[PATCH v4 0/2] Improving frame printing with recursive calls

[PATCH v4 0/2] Improving frame printing with recursive calls

[Guinevere Larsen]

This started with the first patch, just fixing PR record/29178. However,
Kevin pointed out that I could reuse some of the local variables to make
the function as a whole simpler, which I did on patch 2.
My changes on v3 introduced a regression in a dwarf2 test. I gave some
time for people to comment on Kevin's solution (then forgot about this
patch), but since no one disagreed, this new version changes thetest,
rather than the code.

Changelog for v4:
* changed gdb.dwarf2/dw2-out-of-range... because it was reporting a
  failure, but it is just some symbols being read earlier than before.

Changelog for v3:
* Fix remaining style issues in the testsuite

Changelog for v2:
* Added second patch in the series
* Fixed some tyle issues

Guinevere Larsen (2):
  gdb/record: print frame information when exiting a recursive call
  gdb/infrun: simplify process_event_stop_test

 gdb/infrun.c                                  | 36 ++++++++++-----
 .../dw2-out-of-range-end-of-seq.exp           |  2 +-
 gdb/testsuite/gdb.reverse/recursion.c         | 44 ++++++++++++++++++
 gdb/testsuite/gdb.reverse/recursion.exp       | 45 +++++++++++++++++++
 4 files changed, 114 insertions(+), 13 deletions(-)
 create mode 100644 gdb/testsuite/gdb.reverse/recursion.c
 create mode 100644 gdb/testsuite/gdb.reverse/recursion.exp

-- 
2.41.0

[PATCH v4 1/2] gdb/record: print frame information when exiting a recursive call

[Guinevere Larsen]

Currently,  when GDB is reverse stepping out of a function into the same
function due to a recursive call, it doesn't print frame information, as
reported by PR record/29178. This happens because when the inferior
leaves the current frame, GDB decides to refresh the step information,
clobbering the original step_frame_id, making it impossible to figure
out later on that the frame has been changed.

This commit changes GDB so that, if we notice we're in this exact
situation, we won't refresh the step information.

Because of implementation details, this change can cause some debug
information to be read when it normally wouldn't before, which showed up
as a regression on gdb.dwarf2/dw2-out-of-range-end-of-seq. Since that
isn't a problem, the test was changed to allow for the new output.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29178
---
 gdb/infrun.c                                  | 18 ++++++++
 .../dw2-out-of-range-end-of-seq.exp           |  2 +-
 gdb/testsuite/gdb.reverse/recursion.c         | 44 ++++++++++++++++++
 gdb/testsuite/gdb.reverse/recursion.exp       | 45 +++++++++++++++++++
 4 files changed, 108 insertions(+), 1 deletion(-)
 create mode 100644 gdb/testsuite/gdb.reverse/recursion.c
 create mode 100644 gdb/testsuite/gdb.reverse/recursion.exp

diff --git a/gdb/infrun.c b/gdb/infrun.c
index 4fde96800fb..9571acef1fa 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -6925,6 +6925,11 @@ process_event_stop_test (struct execution_control_state *ecs)
   frame = get_current_frame ();
   gdbarch = get_frame_arch (frame);
 
+  /* Shorthand to make if statements smaller.  */
+  struct frame_id original_frame_id
+    = ecs->event_thread->control.step_frame_id;
+  struct frame_id curr_frame_id = get_frame_id (get_current_frame ());
+
   switch (what.main_action)
     {
     case BPSTAT_WHAT_SET_LONGJMP_RESUME:
@@ -7724,6 +7729,19 @@ process_event_stop_test (struct execution_control_state *ecs)
 			       "it's not the start of a statement");
 	}
     }
+  else if (execution_direction == EXEC_REVERSE
+	  && curr_frame_id != original_frame_id
+	  && original_frame_id.code_addr_p && curr_frame_id.code_addr_p
+	  && original_frame_id.code_addr == curr_frame_id.code_addr)
+    {
+      /* If we enter here, we're leaving a recursive function call.  In this
+	 situation, we shouldn't refresh the step information, because if we
+	 do, we'll lose the frame_id of when we started stepping, and this
+	 will make GDB not know we need to print frame information.  */
+      refresh_step_info = false;
+      infrun_debug_printf ("reverse stepping, left a recursive call, don't "
+			   "update step info so we remember we left a frame");
+    }
 
   /* We aren't done stepping.
 
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-out-of-range-end-of-seq.exp b/gdb/testsuite/gdb.dwarf2/dw2-out-of-range-end-of-seq.exp
index d2c28a87923..8b4e79644c1 100644
--- a/gdb/testsuite/gdb.dwarf2/dw2-out-of-range-end-of-seq.exp
+++ b/gdb/testsuite/gdb.dwarf2/dw2-out-of-range-end-of-seq.exp
@@ -84,7 +84,7 @@ if ![runto_main] {
 }
 
 set test "END with address 1 eliminated"
-gdb_test_multiple "maint info line-table $srcfile$" $test {
+gdb_test_multiple "maint info line-table \\b$srcfile$" $test {
     -re -wrap "END *0x0*1 *$hex *Y *\r\n.*" {
 	fail $gdb_test_name
     }
diff --git a/gdb/testsuite/gdb.reverse/recursion.c b/gdb/testsuite/gdb.reverse/recursion.c
new file mode 100644
index 00000000000..5ce1c8dbea0
--- /dev/null
+++ b/gdb/testsuite/gdb.reverse/recursion.c
@@ -0,0 +1,44 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2023 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 GDB's ability to handle recursive functions when executing
+   in reverse.  */
+
+/* The recursive foo call must be the first line of the recursive
+   function, to test that we're not stepping too much and skipping
+   multiple calls when we should skip only one.  */
+int
+foo (int x)
+{
+  if (x) return foo (x-1);
+  return 0;
+}
+
+int
+bar (int x)
+{
+  int r = foo (x);
+  return 2*r;
+}
+
+int
+main ()
+{
+  int i = bar (5);
+  int j = foo (5);
+  return 0;			/* END OF MAIN */
+}
diff --git a/gdb/testsuite/gdb.reverse/recursion.exp b/gdb/testsuite/gdb.reverse/recursion.exp
new file mode 100644
index 00000000000..3fead0e8c8d
--- /dev/null
+++ b/gdb/testsuite/gdb.reverse/recursion.exp
@@ -0,0 +1,45 @@
+# Copyright 2008-2023 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/>.  */
+
+# This file is part of the GDB testsuite.  It tests reverse stepping
+# out of recursive functions.
+
+require supports_reverse
+
+standard_testfile
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {
+    return -1
+}
+
+runto_main
+
+if [supports_process_record] {
+    # Activate process record/replay
+    gdb_test_no_output "record" "turn on process record"
+}
+
+set end_of_program [gdb_get_line_number "END OF MAIN" "$srcfile"]
+gdb_breakpoint $end_of_program
+gdb_continue_to_breakpoint ".*$srcfile/$end_of_program.*"
+
+## test if GDB can reverse over a recursive program
+gdb_test "reverse-next" ".*int j = foo.*" "Skipping recursion from outside"
+## setup and next over a recursion for inside a recursive call
+repeat_cmd_until "reverse-step" ".*" ".*foo .x=4.*"
+gdb_test "reverse-next" ".*return foo.*" "Skipping recursion from inside"
+gdb_test "reverse-next" ".*foo .x=5.*" "print frame when stepping out"
+gdb_test "reverse-next" ".*bar .x=5.*" "stepping into a different function"
+gdb_test "reverse-next" "main .. at .*" "stepping back to main"
-- 
2.41.0

[PATCH v4 2/2] gdb/infrun: simplify process_event_stop_test

[Guinevere Larsen]

The previous commit introduced some local variables to make some if
statements simpler. This commit uses them more liberally throughout the
process_event_stop_test in order to simplify the function a little more.
No functional changes are expected.
---
 gdb/infrun.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/gdb/infrun.c b/gdb/infrun.c
index 9571acef1fa..2f4c8632336 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -7016,9 +7016,7 @@ process_event_stop_test (struct execution_control_state *ecs)
 
 	if (init_frame)
 	  {
-	    struct frame_id current_id
-	      = get_frame_id (get_current_frame ());
-	    if (current_id == ecs->event_thread->initiating_frame)
+	    if (curr_frame_id == ecs->event_thread->initiating_frame)
 	      {
 		/* Case 2.  Fall through.  */
 	      }
@@ -7191,7 +7189,7 @@ process_event_stop_test (struct execution_control_state *ecs)
   if (pc_in_thread_step_range (ecs->event_thread->stop_pc (),
 			       ecs->event_thread)
       && (execution_direction != EXEC_REVERSE
-	  || get_frame_id (frame) == ecs->event_thread->control.step_frame_id))
+	  || curr_frame_id == original_frame_id))
     {
       infrun_debug_printf
 	("stepping inside range [%s-%s]",
@@ -7621,8 +7619,7 @@ process_event_stop_test (struct execution_control_state *ecs)
      frame machinery detected some skipped call sites, we have entered
      a new inline function.  */
 
-  if ((get_frame_id (get_current_frame ())
-       == ecs->event_thread->control.step_frame_id)
+  if ((curr_frame_id == original_frame_id)
       && inline_skipped_frames (ecs->event_thread))
     {
       infrun_debug_printf ("stepped into inlined function");
@@ -7670,10 +7667,8 @@ process_event_stop_test (struct execution_control_state *ecs)
      through a more inlined call beyond its call site.  */
 
   if (get_frame_type (get_current_frame ()) == INLINE_FRAME
-      && (get_frame_id (get_current_frame ())
-	  != ecs->event_thread->control.step_frame_id)
-      && stepped_in_from (get_current_frame (),
-			  ecs->event_thread->control.step_frame_id))
+      && (curr_frame_id != original_frame_id)
+      && stepped_in_from (get_current_frame (), original_frame_id))
     {
       infrun_debug_printf ("stepping through inlined function");
 
@@ -7703,8 +7698,7 @@ process_event_stop_test (struct execution_control_state *ecs)
 	  end_stepping_range (ecs);
 	  return;
 	}
-      else if (get_frame_id (get_current_frame ())
-	       == ecs->event_thread->control.step_frame_id)
+      else if (curr_frame_id == original_frame_id)
 	{
 	  /* We are not at the start of a statement, and we have not changed
 	     frame.
-- 
2.41.0

Re: [PATCH v4 0/2] Improving frame printing with recursive calls

[Tom Tromey]

>>>>> "Guinevere" == Guinevere Larsen <blarsen@redhat.com> writes:

Guinevere> This started with the first patch, just fixing PR record/29178. However,
Guinevere> Kevin pointed out that I could reuse some of the local variables to make
Guinevere> the function as a whole simpler, which I did on patch 2.
Guinevere> My changes on v3 introduced a regression in a dwarf2 test. I gave some
Guinevere> time for people to comment on Kevin's solution (then forgot about this
Guinevere> patch), but since no one disagreed, this new version changes thetest,
Guinevere> rather than the code.

These look reasonable to me.  Thank you.
Approved-By: Tom Tromey <tom@tromey.com>

Tom

Re: [PATCH v4 0/2] Improving frame printing with recursive calls

[Guinevere Larsen]

On 17/11/2023 15:38, Tom Tromey wrote:
>>>>>> "Guinevere" == Guinevere Larsen <blarsen@redhat.com> writes:
> Guinevere> This started with the first patch, just fixing PR record/29178. However,
> Guinevere> Kevin pointed out that I could reuse some of the local variables to make
> Guinevere> the function as a whole simpler, which I did on patch 2.
> Guinevere> My changes on v3 introduced a regression in a dwarf2 test. I gave some
> Guinevere> time for people to comment on Kevin's solution (then forgot about this
> Guinevere> patch), but since no one disagreed, this new version changes thetest,
> Guinevere> rather than the code.
>
> These look reasonable to me.  Thank you.
> Approved-By: Tom Tromey <tom@tromey.com>
>
Thanks, I pushed these!

-- 
Cheers,
Guinevere Larsen
She/Her/Hers

Re: [PATCH v4 0/2] Improving frame printing with recursive calls

[Luis Machado]

On 11/20/23 09:54, Guinevere Larsen wrote:
> On 17/11/2023 15:38, Tom Tromey wrote:
>>>>>>> "Guinevere" == Guinevere Larsen <blarsen@redhat.com> writes:
>> Guinevere> This started with the first patch, just fixing PR record/29178. However,
>> Guinevere> Kevin pointed out that I could reuse some of the local variables to make
>> Guinevere> the function as a whole simpler, which I did on patch 2.
>> Guinevere> My changes on v3 introduced a regression in a dwarf2 test. I gave some
>> Guinevere> time for people to comment on Kevin's solution (then forgot about this
>> Guinevere> patch), but since no one disagreed, this new version changes thetest,
>> Guinevere> rather than the code.
>>
>> These look reasonable to me.  Thank you.
>> Approved-By: Tom Tromey <tom@tromey.com>
>>
> Thanks, I pushed these!
> 

Sorry I'm late to the party, but looks like this regresses reverse debugging. I was just
testing Carl's patches for step/next reverse fixes, and I notice a few new FAIL's that
were not related to the fixes by Carl.

I don't see a problem with aarch64-linux, but arm-linux seems to be affected.

It was caught by the Linaro CI here: https://linaro.atlassian.net/browse/GNU-1026

Do you have any ideas on what's up?

Re: [PATCH v4 0/2] Improving frame printing with recursive calls

[Guinevere Larsen]

On 29/11/2023 12:42, Luis Machado wrote:
> On 11/20/23 09:54, Guinevere Larsen wrote:
>> On 17/11/2023 15:38, Tom Tromey wrote:
>>>>>>>> "Guinevere" == Guinevere Larsen <blarsen@redhat.com> writes:
>>> Guinevere> This started with the first patch, just fixing PR record/29178. However,
>>> Guinevere> Kevin pointed out that I could reuse some of the local variables to make
>>> Guinevere> the function as a whole simpler, which I did on patch 2.
>>> Guinevere> My changes on v3 introduced a regression in a dwarf2 test. I gave some
>>> Guinevere> time for people to comment on Kevin's solution (then forgot about this
>>> Guinevere> patch), but since no one disagreed, this new version changes thetest,
>>> Guinevere> rather than the code.
>>>
>>> These look reasonable to me.  Thank you.
>>> Approved-By: Tom Tromey <tom@tromey.com>
>>>
>> Thanks, I pushed these!
>>
> Sorry I'm late to the party, but looks like this regresses reverse debugging. I was just
> testing Carl's patches for step/next reverse fixes, and I notice a few new FAIL's that
> were not related to the fixes by Carl.
>
> I don't see a problem with aarch64-linux, but arm-linux seems to be affected.
>
> It was caught by the Linaro CI here: https://linaro.atlassian.net/browse/GNU-1026
>
> Do you have any ideas on what's up?
>
I have no idea what's up. I'll take a look at it, thanks for bringing it up

-- 
Cheers,
Guinevere Larsen
She/Her/Hers