[PING] [PATCH v4] [PR mi/29554] New PRINT-VALUES option '--scalar-values'.

[Gareth Rees <grees@undo.io>]

Thanks to Andrew Burgess and Eli Zaretskii for reviewing. I've
addressed all the comments, so let me know how I can help progress
this patch.

On Mon, 26 Sept 2022 at 13:46, Gareth Rees <grees@undo.io> wrote:
>
> SUMMARY
>
> The '--simple-values' argument to '-stack-list-arguments' and similar
> GDB/MI commands does not take reference types into account, so that
> references to arbitrarily large structures are considered "simple" and
> printed. This means that the '--simple-values' argument cannot be used
> by IDEs when tracing the stack due to the time taken to print large
> structures passed by reference.
>
> DETAILS
>
> Various GDB/MI commands ('-stack-list-arguments', '-stack-list-locals',
> '-stack-list-variables' and so on) take a PRINT-VALUES argument which
> may be '--no-values' (0), '--all-values' (1) or '--simple-values' (2).
> In the '--simple-values' case, the command is supposed to print the
> name, type, and value of variables with simple types, and print only the
> name and type of variables with compound types.
>
> The '--simple-values' argument ought to be suitable for IDEs that need
> to update their user interface with the program's call stack every time
> the program stops. However, it does not take C++ reference types into
> account, and this makes the argument unsuitable for this purpose.
>
> For example, consider the following C++ program:
>
>     struct s {
>         int v[10];
>     };
>
>     int
>     sum(const struct s &s)
>     {
>         int total =3D 0;
>         for (int i =3D 0; i < 10; ++i) total +=3D s.v[i];
>         return total;
>     }
>
>     int
>     main(void)
>     {
>         struct s s =3D { { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 } };
>         return sum(s);
>     }
>
> If we start GDB in MI mode and continue to 'sum', the behaviour of
> '-stack-list-arguments' is as follows:
>
>     (gdb)
>     -stack-list-arguments --simple-values
>     ^done,stack-args=3D[frame=3D{level=3D"0",args=3D[{name=3D"s",type=3D"=
const s &",value=3D"@0x7fffffffe310: {v =3D {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}=
}"}]},frame=3D{level=3D"1",args=3D[]}]
>
> Note that the value of the argument 's' was printed, even though 's' is
> a reference to a structure, which is not a simple value.
>
> See https://github.com/microsoft/MIEngine/pull/673 for a case where this
> behaviour caused Microsoft to avoid the use of '--simple-values' in
> their MIEngine debug adapter, because it caused Visual Studio Code to
> take too long to refresh the call stack in the user interface.
>
> SOLUTIONS
>
> There are two ways we could fix this problem, depending on whether we
> consider the current behaviour to be a bug that can be fixed.
>
> 1. If the current behaviour is a bug that can be fixed, then we can
>    update the behaviour of '--simple-values' so that it takes
>    reference types into account: that is, a value is simple if it is
>    neither an array, struct, or union, nor a reference to an array,
>    struct or union.
>
>    In this case we must add a feature to the '-list-features' command so
>    that IDEs can detect that it is safe to use the '--simple-values'
>    argument when refreshing the call stack.
>
> 2. If the current behaviour is not a bug, or cannot be changed due to
>    backwards compatibility concerns, then we can add a new option for
>    the PRINT-VALUES argument, for example, '--scalar-values' (3), that
>    would be suitable for use by IDEs.
>
>    In this case we must add a feature to the '-list-features' command so
>    that IDEs can detect that the '--scalar-values' argument is
>    available for use when refreshing the call stack.
>
> PATCH
>
> This patch implements solution (2), adding a '--scalar-values' option
> for the PRINT-VALUES argument to '-stack-list-arguments' and similar
> commands. This option prints the value only for scalars and so matches
> the behaviour of the 'scalars' argument to the 'set print
> frame-arguments' command. References to structures are not scalars,
> and so the option is suitable for use by IDEs.
>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=3D29554
> ---
>  gdb/NEWS                                     |  9 +++
>  gdb/doc/gdb.texinfo                          | 59 ++++++++++++--------
>  gdb/extension.h                              |  3 +
>  gdb/mi/mi-cmd-stack.c                        | 35 ++++++++----
>  gdb/mi/mi-cmd-var.c                          | 26 ++++++---
>  gdb/mi/mi-cmds.h                             |  8 ++-
>  gdb/mi/mi-main.c                             | 54 ++++++++++--------
>  gdb/mi/mi-parse.c                            |  8 ++-
>  gdb/python/py-framefilter.c                  | 23 ++++----
>  gdb/testsuite/gdb.mi/mi-stack.exp            | 17 +++++-
>  gdb/testsuite/gdb.mi/print-scalar-values.cc  | 58 +++++++++++++++++++
>  gdb/testsuite/gdb.mi/print-scalar-values.exp | 51 +++++++++++++++++
>  12 files changed, 272 insertions(+), 79 deletions(-)
>  create mode 100644 gdb/testsuite/gdb.mi/print-scalar-values.cc
>  create mode 100644 gdb/testsuite/gdb.mi/print-scalar-values.exp
>
> diff --git a/gdb/NEWS b/gdb/NEWS
> index dee0ac2ecd8..62b15094dee 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -114,6 +114,15 @@ maintenance info line-table
>    entry corresponds to an address where a breakpoint should be placed
>    to be at the first instruction past a function's prologue.
>
> +* MI changes
> +
> +  ** The '-stack-list-arguments', '-stack-list-locals',
> +     '-stack-list-variables', and '-var-list-children' commands
> +     support the '--scalar-values' option, which requests the command
> +     to print values only for scalar types.  Support for this feature
> +     can be verified by using the '-list-features' command, which
> +     should contain "scalar-values".
> +
>  * New targets
>
>  GNU/Linux/LoongArch (gdbserver)        loongarch*-*-linux*
> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
> index 238a49b027d..b2b53de1022 100644
> --- a/gdb/doc/gdb.texinfo
> +++ b/gdb/doc/gdb.texinfo
> @@ -33326,12 +33326,14 @@ larger than the actual number of frames.  On th=
e other hand,
>  @var{high-frame} may be larger than the actual number of frames, in
>  which case only existing frames will be returned.
>
> -If @var{print-values} is 0 or @code{--no-values}, print only the names o=
f
> -the variables; if it is 1 or @code{--all-values}, print also their
> -values; and if it is 2 or @code{--simple-values}, print the name,
> -type and value for simple data types, and the name and type for arrays,
> -structures and unions.  If the option @code{--no-frame-filters} is
> -supplied, then Python frame filters will not be executed.
> +If @var{print-values} is 0 or @code{--no-values}, print only the names
> +of the variables; if it is 1 or @code{--all-values}, print also their
> +values; if it is 2 or @code{--simple-values}, print the name, type and
> +value for simple data types, and the name and type for arrays,
> +structures and unions; and if it is 3 or @code{--scalar-values}, print
> +the name, type and value for scalar data types, and the name and type
> +otherwise.  If the option @code{--no-frame-filters} is supplied, then
> +Python frame filters will not be executed.
>
>  If the @code{--skip-unavailable} option is specified, arguments that
>  are not available are not listed.  Partially available arguments
> @@ -33549,13 +33551,15 @@ Show a single frame:
>  Display the local variable names for the selected frame.  If
>  @var{print-values} is 0 or @code{--no-values}, print only the names of
>  the variables; if it is 1 or @code{--all-values}, print also their
> -values; and if it is 2 or @code{--simple-values}, print the name,
> -type and value for simple data types, and the name and type for arrays,
> -structures and unions.  In this last case, a frontend can immediately
> -display the value of simple data types and create variable objects for
> -other data types when the user wishes to explore their values in
> -more detail.  If the option @code{--no-frame-filters} is supplied, then
> -Python frame filters will not be executed.
> +values; if it is 2 or @code{--simple-values}, print the name, type and
> +value for simple data types, and the name and type for arrays,
> +structures and unions; and if it is 3 or @code{--scalar-values}, print
> +the name, type and value for scalar data types, and the name and type
> +otherwise.  In the last two cases, a frontend can immediately display
> +the value of simple or scalar data types and create variable objects
> +for other data types when the user wishes to explore their values in
> +more detail.  If the option @code{--no-frame-filters} is supplied,
> +then Python frame filters will not be executed.
>
>  If the @code{--skip-unavailable} option is specified, local variables
>  that are not available are not listed.  Partially available local
> @@ -33594,13 +33598,16 @@ This command is deprecated in favor of the
>   -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @va=
r{print-values}
>  @end smallexample
>
> -Display the names of local variables and function arguments for the sele=
cted frame.  If
> -@var{print-values} is 0 or @code{--no-values}, print only the names of
> -the variables; if it is 1 or @code{--all-values}, print also their
> -values; and if it is 2 or @code{--simple-values}, print the name,
> -type and value for simple data types, and the name and type for arrays,
> -structures and unions.  If the option @code{--no-frame-filters} is
> -supplied, then Python frame filters will not be executed.
> +Display the names of local variables and function arguments for the
> +selected frame.  If @var{print-values} is 0 or @code{--no-values},
> +print only the names of the variables; if it is 1 or
> +@code{--all-values}, print also their values; if it is 2 or
> +@code{--simple-values}, print the name, type and value for simple data
> +types, and the name and type for arrays, structures and unions; and if
> +it is 3 or @code{--scalar-values}, print the name, type and value for
> +scalar data types, and the name and type otherwise.  If the option
> +@code{--no-frame-filters} is supplied, then Python frame filters will
> +not be executed.
>
>  If the @code{--skip-unavailable} option is specified, local variables
>  and arguments that are not available are not listed.  Partially
> @@ -34029,9 +34036,10 @@ create variable objects for them, if they do not=
 already exist.  With
>  a single argument or if @var{print-values} has a value of 0 or
>  @code{--no-values}, print only the names of the variables; if
>  @var{print-values} is 1 or @code{--all-values}, also print their
> -values; and if it is 2 or @code{--simple-values} print the name and
> -value for simple data types and just the name for arrays, structures
> -and unions.
> +values; if it is 2 or @code{--simple-values} print the name and value
> +for simple data types and just the name for arrays, structures and
> +unions; and if it is 3 or @code{--scalar-values}, print the name and
> +value for scalar data types, and just the name otherwise.
>
>  @var{from} and @var{to}, if specified, indicate the range of children
>  to report.  If @var{from} or @var{to} is less than zero, the range is
> @@ -37295,6 +37303,11 @@ option (@pxref{GDB/MI Program Execution}).
>  @item data-disassemble-a-option
>  Indicates that the @code{-data-disassemble} command supports the @option=
{-a}
>  option (@pxref{GDB/MI Data Manipulation}).
> +@item scalar-values
> +Indicates that the @code{-stack-list-arguments},
> +@code{-stack-list-locals}, @code{-stack-list-variables}, and
> +@code{-var-list-children} commands support the
> +@option{--scalar-values} option (@pxref{GDB/MI Stack Manipulation}).
>  @end ftable
>
>  @subheading The @code{-list-target-features} Command
> diff --git a/gdb/extension.h b/gdb/extension.h
> index 47839ea50be..16d12f00f41 100644
> --- a/gdb/extension.h
> +++ b/gdb/extension.h
> @@ -121,6 +121,9 @@ enum ext_lang_frame_args
>         arguments when invoked from the MI. */
>      MI_PRINT_SIMPLE_VALUES =3D PRINT_SIMPLE_VALUES,
>
> +    /* Print only scalar values for arguments when invoked from the MI. =
 */
> +    MI_PRINT_SCALAR_VALUES =3D PRINT_SCALAR_VALUES,
> +
>      /* Print only scalar values for arguments when invoked from the CLI.=
 */
>      CLI_SCALAR_VALUES,
>
> diff --git a/gdb/mi/mi-cmd-stack.c b/gdb/mi/mi-cmd-stack.c
> index 0fe204dbc66..d3ae350f166 100644
> --- a/gdb/mi/mi-cmd-stack.c
> +++ b/gdb/mi/mi-cmd-stack.c
> @@ -494,6 +494,7 @@ list_arg_or_local (const struct frame_arg *arg, enum =
what_to_list what,
>    gdb_assert ((values =3D=3D PRINT_NO_VALUES && arg->val =3D=3D NULL
>                && arg->error =3D=3D NULL)
>               || values =3D=3D PRINT_SIMPLE_VALUES
> +             || values =3D=3D PRINT_SCALAR_VALUES
>               || (values =3D=3D PRINT_ALL_VALUES
>                   && (arg->val !=3D NULL || arg->error !=3D NULL)));
>    gdb_assert (arg->entry_kind =3D=3D print_entry_values_no
> @@ -525,7 +526,8 @@ list_arg_or_local (const struct frame_arg *arg, enum =
what_to_list what,
>    if (what =3D=3D all && arg->sym->is_argument ())
>      uiout->field_signed ("arg", 1);
>
> -  if (values =3D=3D PRINT_SIMPLE_VALUES)
> +  if (values =3D=3D PRINT_SIMPLE_VALUES
> +      || values =3D=3D PRINT_SCALAR_VALUES)
>      {
>        check_typedef (arg->sym->type ());
>        type_print (arg->sym->type (), "", &stb, -1);
> @@ -557,6 +559,25 @@ list_arg_or_local (const struct frame_arg *arg, enum=
 what_to_list what,
>      }
>  }
>
> +/* Print SYM according to VALUES?  */
> +
> +static bool
> +print_symbol_p (struct symbol *sym, enum print_values values)
> +{
> +  switch (values)
> +    {
> +    default:
> +    case PRINT_NO_VALUES:
> +      return false;
> +    case PRINT_ALL_VALUES:
> +      return true;
> +    case PRINT_SIMPLE_VALUES:
> +      return mi_simple_values_type_p (sym->type ());
> +    case PRINT_SCALAR_VALUES:
> +      return val_print_scalar_type_p (sym->type ());
> +    }
> +}
> +
>  /* Print a list of the objects for the frame FI in a certain form,
>     which is determined by VALUES.  The objects can be locals,
>     arguments or both, which is determined by WHAT.  If SKIP_UNAVAILABLE
> @@ -571,7 +592,6 @@ list_args_or_locals (const frame_print_options &fp_op=
ts,
>    const struct block *block;
>    struct symbol *sym;
>    struct block_iterator iter;
> -  struct type *type;
>    const char *name_of_result;
>    struct ui_out *uiout =3D current_uiout;
>
> @@ -647,21 +667,12 @@ list_args_or_locals (const frame_print_options &fp_=
opts,
>               entryarg.sym =3D sym2;
>               entryarg.entry_kind =3D print_entry_values_no;
>
> -             switch (values)
> +             if (print_symbol_p (sym, values))
>                 {
> -               case PRINT_SIMPLE_VALUES:
> -                 type =3D check_typedef (sym2->type ());
> -                 if (type->code () !=3D TYPE_CODE_ARRAY
> -                     && type->code () !=3D TYPE_CODE_STRUCT
> -                     && type->code () !=3D TYPE_CODE_UNION)
> -                   {
> -               case PRINT_ALL_VALUES:
>                   if (sym->is_argument ())
>                     read_frame_arg (fp_opts, sym2, fi, &arg, &entryarg);
>                   else
>                     read_frame_local (sym2, fi, &arg);
> -                   }
> -                 break;
>                 }
>
>               if (arg.entry_kind !=3D print_entry_values_only)
> diff --git a/gdb/mi/mi-cmd-var.c b/gdb/mi/mi-cmd-var.c
> index 3db09cf7815..064d13a3729 100644
> --- a/gdb/mi/mi-cmd-var.c
> +++ b/gdb/mi/mi-cmd-var.c
> @@ -32,6 +32,7 @@
>  #include "mi-parse.h"
>  #include "gdbsupport/gdb_optional.h"
>  #include "inferior.h"
> +#include "valprint.h"
>
>  static void varobj_update_one (struct varobj *var,
>                                enum print_values print_values,
> @@ -334,15 +335,26 @@ mi_print_value_p (struct varobj *var, enum print_va=
lues print_values)
>    type =3D varobj_get_gdb_type (var);
>    if (type =3D=3D NULL)
>      return 1;
> +  else if (print_values =3D=3D PRINT_SCALAR_VALUES)
> +    return val_print_scalar_type_p (type);
>    else
> -    {
> -      type =3D check_typedef (type);
> +    return mi_simple_values_type_p (type);
> +}
> +
> +/* See mi-cmds.h.  */
>
> -      /* For PRINT_SIMPLE_VALUES, only print the value if it has a type
> -        and that type is not a compound type.  */
> -      return (type->code () !=3D TYPE_CODE_ARRAY
> -             && type->code () !=3D TYPE_CODE_STRUCT
> -             && type->code () !=3D TYPE_CODE_UNION);
> +bool
> +mi_simple_values_type_p (struct type *type)
> +{
> +  type =3D check_typedef (type);
> +  switch (type->code ())
> +    {
> +    case TYPE_CODE_ARRAY:
> +    case TYPE_CODE_STRUCT:
> +    case TYPE_CODE_UNION:
> +      return false;
> +    default:
> +      return true;
>      }
>  }
>
> diff --git a/gdb/mi/mi-cmds.h b/gdb/mi/mi-cmds.h
> index 9ffb11bf997..56c3ccb8b8a 100644
> --- a/gdb/mi/mi-cmds.h
> +++ b/gdb/mi/mi-cmds.h
> @@ -29,7 +29,8 @@
>  enum print_values {
>     PRINT_NO_VALUES,
>     PRINT_ALL_VALUES,
> -   PRINT_SIMPLE_VALUES
> +   PRINT_SIMPLE_VALUES,
> +   PRINT_SCALAR_VALUES
>  };
>
>  typedef void (mi_cmd_argv_ftype) (const char *command, char **argv, int =
argc);
> @@ -226,4 +227,9 @@ using remove_mi_cmd_entries_ftype
>    =3D gdb::function_view<bool (mi_command *)>;
>  extern void remove_mi_cmd_entries (remove_mi_cmd_entries_ftype callback)=
;
>
> +/* Return true if type is suitable for printing with PRINT_SIMPLE_VALUES=
: that
> +   is, if type is not an array, structure or union.  */
> +
> +extern bool mi_simple_values_type_p (struct type *type);
> +
>  #endif /* MI_MI_CMDS_H */
> diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
> index b758f398e2a..2e70bcde2da 100644
> --- a/gdb/mi/mi-main.c
> +++ b/gdb/mi/mi-main.c
> @@ -1663,6 +1663,7 @@ mi_cmd_list_features (const char *command, char **a=
rgv, int argc)
>        uiout->field_string (NULL, "undefined-command-error-code");
>        uiout->field_string (NULL, "exec-run-start-option");
>        uiout->field_string (NULL, "data-disassemble-a-option");
> +      uiout->field_string (NULL, "scalar-values");
>
>        if (ext_lang_initialized_p (get_ext_lang_defn (EXT_LANG_PYTHON)))
>         uiout->field_string (NULL, "python");
> @@ -2456,20 +2457,39 @@ mi_cmd_ada_task_info (const char *command, char *=
*argv, int argc)
>    print_ada_task_info (current_uiout, argv[0], current_inferior ());
>  }
>
> +/* Print VAL according to VALUES?  */
> +
> +static bool
> +print_value_p (struct value *val, enum print_values values)
> +{
> +  switch (values)
> +    {
> +    default:
> +    case PRINT_NO_VALUES:
> +      return false;
> +    case PRINT_ALL_VALUES:
> +      return true;
> +    case PRINT_SIMPLE_VALUES:
> +      return mi_simple_values_type_p (value_type (val));
> +    case PRINT_SCALAR_VALUES:
> +      return val_print_scalar_type_p (value_type (val));
> +    }
> +}
> +
>  /* Print EXPRESSION according to VALUES.  */
>
>  static void
>  print_variable_or_computed (const char *expression, enum print_values va=
lues)
>  {
>    struct value *val;
> -  struct type *type;
>    struct ui_out *uiout =3D current_uiout;
>
>    string_file stb;
>
>    expression_up expr =3D parse_expression (expression);
>
> -  if (values =3D=3D PRINT_SIMPLE_VALUES)
> +  if (values =3D=3D PRINT_SIMPLE_VALUES
> +      || values =3D=3D PRINT_SCALAR_VALUES)
>      val =3D evaluate_type (expr.get ());
>    else
>      val =3D evaluate_expression (expr.get ());
> @@ -2482,31 +2502,19 @@ print_variable_or_computed (const char *expressio=
n, enum print_values values)
>    switch (values)
>      {
>      case PRINT_SIMPLE_VALUES:
> -      type =3D check_typedef (value_type (val));
> +    case PRINT_SCALAR_VALUES:
>        type_print (value_type (val), "", &stb, -1);
>        uiout->field_stream ("type", stb);
> -      if (type->code () !=3D TYPE_CODE_ARRAY
> -         && type->code () !=3D TYPE_CODE_STRUCT
> -         && type->code () !=3D TYPE_CODE_UNION)
> -       {
> -         struct value_print_options opts;
> -
> -         get_no_prettyformat_print_options (&opts);
> -         opts.deref_ref =3D 1;
> -         common_val_print (val, &stb, 0, &opts, current_language);
> -         uiout->field_stream ("value", stb);
> -       }
>        break;
> -    case PRINT_ALL_VALUES:
> -      {
> -       struct value_print_options opts;
> +    }
>
> -       get_no_prettyformat_print_options (&opts);
> -       opts.deref_ref =3D 1;
> -       common_val_print (val, &stb, 0, &opts, current_language);
> -       uiout->field_stream ("value", stb);
> -      }
> -      break;
> +  if (print_value_p (val, values))
> +    {
> +      struct value_print_options opts;
> +      get_no_prettyformat_print_options (&opts);
> +      opts.deref_ref =3D 1;
> +      common_val_print (val, &stb, 0, &opts, current_language);
> +      uiout->field_stream ("value", stb);
>      }
>  }
>
> diff --git a/gdb/mi/mi-parse.c b/gdb/mi/mi-parse.c
> index dfa7b462714..dd70e4648a1 100644
> --- a/gdb/mi/mi-parse.c
> +++ b/gdb/mi/mi-parse.c
> @@ -29,6 +29,7 @@
>  #include "language.h"
>
>  static const char mi_no_values[] =3D "--no-values";
> +static const char mi_scalar_values[] =3D "--scalar-values";
>  static const char mi_simple_values[] =3D "--simple-values";
>  static const char mi_all_values[] =3D "--all-values";
>
> @@ -383,8 +384,11 @@ mi_parse_print_values (const char *name)
>     else if (strcmp (name, "2") =3D=3D 0
>             || strcmp (name, mi_simple_values) =3D=3D 0)
>       return PRINT_SIMPLE_VALUES;
> +   else if (strcmp (name, "3") =3D=3D 0
> +           || strcmp (name, mi_scalar_values) =3D=3D 0)
> +     return PRINT_SCALAR_VALUES;
>     else
>       error (_("Unknown value for PRINT_VALUES: must be: \
> -0 or \"%s\", 1 or \"%s\", 2 or \"%s\""),
> -           mi_no_values, mi_all_values, mi_simple_values);
> +0 or \"%s\", 1 or \"%s\", 2 or \"%s\", 3 or \"%s\""),
> +           mi_no_values, mi_all_values, mi_simple_values, mi_scalar_valu=
es);
>  }
> diff --git a/gdb/python/py-framefilter.c b/gdb/python/py-framefilter.c
> index 366f3745b9d..a746f309187 100644
> --- a/gdb/python/py-framefilter.c
> +++ b/gdb/python/py-framefilter.c
> @@ -232,17 +232,17 @@ py_print_value (struct ui_out *out, struct value *v=
al,
>    /* MI does not print certain values, differentiated by type,
>       depending on what ARGS_TYPE indicates.  Test type against option.
>       For CLI print all values.  */
> -  if (args_type =3D=3D MI_PRINT_SIMPLE_VALUES
> +  if (args_type =3D=3D MI_PRINT_SCALAR_VALUES
> +      || args_type =3D=3D MI_PRINT_SIMPLE_VALUES
>        || args_type =3D=3D MI_PRINT_ALL_VALUES)
>      {
> -      struct type *type =3D check_typedef (value_type (val));
> -
>        if (args_type =3D=3D MI_PRINT_ALL_VALUES)
>         should_print =3D 1;
> +      else if (args_type =3D=3D MI_PRINT_SCALAR_VALUES
> +              && val_print_scalar_type_p (value_type (val)))
> +       should_print =3D 1;
>        else if (args_type =3D=3D MI_PRINT_SIMPLE_VALUES
> -              && type->code () !=3D TYPE_CODE_ARRAY
> -              && type->code () !=3D TYPE_CODE_STRUCT
> -              && type->code () !=3D TYPE_CODE_UNION)
> +              && mi_simple_values_type_p (value_type (val)))
>         should_print =3D 1;
>      }
>    else if (args_type !=3D NO_VALUES)
> @@ -371,10 +371,12 @@ py_print_single_arg (struct ui_out *out,
>    if (print_args_field)
>      out->field_signed ("arg", 1);
>
> -  /* For MI print the type, but only for simple values.  This seems
> -     weird, but this is how MI choose to format the various output
> +  /* For MI print the type, but only for scalar and simple values. This
> +     seems weird, but this is how MI chooses to format the various outpu=
t
>       types.  */
> -  if (args_type =3D=3D MI_PRINT_SIMPLE_VALUES && val !=3D NULL)
> +  if ((args_type =3D=3D MI_PRINT_SCALAR_VALUES
> +       || args_type =3D=3D MI_PRINT_SIMPLE_VALUES)
> +      && val !=3D NULL)
>      py_print_type (out, val);
>
>    if (val !=3D NULL)
> @@ -603,7 +605,8 @@ enumerate_locals (PyObject *iter,
>        out->field_string ("name", sym_name.get ());
>        out->text (" =3D ");
>
> -      if (args_type =3D=3D MI_PRINT_SIMPLE_VALUES)
> +      if (args_type =3D=3D MI_PRINT_SCALAR_VALUES
> +          || args_type =3D=3D MI_PRINT_SIMPLE_VALUES)
>         py_print_type (out, val);
>
>        /* CLI always prints values for locals.  MI uses the
> diff --git a/gdb/testsuite/gdb.mi/mi-stack.exp b/gdb/testsuite/gdb.mi/mi-=
stack.exp
> index d04c8153c65..8aa4e2234ff 100644
> --- a/gdb/testsuite/gdb.mi/mi-stack.exp
> +++ b/gdb/testsuite/gdb.mi/mi-stack.exp
> @@ -93,6 +93,9 @@ proc test_stack_args_listing {} {
>      # -stack-list-arguments 1 1 1
>      # -stack-list-arguments 1 1 3
>      # -stack-list-arguments
> +    # -stack-list-arguments 1 1 300
> +    # -stack-list-arguments 2 1 1
> +    # -stack-list-arguments 3 1 1
>
>      mi_gdb_test "231-stack-list-arguments 0" \
>         "231\\^done,stack-args=3D\\\[frame=3D\{level=3D\"0\",args=3D\\\[\=
\\]\},frame=3D\{level=3D\"1\",args=3D\\\[name=3D\"strarg\"\\\]\},frame=3D\{=
level=3D\"2\",args=3D\\\[name=3D\"intarg\",name=3D\"strarg\"\\\]\},frame=3D=
\{level=3D\"3\",args=3D\\\[name=3D\"intarg\",name=3D\"strarg\",name=3D\"flt=
arg\"\\\]\},frame=3D\{level=3D\"4\",args=3D\\\[\\\]\}\\\]" \
> @@ -125,6 +128,14 @@ proc test_stack_args_listing {} {
>      mi_gdb_test "235-stack-list-arguments 1 1 300" \
>         "235\\^done,stack-args=3D\\\[frame=3D\{level=3D\"1\",args=3D\\\[\=
{name=3D\"strarg\",value=3D\"$hex \\\\\"A string argument.\\\\\"\"\}\\\]\},=
frame=3D\{level=3D\"2\",args=3D\\\[\{name=3D\"intarg\",value=3D\"2\"\},\{na=
me=3D\"strarg\",value=3D\"$hex \\\\\"A string argument.\\\\\"\"\}\\\]\},fra=
me=3D\{level=3D\"3\",args=3D\\\[\{name=3D\"intarg\",value=3D\"2\"\},\{name=
=3D\"strarg\",value=3D\"$hex \\\\\"A string argument.\\\\\"\"\},\{name=3D\"=
fltarg\",value=3D\"3.5\"\}\\\]\},frame=3D\{level=3D\"4\",args=3D\\\[\\\]\}\=
\\]" \
>         "stack args listing 1 1 300"
> +
> +    mi_gdb_test "236-stack-list-arguments 2 1 1" \
> +       "236\\^done,stack-args=3D\\\[frame=3D\{level=3D\"1\",args=3D\\\[\=
{name=3D\"strarg\",type=3D\"char \\*\",value=3D\"$hex \\\\\"A string argume=
nt.\\\\\"\"\}\\\]\}\\\]" \
> +       "stack args listing --simple-values 1 1"
> +
> +    mi_gdb_test "237-stack-list-arguments 3 1 1" \
> +       "237\\^done,stack-args=3D\\\[frame=3D\{level=3D\"1\",args=3D\\\[\=
{name=3D\"strarg\",type=3D\"char \\*\",value=3D\"$hex \\\\\"A string argume=
nt.\\\\\"\"\}\\\]\}\\\]" \
> +       "stack args listing --scalar-values 1 1"
>  }
>
>  proc test_stack_info_depth {} {
> @@ -163,7 +174,7 @@ proc test_stack_locals_listing {} {
>      # -stack-list-locals 0 (--no-values)
>      # -stack-list-locals 1 (--all-values)
>      # -stack-list-locals 2 (--simple-values)
> -    # -stack-list-arguments
> +    # -stack-list-locals 3 (--scalar-values)
>
>      mi_gdb_test "232-stack-list-locals 0" \
>         "232\\^done,locals=3D\\\[name=3D\"A\",name=3D\"B\",name=3D\"C\",n=
ame=3D\"D\"\\\]" \
> @@ -183,6 +194,10 @@ proc test_stack_locals_listing {} {
>         "232\\^done,locals=3D\\\[\{name=3D\"A\",type=3D\"int\",value=3D\"=
1\"\},\{name=3D\"B\",type=3D\"int\",value=3D\"2\"\},\{name=3D\"C\",type=3D\=
"int\",value=3D\"3\"\},\{name=3D\"D\",type=3D\"int \\\[3\\\]\"\}\\\]" \
>         "stack locals listing, simple types: names and values, complex ty=
pe: names and types"
>
> +    mi_gdb_test "233-stack-list-locals --scalar-values" \
> +       "233\\^done,locals=3D\\\[\{name=3D\"A\",type=3D\"int\",value=3D\"=
1\"\},\{name=3D\"B\",type=3D\"int\",value=3D\"2\"\},\{name=3D\"C\",type=3D\=
"int\",value=3D\"3\"\},\{name=3D\"D\",type=3D\"int \\\[3\\\]\"\}\\\]" \
> +       "stack locals listing, scalar types: names and values, otherwise:=
 names and types"
> +
>      mi_gdb_test "234-stack-list-locals" \
>         "234\\^error,msg=3D\"-stack-list-locals: Usage.*PRINT_VALUES.*\""=
 \
>         "stack locals listing wrong"
> diff --git a/gdb/testsuite/gdb.mi/print-scalar-values.cc b/gdb/testsuite/=
gdb.mi/print-scalar-values.cc
> new file mode 100644
> index 00000000000..fd9daf1d962
> --- /dev/null
> +++ b/gdb/testsuite/gdb.mi/print-scalar-values.cc
> @@ -0,0 +1,58 @@
> +/* This test case 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/>.=
  */
> +
> +/* PRINT_SCALAR_VALUES test program.
> +
> +   Test that PRINT_SCALAR_VALUES distinguishes scalar and non-scalar
> +   types, including C++ reference and rvalue reference types.
> +
> +   In the function f(), arguments i, ir, and irr are ints or references
> +   to ints, and their values should be printed by PRINT_SCALAR_VALUES;
> +   but the other arguments are non-scalar, and so their values should
> +   not be printed by PRINT_SCALAR_VALUES.  */
> +
> +struct s
> +{
> +  int v;
> +};
> +
> +union u
> +{
> +  int v;
> +};
> +
> +int
> +f (int i, int &ir, int &&irr,
> +   int a[1], int (&ar)[1], int (&&arr)[1],
> +   struct s s, struct s &sr, struct s &&srr,
> +   union u u, union u &ur, union u &&urr)
> +{
> +  return (i + ir + irr
> +          + a[0] + ar[0] + arr[0]
> +          + s.v + sr.v + srr.v
> +          + u.v + ur.v + urr.v);
> +}
> +
> +int
> +main (void)
> +{
> +  int i =3D 1, j =3D 2;
> +  int a[1] =3D { 4 }, b[1] =3D { 5 };
> +  struct s s =3D { 7 }, t =3D { 8 };
> +  union u u =3D { 10 }, v =3D { 11 };
> +  return f (i, j, 3, a, b, { 6 }, s, t, { 9 }, u, v, { 12 });
> +}
> diff --git a/gdb/testsuite/gdb.mi/print-scalar-values.exp b/gdb/testsuite=
/gdb.mi/print-scalar-values.exp
> new file mode 100644
> index 00000000000..3398218c063
> --- /dev/null
> +++ b/gdb/testsuite/gdb.mi/print-scalar-values.exp
> @@ -0,0 +1,51 @@
> +# 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/>.
> +
> +# PRINT_SCALAR_VALUES test.
> +#
> +# Test that PRINT_SCALAR_VALUES distinguishes scalar and non-scalar
> +# types, including C++ reference and rvalue reference types.
> +#
> +# In the function f(), arguments i, ir, and irr are ints or references
> +# to ints, and their values should be printed by PRINT_SCALAR_VALUES;
> +# but the other arguments are non-scalar, and so their values should not
> +# be printed by PRINT_SCALAR_VALUES.
> +
> +if { [skip_cplus_tests] } { continue }
> +
> +load_lib mi-support.exp
> +standard_testfile .cc
> +
> +if { [gdb_compile "$srcdir/$subdir/$srcfile" $binfile executable {debug =
c++}] !=3D "" } {
> +    untested "failed to compile"
> +    return -1
> +}
> +
> +mi_clean_restart $binfile
> +
> +mi_runto_main
> +
> +mi_gdb_test "-break-insert f" "\\^done.*" "set breakpoint on f"
> +
> +mi_send_resuming_command "exec-continue" "exec-continue to breakpoint on=
 f"
> +
> +mi_expect_stop "breakpoint-hit" "f" ".*" ".*" ".*" {.* disp=3D"keep"} \
> +    "run until breakpoint on f"
> +
> +mi_gdb_test "-stack-list-arguments --scalar-values" \
> +    "\\^done,stack-args=3D\\\[frame=3D\{level=3D\"0\",args=3D\\\[\{name=
=3D\"i\",type=3D\"int\",value=3D\"1\"\},\{name=3D\"ir\",type=3D\"int &\",va=
lue=3D\"@$hex: 2\"\},\{name=3D\"irr\",type=3D\"int &&\",value=3D\"@$hex: 3\=
"\},\{name=3D\"a\",type=3D\"int \\*\",value=3D\"$hex\"\},\{name=3D\"ar\",ty=
pe=3D\"int \\(&\\)\\\[1\\\]\"\},\{name=3D\"arr\",type=3D\"int \\(&&\\)\\\[1=
\\\]\"\},\{name=3D\"s\",type=3D\"s\"\},\{name=3D\"sr\",type=3D\"s &\"\},\{n=
ame=3D\"srr\",type=3D\"s &&\"\},\{name=3D\"u\",type=3D\"u\"\},\{name=3D\"ur=
\",type=3D\"u &\"\},\{name=3D\"urr\",type=3D\"u &&\"\}\\\]\},frame=3D\{leve=
l=3D\"1\",args=3D\\\[\\\]\}\\\]" \
> +    "stack list arguments, scalar types: names, types and values, compou=
nd types: names and types"
> +
> +mi_gdb_exit
> --
> 2.26.0
>