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.

1 files changed, 9 insertions, 9 deletions

diff --git a/gdb/rust-lang.c b/gdb/rust-lang.c
index 3b15bb2..60ea89b 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);
 	}