dwarfread.c

早期freebsd实现

    {
      basicdieinfo (&mbr, thisdie, objfile);
      completedieinfo (&mbr, objfile);
      if (mbr.die_length <= SIZEOF_DIE_LENGTH)
	{
	  break;
	}
      else if (mbr.at_sibling != 0)
	{
	  nextdie = dbbase + mbr.at_sibling - dbroff;
	}
      else
	{
	  nextdie = thisdie + mbr.die_length;
	}
      switch (mbr.die_tag)
	{
	case TAG_member:
	  /* Get space to record the next field's data.  */
	  new = (struct nextfield *) alloca (sizeof (struct nextfield));
	  new -> next = list;
	  list = new;
	  /* Save the data.  */
	  list -> field.name =
	      obsavestring (mbr.at_name, strlen (mbr.at_name),
			    &objfile -> type_obstack);
	  list -> field.type = decode_die_type (&mbr);
	  list -> field.bitpos = 8 * locval (mbr.at_location);
	  /* Handle bit fields. */
	  list -> field.bitsize = mbr.at_bit_size;
#if BITS_BIG_ENDIAN
	  /* For big endian bits, the at_bit_offset gives the additional
	     bit offset from the MSB of the containing anonymous object to
	     the MSB of the field.  We don't have to do anything special
	     since we don't need to know the size of the anonymous object. */
	  list -> field.bitpos += mbr.at_bit_offset;
#else
	  /* For little endian bits, we need to have a non-zero at_bit_size,
	     so that we know we are in fact dealing with a bitfield.  Compute
	     the bit offset to the MSB of the anonymous object, subtract off
	     the number of bits from the MSB of the field to the MSB of the
	     object, and then subtract off the number of bits of the field
	     itself.  The result is the bit offset of the LSB of the field. */
	  if (mbr.at_bit_size > 0)
	    {
	      if (mbr.has_at_byte_size)
		{
		  /* The size of the anonymous object containing the bit field
		     is explicit, so use the indicated size (in bytes). */
		  anonymous_size = mbr.at_byte_size;
		}
	      else
		{
		  /* The size of the anonymous object containing the bit field
		     matches the size of an object of the bit field's type.
		     DWARF allows at_byte_size to be left out in such cases,
		     as a debug information size optimization. */
		  anonymous_size = TYPE_LENGTH (list -> field.type);
		}
	      list -> field.bitpos +=
		anonymous_size * 8 - mbr.at_bit_offset - mbr.at_bit_size;
	    }
#endif
	  nfields++;
	  break;
	default:
	  process_dies (thisdie, nextdie, objfile);
	  break;
	}
      thisdie = nextdie;
    }
  /* Now create the vector of fields, and record how big it is.  We may
     not even have any fields, if this DIE was generated due to a reference
     to an anonymous structure or union.  In this case, TYPE_FLAG_STUB is
     set, which clues gdb in to the fact that it needs to search elsewhere
     for the full structure definition. */
  if (nfields == 0)
    {
      TYPE_FLAGS (type) |= TYPE_FLAG_STUB;
    }
  else
    {
      TYPE_NFIELDS (type) = nfields;
      TYPE_FIELDS (type) = (struct field *)
	TYPE_ALLOC (type, sizeof (struct field) * nfields);
      /* Copy the saved-up fields into the field vector.  */
      for (n = nfields; list; list = list -> next)
	{
	  TYPE_FIELD (type, --n) = list -> field;
	}	
    }
  return (type);
}

/*

LOCAL FUNCTION

	read_structure_scope -- process all dies within struct or union

SYNOPSIS

	static void read_structure_scope (struct dieinfo *dip,
		char *thisdie, char *enddie, struct objfile *objfile)

DESCRIPTION

	Called when we find the DIE that starts a structure or union
	scope (definition) to process all dies that define the members
	of the structure or union.  DIP is a pointer to the die info
	struct for the DIE that names the structure or union.

NOTES

	Note that we need to call struct_type regardless of whether or not
	the DIE has an at_name attribute, since it might be an anonymous
	structure or union.  This gets the type entered into our set of
	user defined types.

	However, if the structure is incomplete (an opaque struct/union)
	then suppress creating a symbol table entry for it since gdb only
	wants to find the one with the complete definition.  Note that if
	it is complete, we just call new_symbol, which does it's own
	checking about whether the struct/union is anonymous or not (and
	suppresses creating a symbol table entry itself).
	
 */

static void
read_structure_scope (dip, thisdie, enddie, objfile)
     struct dieinfo *dip;
     char *thisdie;
     char *enddie;
     struct objfile *objfile;
{
  struct type *type;
  struct symbol *sym;
  
  type = struct_type (dip, thisdie, enddie, objfile);
  if (!(TYPE_FLAGS (type) & TYPE_FLAG_STUB))
    {
      sym = new_symbol (dip, objfile);
      if (sym != NULL)
	{
	  SYMBOL_TYPE (sym) = type;
	  if (cu_language == language_cplus)
	    {
	      synthesize_typedef (dip, objfile, type);
	    }
	}
    }
}

/*

LOCAL FUNCTION

	decode_array_element_type -- decode type of the array elements

SYNOPSIS

	static struct type *decode_array_element_type (char *scan, char *end)

DESCRIPTION

	As the last step in decoding the array subscript information for an
	array DIE, we need to decode the type of the array elements.  We are
	passed a pointer to this last part of the subscript information and
	must return the appropriate type.  If the type attribute is not
	recognized, just warn about the problem and return type int.
 */

static struct type *
decode_array_element_type (scan)
     char *scan;
{
  struct type *typep;
  DIE_REF die_ref;
  unsigned short attribute;
  unsigned short fundtype;
  int nbytes;
  
  attribute = target_to_host (scan, SIZEOF_ATTRIBUTE, GET_UNSIGNED,
			      current_objfile);
  scan += SIZEOF_ATTRIBUTE;
  if ((nbytes = attribute_size (attribute)) == -1)
    {
      SQUAWK (("bad array element type attribute 0x%x", attribute));
      typep = lookup_fundamental_type (current_objfile, FT_INTEGER);
    }
  else
    {
      switch (attribute)
	{
	  case AT_fund_type:
	    fundtype = target_to_host (scan, nbytes, GET_UNSIGNED,
				       current_objfile);
	    typep = decode_fund_type (fundtype);
	    break;
	  case AT_mod_fund_type:
	    typep = decode_mod_fund_type (scan);
	    break;
	  case AT_user_def_type:
	    die_ref = target_to_host (scan, nbytes, GET_UNSIGNED,
				      current_objfile);
	    if ((typep = lookup_utype (die_ref)) == NULL)
	      {
		typep = alloc_utype (die_ref, NULL);
	      }
	    break;
	  case AT_mod_u_d_type:
	    typep = decode_mod_u_d_type (scan);
	    break;
	  default:
	    SQUAWK (("bad array element type attribute 0x%x", attribute));
	    typep = lookup_fundamental_type (current_objfile, FT_INTEGER);
	    break;
	  }
    }
  return (typep);
}

/*

LOCAL FUNCTION

	decode_subscr_data -- decode array subscript and element type data

SYNOPSIS

	static struct type *decode_subscr_data (char *scan, char *end)

DESCRIPTION

	The array subscripts and the data type of the elements of an
	array are described by a list of data items, stored as a block
	of contiguous bytes.  There is a data item describing each array
	dimension, and a final data item describing the element type.
	The data items are ordered the same as their appearance in the
	source (I.E. leftmost dimension first, next to leftmost second,
	etc).

	We are passed a pointer to the start of the block of bytes
	containing the data items, and a pointer to the first byte past
	the data.  This function decodes the data and returns a type.

BUGS
	FIXME:  This code only implements the forms currently used
	by the AT&T and GNU C compilers.

	The end pointer is supplied for error checking, maybe we should
	use it for that...
 */

static struct type *
decode_subscr_data (scan, end)
     char *scan;
     char *end;
{
  struct type *typep = NULL;
  struct type *nexttype;
  unsigned int format;
  unsigned short fundtype;
  unsigned long lowbound;
  unsigned long highbound;
  int nbytes;
  
  format = target_to_host (scan, SIZEOF_FORMAT_SPECIFIER, GET_UNSIGNED,
			   current_objfile);
  scan += SIZEOF_FORMAT_SPECIFIER;
  switch (format)
    {
    case FMT_ET:
      typep = decode_array_element_type (scan);
      break;
    case FMT_FT_C_C:
      fundtype = target_to_host (scan, SIZEOF_FMT_FT, GET_UNSIGNED,
				 current_objfile);
      scan += SIZEOF_FMT_FT;
      if (fundtype != FT_integer && fundtype != FT_signed_integer
	  && fundtype != FT_unsigned_integer)
	{
	  SQUAWK (("array subscripts must be integral types, not type 0x%x",
		   fundtype));
	}
      else
	{
	  nbytes = TARGET_FT_LONG_SIZE (current_objfile);
	  lowbound = target_to_host (scan, nbytes, GET_UNSIGNED,
				     current_objfile);
	  scan += nbytes;
	  highbound = target_to_host (scan, nbytes, GET_UNSIGNED,
				      current_objfile);
	  scan += nbytes;
	  nexttype = decode_subscr_data (scan, end);
	  if (nexttype != NULL)
	    {
	      typep = alloc_type (current_objfile);
	      TYPE_CODE (typep) = TYPE_CODE_ARRAY;
	      TYPE_LENGTH (typep) = TYPE_LENGTH (nexttype);
	      TYPE_LENGTH (typep) *= (highbound - lowbound) + 1;
	      TYPE_TARGET_TYPE (typep) = nexttype;
	    }		    
	}
      break;
    case FMT_FT_C_X:
    case FMT_FT_X_C:
    case FMT_FT_X_X:
    case FMT_UT_C_C:
    case FMT_UT_C_X:
    case FMT_UT_X_C:
    case FMT_UT_X_X:
      SQUAWK (("array subscript format 0x%x not handled yet", format));
      break;
    default:
      SQUAWK (("unknown array subscript format %x", format));
      break;
    }
  return (typep);
}

/*

LOCAL FUNCTION

	dwarf_read_array_type -- read TAG_array_type DIE

SYNOPSIS

	static void dwarf_read_array_type (struct dieinfo *dip)

DESCRIPTION

	Extract all information from a TAG_array_type DIE and add to
	the user defined type vector.
 */

static void
dwarf_read_array_type (dip)
     struct dieinfo *dip;
{
  struct type *type;
  struct type *utype;
  char *sub;
  char *subend;
  unsigned short blocksz;
  int nbytes;
  
  if (dip -> at_ordering != ORD_row_major)
    {
      /* FIXME:  Can gdb even handle column major arrays? */
      SQUAWK (("array not row major; not handled correctly"));
    }
  if ((sub = dip -> at_subscr_data) != NULL)
    {
      nbytes = attribute_size (AT_subscr_data);
      blocksz = target_to_host (sub, nbytes, GET_UNSIGNED, current_objfile);
      subend = sub + nbytes + blocksz;
      sub += nbytes;
      type = decode_subscr_data (sub, subend);
      if (type == NULL)
	{
	  if ((utype = lookup_utype (dip -> die_ref)) == NULL)
	    {
	      utype = alloc_utype (dip -> die_ref, NULL);
	    }
	  TYPE_CODE (utype) = TYPE_CODE_ARRAY;
	  TYPE_TARGET_TYPE (utype) = 
      	    lookup_fundamental_type (current_objfile, FT_INTEGER);
	  TYPE_LENGTH (utype) = 1 * TYPE_LENGTH (TYPE_TARGET_TYPE (utype));
	}
      else
	{
	  if ((utype = lookup_utype (dip -> die_ref)) == NULL)
	    {
	      alloc_utype (dip -> die_ref, type);
	    }
	  else
	    {
	      TYPE_CODE (utype) = TYPE_CODE_ARRAY;
	      TYPE_LENGTH (utype) = TYPE_LENGTH (type);
	      TYPE_TARGET_TYPE (utype) = TYPE_TARGET_TYPE (type);
	    }
	}
    }
}

/*

LOCAL FUNCTION

	read_tag_pointer_type -- read TAG_pointer_type DIE

SYNOPSIS

	static void read_tag_pointer_type (struct dieinfo *dip)

DESCRIPTION

	Extract all information from a TAG_pointer_type DIE and add to
	the user defined type vector.
 */

static void
read_tag_pointer_type (dip)
     struct dieinfo *dip;
{
  struct type *type;
  struct type *utype;
  
  type = decode_die_type (dip);
  if ((utype = lookup_utype (dip -> die_ref)) == NULL)
    {
      utype = lookup_pointer_type (type);
      alloc_utype (dip -> die_ref, utype);
    }
  else
    {
      TYPE_TARGET_TYPE (utype) = type;
      TYPE_POINTER_TYPE (type) = utype;

      /* We assume the machine has only one representation for pointers!  */
      /* FIXME:  This confuses host<->target data representations, and is a
	 poor assumption besides. */
      
      TYPE_LENGTH (utype) = sizeof (char *);
      TYPE_CODE (utype) = TYPE_CODE_PTR;
    }
}

/*

LOCAL FUNCTION

	read_subroutine_type -- process TAG_subroutine_type dies

SYNOPSIS

	static void read_subroutine_type (struct dieinfo *dip, char thisdie,
		char *enddie)

DESCRIPTION

	Handle DIES due to C code like:

	struct foo {
	    int (*funcp)(int a, long l);  (Generates TAG_subroutine_type DIE)
	    int b;
	};

NOTES

	The parameter DIES are currently ignored.  See if gdb has a way to
	include this info in it's type system, and decode them if so.  Is
	this what the type structure's "arg_types" field is for?  (FIXME)
 */

static void
read_subroutine_type (dip, thisdie, enddie)
     struct dieinfo *dip;
     char *thisdie;
     char *enddie;
{
  struct type *type;		/* Type that this function returns */
  struct type *ftype;		/* Function that returns above type */