[PATCH 4/6]: Create xml from target descriptions

[Alan Hayward <Alan dot Hayward at arm dot com>]

This patch adds a print_xml_feature visitor class which turns a C
target description into xml.

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.

I have added a new function void debug(const struct target_desc *)
which simply prints a given target description out as xml.
This follows the style of GCC which has debug functions for all major
structure types (eg rtx). When debugging GCC I can usually take any
tree or expression and just "call debug(x)" to get a nice dump of it,
or sprinkle debug(x) calls through my failing code. I find this really
useful, however I'm happy to remove (or rename) the function if people
don't like it.

Alan.

2018-01-16  Alan Hayward  <alan.hayward@arm.com>

gdb/
	* arch/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.
	* arch/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.
	(debug): Add target_desc debug function.
	(maintenance_check_xml_descriptions): Test xml generation.
	* target-descriptions.h (debug): Add declaration.
	* 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.

diff --git a/gdb/arch/tdesc.h b/gdb/arch/tdesc.h
index 633853447d98c952cfed462939b486afd2738742..edd7de104973676fe69873ffe696e99eb77fbc84 100644
--- a/gdb/arch/tdesc.h
+++ b/gdb/arch/tdesc.h
@@ -359,4 +359,33 @@ 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/arch/tdesc.c b/gdb/arch/tdesc.c
index e6005a75a7264bba4cd177e4ec1efd90809e25c8..e43f37095d636cf680ce2b55c653deedd2c59eae 100644
--- a/gdb/arch/tdesc.c
+++ b/gdb/arch/tdesc.c
@@ -323,3 +323,138 @@ tdesc_add_enum_value (tdesc_type_with_fields *type, int value,
 			     tdesc_predefined_type (TDESC_TYPE_INT32),
 			     value, -1);
 }
+
+
+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";
+}
diff --git a/gdb/gdbserver/tdesc.c b/gdb/gdbserver/tdesc.c
index a96b3f07e7aff81f32a160d6498c8012d18bd0c7..08b896ba790a0bbf7a47f35952555e278830800c 100644
--- a/gdb/gdbserver/tdesc.c
+++ b/gdb/gdbserver/tdesc.c
@@ -31,7 +31,16 @@ target_desc::~target_desc ()
 }

 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
+}

 bool target_desc::operator== (const target_desc &other) const
 {
@@ -158,30 +167,9 @@ 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->arch;
-      buffer += "</architecture>";
-
-      if (tdesc->osabi != nullptr)
-	{
-	  buffer += "<osabi>";
-	  buffer += tdesc->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 ());
     }

@@ -213,4 +201,24 @@ type *tdesc_type_vector::make_gdb_type (struct gdbarch *gdbarch) const
 type *tdesc_type_with_fields::make_gdb_type (struct gdbarch *gdbarch) const
 {
   error (_("Cannot create gdbtypes."));
-}
\ No newline at end of file
+}
+
+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 += e->arch;
+  *m_buffer += "</architecture>\n";
+
+  if (e->osabi != nullptr)
+    {
+      *m_buffer += "<osabi>";
+      *m_buffer += e->osabi;
+      *m_buffer += "</osabi>\n";
+    }
+#endif
+  }
+
diff --git a/gdb/regformats/regdat.sh b/gdb/regformats/regdat.sh
index 8341e11ba76031cc260d60fdc2071bc8a2188f8e..31312fae43dcd369d43e951ffa9e63af4bef450d 100755
--- a/gdb/regformats/regdat.sh
+++ b/gdb/regformats/regdat.sh
@@ -189,7 +189,7 @@ fi

 cat <<EOF
   result->expedite_regs = expedite_regs_${name};
-  result->xmltarget = xmltarget_${name};
+  tdesc_get_features_xml (result);
 #endif

   init_target_desc (result);
diff --git a/gdb/target-descriptions.h b/gdb/target-descriptions.h
index 759fd34a0fe31f84a8531c799e5a3556e768c604..2a177d5b003c1461d837d22cc4fd5d52c0482ccc 100644
--- a/gdb/target-descriptions.h
+++ b/gdb/target-descriptions.h
@@ -218,6 +218,8 @@ void tdesc_add_typed_bitfield (tdesc_type_with_fields *type, const char *field_n
 void tdesc_add_enum_value (tdesc_type_with_fields *type, int value,
 			   const char *name);

+void debug (const struct target_desc *);
+
 #if GDB_SELF_TEST
 namespace selftests {

diff --git a/gdb/target-descriptions.c b/gdb/target-descriptions.c
index cef65a8fe61e22362e0bc4e6dbd7e3c0a0f4d1b4..6787848b287414cd218ad62e274707d5b4b5a368 100644
--- a/gdb/target-descriptions.c
+++ b/gdb/target-descriptions.c
@@ -86,6 +86,8 @@ 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);
@@ -1622,6 +1624,44 @@ private:
   int m_next_regnum = 0;
 };

+void print_xml_feature::visit_pre (const target_desc *e)
+{
+  *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 (e)->printable_name;
+  *m_buffer += "</architecture>\n";
+
+  if (e->osabi != GDB_OSABI_UNKNOWN)
+    {
+      *m_buffer += "<osabi>";
+      *m_buffer += gdbarch_osabi_name (tdesc_osabi (e));
+      *m_buffer += "</osabi>\n";
+    }
+}
+
+/* Return a string which is of XML format, including XML target
+   description to be sent to GDB.  */
+
+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;
+}
+
+void debug (const struct target_desc *tdesc)
+{
+  printf_filtered (_("%s\n"), tdesc_get_features_xml ((target_desc*) tdesc));
+}
+
 static void
 maint_print_c_tdesc_cmd (const char *args, int from_tty)
 {
@@ -1715,7 +1755,34 @@ 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);
+      const target_desc *t_trans = target_read_description_xml_string (xml);
+      const target_desc *t_trans2 = target_read_description_xml_string (xml2);
+
+      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.h b/gdb/xml-tdesc.h
index 8f0679707ad0f1e04d803f955f7fb98b4cc0c8c8..fee60e86dd10e1543b935c3cebce505d4dc828e2 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 */

diff --git a/gdb/xml-tdesc.c b/gdb/xml-tdesc.c
index 9190d5f3c64ffdc6d7987d651527f597d695c5a6..f793f07c96847a3d61188fff1c5d63952cc37565 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);
+}