[PING][PATCH v2] gdb/record: fix missing "no history" message in some situations

[Guinevere Larsen <guinevere@redhat.com>]

Ping!

I plan on pushing this change next week if there's no comments

On 9/8/26 5:53 PM, Guinevere Larsen wrote:
> I recently noticed that the end of recorded history message wasn't
> shown when replaying an inferior until the end for the first time, it
> was only shown when trying to reverse past the start of
> history. Executing forward past the end will not warn the user that
> recording is going to start again, it just does so. This is the
> behavior before the change:
>
>      (gdb) start
>      Temporary breakpoint 1 at 0x40044a: file t.c, line 2.
>      Starting program: /home/glarsen/a.out
>      [Thread debugging using libthread_db enabled]
>      Using host libthread_db library "/lib64/libthread_db.so.1".
>
>      Temporary breakpoint 1, main () at t.c:2
>      2	  int x = 0;
>      (gdb) record
>      (gdb) n
>      3	  x ++;
>      (gdb) rn
>
>      Reached end of recorded history; stopping.
>      Backward execution from here not possible.
>      main () at t.c:2
>      2	  int x = 0;
>      (gdb) n
>
>      Reached end of recorded history; stopping.
>      Following forward execution will be added to history.
>      main () at t.c:3
>      3	  x ++;
>      (gdb)
>
> And this is the behavior after the change:
>
>      (gdb) start
>      Temporary breakpoint 1 at 0x40044a: file t.c, line 2.
>      Starting program: /home/glarsen/a.out
>      [Thread debugging using libthread_db enabled]
>      Using host libthread_db library "/lib64/libthread_db.so.1".
>
>      Temporary breakpoint 1, main () at t.c:2
>      2	  int x = 0;
>      (gdb) record
>      (gdb) n
>      3	  x ++;
>      (gdb) rn
>      2	  int x = 0;
>      (gdb) rn
>
>      Reached end of recorded history; stopping.
>      Backward execution from here not possible.
>      main () at t.c:2
>      2	  int x = 0;
>      (gdb) n
>      3	  x ++;
>      (gdb) n
>      4	  return x;
>
> This was happening because the out-of-history was only set when it
> caused the execution loop to stop, so using "next" to reach the end of
> history, for example, wouldn't trigger it as I expected.  This commit
> fixes that to make out-of-history check only happen after the loop is
> finished.
>
> Also add a test to ensure we dont regress again.
> ---
>   gdb/record-full.c                        | 22 +++++--------
>   gdb/testsuite/gdb.reverse/no-history.c   | 26 +++++++++++++++
>   gdb/testsuite/gdb.reverse/no-history.exp | 40 ++++++++++++++++++++++++
>   3 files changed, 74 insertions(+), 14 deletions(-)
>   create mode 100644 gdb/testsuite/gdb.reverse/no-history.c
>   create mode 100644 gdb/testsuite/gdb.reverse/no-history.exp
>
> diff --git a/gdb/record-full.c b/gdb/record-full.c
> index 26bd85d34f6..e9ec65b161b 100644
> --- a/gdb/record-full.c
> +++ b/gdb/record-full.c
> @@ -1362,19 +1362,11 @@ record_full_wait_1 (struct target_ops *ops,
>   	      /* Check for beginning and end of log.  */
>   	      if (execution_direction == EXEC_REVERSE
>   		  && record_full_next_insn < 0)
> -		{
> -		  /* Hit beginning of record log in reverse.  */
> -		  status->set_no_history ();
> -		  record_full_next_insn = 0;
> -		  break;
> -		}
> -	      if (execution_direction != EXEC_REVERSE
> -		  && record_full_next_insn == record_full_log.size ())
> -		{
> -		  /* Hit end of record log going forward.  */
> -		  status->set_no_history ();
> -		  break;
> -		}
> +		break;
> +
> +	      else if (execution_direction != EXEC_REVERSE
> +		       && record_full_next_insn == record_full_log.size ())
> +		break;
>   
>   	      record_full_log[record_full_next_insn].exec_insn (regcache);
>   
> @@ -1424,11 +1416,13 @@ record_full_wait_1 (struct target_ops *ops,
>   	    {
>   	      gdb_assert (execution_direction == EXEC_REVERSE);
>   	      record_full_next_insn = 0;
> +	      status->set_no_history ();
>   	    }
> -	  else if (record_full_next_insn > record_full_log.size ())
> +	  else if (record_full_next_insn >= record_full_log.size ())
>   	    {
>   	      gdb_assert (execution_direction == EXEC_FORWARD);
>   	      record_full_next_insn = record_full_log.size ();
> +	      status->set_no_history ();
>   	    }
>   	  /* Reset the current instruction to point to the one to be replayed
>   	     moving forward.  */
> diff --git a/gdb/testsuite/gdb.reverse/no-history.c b/gdb/testsuite/gdb.reverse/no-history.c
> new file mode 100644
> index 00000000000..4e7cf3786fd
> --- /dev/null
> +++ b/gdb/testsuite/gdb.reverse/no-history.c
> @@ -0,0 +1,26 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2026 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 that GDB is printing the no-history messages as it should.  */
> +
> +int
> +main ()
> +{
> +  int x = 0;
> +  x++;
> +  return 0;			/* END OF MAIN */
> +}
> diff --git a/gdb/testsuite/gdb.reverse/no-history.exp b/gdb/testsuite/gdb.reverse/no-history.exp
> new file mode 100644
> index 00000000000..443d3b66497
> --- /dev/null
> +++ b/gdb/testsuite/gdb.reverse/no-history.exp
> @@ -0,0 +1,40 @@
> +# Copyright 2008-2026 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 the printing of
> +# the "out of history" warnings.
> +
> +require supports_reverse
> +
> +standard_testfile
> +
> +if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {
> +    return
> +}
> +
> +runto_main
> +
> +if {[supports_process_record]} {
> +    # Activate process record/replay
> +    gdb_test_no_output "record" "turn on process record"
> +}
> +
> +gdb_test "next" "x\\\+\\\+;" "Record a line of execution"
> +gdb_test "reverse-next" \
> +    ".*Reached end of recorded history; stopping.*" \
> +    "Reverse to start of history"
> +gdb_test "next" \
> +    ".*Reached end of recorded history; stopping.*" \
> +    "Forward to end of history"
>
> base-commit: 0ca0b8de31ec76ff71f4a051db3dc1fcc9325154

-- 
Cheers,
Guinevere Larsen
it/its
she/her (deprecated)