gdb: use gdb::optional instead of passing a pointer to gdb::array_view

Following on from the previous commit, this commit changes the API of
value_struct_elt to take gdb::optional<gdb::array_view<value *>>
instead of a pointer to the gdb::array_view.

This makes the optional nature of the array_view parameter explicit.

This commit is purely a refactoring commit, there should be no user
visible change after this commit.

I have deliberately kept this refactor separate from the previous two
commits as this is a more extensive change, and I'm not 100% sure that
using gdb::optional for the parameter type, instead of a pointer, is
going to be to everyone's taste.  If there's push back on this patch
then this one can be dropped from the series.

gdb/ChangeLog:

	* ada-lang.c (desc_bounds): Use '{}' instead of NULL to indicate
	an empty gdb::optional when calling value_struct_elt.
	(desc_data): Likewise.
	(desc_one_bound): Likewise.
	* eval.c (structop_base_operation::evaluate_funcall): Pass
	gdb::array_view, not a gdb::array_view* to value_struct_elt.
	(eval_op_structop_struct): Use '{}' instead of NULL to indicate
	an empty gdb::optional when calling value_struct_elt.
	(eval_op_structop_ptr): Likewise.
	* f-lang.c (fortran_structop_operation::evaluate): Likewise.
	* guile/scm-value.c (gdbscm_value_field): Likewise.
	* m2-lang.c (eval_op_m2_high): Likewise.
	(eval_op_m2_subscript): Likewise.
	* opencl-lang.c (opencl_structop_operation::evaluate): Likewise.
	* python/py-value.c (valpy_getitem): Likewise.
	* rust-lang.c (rust_val_print_str): Likewise.
	(rust_range): Likewise.
	(rust_subscript): Likewise.
	(eval_op_rust_structop): Likewise.
	(rust_aggregate_operation::evaluate): Likewise.
	* valarith.c (value_user_defined_op): Likewise.
	* valops.c (search_struct_method): Change parameter type, update
	function body accordingly, and update header comment.
	(value_struct_elt): Change parameter type, update function body
	accordingly.
	* value.h (value_struct_elt): Update declaration.

12 files changed, 65 insertions, 34 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 9396aadca9d..1d10ae0f6c8 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,34 @@
 2021-06-25  Andrew Burgess  <andrew.burgess@embecosm.com>
 
+	* ada-lang.c (desc_bounds): Use '{}' instead of NULL to indicate
+	an empty gdb::optional when calling value_struct_elt.
+	(desc_data): Likewise.
+	(desc_one_bound): Likewise.
+	* eval.c (structop_base_operation::evaluate_funcall): Pass
+	gdb::array_view, not a gdb::array_view* to value_struct_elt.
+	(eval_op_structop_struct): Use '{}' instead of NULL to indicate
+	an empty gdb::optional when calling value_struct_elt.
+	(eval_op_structop_ptr): Likewise.
+	* f-lang.c (fortran_structop_operation::evaluate): Likewise.
+	* guile/scm-value.c (gdbscm_value_field): Likewise.
+	* m2-lang.c (eval_op_m2_high): Likewise.
+	(eval_op_m2_subscript): Likewise.
+	* opencl-lang.c (opencl_structop_operation::evaluate): Likewise.
+	* python/py-value.c (valpy_getitem): Likewise.
+	* rust-lang.c (rust_val_print_str): Likewise.
+	(rust_range): Likewise.
+	(rust_subscript): Likewise.
+	(eval_op_rust_structop): Likewise.
+	(rust_aggregate_operation::evaluate): Likewise.
+	* valarith.c (value_user_defined_op): Likewise.
+	* valops.c (search_struct_method): Change parameter type, update
+	function body accordingly, and update header comment.
+	(value_struct_elt): Change parameter type, update function body
+	accordingly.
+	* value.h (value_struct_elt): Update declaration.
+
+2021-06-25  Andrew Burgess  <andrew.burgess@embecosm.com>
+
 	PR gdb/27994
 	* eval.c (structop_base_operation::evaluate_funcall): Pass
 	array_view instead of array to value_struct_elt.
diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index 49a7d5b36b6..f2270c0f6af 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -1484,7 +1484,7 @@ desc_bounds (struct value *arr)
 
   else if (is_thick_pntr (type))
     {
-      struct value *p_bounds = value_struct_elt (&arr, NULL, "P_BOUNDS", NULL,
+      struct value *p_bounds = value_struct_elt (&arr, {}, "P_BOUNDS", NULL,
 					       _("Bad GNAT array descriptor"));
       struct type *p_bounds_type = value_type (p_bounds);
 
@@ -1566,7 +1566,7 @@ desc_data (struct value *arr)
   if (is_thin_pntr (type))
     return thin_data_pntr (arr);
   else if (is_thick_pntr (type))
-    return value_struct_elt (&arr, NULL, "P_ARRAY", NULL,
+    return value_struct_elt (&arr, {}, "P_ARRAY", NULL,
 			     _("Bad GNAT array descriptor"));
   else
     return NULL;
@@ -1606,7 +1606,7 @@ desc_one_bound (struct value *bounds, int i, int which)
   char bound_name[20];
   xsnprintf (bound_name, sizeof (bound_name), "%cB%d",
 	     which ? 'U' : 'L', i - 1);
-  return value_struct_elt (&bounds, NULL, bound_name, NULL,
+  return value_struct_elt (&bounds, {}, bound_name, NULL,
 			   _("Bad GNAT array descriptor bounds"));
 }
 
diff --git a/gdb/eval.c b/gdb/eval.c
index 5a72bf1becb..5c348c34e66 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -947,7 +947,7 @@ structop_base_operation::evaluate_funcall
     {
       struct value *temp = vals[0];
 
-      callee = value_struct_elt (&temp, &arg_view, tstr,
+      callee = value_struct_elt (&temp, arg_view, tstr,
 				 &static_memfuncp,
 				 op == STRUCTOP_STRUCT
 				 ? "structure" : "structure pointer");
@@ -1132,7 +1132,7 @@ eval_op_structop_struct (struct type *expect_type, struct expression *exp,
 			 enum noside noside,
 			 struct value *arg1, const char *string)
 {
-  struct value *arg3 = value_struct_elt (&arg1, NULL, string,
+  struct value *arg3 = value_struct_elt (&arg1, {}, string,
 					 NULL, "structure");
   if (noside == EVAL_AVOID_SIDE_EFFECTS)
     arg3 = value_zero (value_type (arg3), VALUE_LVAL (arg3));
@@ -1188,7 +1188,7 @@ eval_op_structop_ptr (struct type *expect_type, struct expression *exp,
       }
   }
 
-  struct value *arg3 = value_struct_elt (&arg1, NULL, string,
+  struct value *arg3 = value_struct_elt (&arg1, {}, string,
 					 NULL, "structure pointer");
   if (noside == EVAL_AVOID_SIDE_EFFECTS)
     arg3 = value_zero (value_type (arg3), VALUE_LVAL (arg3));
diff --git a/gdb/f-lang.c b/gdb/f-lang.c
index 5731c400305..16ec9e04044 100644
--- a/gdb/f-lang.c
+++ b/gdb/f-lang.c
@@ -1511,7 +1511,7 @@ fortran_structop_operation::evaluate (struct type *expect_type,
 	arg1 = std::get<0> (m_storage)->evaluate (nullptr, exp, EVAL_NORMAL);
     }
 
-  value *elt = value_struct_elt (&arg1, NULL, str, NULL, "structure");
+  value *elt = value_struct_elt (&arg1, {}, str, NULL, "structure");
 
   if (noside == EVAL_AVOID_SIDE_EFFECTS)
     {
diff --git a/gdb/guile/scm-value.c b/gdb/guile/scm-value.c
index 24bb5547957..d4d76df0411 100644
--- a/gdb/guile/scm-value.c
+++ b/gdb/guile/scm-value.c
@@ -694,7 +694,7 @@ gdbscm_value_field (SCM self, SCM field_scm)
 
       struct value *tmp = v_smob->value;
 
-      struct value *res_val = value_struct_elt (&tmp, NULL, field.get (), NULL,
+      struct value *res_val = value_struct_elt (&tmp, {}, field.get (), NULL,
 						"struct/class/union");
 
       return vlscm_scm_from_value (res_val);
diff --git a/gdb/m2-lang.c b/gdb/m2-lang.c
index be1a8ed1437..911d67d8672 100644
--- a/gdb/m2-lang.c
+++ b/gdb/m2-lang.c
@@ -50,7 +50,7 @@ eval_op_m2_high (struct type *expect_type, struct expression *exp,
 
 	  type = type->field (1).type ();
 	  /* i18n: Do not translate the "_m2_high" part!  */
-	  arg1 = value_struct_elt (&temp, NULL, "_m2_high", NULL,
+	  arg1 = value_struct_elt (&temp, {}, "_m2_high", NULL,
 				   _("unbounded structure "
 				     "missing _m2_high field"));
 
@@ -83,7 +83,7 @@ eval_op_m2_subscript (struct type *expect_type, struct expression *exp,
 	error (_("internal error: unbounded "
 		 "array structure is unknown"));
       /* i18n: Do not translate the "_m2_contents" part!  */
-      arg1 = value_struct_elt (&temp, NULL, "_m2_contents", NULL,
+      arg1 = value_struct_elt (&temp, {}, "_m2_contents", NULL,
 			       _("unbounded structure "
 				 "missing _m2_contents field"));
 	  
diff --git a/gdb/opencl-lang.c b/gdb/opencl-lang.c
index 1d6117a9285..136969ead76 100644
--- a/gdb/opencl-lang.c
+++ b/gdb/opencl-lang.c
@@ -708,7 +708,7 @@ opencl_structop_operation::evaluate (struct type *expect_type,
 				 noside);
   else
     {
-      struct value *v = value_struct_elt (&arg1, NULL,
+      struct value *v = value_struct_elt (&arg1, {},
 					  std::get<1> (m_storage).c_str (),
 					  NULL, "structure");
 
diff --git a/gdb/python/py-value.c b/gdb/python/py-value.c
index 43da8f0fbc4..8df8a15f8d6 100644
--- a/gdb/python/py-value.c
+++ b/gdb/python/py-value.c
@@ -992,7 +992,7 @@ valpy_getitem (PyObject *self, PyObject *key)
       scoped_value_mark free_values;
 
       if (field)
-	res_val = value_struct_elt (&tmp, NULL, field.get (), NULL,
+	res_val = value_struct_elt (&tmp, {}, field.get (), NULL,
 				    "struct/class/union");
       else if (bitpos >= 0)
 	res_val = value_struct_elt_bitpos (&tmp, bitpos, field_type,
diff --git a/gdb/rust-lang.c b/gdb/rust-lang.c
index 3b15bb22a27..60ea89b1394 100644
--- a/gdb/rust-lang.c
+++ b/gdb/rust-lang.c
@@ -302,9 +302,9 @@ static void
 rust_val_print_str (struct ui_file *stream, struct value *val,
 		    const struct value_print_options *options)
 {
-  struct value *base = value_struct_elt (&val, NULL, "data_ptr", NULL,
+  struct value *base = value_struct_elt (&val, {}, "data_ptr", NULL,
 					 "slice");
-  struct value *len = value_struct_elt (&val, NULL, "length", NULL, "slice");
+  struct value *len = value_struct_elt (&val, {}, "length", NULL, "slice");
 
   val_print_string (TYPE_TARGET_TYPE (value_type (base)), "UTF-8",
 		    value_as_address (base), value_as_long (len), stream,
@@ -1030,7 +1030,7 @@ rust_range (struct type *expect_type, struct expression *exp,
 
   if (low != NULL)
     {
-      struct value *start = value_struct_elt (&result, NULL, "start", NULL,
+      struct value *start = value_struct_elt (&result, {}, "start", NULL,
 					      "range");
 
       value_assign (start, low);
@@ -1038,7 +1038,7 @@ rust_range (struct type *expect_type, struct expression *exp,
 
   if (high != NULL)
     {
-      struct value *end = value_struct_elt (&result, NULL, "end", NULL,
+      struct value *end = value_struct_elt (&result, {}, "end", NULL,
 					    "range");
 
       value_assign (end, high);
@@ -1176,8 +1176,8 @@ rust_subscript (struct type *expect_type, struct expression *exp,
 	{
 	  struct value *len;
 
-	  base = value_struct_elt (&lhs, NULL, "data_ptr", NULL, "slice");
-	  len = value_struct_elt (&lhs, NULL, "length", NULL, "slice");
+	  base = value_struct_elt (&lhs, {}, "data_ptr", NULL, "slice");
+	  len = value_struct_elt (&lhs, {}, "length", NULL, "slice");
 	  low_bound = 0;
 	  high_bound = value_as_long (len);
 	}
@@ -1400,7 +1400,7 @@ eval_op_rust_structop (struct type *expect_type, struct expression *exp,
 
       try
 	{
-	  result = value_struct_elt (&lhs, NULL, field_name,
+	  result = value_struct_elt (&lhs, {}, field_name,
 				     NULL, "structure");
 	}
       catch (const gdb_exception_error &except)
@@ -1411,7 +1411,7 @@ eval_op_rust_structop (struct type *expect_type, struct expression *exp,
 	}
     }
   else
-    result = value_struct_elt (&lhs, NULL, field_name, NULL, "structure");
+    result = value_struct_elt (&lhs, {}, field_name, NULL, "structure");
   if (noside == EVAL_AVOID_SIDE_EFFECTS)
     result = value_zero (value_type (result), VALUE_LVAL (result));
   return result;
@@ -1457,7 +1457,7 @@ rust_aggregate_operation::evaluate (struct type *expect_type,
       if (noside == EVAL_NORMAL)
 	{
 	  const char *fieldname = item.first.c_str ();
-	  value *field = value_struct_elt (&result, nullptr, fieldname,
+	  value *field = value_struct_elt (&result, {}, fieldname,
 					   nullptr, "structure");
 	  value_assign (field, val);
 	}
diff --git a/gdb/valarith.c b/gdb/valarith.c
index d61ad9170f8..9ebad648b27 100644
--- a/gdb/valarith.c
+++ b/gdb/valarith.c
@@ -344,7 +344,7 @@ value_user_defined_op (struct value **argp, gdb::array_view<value *> args,
 					  noside);
     }
   else
-    result = value_struct_elt (argp, &args, name, static_memfuncp,
+    result = value_struct_elt (argp, args, name, static_memfuncp,
 			       "structure");
 
   return result;
diff --git a/gdb/valops.c b/gdb/valops.c
index 0af7a6c3f27..bd547923496 100644
--- a/gdb/valops.c
+++ b/gdb/valops.c
@@ -51,7 +51,7 @@ static struct value *search_struct_field (const char *, struct value *,
 					  struct type *, int);
 
 static struct value *search_struct_method (const char *, struct value **,
-					   gdb::array_view<value *> *,
+					   gdb::optional<gdb::array_view<value *>>,
 					   LONGEST, int *, struct type *);
 
 static int find_oload_champ_namespace (gdb::array_view<value *> args,
@@ -2177,17 +2177,18 @@ search_struct_field (const char *name, struct value *arg1,
    ARG1 by OFFSET bytes, and search in it assuming it has (class) type
    TYPE.
 
-   The ARGS array pointer is to a list of argument values used to help
-   finding NAME, though ARGS can be nullptr.  The contents of ARGS can be
-   adjusted if type coercion is required in order to find a matching NAME.
+   ARGS is an optional array of argument values used to help finding NAME.
+   The contents of ARGS can be adjusted if type coercion is required in
+   order to find a matching NAME.
 
    If found, return value, else if name matched and args not return
    (value) -1, else return NULL.  */
 
 static struct value *
 search_struct_method (const char *name, struct value **arg1p,
-		      gdb::array_view<value *> *args, LONGEST offset,
-		      int *static_memfuncp, struct type *type)
+		      gdb::optional<gdb::array_view<value *>> args,
+		      LONGEST offset, int *static_memfuncp,
+		      struct type *type)
 {
   int i;
   struct value *v;
@@ -2205,10 +2206,10 @@ search_struct_method (const char *name, struct value **arg1p,
 
 	  name_matched = 1;
 	  check_stub_method_group (type, i);
-	  if (j > 0 && args == nullptr)
+	  if (j > 0 && !args.has_value ())
 	    error (_("cannot resolve overloaded method "
 		     "`%s': no arguments supplied"), name);
-	  else if (j == 0 && args == nullptr)
+	  else if (j == 0 && !args.has_value ())
 	    {
 	      v = value_fn_field (arg1p, f, j, type, offset);
 	      if (v != NULL)
@@ -2217,7 +2218,7 @@ search_struct_method (const char *name, struct value **arg1p,
 	  else
 	    while (j >= 0)
 	      {
-		gdb_assert (args != nullptr);
+		gdb_assert (args.has_value ());
 		if (!typecmp (TYPE_FN_FIELD_STATIC_P (f, j),
 			      TYPE_FN_FIELD_TYPE (f, j)->has_varargs (),
 			      TYPE_FN_FIELD_TYPE (f, j)->num_fields (),
@@ -2320,7 +2321,8 @@ search_struct_method (const char *name, struct value **arg1p,
    found.  */
 
 struct value *
-value_struct_elt (struct value **argp, gdb::array_view<value *> *args,
+value_struct_elt (struct value **argp,
+		  gdb::optional<gdb::array_view<value *>> args,
 		  const char *name, int *static_memfuncp, const char *err)
 {
   struct type *t;
@@ -2350,7 +2352,7 @@ value_struct_elt (struct value **argp, gdb::array_view<value *> *args,
   if (static_memfuncp)
     *static_memfuncp = 0;
 
-  if (args == nullptr)
+  if (!args.has_value ())
     {
       /* if there are no arguments ...do this...  */
 
diff --git a/gdb/value.h b/gdb/value.h
index 40ad28e3dbb..379cddafbe7 100644
--- a/gdb/value.h
+++ b/gdb/value.h
@@ -826,7 +826,7 @@ extern struct value *value_neg (struct value *arg1);
 extern struct value *value_complement (struct value *arg1);
 
 extern struct value *value_struct_elt (struct value **argp,
-				       gdb::array_view <value *> *args,
+				       gdb::optional<gdb::array_view <value *>> args,
 				       const char *name, int *static_memfuncp,
 				       const char *err);