rtti.c

gcc-2.95.3 Linux下最常用的C编译器

  TREE_TYPE (name) = copy_to_permanent (type);

  pushdecl_top_level (d);
  make_function_rtl (d);
  mark_inline_for_output (d);
  pop_obstacks ();

  return d;
}

/* Likewise, but also mark it used.  Called by various EH and RTTI code.  */

tree
get_tinfo_fn (type)
     tree type;
{
  tree d = get_tinfo_fn_unused (type);
  mark_used (d);
  return d;
}

tree
get_typeid_1 (type)
     tree type;
{
  tree t;

  t = build_call
    (get_tinfo_fn (type), TREE_TYPE (tinfo_fn_type), NULL_TREE);
  return convert_from_reference (t);
}
  
/* Return the type_info object for TYPE, creating it if necessary.  */

tree
get_typeid (type)
     tree type;
{
  if (type == error_mark_node)
    return error_mark_node;

  if (TYPE_SIZE (type_info_type_node) == NULL_TREE)
    {
      error ("must #include <typeinfo> before using typeid");
      return error_mark_node;
    }
  
  if (! flag_rtti)
    error ("requesting typeid with -fno-rtti");

  if (processing_template_decl)
    return build_min_nt (TYPEID_EXPR, type);

  /* If the type of the type-id is a reference type, the result of the
     typeid expression refers to a type_info object representing the
     referenced type.  */
  if (TREE_CODE (type) == REFERENCE_TYPE)
    type = TREE_TYPE (type);

  /* The top-level cv-qualifiers of the lvalue expression or the type-id
     that is the operand of typeid are always ignored.  */
  type = TYPE_MAIN_VARIANT (type);

  if (TYPE_SIZE (complete_type (type)) == NULL_TREE)
    {
      cp_error ("taking typeid of incomplete type `%T'", type);
      return error_mark_node;
    }

  return get_typeid_1 (type);
}

/* Check whether TEST is null before returning RESULT.  If TEST is used in
   RESULT, it must have previously had a save_expr applied to it.  */

static tree
ifnonnull (test, result)
     tree test, result;
{
  return build (COND_EXPR, TREE_TYPE (result),
		build (EQ_EXPR, boolean_type_node, test, integer_zero_node),
		cp_convert (TREE_TYPE (result), integer_zero_node),
		result);
}

/* Execute a dynamic cast, as described in section 5.2.6 of the 9/93 working
   paper.  */

static tree
build_dynamic_cast_1 (type, expr)
     tree type, expr;
{
  enum tree_code tc = TREE_CODE (type);
  tree exprtype;
  enum tree_code ec;
  tree dcast_fn;
  tree old_expr = expr;

  if (TREE_CODE (expr) == OFFSET_REF)
    expr = resolve_offset_ref (expr);
  
  exprtype = TREE_TYPE (expr);
  assert (exprtype != NULL_TREE);
  ec = TREE_CODE (exprtype);

  switch (tc)
    {
    case POINTER_TYPE:
      if (ec == REFERENCE_TYPE)
	{
	  expr = convert_from_reference (expr);
	  exprtype = TREE_TYPE (expr);
	  ec = TREE_CODE (exprtype);
	}
      if (ec != POINTER_TYPE)
	goto fail;
      if (TREE_CODE (TREE_TYPE (exprtype)) != RECORD_TYPE)
	goto fail;
      if (TYPE_SIZE (complete_type (TREE_TYPE (exprtype))) == NULL_TREE)
	goto fail;
      if (!at_least_as_qualified_p (TREE_TYPE (type),
				    TREE_TYPE (exprtype)))
	goto fail;
      if (TYPE_MAIN_VARIANT (TREE_TYPE (type)) == void_type_node)
	break;
      /* else fall through */
    case REFERENCE_TYPE:
      if (TREE_CODE (TREE_TYPE (type)) != RECORD_TYPE)
	goto fail;
      if (TYPE_SIZE (complete_type (TREE_TYPE (type))) == NULL_TREE)
	goto fail;
      break;
      /* else fall through */
    default:
      goto fail;
    }

  /* Apply trivial conversion T -> T& for dereferenced ptrs.  */
  if (ec == RECORD_TYPE)
    {
      exprtype = build_reference_type (exprtype);
      expr = convert_to_reference (exprtype, expr, CONV_IMPLICIT,
				   LOOKUP_NORMAL, NULL_TREE);
      ec = REFERENCE_TYPE;
    }

  if (tc == REFERENCE_TYPE)
    {
      if (ec != REFERENCE_TYPE)
	goto fail;
      if (TREE_CODE (TREE_TYPE (exprtype)) != RECORD_TYPE)
	goto fail;
      if (TYPE_SIZE (complete_type (TREE_TYPE (exprtype))) == NULL_TREE)
	goto fail;
      if (!at_least_as_qualified_p (TREE_TYPE (type),
				    TREE_TYPE (exprtype)))
	goto fail;
    }

  /* If *type is an unambiguous accessible base class of *exprtype,
     convert statically.  */
  {
    int distance;
    tree path;

    distance = get_base_distance (TREE_TYPE (type), TREE_TYPE (exprtype), 1,
				  &path);

    if (distance == -2)
      {
	cp_error ("dynamic_cast from `%T' to ambiguous base class `%T'",
		  TREE_TYPE (exprtype), TREE_TYPE (type));
	return error_mark_node;
      }
    if (distance == -3)
      {
	cp_error ("dynamic_cast from `%T' to private base class `%T'",
		  TREE_TYPE (exprtype), TREE_TYPE (type));
	return error_mark_node;
      }

    if (distance >= 0)
      return build_vbase_path (PLUS_EXPR, type, expr, path, 0);
  }

  /* Otherwise *exprtype must be a polymorphic class (have a vtbl).  */
  if (TYPE_VIRTUAL_P (TREE_TYPE (exprtype)))
    {
      tree expr1;
      /* if TYPE is `void *', return pointer to complete object.  */
      if (tc == POINTER_TYPE
	  && TYPE_MAIN_VARIANT (TREE_TYPE (type)) == void_type_node)
	{
	  /* if b is an object, dynamic_cast<void *>(&b) == (void *)&b.  */
	  if (TREE_CODE (expr) == ADDR_EXPR
	      && TREE_CODE (TREE_OPERAND (expr, 0)) == VAR_DECL
	      && TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0))) == RECORD_TYPE)
	    return build1 (NOP_EXPR, type, expr);

	  /* Since expr is used twice below, save it.  */
	  expr = save_expr (expr);

	  expr1 = build_headof (expr);
	  if (TREE_TYPE (expr1) != type)
	    expr1 = build1 (NOP_EXPR, type, expr1);
	  return ifnonnull (expr, expr1);
	}
      else
	{
	  tree retval;
          tree result, td1, td2, td3, elems, expr2;

 	  /* If we got here, we can't convert statically.  Therefore,
	     dynamic_cast<D&>(b) (b an object) cannot succeed.  */
	  if (ec == REFERENCE_TYPE)
	    {
	      if (TREE_CODE (old_expr) == VAR_DECL
		  && TREE_CODE (TREE_TYPE (old_expr)) == RECORD_TYPE)
		{
		  cp_warning ("dynamic_cast of `%#D' to `%#T' can never succeed",
			      old_expr, type);
		  return throw_bad_cast ();
		}
	    }
	  /* Ditto for dynamic_cast<D*>(&b).  */
	  else if (TREE_CODE (expr) == ADDR_EXPR)
	    {
	      tree op = TREE_OPERAND (expr, 0);
	      if (TREE_CODE (op) == VAR_DECL
		  && TREE_CODE (TREE_TYPE (op)) == RECORD_TYPE)
		{
		  cp_warning ("dynamic_cast of `%#D' to `%#T' can never succeed",
			      op, type);
		  retval = build_int_2 (0, 0); 
		  TREE_TYPE (retval) = type; 
		  return retval;
		}
	    }

	  /* Since expr is used twice below, save it.  */
	  expr = save_expr (expr);

	  expr1 = expr;
	  if (tc == REFERENCE_TYPE)
	    expr1 = build_unary_op (ADDR_EXPR, expr1, 0);

	  /* Build run-time conversion.  */
	  expr2 = build_headof (expr1);

	  if (ec == POINTER_TYPE)
	    td1 = get_tinfo_fn_dynamic (build_indirect_ref (expr, NULL_PTR));
	  else
	    td1 = get_tinfo_fn_dynamic (expr);
	  td1 = decay_conversion (td1);
	  
	  td2 = decay_conversion
	    (get_tinfo_fn (TYPE_MAIN_VARIANT (TREE_TYPE (type))));
	  td3 = decay_conversion
	    (get_tinfo_fn (TYPE_MAIN_VARIANT (TREE_TYPE (exprtype))));

          elems = tree_cons
	    (NULL_TREE, td1, tree_cons
	     (NULL_TREE, td2, tree_cons
	      (NULL_TREE, build_int_2 (1, 0), tree_cons
	       (NULL_TREE, expr2, tree_cons
		(NULL_TREE, td3, tree_cons
		 (NULL_TREE, expr1, NULL_TREE))))));

	  dcast_fn = get_identifier ("__dynamic_cast");
	  if (IDENTIFIER_GLOBAL_VALUE (dcast_fn))
	    dcast_fn = IDENTIFIER_GLOBAL_VALUE (dcast_fn);
	  else
	    {
	      tree tmp;

	      push_obstacks (&permanent_obstack, &permanent_obstack);
	      tmp = tree_cons
		(NULL_TREE, TREE_TYPE (td1), tree_cons
		 (NULL_TREE, TREE_TYPE (td1), tree_cons
		  (NULL_TREE, integer_type_node, tree_cons
		   (NULL_TREE, ptr_type_node, tree_cons
		    (NULL_TREE, TREE_TYPE (td1), tree_cons
		     (NULL_TREE, ptr_type_node, void_list_node))))));
	      tmp = build_function_type (ptr_type_node, tmp);
	      dcast_fn = build_lang_decl (FUNCTION_DECL, dcast_fn, tmp);
	      DECL_EXTERNAL (dcast_fn) = 1;
	      TREE_PUBLIC (dcast_fn) = 1;
	      DECL_ARTIFICIAL (dcast_fn) = 1;
	      pushdecl_top_level (dcast_fn);
	      make_function_rtl (dcast_fn);
	      pop_obstacks ();
	    }
	  
	  mark_used (dcast_fn);
          result = build_call
	    (dcast_fn, TREE_TYPE (TREE_TYPE (dcast_fn)), elems);

	  if (tc == REFERENCE_TYPE)
	    {
	      expr1 = throw_bad_cast ();
	      expr1 = build_compound_expr
		(expr_tree_cons (NULL_TREE, expr1,
			    build_expr_list (NULL_TREE, cp_convert (type, integer_zero_node))));
	      TREE_TYPE (expr1) = type;
	      result = save_expr (result);
	      return build (COND_EXPR, type, result, result, expr1);
	    }

	  /* Now back to the type we want from a void*.  */
	  result = cp_convert (type, result);
          return ifnonnull (expr, result);
	}
    }

 fail:
  cp_error ("cannot dynamic_cast `%E' (of type `%#T') to type `%#T'",
	    expr, exprtype, type);
  return error_mark_node;
}

tree
build_dynamic_cast (type, expr)
     tree type, expr;
{
  if (type == error_mark_node || expr == error_mark_node)
    return error_mark_node;
  
  if (processing_template_decl)
    return build_min (DYNAMIC_CAST_EXPR, copy_to_permanent (type), expr);

  return convert_from_reference (build_dynamic_cast_1 (type, expr));
}

/* Build and initialize various sorts of descriptors.  Every descriptor
   node has a name associated with it (the name created by mangling).
   For this reason, we use the identifier as our access to the __*_desc
   nodes, instead of sticking them directly in the types.  Otherwise we
   would burden all built-in types (and pointer types) with slots that
   we don't necessarily want to use.

   For each descriptor we build, we build a variable that contains
   the descriptor's information.  When we need this info at runtime,
   all we need is access to these variables.

   Note: these constructors always return the address of the descriptor
   info, since that is simplest for their mutual interaction.  */

extern tree const_string_type_node;

/* Build an initializer for a __si_type_info node.  */

static void
expand_si_desc (tdecl, type)
     tree tdecl;
     tree type;
{
  tree t, elems, fn;
  const char *name = build_overload_name (type, 1, 1);
  tree name_string = combine_strings (build_string (strlen (name)+1, name));

  type = BINFO_TYPE (TREE_VEC_ELT (TYPE_BINFO_BASETYPES (type), 0));
  expand_expr_stmt (get_typeid_1 (type));
  t = decay_conversion (get_tinfo_var (type));
  elems = tree_cons
    (NULL_TREE, decay_conversion (tdecl), tree_cons
     (NULL_TREE, decay_conversion (name_string), tree_cons
      (NULL_TREE, t, NULL_TREE)));

  fn = get_identifier ("__rtti_si");
  if (IDENTIFIER_GLOBAL_VALUE (fn))
    fn = IDENTIFIER_GLOBAL_VALUE (fn);
  else
    {
      tree tmp;
      push_obstacks (&permanent_obstack, &permanent_obstack);
      tmp = tree_cons
	(NULL_TREE, ptr_type_node, tree_cons
	 (NULL_TREE, const_string_type_node, tree_cons
	  (NULL_TREE, build_pointer_type (type_info_type_node),
	   void_list_node)));
      tmp = build_function_type	(void_type_node, tmp);
  
      fn = build_lang_decl (FUNCTION_DECL, fn, tmp);
      DECL_EXTERNAL (fn) = 1;
      TREE_PUBLIC (fn) = 1;
      DECL_ARTIFICIAL (fn) = 1;
      pushdecl_top_level (fn);
      make_function_rtl (fn);
      pop_obstacks ();
    }

  mark_used (fn);
  fn = build_call (fn, TREE_TYPE (TREE_TYPE (fn)), elems);
  expand_expr_stmt (fn);
}

/* Build an initializer for a __class_type_info node.  */

static void
expand_class_desc (tdecl, type)
     tree tdecl;
     tree type;