Add 'summary' mode to Value.format_string

This adds a 'summary' mode to Value.format_string and to
gdb.print_options.  For the former, it lets Python code format values
using this mode.  For the latter, it lets a printer potentially detect
if it is being called in a backtrace with 'set print frame-arguments'
set to 'scalars'.

I considered adding a new mode here to let a pretty-printer see
whether it was being called in a 'backtrace' context at all, but I'm
not sure if this is really desirable.

gdb/NEWS

@@ -156,6 +156,10 @@ GNU/Linux/LoongArch (gdbserver)	loongarch*-*-linux*
   ** gdb.Value.format_string now uses the format provided by 'print',
      if it is called during a 'print' or other similar operation.
 
+  ** gdb.Value.format_string now accepts the 'summary' keyword.  This
+     can be used to request a shorter representation of a value, the
+     way that 'set print frame-arguments scalars' does.
+
 * New features in the GDB remote stub, GDBserver
 
   ** GDBserver is now supported on LoongArch GNU/Linux.

gdb/doc/python.texi

@@ -1160,6 +1160,12 @@ Additionally, @value{GDBN} only styles some value contents, so not
 every output string will contain escape sequences.
 
 When @code{False}, which is the default, no output styling is applied.
+
+@item summary
+@code{True} when just a summary should be printed.  In this mode,
+scalar values are printed in their entirety, but aggregates such as
+structures or unions are omitted.  This mode is used by @code{set
+print frame-arguments scalars} (@pxref{Print Settings}).
 @end table
 @end defun
 

gdb/python/py-prettyprint.c

@@ -753,6 +753,8 @@ gdbpy_print_options (PyObject *unused1, PyObject *unused2)
 		      opts.static_field_print) < 0
       || set_boolean (result.get (), "deref_refs",
 		      opts.deref_ref) < 0
+      || set_boolean (result.get (), "summary",
+		      opts.summary) < 0
       || set_unsigned (result.get (), "max_elements",
 		       opts.print_max) < 0
       || set_unsigned (result.get (), "max_depth",

gdb/python/py-value.c

@@ -641,6 +641,7 @@ valpy_format_string (PyObject *self, PyObject *args, PyObject *kw)
       "address",		/* See set print address on|off.  */
       "styling",		/* Should we apply styling.  */
       "nibbles",		/* See set print nibbles on|off.  */
+      "summary",		/* Summary mode for non-scalars.  */
       /* C++ options.  */
       "deref_refs",		/* No corresponding setting.  */
       "actual_objects",		/* See set print object on|off.  */
@@ -690,10 +691,11 @@ valpy_format_string (PyObject *self, PyObject *args, PyObject *kw)
   PyObject *deref_refs_obj = NULL;
   PyObject *actual_objects_obj = NULL;
   PyObject *static_members_obj = NULL;
+  PyObject *summary_obj = NULL;
   char *format = NULL;
   if (!gdb_PyArg_ParseTupleAndKeywords (args,
 					kw,
-					"|O!O!O!O!O!O!O!O!O!O!O!O!IIIs",
+					"|O!O!O!O!O!O!O!O!O!O!O!O!O!IIIs",
 					keywords,
 					&PyBool_Type, &raw_obj,
 					&PyBool_Type, &pretty_arrays_obj,
@@ -704,6 +706,7 @@ valpy_format_string (PyObject *self, PyObject *args, PyObject *kw)
 					&PyBool_Type, &address_obj,
 					&PyBool_Type, &styling_obj,
 					&PyBool_Type, &nibbles_obj,
+					&PyBool_Type, &summary_obj,
 					&PyBool_Type, &deref_refs_obj,
 					&PyBool_Type, &actual_objects_obj,
 					&PyBool_Type, &static_members_obj,
@@ -736,6 +739,8 @@ valpy_format_string (PyObject *self, PyObject *args, PyObject *kw)
     return NULL;
   if (!copy_py_bool_obj (&opts.static_field_print, static_members_obj))
     return NULL;
+  if (!copy_py_bool_obj (&opts.summary, summary_obj))
+    return nullptr;
 
   /* Numeric arguments for which 0 means unlimited (which we represent as
      UINT_MAX).  Note that the max-depth numeric argument uses -1 as

gdb/testsuite/gdb.python/py-format-string.exp

@@ -1127,6 +1127,12 @@ proc test_print_options {} {
 	"print in binary to fetch options"
     gdb_test "python print(saved_options\['format'\] == 't')" "True" \
 	"format was set"
+
+    check_format_string "a_point_t" "summary=True" \
+	"No Data" \
+	"print in summary mode"
+    gdb_test "python print(saved_options\['summary'\])" "True" \
+	"summary was set"
 }
 
 # Run all the tests in common for both C and C++.

gdb/testsuite/gdb.python/py-format-string.py

@@ -28,6 +28,8 @@ class PointPrinter(object):
     def to_string(self):
         global saved_options
         saved_options = gdb.print_options()
+        if saved_options["summary"]:
+            return "No Data"
         return "Pretty Point (%s, %s)" % (self.val["x"], self.val["y"])