Re: [PATCH v2] Fix raw-frame-arguments in combination with frame-filters

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

* Hannes Domani via Gdb-patches <gdb-patches@sourceware.org> [2021-01-31 14:46:11 +0100]:

> Currently, if frame-filters are active, raw-values is used instead of
> raw-frame-arguments to decide if a pretty-printer should be invoked for
> frame arguments in a backtrace.
>
> In this example, "super struct" is the output of the pretty-printer:
>
>     (gdb) disable frame-filter global BasicFrameFilter
>     (gdb) bt
>     #0  foo (x=42, ss=super struct = {...}) at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:47
>     #1  0x004016aa in main () at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:57
>
> If no frame-filter is active, then the raw-values print option does not
> affect the backtrace output:
>
>     (gdb) set print raw-values on
>     (gdb) bt
>     #0  foo (x=42, ss=super struct = {...}) at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:47
>     #1  0x004016aa in main () at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:57
>     (gdb) set print raw-values off
>
> Instead, the raw-frame-arguments option disables the pretty-printer in the
> backtrace:
>
>     (gdb) bt -raw-frame-arguments on
>     #0  foo (x=42, ss=...) at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:47
>     #1  0x004016aa in main () at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:57
>
> But if a frame-filter is active, the same rules don't apply.
> The option raw-frame-arguments is ignored, but raw-values decides if the
> pretty-printer is used:
>
>     (gdb) enable frame-filter global BasicFrameFilter
>     (gdb) bt
>     #0  foo (x=42, ss=super struct = {...}) at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:47
>     #1  0x004016aa in main () at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:57
>     (gdb) set print raw-values on
>     (gdb) bt
>     #0  foo (x=42, ss=...) at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:47
>     #1  0x004016aa in main () at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:57
>     (gdb) set print raw-values off
>     (gdb) bt -raw-frame-arguments on
>     #0  foo (x=42, ss=super struct = {...}) at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:47
>     #1  0x004016aa in main () at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:57
>
> So this adds the PRINT_RAW_FRAME_ARGUMENTS flag to frame_filter_flag, which
> is then used in the frame-filter to override the raw flag in enumerate_args.
>
> Then the output is the same if a frame-filter is active, the pretty-printer
> for backtraces is only disabled with the raw-frame-arguments option:
>
>     (gdb) enable frame-filter global BasicFrameFilter
>     (gdb) bt
>     #0  foo (x=42, ss=super struct = {...}) at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:47
>     #1  0x004016aa in main () at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:57
>     (gdb) set print raw-values on
>     (gdb) bt
>     #0  foo (x=42, ss=super struct = {...}) at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:47
>     #1  0x004016aa in main () at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:57
>     (gdb) set print raw-values off
>     (gdb) bt -raw-frame-arguments on
>     #0  foo (x=42, ss=...) at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:47
>     #1  0x004016aa in main () at C:/src/repos/gdb-testsuite/gdb/testsuite/gdb.python/py-frame-args.c:57

Thanks for working on improving this behaviour.

I think that there's something weird going on with the MI behaviour.

I ran the py-frame-args.c test program, stopped at line 47, then I see
this:

  (gdb) set print raw-frame-arguments off
  (gdb) set print raw-values off
  (gdb) interpreter-exec mi "-stack-list-variables 1"
  ^done,variables=[{name="x",arg="1",value="42"},{name="ss",arg="1",value="super struct = {\n  a = m=<1>,\n  b = m=<2>\n}"}]
  (gdb) interpreter-exec mi "-stack-list-arguments 1"
  ^done,stack-args=[frame={level="0",args=[{name="x",value="42"},{name="ss",value="super struct = {\n  a = m=<1>,\n  b = m=<2>\n}"}]},frame={level="1",args=[]}]

  (gdb) set print raw-frame-arguments on
  (gdb) interpreter-exec mi "-stack-list-arguments 1"
  ^done,stack-args=[frame={level="0",args=[{name="x",value="42"},{name="ss",value="super struct = {\n  a = m=<1>,\n  b = m=<2>\n}"}]},frame={level="1",args=[]}]
  (gdb) interpreter-exec mi "-stack-list-variables 1"
  ^done,variables=[{name="x",arg="1",value="42"},{name="ss",arg="1",value="super struct = {\n  a = m=<1>,\n  b = m=<2>\n}"}]

  (gdb) set print raw-values on
  (gdb) interpreter-exec mi "-stack-list-arguments 1"
  ^done,stack-args=[frame={level="0",args=[{name="x",value="42"},{name="ss",value="super struct = {\n  a = m=<1>,\n  b = m=<2>\n}"}]},frame={level="1",args=[]}]
  (gdb) interpreter-exec mi "-stack-list-variables 1"
  ^done,variables=[{name="x",arg="1",value="42"},{name="ss",arg="1",value="{\n  a = {\n    m = 1\n  },\n  b = {\n    m = 2\n  }\n}"}]
  (gdb)

The summary is:

  - when just doing '-stack-list-arguments' neither 'set print
    raw-values' or 'set print raw-frame-arguments' seem to effect what
    is printed, and

  - when doing '-stack-list-variables', 'set print raw-values' seems
    to effect how arguments are printed, but 'set print
    raw-frame-arguments' does not.

I guess I would expect 'set print raw-frame-arguments' to be the
controlling option in both these cases.

Thanks,
Andrew

>
> gdb/ChangeLog:
>
> 2021-01-31  Hannes Domani  <ssbssa@yahoo.de>
>
> 	* extension.h (enum frame_filter_flag): Add
> 	PRINT_RAW_FRAME_ARGUMENTS.
> 	* python/py-framefilter.c (enumerate_args): Override raw flag.
> 	raw_frame_args argument.
> 	(py_mi_print_variables): Forward raw flag.
> 	(py_print_args): Forward raw_frame_args flag.
> 	(py_print_frame): Handle PRINT_RAW_FRAME_ARGUMENTS.
> 	* stack.c (backtrace_command_1): Set PRINT_RAW_FRAME_ARGUMENTS.
>
> gdb/testsuite/ChangeLog:
>
> 2021-01-31  Hannes Domani  <ssbssa@yahoo.de>
>
> 	* gdb.python/py-frame-args.exp: Add bt raw-frame-arguments tests.
> 	* gdb.python/py-frame-args.py: Add basic frame-filter.
> ---
> v2:
> - More detailed commit message describing the problem.
> ---
>  gdb/extension.h                            |  4 ++++
>  gdb/python/py-framefilter.c                | 14 ++++++++++----
>  gdb/stack.c                                |  2 ++
>  gdb/testsuite/gdb.python/py-frame-args.exp | 20 ++++++++++++++++++++
>  gdb/testsuite/gdb.python/py-frame-args.py  | 13 +++++++++++++
>  5 files changed, 49 insertions(+), 4 deletions(-)
>
> diff --git a/gdb/extension.h b/gdb/extension.h
> index a505c68d25e..7067e232cd3 100644
> --- a/gdb/extension.h
> +++ b/gdb/extension.h
> @@ -103,6 +103,10 @@ enum frame_filter_flag
>
>      /* Set this flag if elided frames should not be printed.  */
>      PRINT_HIDE = 1 << 5,
> +
> +    /* Set this flag if pretty printers for frame arguments should not
> +       be invoked.  */
> +    PRINT_RAW_FRAME_ARGUMENTS = 1 << 6,
>    };
>
>  DEF_ENUM_FLAGS_TYPE (enum frame_filter_flag, frame_filter_flags);
> diff --git a/gdb/python/py-framefilter.c b/gdb/python/py-framefilter.c
> index 6dd741ab704..e53e3409235 100644
> --- a/gdb/python/py-framefilter.c
> +++ b/gdb/python/py-framefilter.c
> @@ -422,12 +422,14 @@ static enum ext_lang_bt_status
>  enumerate_args (PyObject *iter,
>  		struct ui_out *out,
>  		enum ext_lang_frame_args args_type,
> +		bool raw_frame_args,
>  		int print_args_field,
>  		struct frame_info *frame)
>  {
>    struct value_print_options opts;
>
>    get_user_print_options (&opts);
> +  opts.raw = raw_frame_args;
>
>    if (args_type == CLI_SCALAR_VALUES)
>      {
> @@ -655,8 +657,8 @@ py_mi_print_variables (PyObject *filter, struct ui_out *out,
>    ui_out_emit_list list_emitter (out, "variables");
>
>    if (args_iter != Py_None
> -      && (enumerate_args (args_iter.get (), out, args_type, 1, frame)
> -	  == EXT_LANG_BT_ERROR))
> +      && (enumerate_args (args_iter.get (), out, args_type, opts->raw, 1,
> +			  frame) == EXT_LANG_BT_ERROR))
>      return EXT_LANG_BT_ERROR;
>
>    if (locals_iter != Py_None
> @@ -701,6 +703,7 @@ static enum ext_lang_bt_status
>  py_print_args (PyObject *filter,
>  	       struct ui_out *out,
>  	       enum ext_lang_frame_args args_type,
> +	       bool raw_frame_args,
>  	       struct frame_info *frame)
>  {
>    gdbpy_ref<> args_iter (get_py_iter_from_func (filter, "frame_args"));
> @@ -726,7 +729,8 @@ py_print_args (PyObject *filter,
>  	}
>      }
>    else if (args_iter != Py_None
> -	   && (enumerate_args (args_iter.get (), out, args_type, 0, frame)
> +	   && (enumerate_args (args_iter.get (), out, args_type,
> +			       raw_frame_args, 0, frame)
>  	       == EXT_LANG_BT_ERROR))
>      return EXT_LANG_BT_ERROR;
>
> @@ -957,7 +961,9 @@ py_print_frame (PyObject *filter, frame_filter_flags flags,
>       wrong.  */
>    if (print_args && (location_print || out->is_mi_like_p ()))
>      {
> -      if (py_print_args (filter, out, args_type, frame) == EXT_LANG_BT_ERROR)
> +      bool raw_frame_args = (flags & PRINT_RAW_FRAME_ARGUMENTS) != 0;
> +      if (py_print_args (filter, out, args_type, raw_frame_args, frame)
> +	  == EXT_LANG_BT_ERROR)
>  	return EXT_LANG_BT_ERROR;
>      }
>
> diff --git a/gdb/stack.c b/gdb/stack.c
> index bce6a2f42f8..dbca5ade1c2 100644
> --- a/gdb/stack.c
> +++ b/gdb/stack.c
> @@ -2028,6 +2028,8 @@ backtrace_command_1 (const frame_print_options &fp_opts,
>      flags |= PRINT_LOCALS;
>    if (bt_opts.hide)
>      flags |= PRINT_HIDE;
> +  if (fp_opts.print_raw_frame_arguments)
> +    flags |= PRINT_RAW_FRAME_ARGUMENTS;
>
>    if (!bt_opts.no_filters)
>      {
> diff --git a/gdb/testsuite/gdb.python/py-frame-args.exp b/gdb/testsuite/gdb.python/py-frame-args.exp
> index 5d35323c0e6..dae0c0ac29e 100644
> --- a/gdb/testsuite/gdb.python/py-frame-args.exp
> +++ b/gdb/testsuite/gdb.python/py-frame-args.exp
> @@ -34,6 +34,26 @@ gdb_test_no_output "source ${remote_python_file}" "load python file"
>  gdb_breakpoint [gdb_get_line_number "break-here"]
>  gdb_continue_to_breakpoint "break-here" ".* break-here .*"
>
> +# Test raw-frame-arguments on backtrace with and without frame-filter
> +foreach_with_prefix filtered {enable disable} {
> +    gdb_test_no_output "$filtered frame-filter global BasicFrameFilter"
> +
> +    gdb_test "bt 1" \
> +	".*foo \\(x=42, ss=super struct = {\[.\]{3}}\\).*" \
> +	"bt pretty"
> +
> +    gdb_test "bt -raw-frame-arguments on 1" \
> +	".*foo \\(x=42, ss=\[.\]{3}\\).*" \
> +	"bt raw"
> +
> +    # "set print raw-values" should not affect frame arguments
> +    gdb_test_no_output "set print raw-values on"
> +    gdb_test "bt 1" \
> +	".*foo \\(x=42, ss=super struct = {\[.\]{3}}\\).*" \
> +	"bt pretty,raw-values"
> +    gdb_test_no_output "set print raw-values off"
> +}
> +
>  # Test all combinations with raw off.
>
>  gdb_test_no_output "set print raw-frame-arguments off"
> diff --git a/gdb/testsuite/gdb.python/py-frame-args.py b/gdb/testsuite/gdb.python/py-frame-args.py
> index d80d761b995..3b65eed0dad 100644
> --- a/gdb/testsuite/gdb.python/py-frame-args.py
> +++ b/gdb/testsuite/gdb.python/py-frame-args.py
> @@ -73,3 +73,16 @@ pretty_printers_dict = {}
>
>  register_pretty_printers ()
>  gdb.pretty_printers.append (lookup_function)
> +
> +
> +class BasicFrameFilter (object):
> +    def __init__ (self):
> +        self.name = "BasicFrameFilter"
> +        self.priority = 100
> +        self.enabled = True
> +        gdb.frame_filters[self.name] = self
> +
> +    def filter (self, frame_iter):
> +        return frame_iter
> +
> +BasicFrameFilter ()
> --
> 2.30.0
>