[v2,6/8] Create xml from target descriptions

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

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.

2018-01-24  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.
	(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.

i don't really like print_xml_feature::visit_pre being declared in arch/tdesc.h
with different implementations in target-descriptions.c and gdbserver/tdesc.c
while all other visit_* implementations are in arch/tdesc.c.  I would prefere
visit_pre being implemented in arch/tdesc.c, too.  Even when it means to add
some #ifdef GDBSERVER ... #else ... #endif blocks until there is a common tdesc.

Same for tdesc_type::make_gdb_type (patch #5).  But here i would prefer to not
even declare the method for GDBserver, i.e.

struct tdesc_type
{

  [...]

#ifndef GDBSERVER
  virtual type *make_gdb_type (struct gdbarch *gdbarch) const = 0;
#endif
};

The problem i see with implementing stubs calling error is that you cannot find
out you made a mistake until you call the function during run-time.  This gives
room to nasty bugs which could easily be prevented when there is a compile bug.

Philipp


On Wed, 24 Jan 2018 09:29:50 +0000
Alan Hayward <Alan.Hayward@arm.com> wrote:

> This patch adds a print_xml_feature visitor class which turns a C
> target description into xml.
> 
> 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.
> 
> 2018-01-24  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.
> 	(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.
> 
> 
> diff --git a/gdb/arch/tdesc.h b/gdb/arch/tdesc.h
> index 9a5bf6f11b670e04e2b51f8334bc0adaf0b43962..b2e99c5ce1f7da0e6a194ca721eea96082e1fa68 100644
> --- a/gdb/arch/tdesc.h
> +++ b/gdb/arch/tdesc.h
> @@ -195,7 +195,7 @@ struct tdesc_type_builtin : tdesc_type
>    : tdesc_type (name, kind)
>    {}
> 
> -  void accept (tdesc_element_visitor &v) const override;
> +  void accept (tdesc_element_visitor &v) const override
>    {
>      v.visit (this);
>    }
> @@ -366,4 +366,33 @@ 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 9518571d03d394ee7cbf78b31974818201c889cd..388c6af1b93d40cf7cb5fb97c55912b91601814b 100644
> --- a/gdb/arch/tdesc.c
> +++ b/gdb/arch/tdesc.c
> @@ -288,4 +288,138 @@ 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";
> +}
> diff --git a/gdb/gdbserver/tdesc.h b/gdb/gdbserver/tdesc.h
> index 8ae6cddc1896af99d86206d159fb952a0f666043..6a86f66cf2aaf9aa2b20203cad1d272d70026822 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.  */
> @@ -72,7 +72,10 @@ public:
>    {
>      return !(*this == other);
>    }
> +
>  #endif
> +
> +  void accept (tdesc_element_visitor &v) const;
>  };
> 
>  /* Copy target description SRC to DEST.  */
> diff --git a/gdb/gdbserver/tdesc.c b/gdb/gdbserver/tdesc.c
> index f0bd266a54601484df74ee1c5f8dce6fe04661c4..42a657f6827ed06c9d98275c7566d0c02890e7b3 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)
>  {
> @@ -155,30 +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 ());
>      }
> 
> @@ -211,3 +202,22 @@ type *tdesc_type_with_fields::make_gdb_type (struct gdbarch *gdbarch) const
>  {
>    error (_("Cannot create gdbtypes."));
>  }
> +
> +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 8c6e191596350fb4e983f8736985d9832f41e2d3..e6e06bdab0bdecc579686f3525e9f93555e0dd83 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 4f11120dce4092f15de99680a7c4868c4a2f4493..68a85758f7f63e6b862afa29697adee77e776d89 100644
> --- a/gdb/target-descriptions.c
> +++ b/gdb/target-descriptions.c
> @@ -316,6 +316,8 @@ 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);
> @@ -1633,6 +1635,39 @@ 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;
> +}
> +
>  static void
>  maint_print_c_tdesc_cmd (const char *args, int from_tty)
>  {
> @@ -1726,7 +1761,34 @@ 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);
> +}
> 
>

Philipp Rudo <prudo@linux.vnet.ibm.com> writes:

> Same for tdesc_type::make_gdb_type (patch #5).  But here i would prefer to not
> even declare the method for GDBserver, i.e.
>
> struct tdesc_type
> {
>
>   [...]
>
> #ifndef GDBSERVER
>   virtual type *make_gdb_type (struct gdbarch *gdbarch) const = 0;
> #endif
> };
>
> The problem i see with implementing stubs calling error is that you cannot find
> out you made a mistake until you call the function during run-time.  This gives
> room to nasty bugs which could easily be prevented when there is a compile bug.


make_gdb_type and gdbarch shouldn't be put into arch/tdesc.h at all, if
possible.  You can create an sub-class of tdesc_element_visitor in gdb
side, and create the gdb type by visiting these elements, like this,

class gdb_type_creator : public tdesc_element_visitor
{
public:
  gdb_type_createor (struct gdbarch *gdbarch)
    : m_gdbarch (gdbarch)
  {}

  void visit (const tdesc_type_builtin *e) override
  {
     switch (e->kind)
     {
        case TDESC_TYPE_BOOL:
          m_type = builtin_type (m_gdbarch)->builtin_bool;
          break;
        ....
     };
  }

  void visit (const tdesc_type_vector *e) override
  {
     // do what tdesc_type_vector::make_gdb_type does.
  }

  void visit (const tdesc_type_with_fields *e) override
  {
     // likewise.
  }
  
private:
  // input
  struct * const m_gdbarch;
  // output
  type *m_type;
};

gdb_type_creator gdb_type (gdbarch);

tdesc_type->accept (gdb_type);

gdb_type.m_type is the type we need.

> On 25 Jan 2018, at 13:14, Philipp Rudo <prudo@linux.vnet.ibm.com> wrote:

> 

> 

> i don't really like print_xml_feature::visit_pre being declared in arch/tdesc.h

> with different implementations in target-descriptions.c and gdbserver/tdesc.c

> while all other visit_* implementations are in arch/tdesc.c.  I would prefere

> visit_pre being implemented in arch/tdesc.c, too.  Even when it means to add

> some #ifdef GDBSERVER ... #else ... #endif blocks until there is a common tdesc.


Thanks for the review!

A common print_xml_feature would require 4 ifdefs, which would be too messy.
I’ll take a look see if I can communise the tdesc_architecture and tdesc_osabi
interfaces - it should be fairly simple to do.
Once done, I should be able to add a common print_xml_feature without any
ifdefs. Hopefully.


> On 25 Jan 2018, at 15:44, Yao Qi <qiyaoltc@gmail.com> wrote:

> 

> Philipp Rudo <prudo@linux.vnet.ibm.com> writes:

> 

>> Same for tdesc_type::make_gdb_type (patch #5).  But here i would prefer to not

>> even declare the method for GDBserver, i.e.

>> 

>> struct tdesc_type

>> {

>> 

>>  [...]

>> 

>> #ifndef GDBSERVER

>>  virtual type *make_gdb_type (struct gdbarch *gdbarch) const = 0;

>> #endif

>> };

>> 

>> The problem i see with implementing stubs calling error is that you cannot find

>> out you made a mistake until you call the function during run-time.  This gives

>> room to nasty bugs which could easily be prevented when there is a compile bug.

> 

> 

> make_gdb_type and gdbarch shouldn't be put into arch/tdesc.h at all, if

> possible.  You can create an sub-class of tdesc_element_visitor in gdb

> side, and create the gdb type by visiting these elements, like this,

> 

> class gdb_type_creator : public tdesc_element_visitor

….

Nice idea. I can add an extra patch into the series to do this.

On Thu, 25 Jan 2018 16:13:16 +0000
Alan Hayward <Alan.Hayward@arm.com> wrote:

> > On 25 Jan 2018, at 13:14, Philipp Rudo <prudo@linux.vnet.ibm.com> wrote:
> > 
> > 
> > i don't really like print_xml_feature::visit_pre being declared in arch/tdesc.h
> > with different implementations in target-descriptions.c and gdbserver/tdesc.c
> > while all other visit_* implementations are in arch/tdesc.c.  I would prefere
> > visit_pre being implemented in arch/tdesc.c, too.  Even when it means to add
> > some #ifdef GDBSERVER ... #else ... #endif blocks until there is a common tdesc.  
> 
> Thanks for the review!
> 
> A common print_xml_feature would require 4 ifdefs, which would be too messy.
> I’ll take a look see if I can communise the tdesc_architecture and tdesc_osabi
> interfaces - it should be fairly simple to do.
> Once done, I should be able to add a common print_xml_feature without any
> ifdefs. Hopefully.
> 

Having a common interface would be even better :)

> 
> > On 25 Jan 2018, at 15:44, Yao Qi <qiyaoltc@gmail.com> wrote:
> > 
> > Philipp Rudo <prudo@linux.vnet.ibm.com> writes:
> >   
> >> Same for tdesc_type::make_gdb_type (patch #5).  But here i would prefer to not
> >> even declare the method for GDBserver, i.e.
> >> 
> >> struct tdesc_type
> >> {
> >> 
> >>  [...]
> >> 
> >> #ifndef GDBSERVER
> >>  virtual type *make_gdb_type (struct gdbarch *gdbarch) const = 0;
> >> #endif
> >> };
> >> 
> >> The problem i see with implementing stubs calling error is that you cannot find
> >> out you made a mistake until you call the function during run-time.  This gives
> >> room to nasty bugs which could easily be prevented when there is a compile bug.  
> > 
> > 
> > make_gdb_type and gdbarch shouldn't be put into arch/tdesc.h at all, if
> > possible.  You can create an sub-class of tdesc_element_visitor in gdb
> > side, and create the gdb type by visiting these elements, like this,
> > 
> > class gdb_type_creator : public tdesc_element_visitor  
> ….
> 
> Nice idea. I can add an extra patch into the series to do this.

Yeah, Yao's solution is better than mine.

Oh i forgot to tell you, great series.

Philipp