Re: [PATCH 3/5] gdb/python: add PendingFrame.level and Frame.level methods

[Andrew Burgess <andrew.burgess@embecosm.com>]

I've pushed this patch now.

Thanks,
Andrew

* Andrew Burgess <andrew.burgess@embecosm.com> [2021-05-29 21:57:12 +0100]:

> Add new methods to the PendingFrame and Frame classes to obtain the
> stack frame level for each object.
> 
> The use of 'level' as the method name is consistent with the existing
> attribute RecordFunctionSegment.level (though this is an attribute
> rather than a method).
> 
> For Frame/PendingFrame I went with methods as these classes currently
> only use methods, including for simple data like architecture, so I
> want to be consistent with this interface.
> 
> gdb/ChangeLog:
> 
> 	* python/py-frame.c (frapy_level): New function.
> 	(frame_object_methods): Register 'level' method.
> 	* python/py-unwind.c (pending_framepy_level): New function.
> 	(pending_frame_object_methods): Register 'level' method.
> 
> gdb/doc/ChangeLog:
> 
> 	* python.texi (Unwinding Frames in Python): Mention
> 	PendingFrame.level.
> 	(Frames In Python): Mention Frame.level.
> 
> gdb/testsuite/ChangeLog:
> 
> 	* gdb.python/py-frame.exp: Add Frame.level tests.
> 	* gdb.python/py-pending-frame-level.c: New file.
> 	* gdb.python/py-pending-frame-level.exp: New file.
> 	* gdb.python/py-pending-frame-level.py: New file.
> ---
>  gdb/ChangeLog                                 |  7 ++
>  gdb/doc/ChangeLog                             |  6 ++
>  gdb/doc/python.texi                           |  9 +++
>  gdb/python/py-frame.c                         | 23 +++++++
>  gdb/python/py-unwind.c                        | 19 ++++++
>  gdb/testsuite/ChangeLog                       |  7 ++
>  gdb/testsuite/gdb.python/py-frame.exp         | 11 ++++
>  .../gdb.python/py-pending-frame-level.c       | 49 ++++++++++++++
>  .../gdb.python/py-pending-frame-level.exp     | 65 +++++++++++++++++++
>  .../gdb.python/py-pending-frame-level.py      | 55 ++++++++++++++++
>  10 files changed, 251 insertions(+)
>  create mode 100644 gdb/testsuite/gdb.python/py-pending-frame-level.c
>  create mode 100644 gdb/testsuite/gdb.python/py-pending-frame-level.exp
>  create mode 100644 gdb/testsuite/gdb.python/py-pending-frame-level.py
> 
> diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
> index 23e6ac666ff..b7e16351a5d 100644
> --- a/gdb/doc/python.texi
> +++ b/gdb/doc/python.texi
> @@ -2605,6 +2605,11 @@
>  the particular frame being unwound.
>  @end defun
>  
> +@defun PendingFrame.level ()
> +Return an integer, the stack frame level for this frame.
> +@xref{Frames, ,Stack Frames}.
> +@end defun
> +
>  @subheading Unwinder Output: UnwindInfo
>  
>  Use @code{PendingFrame.create_unwind_info} method described above to
> @@ -4813,6 +4818,10 @@
>  Stack}.
>  @end defun
>  
> +@defun Frame.level ()
> +Return an integer, the stack frame level for this frame.  @xref{Frames, ,Stack Frames}.
> +@end defun
> +
>  @node Blocks In Python
>  @subsubsection Accessing blocks from Python
>  
> diff --git a/gdb/python/py-frame.c b/gdb/python/py-frame.c
> index c8eab5291ea..4f218c40367 100644
> --- a/gdb/python/py-frame.c
> +++ b/gdb/python/py-frame.c
> @@ -577,6 +577,27 @@ frapy_select (PyObject *self, PyObject *args)
>    Py_RETURN_NONE;
>  }
>  
> +/* The stack frame level for this frame.  */
> +
> +static PyObject *
> +frapy_level (PyObject *self, PyObject *args)
> +{
> +  struct frame_info *fi;
> +
> +  try
> +    {
> +      FRAPY_REQUIRE_VALID (self, fi);
> +
> +      return gdb_py_object_from_int (frame_relative_level (fi)).release ();
> +    }
> +  catch (const gdb_exception &except)
> +    {
> +      GDB_PY_HANDLE_EXCEPTION (except);
> +    }
> +
> +  Py_RETURN_NONE;
> +}
> +
>  /* Implementation of gdb.newest_frame () -> gdb.Frame.
>     Returns the newest frame object.  */
>  
> @@ -748,6 +769,8 @@ Return the frame's symtab and line." },
>  Return the value of the variable in this frame." },
>    { "select", frapy_select, METH_NOARGS,
>      "Select this frame as the user's current frame." },
> +  { "level", frapy_level, METH_NOARGS,
> +    "The stack level of this frame." },
>    {NULL}  /* Sentinel */
>  };
>  
> diff --git a/gdb/python/py-unwind.c b/gdb/python/py-unwind.c
> index d6e2f85dbc1..ff1a7e922a7 100644
> --- a/gdb/python/py-unwind.c
> +++ b/gdb/python/py-unwind.c
> @@ -463,6 +463,23 @@ pending_framepy_architecture (PyObject *self, PyObject *args)
>    return gdbarch_to_arch_object (pending_frame->gdbarch);
>  }
>  
> +/* Implementation of PendingFrame.level (self) -> Integer.  */
> +
> +static PyObject *
> +pending_framepy_level (PyObject *self, PyObject *args)
> +{
> +  pending_frame_object *pending_frame = (pending_frame_object *) self;
> +
> +  if (pending_frame->frame_info == NULL)
> +    {
> +      PyErr_SetString (PyExc_ValueError,
> +		       "Attempting to read stack level from stale PendingFrame");
> +      return NULL;
> +    }
> +  int level = frame_relative_level (pending_frame->frame_info);
> +  return gdb_py_object_from_int (level).release ();
> +}
> +
>  /* frame_unwind.this_id method.  */
>  
>  static void
> @@ -704,6 +721,8 @@ static PyMethodDef pending_frame_object_methods[] =
>      pending_framepy_architecture, METH_NOARGS,
>      "architecture () -> gdb.Architecture\n"
>      "The architecture for this PendingFrame." },
> +  { "level", pending_framepy_level, METH_NOARGS,
> +    "The stack level of this frame." },
>    {NULL}  /* Sentinel */
>  };
>  
> diff --git a/gdb/testsuite/gdb.python/py-frame.exp b/gdb/testsuite/gdb.python/py-frame.exp
> index a6a5c0de726..05c7fb00dfd 100644
> --- a/gdb/testsuite/gdb.python/py-frame.exp
> +++ b/gdb/testsuite/gdb.python/py-frame.exp
> @@ -70,6 +70,17 @@ gdb_test "up" ".*" ""
>  
>  gdb_py_test_silent_cmd "python f1 = gdb.selected_frame ()" "get second frame" 0
>  gdb_py_test_silent_cmd "python f0 = f1.newer ()" "get first frame" 0
> +gdb_py_test_silent_cmd "python f2 = f1.older ()" "get last frame" 0
> +
> +# Check the Frame.level method.
> +gdb_test "python print ('bframe.level = %d' % bframe.level ())" \
> +    "bframe\\.level = 0"
> +gdb_test "python print ('f0.level = %d' % f0.level ())" \
> +    "f0\\.level = 0"
> +gdb_test "python print ('f1.level = %d' % f1.level ())" \
> +    "f1\\.level = 1"
> +gdb_test "python print ('f2.level = %d' % f2.level ())" \
> +    "f2\\.level = 2"
>  
>  gdb_test "python print (f1 == gdb.newest_frame())" False \
>      "selected frame -vs- newest frame"
> diff --git a/gdb/testsuite/gdb.python/py-pending-frame-level.c b/gdb/testsuite/gdb.python/py-pending-frame-level.c
> new file mode 100644
> index 00000000000..5e5495c1d71
> --- /dev/null
> +++ b/gdb/testsuite/gdb.python/py-pending-frame-level.c
> @@ -0,0 +1,49 @@
> +/* This test program is part of GDB, the GNU debugger.
> +
> +   Copyright 2021 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/>.  */
> +
> +volatile int global_var;
> +
> +void __attribute__ ((noinline))
> +f0 (void)
> +{
> +  ++global_var;		/* Break here.  */
> +}
> +
> +void __attribute__ ((noinline))
> +f1 (void)
> +{
> +  f0 ();
> +}
> +
> +void __attribute__ ((noinline))
> +f2 (void)
> +{
> +  f1 ();
> +}
> +
> +void __attribute__ ((noinline))
> +f3 (void)
> +{
> +  f2 ();
> +}
> +
> +int
> +main (void)
> +{
> +  f3 ();
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.python/py-pending-frame-level.exp b/gdb/testsuite/gdb.python/py-pending-frame-level.exp
> new file mode 100644
> index 00000000000..1aadcaeacae
> --- /dev/null
> +++ b/gdb/testsuite/gdb.python/py-pending-frame-level.exp
> @@ -0,0 +1,65 @@
> +# Copyright (C) 2021 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.PendingFrame.level method.
> +
> +load_lib gdb-python.exp
> +
> +standard_testfile
> +
> +if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
> +    return -1
> +}
> +
> +# Skip all tests if Python scripting is not enabled.
> +if { [skip_python_tests] } { continue }
> +
> +if ![runto_main] then {
> +    fail "can't run to main"
> +    return 0
> +}
> +
> +set pyfile [gdb_remote_download host ${srcdir}/${subdir}/${testfile}.py]
> +
> +gdb_breakpoint [gdb_get_line_number "Break here"]
> +gdb_continue_to_breakpoint "stop at test breakpoint"
> +
> +# An initial look at the stack to ensure it is correct.
> +gdb_test_sequence "bt"  "Initial backtrace" {
> +    "\\r\\n#0 \[^\r\n\]* f0 \\(\\) at "
> +    "\\r\\n#1 \[^\r\n\]* f1 \\(\\) at "
> +    "\\r\\n#2 \[^\r\n\]* f2 \\(\\) at "
> +    "\\r\\n#3 \[^\r\n\]* f3 \\(\\) at "
> +    "\\r\\n#4 \[^\r\n\]* main \\(\\) at "
> +}
> +
> +# Load the script containing the unwinder.
> +gdb_test_no_output "source ${pyfile}"\
> +    "import python scripts"
> +
> +# Now look at the stack again, we should see output from the Python
> +# unwinder mixed in.
> +gdb_test_sequence "bt"  "Backtrace with extra Python output" {
> +    "Func f0, Level 0"
> +    "Func f1, Level 1"
> +    "\\r\\n#0 \[^\r\n\]* f0 \\(\\) at "
> +    "\\r\\n#1 \[^\r\n\]* f1 \\(\\) at "
> +    "Func f2, Level 2"
> +    "\\r\\n#2 \[^\r\n\]* f2 \\(\\) at "
> +    "Func f3, Level 3"
> +    "\\r\\n#3 \[^\r\n\]* f3 \\(\\) at "
> +    "Func main, Level 4"
> +    "\\r\\n#4 \[^\r\n\]* main \\(\\) at "
> +}
> diff --git a/gdb/testsuite/gdb.python/py-pending-frame-level.py b/gdb/testsuite/gdb.python/py-pending-frame-level.py
> new file mode 100644
> index 00000000000..182edcdc0df
> --- /dev/null
> +++ b/gdb/testsuite/gdb.python/py-pending-frame-level.py
> @@ -0,0 +1,55 @@
> +# Copyright (C) 2021 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/>.
> +
> +import gdb
> +from gdb.unwinder import Unwinder
> +
> +
> +class FrameId(object):
> +    def __init__(self, sp, pc):
> +        self._sp = sp
> +        self._pc = pc
> +
> +    @property
> +    def sp(self):
> +        return self._sp
> +
> +    @property
> +    def pc(self):
> +        return self._pc
> +
> +
> +class TestUnwinder(Unwinder):
> +    def __init__(self):
> +        Unwinder.__init__(self, "show level")
> +
> +    def __call__(self, pending_frame):
> +        pc_desc = pending_frame.architecture().registers().find("pc")
> +        pc = pending_frame.read_register(pc_desc)
> +
> +        block = gdb.block_for_pc(int(pc))
> +        if block == None:
> +            return None
> +        func = block.function
> +        if func == None:
> +            return None
> +
> +        print("Func %s, Level %d" % (str(func), pending_frame.level()))
> +
> +        # This unwinder never claims any frames.
> +        return None
> +
> +
> +gdb.unwinder.register_unwinder(None, TestUnwinder(), True)
> -- 
> 2.25.4
>