path: root/gdb/cp-valprint.c

/* Support for printing C++ values for GDB, the GNU debugger.

   Copyright (C) 1986, 1988, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997,
   2000, 2001, 2002, 2003, 2005, 2006, 2007, 2008, 2009, 2010
   Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"
#include "gdb_obstack.h"
#include "symtab.h"
#include "gdbtypes.h"
#include "expression.h"
#include "value.h"
#include "command.h"
#include "gdbcmd.h"
#include "demangle.h"
#include "annotate.h"
#include "gdb_string.h"
#include "c-lang.h"
#include "target.h"
#include "cp-abi.h"
#include "valprint.h"
#include "cp-support.h"
#include "language.h"
#include "python/python.h"

/* Controls printing of vtbl's */
static void
show_vtblprint (struct ui_file *file, int from_tty,
		struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("\
Printing of C++ virtual function tables is %s.\n"),
		    value);
}

/* Controls looking up an object's derived type using what we find in
   its vtables.  */
static void
show_objectprint (struct ui_file *file, int from_tty,
		  struct cmd_list_element *c,
		  const char *value)
{
  fprintf_filtered (file, _("\
Printing of object's derived type based on vtable info is %s.\n"),
		    value);
}

static void
show_static_field_print (struct ui_file *file, int from_tty,
			 struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Printing of C++ static members is %s.\n"),
		    value);
}


static struct obstack dont_print_vb_obstack;
static struct obstack dont_print_statmem_obstack;

extern void _initialize_cp_valprint (void);

static void cp_print_static_field (struct type *, struct value *,
				   struct ui_file *, int,
				   const struct value_print_options *);

static void cp_print_value (struct type *, struct type *, const gdb_byte *,
			    int, CORE_ADDR, struct ui_file *, int,
			    const struct value_print_options *, struct type **);


/* GCC versions after 2.4.5 use this.  */
const char vtbl_ptr_name[] = "__vtbl_ptr_type";

/* Return truth value for assertion that TYPE is of the type
   "pointer to virtual function".  */

int
cp_is_vtbl_ptr_type (struct type *type)
{
  char *typename = type_name_no_tag (type);

  return (typename != NULL && !strcmp (typename, vtbl_ptr_name));
}

/* Return truth value for the assertion that TYPE is of the type
   "pointer to virtual function table".  */

int
cp_is_vtbl_member (struct type *type)
{
  /* With older versions of g++, the vtbl field pointed to an array
     of structures.  Nowadays it points directly to the structure. */
  if (TYPE_CODE (type) == TYPE_CODE_PTR)
    {
      type = TYPE_TARGET_TYPE (type);
      if (TYPE_CODE (type) == TYPE_CODE_ARRAY)
	{
	  type = TYPE_TARGET_TYPE (type);
	  if (TYPE_CODE (type) == TYPE_CODE_STRUCT	/* if not using thunks */
	      || TYPE_CODE (type) == TYPE_CODE_PTR)	/* if using thunks */
	    {
	      /* Virtual functions tables are full of pointers
	         to virtual functions. */
	      return cp_is_vtbl_ptr_type (type);
	    }
	}
      else if (TYPE_CODE (type) == TYPE_CODE_STRUCT)  /* if not using thunks */
	{
	  return cp_is_vtbl_ptr_type (type);
	}
      else if (TYPE_CODE (type) == TYPE_CODE_PTR)     /* if using thunks */
	{
	  /* The type name of the thunk pointer is NULL when using dwarf2.
	     We could test for a pointer to a function, but there is
	     no type info for the virtual table either, so it wont help.  */
	  return cp_is_vtbl_ptr_type (type);
	}
    }
  return 0;
}

/* Mutually recursive subroutines of cp_print_value and c_val_print to
   print out a structure's fields: cp_print_value_fields and cp_print_value.

   TYPE, VALADDR, ADDRESS, STREAM, RECURSE, and OPTIONS have the
   same meanings as in cp_print_value and c_val_print.

   2nd argument REAL_TYPE is used to carry over the type of the derived
   class across the recursion to base classes. 

   DONT_PRINT is an array of baseclass types that we
   should not print, or zero if called from top level.  */

void
cp_print_value_fields (struct type *type, struct type *real_type,
		       const gdb_byte *valaddr, int offset, CORE_ADDR address,
		       struct ui_file *stream, int recurse,
		       const struct value_print_options *options,
		       struct type **dont_print_vb, int dont_print_statmem)
{
  int i, len, n_baseclasses;
  char *last_dont_print = obstack_next_free (&dont_print_statmem_obstack);
  int fields_seen = 0;

  CHECK_TYPEDEF (type);

  fprintf_filtered (stream, "{");
  len = TYPE_NFIELDS (type);
  n_baseclasses = TYPE_N_BASECLASSES (type);

  /* First, print out baseclasses such that we don't print
     duplicates of virtual baseclasses.  */

  if (n_baseclasses > 0)
    cp_print_value (type, real_type, valaddr, offset, address, stream,
		    recurse + 1, options, dont_print_vb);

  /* Second, print out data fields */

  /* If there are no data fields, skip this part */
  if (len == n_baseclasses || !len)
    fprintf_filtered (stream, "<No data fields>");
  else
    {
      struct obstack tmp_obstack = dont_print_statmem_obstack;

      if (dont_print_statmem == 0)
	{
	  /* If we're at top level, carve out a completely fresh
	     chunk of the obstack and use that until this particular
	     invocation returns.  */
	  obstack_finish (&dont_print_statmem_obstack);
	}

      for (i = n_baseclasses; i < len; i++)
	{
	  /* If requested, skip printing of static fields.  */
	  if (!options->static_field_print
	      && field_is_static (&TYPE_FIELD (type, i)))
	    continue;

	  if (fields_seen)
	    fprintf_filtered (stream, ", ");
	  else if (n_baseclasses > 0)
	    {
	      if (options->pretty)
		{
		  fprintf_filtered (stream, "\n");
		  print_spaces_filtered (2 + 2 * recurse, stream);
		  fputs_filtered ("members of ", stream);
		  fputs_filtered (type_name_no_tag (type), stream);
		  fputs_filtered (": ", stream);
		}
	    }
	  fields_seen = 1;

	  if (options->pretty)
	    {
	      fprintf_filtered (stream, "\n");
	      print_spaces_filtered (2 + 2 * recurse, stream);
	    }
	  else
	    {
	      wrap_here (n_spaces (2 + 2 * recurse));
	    }
	  if (options->inspect_it)
	    {
	      if (TYPE_CODE (TYPE_FIELD_TYPE (type, i)) == TYPE_CODE_PTR)
		fputs_filtered ("\"( ptr \"", stream);
	      else
		fputs_filtered ("\"( nodef \"", stream);
	      if (field_is_static (&TYPE_FIELD (type, i)))
		fputs_filtered ("static ", stream);
	      fprintf_symbol_filtered (stream, TYPE_FIELD_NAME (type, i),
				       current_language->la_language,
				       DMGL_PARAMS | DMGL_ANSI);
	      fputs_filtered ("\" \"", stream);
	      fprintf_symbol_filtered (stream, TYPE_FIELD_NAME (type, i),
				       current_language->la_language,
				       DMGL_PARAMS | DMGL_ANSI);
	      fputs_filtered ("\") \"", stream);
	    }
	  else
	    {
	      annotate_field_begin (TYPE_FIELD_TYPE (type, i));

	      if (field_is_static (&TYPE_FIELD (type, i)))
		fputs_filtered ("static ", stream);
	      fprintf_symbol_filtered (stream, TYPE_FIELD_NAME (type, i),
				       current_language->la_language,
				       DMGL_PARAMS | DMGL_ANSI);
	      annotate_field_name_end ();
	      /* do not print leading '=' in case of anonymous unions */
	      if (strcmp (TYPE_FIELD_NAME (type, i), ""))
		fputs_filtered (" = ", stream);
	      annotate_field_value ();
	    }

	  if (!field_is_static (&TYPE_FIELD (type, i))
	      && TYPE_FIELD_PACKED (type, i))
	    {
	      struct value *v;

	      /* Bitfields require special handling, especially due to byte
	         order problems.  */
	      if (TYPE_FIELD_IGNORE (type, i))
		{
		  fputs_filtered ("<optimized out or zero length>", stream);
		}
	      else
		{
		  struct value_print_options opts = *options;
		  opts.deref_ref = 0;
		  v = value_from_longest
		    (TYPE_FIELD_TYPE (type, i), 
		     unpack_field_as_long (type, valaddr + offset, i));

		  common_val_print (v, stream, recurse + 1, &opts,
				    current_language);
		}
	    }
	  else
	    {
	      if (TYPE_FIELD_IGNORE (type, i))
		{
		  fputs_filtered ("<optimized out or zero length>", stream);
		}
	      else if (field_is_static (&TYPE_FIELD (type, i)))
		{
		  struct value *v = value_static_field (type, i);
		  if (v == NULL)
		    fputs_filtered ("<optimized out>", stream);
		  else
		    cp_print_static_field (TYPE_FIELD_TYPE (type, i), v,
					   stream, recurse + 1, options);
		}
	      else
		{
		  struct value_print_options opts = *options;
		  opts.deref_ref = 0;
		  val_print (TYPE_FIELD_TYPE (type, i),
			     valaddr, offset + TYPE_FIELD_BITPOS (type, i) / 8,
			     address + TYPE_FIELD_BITPOS (type, i) / 8,
			     stream, recurse + 1, &opts,
			     current_language);
		}
	    }
	  annotate_field_end ();
	}

      if (dont_print_statmem == 0)
	{
	  /* Free the space used to deal with the printing
	     of the members from top level.  */
	  obstack_free (&dont_print_statmem_obstack, last_dont_print);
	  dont_print_statmem_obstack = tmp_obstack;
	}

      if (options->pretty)
	{
	  fprintf_filtered (stream, "\n");
	  print_spaces_filtered (2 * recurse, stream);
	}
    }				/* if there are data fields */

  fprintf_filtered (stream, "}");
}

/* Special val_print routine to avoid printing multiple copies of virtual
   baseclasses.  */

static void
cp_print_value (struct type *type, struct type *real_type,
		const gdb_byte *valaddr, int offset, CORE_ADDR address,
		struct ui_file *stream, int recurse,
		const struct value_print_options *options,
		struct type **dont_print_vb)
{
  struct type **last_dont_print
    = (struct type **) obstack_next_free (&dont_print_vb_obstack);
  struct obstack tmp_obstack = dont_print_vb_obstack;
  int i, n_baseclasses = TYPE_N_BASECLASSES (type);
  int thisoffset;
  struct type *thistype;

  if (dont_print_vb == 0)
    {
      /* If we're at top level, carve out a completely fresh
         chunk of the obstack and use that until this particular
         invocation returns.  */
      /* Bump up the high-water mark.  Now alpha is omega.  */
      obstack_finish (&dont_print_vb_obstack);
    }

  for (i = 0; i < n_baseclasses; i++)
    {
      int boffset;
      int skip;
      struct type *baseclass = check_typedef (TYPE_BASECLASS (type, i));
      char *basename = TYPE_NAME (baseclass);
      const gdb_byte *base_valaddr;

      if (BASETYPE_VIA_VIRTUAL (type, i))
	{
	  struct type **first_dont_print
	    = (struct type **) obstack_base (&dont_print_vb_obstack);

	  int j = (struct type **) obstack_next_free (&dont_print_vb_obstack)
	    - first_dont_print;

	  while (--j >= 0)
	    if (baseclass == first_dont_print[j])
	      goto flush_it;

	  obstack_ptr_grow (&dont_print_vb_obstack, baseclass);
	}

      thisoffset = offset;
      thistype = real_type;

      boffset = baseclass_offset (type, i, valaddr + offset, address);
      skip = ((boffset == -1) || (boffset + offset) < 0) ? 1 : -1;

      if (BASETYPE_VIA_VIRTUAL (type, i))
	{
	  /* The virtual base class pointer might have been
	     clobbered by the user program. Make sure that it
	     still points to a valid memory location.  */

	  if (boffset != -1
	      && ((boffset + offset) < 0
		  || (boffset + offset) >= TYPE_LENGTH (type)))
	    {
	      /* FIXME (alloca): unsafe if baseclass is really really large. */
	      gdb_byte *buf = alloca (TYPE_LENGTH (baseclass));
	      base_valaddr = buf;
	      if (target_read_memory (address + boffset, buf,
				      TYPE_LENGTH (baseclass)) != 0)
		skip = 1;
	      address = address + boffset;
	      thisoffset = 0;
	      boffset = 0;
	      thistype = baseclass;
	    }
	  else
	    base_valaddr = valaddr;
	}
      else
	base_valaddr = valaddr;

      /* now do the printing */
      if (options->pretty)
	{
	  fprintf_filtered (stream, "\n");
	  print_spaces_filtered (2 * recurse, stream);
	}
      fputs_filtered ("<", stream);
      /* Not sure what the best notation is in the case where there is no
         baseclass name.  */
      fputs_filtered (basename ? basename : "", stream);
      fputs_filtered ("> = ", stream);


      if (skip >= 1)
	fprintf_filtered (stream, "<invalid address>");
      else
	{
	  int result = 0;

	  /* Attempt to run the Python pretty-printers on the
	     baseclass if possible.  */
	  if (!options->raw)
	    result = apply_val_pretty_printer (baseclass, base_valaddr,
					       thisoffset + boffset,
					       address + boffset,
					       stream, recurse,
					       options,
					       current_language);
	  	  
	  if (!result)
	    cp_print_value_fields (baseclass, thistype, base_valaddr,
				   thisoffset + boffset, address + boffset,
				   stream, recurse, options,
				   ((struct type **)
				    obstack_base (&dont_print_vb_obstack)),
				   0);
	}
      fputs_filtered (", ", stream);

    flush_it:
      ;
    }

  if (dont_print_vb == 0)
    {
      /* Free the space used to deal with the printing
         of this type from top level.  */
      obstack_free (&dont_print_vb_obstack, last_dont_print);
      /* Reset watermark so that we can continue protecting
         ourselves from whatever we were protecting ourselves.  */
      dont_print_vb_obstack = tmp_obstack;
    }
}

/* Print value of a static member.
   To avoid infinite recursion when printing a class that contains
   a static instance of the class, we keep the addresses of all printed
   static member classes in an obstack and refuse to print them more
   than once.

   VAL contains the value to print, TYPE, STREAM, RECURSE, and OPTIONS
   have the same meanings as in c_val_print.  */

static void
cp_print_static_field (struct type *type,
		       struct value *val,
		       struct ui_file *stream,
		       int recurse,
		       const struct value_print_options *options)
{
  struct value_print_options opts;
  if (TYPE_CODE (type) == TYPE_CODE_STRUCT)
    {
      CORE_ADDR *first_dont_print;
      CORE_ADDR addr;
      int i;

      first_dont_print
	= (CORE_ADDR *) obstack_base (&dont_print_statmem_obstack);
      i = (CORE_ADDR *) obstack_next_free (&dont_print_statmem_obstack)
	- first_dont_print;

      while (--i >= 0)
	{
	  if (value_address (val) == first_dont_print[i])
	    {
	      fputs_filtered ("<same as static member of an already"
			      " seen type>",
			      stream);
	      return;
	    }
	}

      addr = value_address (val);
      obstack_grow (&dont_print_statmem_obstack, (char *) &addr,
		    sizeof (CORE_ADDR));

      CHECK_TYPEDEF (type);
      cp_print_value_fields (type, type, value_contents_all (val),
			     value_embedded_offset (val), addr,
			     stream, recurse, options, NULL, 1);
      return;
    }

  opts = *options;
  opts.deref_ref = 0;
  val_print (type, value_contents_all (val), 
	     value_embedded_offset (val), value_address (val),
	     stream, recurse, &opts, current_language);
}


/* Find the field in *DOMAIN, or its non-virtual base classes, with bit offset
   OFFSET.  Set *DOMAIN to the containing type and *FIELDNO to the containing
   field number.  If OFFSET is not exactly at the start of some field, set
   *DOMAIN to NULL.  */

static void
cp_find_class_member (struct type **domain_p, int *fieldno,
		      LONGEST offset)
{
  struct type *domain;
  unsigned int i;
  unsigned len;

  *domain_p = check_typedef (*domain_p);
  domain = *domain_p;
  len = TYPE_NFIELDS (domain);

  for (i = TYPE_N_BASECLASSES (domain); i < len; i++)
    {
      LONGEST bitpos = TYPE_FIELD_BITPOS (domain, i);

      QUIT;
      if (offset == bitpos)
	{
	  *fieldno = i;
	  return;
	}
    }

  for (i = 0; i < TYPE_N_BASECLASSES (domain); i++)
    {
      LONGEST bitpos = TYPE_FIELD_BITPOS (domain, i);
      LONGEST bitsize = 8 * TYPE_LENGTH (TYPE_FIELD_TYPE (domain, i));

      if (offset >= bitpos && offset < bitpos + bitsize)
	{
	  *domain_p = TYPE_FIELD_TYPE (domain, i);
	  cp_find_class_member (domain_p, fieldno, offset - bitpos);
	  return;
	}
    }

  *domain_p = NULL;
}

void
cp_print_class_member (const gdb_byte *valaddr, struct type *type,
		       struct ui_file *stream, char *prefix)
{
  enum bfd_endian byte_order = gdbarch_byte_order (get_type_arch (type));

  /* VAL is a byte offset into the structure type DOMAIN.
     Find the name of the field for that offset and
     print it.  */
  struct type *domain = TYPE_DOMAIN_TYPE (type);
  LONGEST val;
  unsigned int fieldno;

  val = extract_signed_integer (valaddr, TYPE_LENGTH (type), byte_order);

  /* Pointers to data members are usually byte offsets into an object.
     Because a data member can have offset zero, and a NULL pointer to
     member must be distinct from any valid non-NULL pointer to
     member, either the value is biased or the NULL value has a
     special representation; both are permitted by ISO C++.  HP aCC
     used a bias of 0x20000000; HP cfront used a bias of 1; g++ 3.x
     and other compilers which use the Itanium ABI use -1 as the NULL
     value.  GDB only supports that last form; to add support for
     another form, make this into a cp-abi hook.  */

  if (val == -1)
    {
      fprintf_filtered (stream, "NULL");
      return;
    }

  cp_find_class_member (&domain, &fieldno, val << 3);

  if (domain != NULL)
    {
      char *name;
      fputs_filtered (prefix, stream);
      name = type_name_no_tag (domain);
      if (name)
	fputs_filtered (name, stream);
      else
	c_type_print_base (domain, stream, 0, 0);
      fprintf_filtered (stream, "::");
      fputs_filtered (TYPE_FIELD_NAME (domain, fieldno), stream);
    }
  else
    fprintf_filtered (stream, "%ld", (long) val);
}


void
_initialize_cp_valprint (void)
{
  add_setshow_boolean_cmd ("static-members", class_support,
			   &user_print_options.static_field_print, _("\
Set printing of C++ static members."), _("\
Show printing of C++ static members."), NULL,
			   NULL,
			   show_static_field_print,
			   &setprintlist, &showprintlist);

  add_setshow_boolean_cmd ("vtbl", class_support,
			   &user_print_options.vtblprint, _("\
Set printing of C++ virtual function tables."), _("\
Show printing of C++ virtual function tables."), NULL,
			   NULL,
			   show_vtblprint,
			   &setprintlist, &showprintlist);

  add_setshow_boolean_cmd ("object", class_support,
			   &user_print_options.objectprint, _("\
Set printing of object's derived type based on vtable info."), _("\
Show printing of object's derived type based on vtable info."), NULL,
			   NULL,
			   show_objectprint,
			   &setprintlist, &showprintlist);

  obstack_begin (&dont_print_vb_obstack, 32 * sizeof (struct type *));
  obstack_specify_allocation (&dont_print_statmem_obstack,
			      32 * sizeof (CORE_ADDR), sizeof (CORE_ADDR),
			      xmalloc, xfree);
}