Create xml from target descriptions

Add a print_xml_feature visitor class which turns a
target description into xml. Both gdb and gdbserver can do this.

gdb/
	* common/tdesc.c (print_xml_feature::visit_pre): Add xml parsing.
	(print_xml_feature::visit_post): Likewise.
	(print_xml_feature::visit): Likewise.
	* common/tdesc.h (tdesc_get_features_xml): Use const tdesc.
	(print_xml_feature): Add new class.
	* regformats/regdat.sh: Null xmltarget on feature targets.
	* target-descriptions.c (struct target_desc): Add xmltarget.
	(maintenance_check_tdesc_xml_convert): Add unittest function.
	(tdesc_get_features_xml): Add function to get xml.
	(maintenance_check_xml_descriptions): Test xml generation.
	* xml-tdesc.c (string_read_description_xml): Add function.
	* xml-tdesc.h (string_read_description_xml): Add declaration.

gdbserver/
	* gdb/gdbserver/server.c (get_features_xml): Remove cast.
	* tdesc.c (void target_desc::accept): Fill in function.
	(tdesc_get_features_xml): Remove old xml creation.
	(print_xml_feature::visit_pre): Add xml vistor.
	* tdesc.h (struct target_desc): Make xmltarget mutable.
	(tdesc_get_features_xml): Remove declaration.

1 files changed, 12 insertions, 0 deletions

diff --git a/gdb/xml-tdesc.c b/gdb/xml-tdesc.c
index 1c3409d..87c6be4 100644
--- a/gdb/xml-tdesc.c
+++ b/gdb/xml-tdesc.c
@@ -752,3 +752,15 @@ target_fetch_description_xml (struct target_ops *ops)
   return output;
 #endif
 }
+
+/* See xml-tdesc.h.  */
+
+const struct target_desc *
+string_read_description_xml (const char *xml)
+{
+  return tdesc_parse_xml (xml, [] (const char *href, void *baton)
+    {
+      error (_("xincludes are unsupported with this method"));
+      return gdb::optional<gdb::char_vector> ();
+    }, nullptr);
+}