sig.c

gcc-2.95.3 Linux下最常用的C编译器

  tree name = NULL_TREE;
  tree decl = NULL_TREE;
  tree init_expr;

  push_obstacks_nochange ();
  end_temporary_allocation ();

  if (! IS_SIGNATURE (rhs_type))
    {
      name = get_sigtable_name (sig_type, rhs_type);
      decl = IDENTIFIER_GLOBAL_VALUE (name);
    }
  if (decl == NULL_TREE)
    {
      tree init = NULL_TREE;

      /* We allow only one signature table to be generated for signatures
	 with opaque types.  Otherwise we create a loophole in the type
	 system since we could cast data from one classes implementation
	 of the opaque type to that of another class.  */
      if (SIGNATURE_HAS_OPAQUE_TYPEDECLS (sig_type)
	  && SIGTABLE_HAS_BEEN_GENERATED (sig_type))
	{
	  error ("signature with opaque type implemented by multiple classes");
	  return error_mark_node;
	}
      SIGTABLE_HAS_BEEN_GENERATED (sig_type) = 1;

      init_expr = build_signature_table_constructor (sig_type, init_from);
      if (init_expr == NULL_TREE || TREE_CODE (init_expr) != CONSTRUCTOR)
	return init_expr;

      if (name == NULL_TREE)
	name = get_sigtable_name (sig_type, rhs_type);
      {
	tree context = current_function_decl;

	/* Make the signature table global, not just static in whichever
	   function a signature pointer/ref is used for the first time.  */
	current_function_decl = NULL_TREE;
	decl = pushdecl_top_level (build_decl (VAR_DECL, name, sig_type));
	current_function_decl = context;
      }
      SET_IDENTIFIER_GLOBAL_VALUE (name, decl);
      store_init_value (decl, init_expr);
      if (IS_SIGNATURE (rhs_type))
	{
	  init = DECL_INITIAL (decl);
	  DECL_INITIAL (decl) = error_mark_node;
	}

      DECL_ALIGN (decl) = MAX (TYPE_ALIGN (double_type_node),
			       DECL_ALIGN (decl));
#if 0
      /* GDB-4.7 doesn't find the initialization value of a signature table
	 when it is constant.  */
      TREE_READONLY (decl) = 1;
#endif
      TREE_STATIC (decl) = 1;
      TREE_USED (decl) = 1;

      make_decl_rtl (decl, NULL, 1);
      if (IS_SIGNATURE (rhs_type))
	expand_static_init (decl, init);
    }

  pop_obstacks ();

  return decl;
}

/* Create a constructor or modify expression if the LHS of an assignment
   is a signature pointer or a signature reference.  If LHS is a record
   type node, we build a constructor, otherwise a compound expression.  */

tree
build_signature_pointer_constructor (lhs, rhs)
     tree lhs, rhs;
{
  register struct obstack *ambient_obstack = current_obstack;
  register struct obstack *ambient_saveable_obstack = saveable_obstack;
  int initp = (TREE_CODE (lhs) == RECORD_TYPE);
  tree lhstype = initp ? lhs : TREE_TYPE (lhs);
  tree rhstype = TREE_TYPE (rhs);
  tree sig_ty  = SIGNATURE_TYPE (lhstype);
  tree sig_tbl, sptr_expr, optr_expr;
  tree result;

  if (! ((TREE_CODE (rhstype) == POINTER_TYPE
	  && TREE_CODE (TREE_TYPE (rhstype)) == RECORD_TYPE)
	 || (TYPE_LANG_SPECIFIC (rhstype)
	     && (IS_SIGNATURE_POINTER (rhstype)
		 || IS_SIGNATURE_REFERENCE (rhstype)))))
    {
      error ("invalid assignment to signature pointer or reference");
      return error_mark_node;
    }

  if (TYPE_SIZE (sig_ty) == NULL_TREE)
    {
      cp_error ("undefined signature `%T' used in signature %s declaration",
		sig_ty,
		IS_SIGNATURE_POINTER (lhstype) ? "pointer" : "reference");
      return error_mark_node;
    }

  /* If SIG_TY is permanent, make the signature table constructor and
     the signature pointer/reference constructor permanent too.  */
  if (TREE_PERMANENT (sig_ty))
    {
      current_obstack = &permanent_obstack;
      saveable_obstack = &permanent_obstack;
    }

  if (TYPE_LANG_SPECIFIC (rhstype)
      && (IS_SIGNATURE_POINTER (rhstype) || IS_SIGNATURE_REFERENCE (rhstype)))
    {
      if (SIGNATURE_TYPE (rhstype) == sig_ty)
	{
	  /* LHS and RHS are signature pointers/refs of the same signature.  */
	  optr_expr = build_optr_ref (rhs);
	  sptr_expr = build_sptr_ref (rhs);
	}
      else
	{
	  /* We need to create a new signature table and copy
	     elements from the rhs signature table.  */
	  tree rhs_sptr_ref = build_sptr_ref (rhs);
	  tree rhs_tbl = build1 (INDIRECT_REF, SIGNATURE_TYPE (rhstype),
				 rhs_sptr_ref);

	  sig_tbl = build_sigtable (sig_ty, SIGNATURE_TYPE (rhstype), rhs_tbl);
	  if (sig_tbl == error_mark_node)
	    return error_mark_node;

	  optr_expr = build_optr_ref (rhs);
	  if (sig_tbl == NULL_TREE)
	    /* The signature was empty.  The signature pointer is
	       pretty useless, but the user has been warned.  */
	    sptr_expr = copy_node (null_pointer_node);
	  else if (sig_tbl == integer_zero_node)
	    sptr_expr = rhs_sptr_ref;
	  else
	    sptr_expr = build_unary_op (ADDR_EXPR, sig_tbl, 0);
	  TREE_TYPE (sptr_expr) = build_pointer_type (sig_ty);
	}
    }
  else
    {
      sig_tbl = build_sigtable (sig_ty, TREE_TYPE (rhstype), rhs);
      if (sig_tbl == error_mark_node)
	return error_mark_node;

      optr_expr = rhs;
      if (sig_tbl == NULL_TREE)
	/* The signature was empty.  The signature pointer is
	   pretty useless, but the user has been warned.  */
	{
	  sptr_expr = copy_node (null_pointer_node);
	  TREE_TYPE (sptr_expr) = build_pointer_type (sig_ty);
	}
      else
	sptr_expr = build_unary_op (ADDR_EXPR, sig_tbl, 0);
    }

  if (initp)
    {
      result = tree_cons (NULL_TREE, optr_expr,
			  build_tree_list (NULL_TREE, sptr_expr));
      result = build_nt (CONSTRUCTOR, NULL_TREE, result);
      result = digest_init (lhstype, result, 0);
    }
  else
    {
      if (TREE_READONLY (lhs) || CP_TYPE_CONST_P (lhstype))
	  readonly_error (lhs, "assignment", 0);

      optr_expr = build_modify_expr (build_optr_ref (lhs), NOP_EXPR,
				     optr_expr);
      sptr_expr = build_modify_expr (build_sptr_ref (lhs), NOP_EXPR,
				     sptr_expr);

      result = tree_cons (NULL_TREE, optr_expr,
			  tree_cons (NULL_TREE, sptr_expr,
				     build_tree_list (NULL_TREE, lhs)));
      result = build_compound_expr (result);
    }

  current_obstack = ambient_obstack;
  saveable_obstack = ambient_saveable_obstack;
  return result;
}

/* Build a temporary variable declaration for the instance of a signature
   member function call if it isn't a declaration node already.  Simply
   using a SAVE_EXPR doesn't work since we need `this' in both branches
   of a conditional expression.  */

static tree
save_this (instance)
     tree instance;
{
  tree decl;

  if (TREE_CODE_CLASS (TREE_CODE (instance)) == 'd')
    decl = instance;
  else
    {
      decl = build_decl (VAR_DECL, NULL_TREE, TREE_TYPE (instance));
      DECL_REGISTER (decl) = 1;
      layout_decl (decl, 0);
      expand_decl (decl);
    }

  return decl;
}

/* Build a signature member function call.  Looks up the signature table
   entry corresponding to FUNCTION.  Depending on the value of the CODE
   field, either call the function in PFN directly, or use OFFSET to
   index the object's virtual function table.  */

tree
build_signature_method_call (function, parms)
     tree function, parms;
{
  tree instance = TREE_VALUE (parms);
  tree saved_instance = save_this (instance);	/* Create temp for `this'.  */
  tree object_ptr = build_optr_ref (saved_instance);
  tree new_object_ptr, new_parms;
  tree signature_tbl_ptr = build_sptr_ref (saved_instance);
  tree sig_field_name = DECL_NAME (DECL_MEMFUNC_POINTER_TO (function));
  tree basetype = DECL_CONTEXT (function);
  tree basetype_path = TYPE_BINFO (basetype);
  tree tbl_entry = build_component_ref (build1 (INDIRECT_REF, basetype,
						signature_tbl_ptr),
					sig_field_name, basetype_path, 1);
  tree tag, delta, pfn, vt_off, idx, vfn;
  tree deflt_call = NULL_TREE, direct_call, virtual_call, result;

  tbl_entry = save_expr (tbl_entry);
  tag = build_component_ref (tbl_entry, tag_identifier, NULL_TREE, 1);
  delta = build_component_ref (tbl_entry, delta_identifier, NULL_TREE, 1);
  pfn = build_component_ref (tbl_entry, pfn_identifier, NULL_TREE, 1);
  vt_off = build_component_ref (tbl_entry, vt_off_identifier, NULL_TREE, 1);
  idx = build_component_ref (tbl_entry, index_identifier, NULL_TREE, 1);
  TREE_TYPE (pfn) = build_pointer_type (TREE_TYPE (function)); 

  if (IS_DEFAULT_IMPLEMENTATION (function))
    {
      pfn = save_expr (pfn);
      deflt_call = build_function_call (pfn, parms);
    }

  new_object_ptr = build (PLUS_EXPR, build_pointer_type (basetype),
			  cp_convert (ptrdiff_type_node, object_ptr),
			  cp_convert (ptrdiff_type_node, delta));

  parms = tree_cons (NULL_TREE,
		     cp_convert (build_pointer_type (basetype), object_ptr),
		     TREE_CHAIN (parms));
  new_parms = tree_cons (NULL_TREE, new_object_ptr, TREE_CHAIN (parms));

  {
    /* Cast the signature method to have `this' of a normal pointer type.  */
    tree old_this = TREE_VALUE (TYPE_ARG_TYPES (TREE_TYPE (TREE_TYPE (pfn))));

    TREE_VALUE (TYPE_ARG_TYPES (TREE_TYPE (TREE_TYPE (pfn))))
      = build_qualified_type (build_pointer_type (basetype),
			      TYPE_QUALS (old_this));

    direct_call = build_function_call (pfn, new_parms);

    {
      tree vfld, vtbl, aref;

      vfld = build (PLUS_EXPR,
		    build_pointer_type (build_pointer_type (vtbl_type_node)),
		    cp_convert (ptrdiff_type_node, object_ptr),
		    cp_convert (ptrdiff_type_node, vt_off));
      vtbl = build_indirect_ref (build_indirect_ref (vfld, NULL_PTR),
				 NULL_PTR);
      aref = build_array_ref (vtbl, idx);

      if (flag_vtable_thunks)
	vfn = aref;
      else
	vfn = build_component_ref (aref, pfn_identifier, NULL_TREE, 0);

      TREE_TYPE (vfn) = build_pointer_type (TREE_TYPE (function));

      virtual_call = build_function_call (vfn, new_parms);
    }

    /* Undo the cast, make `this' a signature pointer again.  */
    TREE_VALUE (TYPE_ARG_TYPES (TREE_TYPE (TREE_TYPE (pfn)))) = old_this;
  }

  /* Once the function was found, there should be no reason why we
     couldn't build the member function pointer call.  */
  if (!direct_call || direct_call == error_mark_node
      || !virtual_call || virtual_call == error_mark_node
      || (IS_DEFAULT_IMPLEMENTATION (function)
	  && (!deflt_call || deflt_call == error_mark_node)))
    {
      compiler_error ("cannot build call of signature member function `%s'",
		      fndecl_as_string (function, 1));
      return error_mark_node;
    }

  if (IS_DEFAULT_IMPLEMENTATION (function))
    {
      tree test = build_binary_op_nodefault (LT_EXPR, tag, integer_zero_node,
					     LT_EXPR);
      result = build_conditional_expr (tag,
				       build_conditional_expr (test,
							       deflt_call,
							       virtual_call),
				       direct_call);
    }
  else
    result = build_conditional_expr (tag, virtual_call, direct_call);

  /* If we created a temporary variable for `this', initialize it first.  */
  if (instance != saved_instance)
    result = build (COMPOUND_EXPR, TREE_TYPE (result),
		    build_modify_expr (saved_instance, NOP_EXPR, instance),
		    result);

  return result;
}

/* Create a COMPONENT_REF expression for referencing the OPTR field
   of a signature pointer or reference.  */

tree
build_optr_ref (instance)
     tree instance;
{
  tree field = get_identifier (SIGNATURE_OPTR_NAME);

  return build_component_ref (instance, field, NULL_TREE, 1);
}

/* Create a COMPONENT_REF expression for referencing the SPTR field
   of a signature pointer or reference.  */

static tree
build_sptr_ref (instance)
     tree instance;
{
  tree field = get_identifier (SIGNATURE_SPTR_NAME);

  return build_component_ref (instance, field, NULL_TREE, 1);
}