[PATCH] gdb: new 'maint print frame-id' command

[Andrew Burgess]

Andrew Burgess <aburgess@redhat.com> writes:

> When debugging a certain class of GDB bug, I often end up wanting to
> know what GDB thinks the frame-id is in a particular frame.  It's
> not too hard to pull this from some debug output, but I thought it
> might be nice if there was a maintenance command that could tell us.
>
> This commit adds 'maint print frame-id' which prints the frame-id of
> the currently selected frame.  You can also pass a frame level number
> to find the frame-id for a specific frame.
>
> There's a new test too.

I've now pushed this patch.

Thanks,
Andrew

> ---
>  gdb/NEWS                                      |  4 ++
>  gdb/doc/gdb.texinfo                           | 17 +++++
>  gdb/frame.c                                   | 28 ++++++++
>  gdb/testsuite/gdb.base/maint-print-frame-id.c | 40 +++++++++++
>  .../gdb.base/maint-print-frame-id.exp         | 68 +++++++++++++++++++
>  5 files changed, 157 insertions(+)
>  create mode 100644 gdb/testsuite/gdb.base/maint-print-frame-id.c
>  create mode 100644 gdb/testsuite/gdb.base/maint-print-frame-id.exp
>
> diff --git a/gdb/NEWS b/gdb/NEWS
> index f2040e26c0c..49ac714efda 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -91,6 +91,10 @@ show style disassembler symbol
>    The 'disassembler address' and 'disassembler symbol' styles are
>    aliases for the 'address' and 'function' styles respectively.
>  
> +maintenance print frame-id [ LEVEL ]
> +  Print GDB's internal frame-id for the frame at LEVEL.  If LEVEL is
> +  not given, then print the frame-id for the currently selected frame.
> +
>  * Changed commands
>  
>  maintenance info line-table
> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
> index 82cb1c8d668..ca958173b57 100644
> --- a/gdb/doc/gdb.texinfo
> +++ b/gdb/doc/gdb.texinfo
> @@ -40142,6 +40142,23 @@
>  
>  Takes an optional file parameter.
>  
> +@kindex maint print frame-id
> +@item maint print frame-id
> +@itemx maint print frame-id @var{level}
> +Print @value{GDBN}'s internal frame-id for the frame at relative
> +@var{level}, or for the currently selected frame when @var{level} is
> +not given.
> +
> +If used, @var{level} should be an integer, as displayed in the
> +@command{backtrace} output.
> +
> +@smallexample
> +(@value{GDBP}) maint print frame-id
> +frame-id for frame #0: {stack=0x7fffffffac70,code=0x0000000000401106,!special}
> +(@value{GDBP}) maint print frame-id 2
> +frame-id for frame #2: {stack=0x7fffffffac90,code=0x000000000040111c,!special}
> +@end smallexample
> +
>  @kindex maint print registers
>  @kindex maint print raw-registers
>  @kindex maint print cooked-registers
> diff --git a/gdb/frame.c b/gdb/frame.c
> index ae45e22d613..e6bebf575ca 100644
> --- a/gdb/frame.c
> +++ b/gdb/frame.c
> @@ -3116,6 +3116,30 @@ the rest of the stack trace."),
>    },
>  };
>  
> +/* Implement the 'maintenance print frame-id' command.  */
> +
> +static void
> +maintenance_print_frame_id (const char *args, int from_tty)
> +{
> +  struct frame_info *frame;
> +
> +  /* Use the currently selected frame, or select a frame based on the level
> +     number passed by the user.  */
> +  if (args == nullptr)
> +    frame = get_selected_frame ("No frame selected");
> +  else
> +    {
> +      int level = value_as_long (parse_and_eval (args));
> +      frame = find_relative_frame (get_current_frame (), &level);
> +    }
> +
> +  /* Print the frame-id.  */
> +  gdb_assert (frame != nullptr);
> +  gdb_printf ("frame-id for frame #%d: %s\n",
> +	      frame_relative_level (frame),
> +	      get_frame_id (frame).to_string ().c_str ());
> +}
> +
>  void _initialize_frame ();
>  void
>  _initialize_frame ()
> @@ -3160,4 +3184,8 @@ When non-zero, frame specific internal debugging is enabled."),
>  			   NULL,
>  			   show_frame_debug,
>  			   &setdebuglist, &showdebuglist);
> +
> +  add_cmd ("frame-id", class_maintenance, maintenance_print_frame_id,
> +	   _("Print the current frame-id."),
> +	   &maintenanceprintlist);
>  }
> diff --git a/gdb/testsuite/gdb.base/maint-print-frame-id.c b/gdb/testsuite/gdb.base/maint-print-frame-id.c
> new file mode 100644
> index 00000000000..bc9eb3000e7
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/maint-print-frame-id.c
> @@ -0,0 +1,40 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2022 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/>.  */
> +
> +int
> +foo (void)
> +{
> +  return 0;
> +}
> +
> +int
> +bar (void)
> +{
> +  return foo ();
> +}
> +
> +int
> +baz (void)
> +{
> +  return bar ();
> +}
> +
> +int
> +main (void)
> +{
> +  return baz ();
> +}
> diff --git a/gdb/testsuite/gdb.base/maint-print-frame-id.exp b/gdb/testsuite/gdb.base/maint-print-frame-id.exp
> new file mode 100644
> index 00000000000..395927a22c4
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/maint-print-frame-id.exp
> @@ -0,0 +1,68 @@
> +# Copyright 2022 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 the 'maint print frame-id' command.
> +
> +standard_testfile
> +
> +if {[prepare_for_testing "failed to prepare" $testfile \
> +	 $srcfile {debug}]} {
> +    return -1
> +}
> +
> +if ![runto_main] then {
> +    return -1
> +}
> +
> +gdb_breakpoint foo
> +gdb_continue_to_breakpoint "run to foo"
> +
> +proc get_frame_id { level } {
> +    set id "**unknown**"
> +
> +    gdb_test_multiple "maint print frame-id ${level}" "" {
> +	-re "^maint print frame-id\[^\r\n\]+\r\n" {
> +	    exp_continue
> +	}
> +
> +	-wrap -re "^frame-id for frame #\[0-9\]+: (\[^\r\n\]+)" {
> +	    set id $expect_out(1,string)
> +	    pass $gdb_test_name
> +	}
> +    }
> +
> +    return $id
> +}
> +
> +# Get the frame-id for each frame using the frame level.
> +array set ids {}
> +with_test_prefix "get id by level" {
> +    for { set i 0 } { $i < 4 } { incr i } {
> +	set ids($i) [get_frame_id $i]
> +    }
> +}
> +
> +# Now get the frame-id of the currently selected frame, and check it
> +# matches the frame-id we got earlier.  Then move up the stack,
> +# selecting a new frame.
> +for { set i 0 } { $i < 4 } { incr i } {
> +    with_test_prefix "frame $i is current" {
> +	set id [get_frame_id ""]
> +	gdb_assert { [string equal $id $ids($i)] } \
> +	    "check frame-id matches"
> +    }
> +    gdb_test "up" ".*" \
> +	"move up from frame $i"
> +}
> -- 
> 2.25.4