[PATCH v3 6/8] Create xml from target descriptions

This patch adds a print_xml_feature visitor class which turns a C
target description into xml. Both gdb and gdbserver can do this.

An accept function is added to gdbserver tdesc to allow it to use
vistor classes.

Tests are added to maintenance_check_xml_descriptions which takes
each pair of tested descriptions, turns them both into xml, then back
again, and confirms the descriptions still match.

Alan.

2018-02-26  Alan Hayward  <alan.hayward@arm.com>

gdb/
	* common/tdesc.c (print_xml_feature::visit_post): Add xml parsing.
	(print_xml_feature::visit_pre): Likewise.
	(print_xml_feature::visit_post): Likewise.
	(print_xml_feature::visit): Likewise.
	(print_xml_feature::visit): Likewise.
	(print_xml_feature::visit): Likewise.
	(print_xml_feature::visit): Likewise.
	* common/tdesc.h (print_xml_feature): Add new class.
	* regformats/regdat.sh: obtain xml.
	* target-descriptions.c (struct target_desc): Add xmltarget.
	(print_xml_feature::visit_pre): Add xml vistor.
	(tdesc_get_features_xml): Add function to get xml.
	(maintenance_check_xml_descriptions): Test xml generation.
	* xml-tdesc.c (target_read_description_xml_string): Add function.
	* xml-tdesc.h (target_read_description_xml_string): Add declaration.

gdbserver/
	* 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.

8 files changed, 264 insertions, 31 deletions

diff --git a/gdb/common/tdesc.c b/gdb/common/tdesc.c
index 115e7cd..ce5b890 100644
--- a/gdb/common/tdesc.c
+++ b/gdb/common/tdesc.c
@@ -288,4 +288,158 @@ tdesc_add_enum_value (tdesc_type_with_fields *type, int value,
   type->fields.emplace_back (name,
 			     tdesc_predefined_type (TDESC_TYPE_INT32),
 			     value, -1);
-}
\ No newline at end of file
+}
+
+void print_xml_feature::visit_post (const target_desc *e)
+{
+  *m_buffer += "</target>\n";
+}
+
+void print_xml_feature::visit_pre (const tdesc_feature *e)
+{
+  *m_buffer += "<feature name=\"";
+  *m_buffer += e->name;
+  *m_buffer += "\">\n";
+}
+
+void print_xml_feature::visit_post (const tdesc_feature *e)
+{
+  *m_buffer += "</feature>\n";
+}
+
+void print_xml_feature::visit (const tdesc_type_builtin *type)
+{
+  error (_("xml output is not supported type \"%s\"."), type->name.c_str ());
+}
+
+void print_xml_feature::visit (const tdesc_type_vector *type)
+{
+  *m_buffer += "<vector id=\"";
+  *m_buffer += type->name;
+  *m_buffer += "\" type=\"";
+  *m_buffer += type->element_type->name;
+  *m_buffer += "\" count=\"";
+  *m_buffer += std::to_string (type->count);
+  *m_buffer += "\"/>\n";
+}
+
+void print_xml_feature::visit (const tdesc_type_with_fields *type)
+{
+  struct tdesc_type_field *f;
+  const static char *types[] = { "struct", "union", "flags", "enum" };
+
+  gdb_assert (type->kind >= TDESC_TYPE_STRUCT && type->kind <= TDESC_TYPE_ENUM);
+  *m_buffer += "<";
+  *m_buffer += types[type->kind - TDESC_TYPE_STRUCT];
+
+  switch (type->kind)
+    {
+    case TDESC_TYPE_STRUCT:
+    case TDESC_TYPE_FLAGS:
+      *m_buffer += " id=\"";
+      *m_buffer += type->name;
+      if (type->size > 0)
+	{
+	  *m_buffer += "\" size=\"";
+	  *m_buffer += std::to_string (type->size);
+	}
+	*m_buffer += "\">\n";
+
+      for (const tdesc_type_field &f : type->fields)
+	{
+	  *m_buffer += "  <field name=\"";
+	  *m_buffer += f.name;
+	  if (f.start == -1)
+	  {
+	    *m_buffer += "\" type=\"";
+	    *m_buffer += f.type->name;
+	  }
+	  else
+	  {
+	    *m_buffer += "\" start=\"";
+	    *m_buffer += std::to_string (f.start);
+	    *m_buffer += "\" end=\"";
+	    *m_buffer += std::to_string (f.end);
+	  }
+
+	  *m_buffer += "\"/>\n";
+	}
+    break;
+
+    case TDESC_TYPE_ENUM:
+      *m_buffer += " id=\"";
+      *m_buffer += type->name;
+      *m_buffer += "\">\n";
+
+      for (const tdesc_type_field &f : type->fields)
+	{
+	  *m_buffer += "  <field name=\"";
+	  *m_buffer += f.name;
+	  *m_buffer += "\" start=\"";
+	  *m_buffer += std::to_string (f.start);
+	  *m_buffer += "\"/>\n";
+	}
+      break;
+
+    case TDESC_TYPE_UNION:
+      *m_buffer += " id=\"";
+      *m_buffer += type->name;
+      *m_buffer += "\">\n";
+
+      for (const tdesc_type_field &f : type->fields)
+	{
+	  *m_buffer += "  <field name=\"";
+	  *m_buffer += f.name;
+	  *m_buffer += "\" type=\"";
+	  *m_buffer += f.type->name;
+	  *m_buffer += "\"/>\n";
+	}
+      break;
+
+    default:
+      error (_("xml output is not supported type \"%s\"."),
+	     type->name.c_str ());
+    }
+
+  *m_buffer += "</";
+  *m_buffer += types[type->kind - TDESC_TYPE_STRUCT];
+  *m_buffer += ">\n";
+}
+
+void print_xml_feature::visit (const tdesc_reg *reg)
+{
+  *m_buffer += "<reg name=\"";
+  *m_buffer += reg->name;
+  *m_buffer += "\" bitsize=\"";
+  *m_buffer += std::to_string (reg->bitsize);
+  *m_buffer += "\" type=\"";
+  *m_buffer += reg->type;
+  *m_buffer += "\" regnum=\"";
+  *m_buffer += std::to_string (reg->target_regnum);
+  if (reg->group.length () > 0)
+    {
+      *m_buffer += "\" group=\"";
+      *m_buffer += reg->group;
+    }
+  *m_buffer += "\"/>\n";
+}
+
+void print_xml_feature::visit_pre (const target_desc *e)
+{
+#ifndef IN_PROCESS_AGENT
+  *m_buffer += "<?xml version=\"1.0\"?>\n";
+  *m_buffer += "<!DOCTYPE target SYSTEM \"gdb-target.dtd\">\n";
+  *m_buffer += "<target>\n";
+  *m_buffer += "<architecture>";
+  *m_buffer += tdesc_architecture_name (e);
+  *m_buffer += "</architecture>\n";
+
+  const char *osabi = tdesc_osabi_name (e);
+  if (osabi != nullptr)
+    {
+      *m_buffer += "<osabi>";
+      *m_buffer += osabi;
+      *m_buffer += "</osabi>\n";
+    }
+#endif
+}
diff --git a/gdb/common/tdesc.h b/gdb/common/tdesc.h
index c0d2a10..1c5ddc5 100644
--- a/gdb/common/tdesc.h
+++ b/gdb/common/tdesc.h
@@ -372,4 +372,33 @@ void tdesc_create_reg (struct tdesc_feature *feature, const char *name,
 		       int regnum, int save_restore, const char *group,
 		       int bitsize, const char *type);
 
+/* Return the tdesc in string XML format.  */
+
+const char *tdesc_get_features_xml (target_desc *tdesc);
+
+/* Print target description as xml.  */
+
+class print_xml_feature : public tdesc_element_visitor
+{
+public:
+  print_xml_feature (std::string *buffer_)
+    : m_buffer (buffer_)
+  {}
+
+  ~print_xml_feature ()
+  {}
+
+  void visit_pre (const target_desc *e) override;
+  void visit_post (const target_desc *e) override;
+  void visit_pre (const tdesc_feature *e) override;
+  void visit_post (const tdesc_feature *e) override;
+  void visit (const tdesc_type_builtin *type) override;
+  void visit (const tdesc_type_vector *type) override;
+  void visit (const tdesc_type_with_fields *type) override;
+  void visit (const tdesc_reg *reg) override;
+
+private:
+  std::string *m_buffer;
+};
+
 #endif /* ARCH_TDESC_H */
diff --git a/gdb/gdbserver/tdesc.c b/gdb/gdbserver/tdesc.c
index e113447..0d9609b 100644
--- a/gdb/gdbserver/tdesc.c
+++ b/gdb/gdbserver/tdesc.c
@@ -59,6 +59,18 @@ bool target_desc::operator== (const target_desc &other) const
 
 #endif
 
+void target_desc::accept (tdesc_element_visitor &v) const
+{
+#ifndef IN_PROCESS_AGENT
+  v.visit_pre (this);
+
+  for (const tdesc_feature_up &feature : features)
+    feature->accept (v);
+
+  v.visit_post (this);
+#endif
+}
+
 void
 init_target_desc (struct target_desc *tdesc)
 {
@@ -158,8 +170,7 @@ set_tdesc_osabi (struct target_desc *target_desc, const char *name)
   target_desc->osabi = xstrdup (name);
 }
 
-/* Return a string which is of XML format, including XML target
-   description to be sent to GDB.  */
+/* See common/tdesc.h.  */
 
 const char *
 tdesc_get_features_xml (target_desc *tdesc)
@@ -171,31 +182,9 @@ tdesc_get_features_xml (target_desc *tdesc)
 
   if (tdesc->xmltarget == NULL)
     {
-      std::string buffer ("@<?xml version=\"1.0\"?>");
-
-      buffer += "<!DOCTYPE target SYSTEM \"gdb-target.dtd\">";
-      buffer += "<target>";
-      buffer += "<architecture>";
-      buffer += tdesc_architecture_name (tdesc);
-      buffer += "</architecture>";
-
-      const char *osabi = tdesc_osabi_name (tdesc);
-      if (osabi != nullptr)
-	{
-	  buffer += "<osabi>";
-	  buffer += osabi;
-	  buffer += "</osabi>";
-	}
-
-      for (const tdesc_feature_up &feature : tdesc->features)
-	{
-	  buffer += "<xi:include href=\"";
-	  buffer += feature->name;
-	  buffer += "\"/>";
-	}
-
-      buffer += "</target>";
-
+      std::string buffer ("@");
+      print_xml_feature v (&buffer);
+      tdesc->accept (v);
       tdesc->xmltarget = xstrdup (buffer.c_str ());
     }
 
diff --git a/gdb/gdbserver/tdesc.h b/gdb/gdbserver/tdesc.h
index 8534069..1c0c4b1 100644
--- a/gdb/gdbserver/tdesc.h
+++ b/gdb/gdbserver/tdesc.h
@@ -27,7 +27,7 @@
 /* A target description.  Inherit from tdesc_feature so that target_desc
    can be used as tdesc_feature.  */
 
-struct target_desc
+struct target_desc : tdesc_element
 {
   /* A vector of elements of register definitions that
      describe the inferior's register set.  */
@@ -73,6 +73,8 @@ public:
     return !(*this == other);
   }
 #endif
+
+  void accept (tdesc_element_visitor &v) const;
 };
 
 /* Copy target description SRC to DEST.  */
diff --git a/gdb/regformats/regdat.sh b/gdb/regformats/regdat.sh
index 8c6e191..e6e06bd 100755
--- a/gdb/regformats/regdat.sh
+++ b/gdb/regformats/regdat.sh
@@ -180,7 +180,6 @@ echo
 cat <<EOF
 #ifndef IN_PROCESS_AGENT
   result->expedite_regs = expedite_regs_${name};
-  result->xmltarget = xmltarget_${name};
 #endif
 
   init_target_desc (result);
diff --git a/gdb/target-descriptions.c b/gdb/target-descriptions.c
index da2c1ce..93e7357 100644
--- a/gdb/target-descriptions.c
+++ b/gdb/target-descriptions.c
@@ -333,6 +333,8 @@ struct target_desc : tdesc_element
   /* The features associated with this target.  */
   std::vector<tdesc_feature_up> features;
 
+  char *xmltarget = nullptr;
+
   void accept (tdesc_element_visitor &v) const override
   {
     v.visit_pre (this);
@@ -1667,6 +1669,21 @@ private:
   int m_next_regnum = 0;
 };
 
+/* See common/tdesc.h.  */
+
+const char *
+tdesc_get_features_xml (target_desc *tdesc)
+{
+  if (tdesc->xmltarget == nullptr)
+    {
+      std::string buffer ("@");
+      print_xml_feature v (&buffer);
+      tdesc->accept (v);
+      tdesc->xmltarget = xstrdup (buffer.c_str ());
+    }
+  return tdesc->xmltarget;
+}
+
 static void
 maint_print_c_tdesc_cmd (const char *args, int from_tty)
 {
@@ -1760,7 +1777,36 @@ maintenance_check_xml_descriptions (const char *dir, int from_tty)
 	= file_read_description_xml (tdesc_xml.data ());
 
       if (tdesc == NULL || *tdesc != *e.second)
-	failed++;
+	{
+	  printf_filtered ( _("Descriptions for %s do not match\n"), e.first);
+	  failed++;
+	  continue;
+	}
+
+      /* Convert both descriptions to xml, and then back again.  Confirm all
+	 descriptions are identical.  */
+
+      const char *xml = tdesc_get_features_xml ((target_desc *) tdesc);
+      const char *xml2 = tdesc_get_features_xml ((target_desc *) e.second);
+      gdb_assert (*xml == '@');
+      gdb_assert (*xml2 == '@');
+      const target_desc *t_trans = target_read_description_xml_string (xml+1);
+      const target_desc *t_trans2 = target_read_description_xml_string (xml2+1);
+
+      if (t_trans == NULL || t_trans2 == NULL)
+	{
+	  printf_filtered (
+	    _("Could not convert descriptions for %s back to xml (%p %p)\n"),
+	    e.first, t_trans, t_trans2);
+	  failed++;
+	}
+      else if (*tdesc != *t_trans || *tdesc != *t_trans2)
+	{
+	  printf_filtered
+	    (_("Translated descriptions for %s do not match (%d %d)\n"),
+	    e.first, *tdesc == *t_trans, *tdesc == *t_trans2);
+	  failed++;
+	}
     }
   printf_filtered (_("Tested %lu XML files, %d failed\n"),
 		   (long) selftests::xml_tdesc.size (), failed);
diff --git a/gdb/xml-tdesc.c b/gdb/xml-tdesc.c
index 9190d5f..f793f07 100644
--- a/gdb/xml-tdesc.c
+++ b/gdb/xml-tdesc.c
@@ -752,3 +752,12 @@ target_fetch_description_xml (struct target_ops *ops)
   return output;
 #endif
 }
+
+/* Take an xml string, parse it, and return the parsed description.  Does not
+   handle a string containing includes.  */
+
+const struct target_desc *
+target_read_description_xml_string (const char *xml_str)
+{
+  return tdesc_parse_xml (xml_str, nullptr, nullptr);
+}
diff --git a/gdb/xml-tdesc.h b/gdb/xml-tdesc.h
index 8f06797..fee60e8 100644
--- a/gdb/xml-tdesc.h
+++ b/gdb/xml-tdesc.h
@@ -44,5 +44,10 @@ const struct target_desc *target_read_description_xml (struct target_ops *);
    otherwise.  */
 gdb::optional<std::string> target_fetch_description_xml (target_ops *ops);
 
+/* Take an xml string, parse it, and return the parsed description.  Does not
+   handle a string containing includes.  */
+
+const struct target_desc *target_read_description_xml_string (const char *);
+
 #endif /* XML_TDESC_H */