define.
(scoped_restore_selected_frame::~scoped_restore_selected_frame):
Define.
* frame.h (class scoped_restore_selected_frame): New class.
* stack.c (print_frame_local_vars): Remove catching and rethrowing
of any exception, use scoped_restore_selected_frame to restore the
frame instead.
gdb/testsuite/ChangeLog:
PR gdb/23203
* gdb.base/bt-selected-frame.c: New file.
* gdb.base/bt-selected-frame.exp: New file.
* lib/gdb.exp (get_current_frame_number): New function.
---
gdb/ChangeLog | 13 ++++++
gdb/frame.c | 16 +++++++
gdb/frame.h | 19 ++++++++
gdb/stack.c | 24 ++--------
gdb/testsuite/ChangeLog | 7 +++
gdb/testsuite/gdb.base/bt-selected-frame.c | 35 ++++++++++++++
gdb/testsuite/gdb.base/bt-selected-frame.exp | 70 ++++++++++++++++++++++++++++
gdb/testsuite/lib/gdb.exp | 16 +++++++
8 files changed, 180 insertions(+), 20 deletions(-)
create mode 100644 gdb/testsuite/gdb.base/bt-selected-frame.c
create mode 100644 gdb/testsuite/gdb.base/bt-selected-frame.exp
diff --git a/gdb/frame.c b/gdb/frame.c
index 07fa2bc77d6..1d0eb725145 100644
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -269,6 +269,22 @@ frame_stash_invalidate (void)
htab_empty (frame_stash);
}
+/* See frame.h */
+scoped_restore_selected_frame::scoped_restore_selected_frame ()
+{
+ m_fid = get_frame_id (get_selected_frame (NULL));
+}
+
+/* See frame.h */
+scoped_restore_selected_frame::~scoped_restore_selected_frame ()
+{
+ frame_info *frame = frame_find_by_id (m_fid);
+ if (frame == NULL)
+ warning (_("Unable to restore previously selected frame."));
+ else
+ select_frame (frame);
+}
+
/* Flag to control debugging. */
unsigned int frame_debug;
diff --git a/gdb/frame.h b/gdb/frame.h
index d5800b78c25..a6f7fd8947d 100644
--- a/gdb/frame.h
+++ b/gdb/frame.h
@@ -164,6 +164,25 @@ struct frame_id
int artificial_depth;
};
+/* Save and restore the currently selected frame. */
+
+class scoped_restore_selected_frame
+{
+public:
+ /* Save the currently selected frame. */
+ scoped_restore_selected_frame ();
+
+ /* Restore the currently selected frame. */
+ ~scoped_restore_selected_frame ();
+
+ DISABLE_COPY_AND_ASSIGN (scoped_restore_selected_frame);
+
+private:
+
+ /* The ID of the previously selected frame. */
+ struct frame_id m_fid;
+};
+
/* Methods for constructing and comparing Frame IDs. */
/* For convenience. All fields are zero. This means "there is no frame". */
diff --git a/gdb/stack.c b/gdb/stack.c
index ecf1ee83793..7e377764865 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -2019,7 +2019,6 @@ print_frame_local_vars (struct frame_info *frame, int num_tabs,
struct print_variable_and_value_data cb_data;
const struct block *block;
CORE_ADDR pc;
- struct gdb_exception except = exception_none;
if (!get_frame_pc_if_available (frame, &pc))
{
@@ -2043,27 +2042,12 @@ print_frame_local_vars (struct frame_info *frame, int num_tabs,
/* Temporarily change the selected frame to the given FRAME.
This allows routines that rely on the selected frame instead
of being given a frame as parameter to use the correct frame. */
+ scoped_restore_selected_frame restore_selected_frame;
select_frame (frame);
- TRY
- {
- iterate_over_block_local_vars (block,
- do_print_variable_and_value,
- &cb_data);
- }
- CATCH (ex, RETURN_MASK_ALL)
- {
- except = ex;
- }
- END_CATCH
-
- /* Restore the selected frame, and then rethrow if there was a problem. */
- select_frame (frame_find_by_id (cb_data.frame_id));
- if (except.reason < 0)
- throw_exception (except);
-
- /* do_print_variable_and_value invalidates FRAME. */
- frame = NULL;
+ iterate_over_block_local_vars (block,
+ do_print_variable_and_value,
+ &cb_data);
if (!cb_data.values_printed)
fprintf_filtered (stream, _("No locals.\n"));
diff --git a/gdb/testsuite/gdb.base/bt-selected-frame.c b/gdb/testsuite/gdb.base/bt-selected-frame.c
new file mode 100644
index 00000000000..708dc69b250
--- /dev/null
+++ b/gdb/testsuite/gdb.base/bt-selected-frame.c
@@ -0,0 +1,35 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2018 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/>. */
+
+void
+breakpt ()
+{
+ asm ("" ::: "memory");
+}
+
+void
+func ()
+{
+ breakpt ();
+}
+
+int
+main ()
+{
+ func ();
+ return 0;
+}
diff --git a/gdb/testsuite/gdb.base/bt-selected-frame.exp b/gdb/testsuite/gdb.base/bt-selected-frame.exp
new file mode 100644
index 00000000000..931c91018c9
--- /dev/null
+++ b/gdb/testsuite/gdb.base/bt-selected-frame.exp
@@ -0,0 +1,70 @@
+# Copyright 2018 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/>.
+
+standard_testfile
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile debug] } {
+ return -1
+}
+
+proc check_selected_frame_after_bt { bt_cmd stack_pattern } {
+ global binfile
+
+ clean_restart $binfile
+
+ with_test_prefix $bt_cmd {
+
+ if ![runto_main] then {
+ fail "can't run to main"
+ return 0
+ }
+
+ gdb_breakpoint "breakpt"
+ gdb_continue_to_breakpoint "breakpt"
+
+ # Visit each frame in the stack and ensure that the selected
+ # frame doesn't change after executing the backtrace command
+ # in BT_CMD.
+ foreach_with_prefix frame {0 1 2} {
+ if { $frame == 0 } {
+ gdb_assert {[get_current_frame_number] == $frame} \
+ "check frame"
+ } else {
+ gdb_test "frame $frame" "#$frame .*" "select frame"
+ }
+
+ gdb_test "$bt_cmd" $stack_pattern \
+ "perform backtrace command"
+
+ gdb_assert {[get_current_frame_number] == $frame} \
+ "check frame is still selected"
+ }
+ }
+}
+
+check_selected_frame_after_bt "bt" \
+ [multi_line \
+ "#0 \[^\n\r\]+" \
+ "#1 \[^\n\r\]+" \
+ "#2 \[^\n\r\]+"]
+
+check_selected_frame_after_bt "bt full" \
+ [multi_line \
+ "#0 \[^\n\r\]+" \
+ "No locals\." \
+ "#1 \[^\n\r\]+" \
+ "No locals\." \
+ "#2 \[^\n\r\]+" \
+ "No locals\."]
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 0f05d043f25..ee66a38e08f 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -5805,6 +5805,22 @@ proc get_var_address { var } {
return ""
}
+# Return the frame number for the currently selected frame
+proc get_current_frame_number {{test_name ""}} {
+ global gdb_prompt
+
+ if { $test_name == "" } {
+ set test_name "get current frame number"
+ }
+ set frame_num -1
+ gdb_test_multiple "frame" $test_name {
+ -re "#(\[0-9\]+) .*$gdb_prompt $" {
+ set frame_num $expect_out(1,string)
+ }
+ }
+ return $frame_num
+}
+
# Get the current value for remotetimeout and return it.
proc get_remotetimeout { } {
global gdb_prompt
--
2.14.3