[pf3gnuchains/gcc-fork.git] / gcc / objc / objc-act.c

/* Implement classes and message passing for Objective C.
   Copyright (C) 1992, 1993, 1994, 1995, 1997, 1998, 1999, 2000, 2001,
   2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010
   Free Software Foundation, Inc.
   Contributed by Steve Naroff.

This file is part of GCC.

GCC 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, or (at your option)
any later version.

GCC 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 GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"

#ifdef OBJCPLUS
#include "cp-tree.h"
#else
#include "c-tree.h"
#include "c-lang.h"
#endif

#include "c-family/c-common.h"
#include "c-family/c-objc.h"
#include "c-family/c-pragma.h"
#include "c-family/c-format.h"
#include "flags.h"
#include "langhooks.h"
#include "objc-act.h"
#include "input.h"
#include "function.h"
#include "output.h"
#include "toplev.h"
#include "ggc.h"
#include "debug.h"
#include "target.h"
#include "diagnostic-core.h"
#include "intl.h"
#include "cgraph.h"
#include "tree-iterator.h"
#include "hashtab.h"
#include "langhooks-def.h"

/* For default_tree_printer ().  */
#include "tree-pretty-print.h"

/* For enum gimplify_status */
#include "gimple.h"

#define OBJC_VOID_AT_END        void_list_node

static unsigned int should_call_super_dealloc = 0;

/* When building Objective-C++, we are not linking against the C front-end
   and so need to replicate the C tree-construction functions in some way.  */
#ifdef OBJCPLUS
#define OBJCP_REMAP_FUNCTIONS
#include "objcp-decl.h"
#endif  /* OBJCPLUS */

/* This is the default way of generating a method name.  */
/* This has the problem that "test_method:argument:" and
   "test:method_argument:" will generate the same name
   ("_i_Test__test_method_argument_" for an instance method of the
   class "Test"), so you can't have them both in the same class!
   Moreover, the demangling (going from
   "_i_Test__test_method_argument" back to the original name) is
   undefined because there are two correct ways of demangling the
   name.  */
#ifndef OBJC_GEN_METHOD_LABEL
#define OBJC_GEN_METHOD_LABEL(BUF, IS_INST, CLASS_NAME, CAT_NAME, SEL_NAME, NUM) \
  do {                                      \
    char *temp;                             \
    sprintf ((BUF), "_%s_%s_%s_%s",         \
             ((IS_INST) ? "i" : "c"),       \
             (CLASS_NAME),                  \
             ((CAT_NAME)? (CAT_NAME) : ""), \
             (SEL_NAME));                   \
    for (temp = (BUF); *temp; temp++)       \
      if (*temp == ':') *temp = '_';        \
  } while (0)
#endif

/* These need specifying.  */
#ifndef OBJC_FORWARDING_STACK_OFFSET
#define OBJC_FORWARDING_STACK_OFFSET 0
#endif

#ifndef OBJC_FORWARDING_MIN_OFFSET
#define OBJC_FORWARDING_MIN_OFFSET 0
#endif
\f
/* Set up for use of obstacks.  */

#include "obstack.h"

/* This obstack is used to accumulate the encoding of a data type.  */
static struct obstack util_obstack;

/* This points to the beginning of obstack contents, so we can free
   the whole contents.  */
char *util_firstobj;

/* The version identifies which language generation and runtime
   the module (file) was compiled for, and is recorded in the
   module descriptor.  */

#define OBJC_VERSION    (flag_next_runtime ? 6 : 8)
#define PROTOCOL_VERSION 2

/* (Decide if these can ever be validly changed.) */
#define OBJC_ENCODE_INLINE_DEFS         0
#define OBJC_ENCODE_DONT_INLINE_DEFS    1

/*** Private Interface (procedures) ***/

/* Used by compile_file.  */

static void init_objc (void);
static void finish_objc (void);

/* Code generation.  */

static tree objc_build_constructor (tree, VEC(constructor_elt,gc) *);
static tree build_objc_method_call (location_t, int, tree, tree, tree, tree);
static tree get_proto_encoding (tree);
static tree lookup_interface (tree);
static tree objc_add_static_instance (tree, tree);

static tree start_class (enum tree_code, tree, tree, tree, tree);
static tree continue_class (tree);
static void finish_class (tree);
static void start_method_def (tree);
#ifdef OBJCPLUS
static void objc_start_function (tree, tree, tree, tree);
#else
static void objc_start_function (tree, tree, tree, struct c_arg_info *);
#endif
static tree start_protocol (enum tree_code, tree, tree, tree);
static tree build_method_decl (enum tree_code, tree, tree, tree, bool);
static tree objc_add_method (tree, tree, int, bool);
static tree add_instance_variable (tree, objc_ivar_visibility_kind, tree);
static tree build_ivar_reference (tree);
static tree is_ivar (tree, tree);

static void build_objc_exception_stuff (void);
static void build_next_objc_exception_stuff (void);

/* We only need the following for ObjC; ObjC++ will use C++'s definition
   of DERIVED_FROM_P.  */
#ifndef OBJCPLUS
static bool objc_derived_from_p (tree, tree);
#define DERIVED_FROM_P(PARENT, CHILD) objc_derived_from_p (PARENT, CHILD)
#endif

/* Property.  */
static void objc_gen_property_data (tree, tree);
static void objc_synthesize_getter (tree, tree, tree);
static void objc_synthesize_setter (tree, tree, tree);
static char *objc_build_property_setter_name (tree);
static int match_proto_with_proto (tree, tree, int);
static tree lookup_property (tree, tree);
static tree lookup_property_in_list (tree, tree);
static tree lookup_property_in_protocol_list (tree, tree);
static void build_objc_property_accessor_helpers (void);

static void objc_xref_basetypes (tree, tree);

static void build_class_template (void);
static void build_selector_template (void);
static void build_category_template (void);
static void build_super_template (void);
static tree build_protocol_initializer (tree, tree, tree, tree, tree);
static tree get_class_ivars (tree, bool);
static tree generate_protocol_list (tree);
static void build_protocol_reference (tree);

static void build_fast_enumeration_state_template (void);

#ifdef OBJCPLUS
static void objc_generate_cxx_cdtors (void);
#endif

/* objc attribute */
static void objc_decl_method_attributes (tree*, tree, int); 
static tree build_keyword_selector (tree);
static const char *synth_id_with_class_suffix (const char *, tree);

/* Hash tables to manage the global pool of method prototypes.  */

hash *nst_method_hash_list = 0;
hash *cls_method_hash_list = 0;

/* Hash tables to manage the global pool of class names.  */

hash *cls_name_hash_list = 0;
hash *als_name_hash_list = 0;

static void hash_class_name_enter (hash *, tree, tree);
static hash hash_class_name_lookup (hash *, tree);

static hash hash_lookup (hash *, tree);
static tree lookup_method (tree, tree);
static tree lookup_method_static (tree, tree, int);

static tree add_class (tree, tree);
static void add_category (tree, tree);
static inline tree lookup_category (tree, tree);

enum string_section
{
  class_names,          /* class, category, protocol, module names */
  meth_var_names,       /* method and variable names */
  meth_var_types        /* method and variable type descriptors */
};

static tree add_objc_string (tree, enum string_section);
static void build_selector_table_decl (void);

/* Protocols.  */

static tree lookup_protocol (tree, bool);
static tree lookup_and_install_protocols (tree);

/* Type encoding.  */

static void encode_type_qualifiers (tree);
static void encode_type (tree, int, int);
static void encode_field_decl (tree, int, int);

#ifdef OBJCPLUS
static void really_start_method (tree, tree);
#else
static void really_start_method (tree, struct c_arg_info *);
#endif
static int comp_proto_with_proto (tree, tree, int);
static tree get_arg_type_list (tree, int, int);
static tree objc_decay_parm_type (tree);
static void objc_push_parm (tree);
#ifdef OBJCPLUS
static tree objc_get_parm_info (int);
#else
static struct c_arg_info *objc_get_parm_info (int);
#endif

/* Utilities for debugging and error diagnostics.  */

static char *gen_type_name (tree);
static char *gen_type_name_0 (tree);
static char *gen_method_decl (tree);
static char *gen_declaration (tree);

/* Everything else.  */

static tree create_field_decl (tree, const char *);
static void add_class_reference (tree);
static void build_protocol_template (void);
static tree encode_method_prototype (tree);
static void generate_classref_translation_entry (tree);
static void handle_class_ref (tree);
static void generate_struct_by_value_array (void)
     ATTRIBUTE_NORETURN;
static void mark_referenced_methods (void);
static void generate_objc_image_info (void);
static bool objc_type_valid_for_messaging (tree type, bool allow_classes);

/*** Private Interface (data) ***/

/* Reserved tag definitions.  */

#define OBJECT_TYPEDEF_NAME             "id"
#define CLASS_TYPEDEF_NAME              "Class"

#define TAG_OBJECT                      "objc_object"
#define TAG_CLASS                       "objc_class"
#define TAG_SUPER                       "objc_super"
#define TAG_SELECTOR                    "objc_selector"

#define UTAG_CLASS                      "_objc_class"
#define UTAG_IVAR                       "_objc_ivar"
#define UTAG_IVAR_LIST                  "_objc_ivar_list"
#define UTAG_METHOD                     "_objc_method"
#define UTAG_METHOD_LIST                "_objc_method_list"
#define UTAG_CATEGORY                   "_objc_category"
#define UTAG_MODULE                     "_objc_module"
#define UTAG_SYMTAB                     "_objc_symtab"
#define UTAG_SUPER                      "_objc_super"
#define UTAG_SELECTOR                   "_objc_selector"

#define UTAG_PROTOCOL                   "_objc_protocol"
#define UTAG_METHOD_PROTOTYPE           "_objc_method_prototype"
#define UTAG_METHOD_PROTOTYPE_LIST      "_objc__method_prototype_list"

/* Note that the string object global name is only needed for the
   NeXT runtime.  */
#define STRING_OBJECT_GLOBAL_FORMAT     "_%sClassReference"

#define PROTOCOL_OBJECT_CLASS_NAME      "Protocol"

#define TAG_ENUMERATION_MUTATION        "objc_enumerationMutation"
#define TAG_FAST_ENUMERATION_STATE      "__objcFastEnumerationState"

static const char *TAG_GETCLASS;
static const char *TAG_GETMETACLASS;
static const char *TAG_MSGSEND;
static const char *TAG_MSGSENDSUPER;
/* The NeXT Objective-C messenger may have two extra entry points, for use
   when returning a structure. */
static const char *TAG_MSGSEND_STRET;
static const char *TAG_MSGSENDSUPER_STRET;
static const char *default_constant_string_class_name;

/* Runtime metadata flags.  */
#define CLS_FACTORY                     0x0001L
#define CLS_META                        0x0002L
#define CLS_HAS_CXX_STRUCTORS           0x2000L

#define OBJC_MODIFIER_STATIC            0x00000001
#define OBJC_MODIFIER_FINAL             0x00000002
#define OBJC_MODIFIER_PUBLIC            0x00000004
#define OBJC_MODIFIER_PRIVATE           0x00000008
#define OBJC_MODIFIER_PROTECTED         0x00000010
#define OBJC_MODIFIER_NATIVE            0x00000020
#define OBJC_MODIFIER_SYNCHRONIZED      0x00000040
#define OBJC_MODIFIER_ABSTRACT          0x00000080
#define OBJC_MODIFIER_VOLATILE          0x00000100
#define OBJC_MODIFIER_TRANSIENT         0x00000200
#define OBJC_MODIFIER_NONE_SPECIFIED    0x80000000

/* NeXT-specific tags.  */

#define TAG_MSGSEND_NONNIL              "objc_msgSendNonNil"
#define TAG_MSGSEND_NONNIL_STRET        "objc_msgSendNonNil_stret"
#define TAG_EXCEPTIONEXTRACT            "objc_exception_extract"
#define TAG_EXCEPTIONTRYENTER           "objc_exception_try_enter"
#define TAG_EXCEPTIONTRYEXIT            "objc_exception_try_exit"
#define TAG_EXCEPTIONMATCH              "objc_exception_match"
#define TAG_EXCEPTIONTHROW              "objc_exception_throw"
#define TAG_SYNCENTER                   "objc_sync_enter"
#define TAG_SYNCEXIT                    "objc_sync_exit"
#define TAG_SETJMP                      "_setjmp"
#define UTAG_EXCDATA                    "_objc_exception_data"

#define TAG_ASSIGNIVAR                  "objc_assign_ivar"
#define TAG_ASSIGNGLOBAL                "objc_assign_global"
#define TAG_ASSIGNSTRONGCAST            "objc_assign_strongCast"

/* Branch entry points.  All that matters here are the addresses;
   functions with these names do not really exist in libobjc.  */

#define TAG_MSGSEND_FAST                "objc_msgSend_Fast"
#define TAG_ASSIGNIVAR_FAST             "objc_assign_ivar_Fast"

#define TAG_CXX_CONSTRUCT               ".cxx_construct"
#define TAG_CXX_DESTRUCT                ".cxx_destruct"

/* GNU-specific tags.  */

#define TAG_EXECCLASS                   "__objc_exec_class"
#define TAG_GNUINIT                     "__objc_gnu_init"

/* Flags for lookup_method_static().  */

/* Look for class methods.  */
#define OBJC_LOOKUP_CLASS       1
/* Do not examine superclasses.  */
#define OBJC_LOOKUP_NO_SUPER    2
/* Disable returning an instance method of a root class when a class
   method can't be found.  */
#define OBJC_LOOKUP_NO_INSTANCE_METHODS_OF_ROOT_CLASS 4 

/* The OCTI_... enumeration itself is in objc/objc-act.h.  */
tree objc_global_trees[OCTI_MAX];

static void handle_impent (struct imp_entry *);

struct imp_entry *imp_list = 0;
int imp_count = 0;      /* `@implementation' */
int cat_count = 0;      /* `@category' */

objc_ivar_visibility_kind objc_ivar_visibility;

/* Use to generate method labels.  */
static int method_slot = 0;

/* Flag to say whether methods in a protocol are optional or
   required.  */
static bool objc_method_optional_flag = false;

static int objc_collecting_ivars = 0;

#define BUFSIZE         1024

static char *errbuf;    /* Buffer for error diagnostics */

/* An array of all the local variables in the current function that
   need to be marked as volatile.  */
VEC(tree,gc) *local_variables_to_volatilize = NULL;

\f
static int flag_typed_selectors;

/* Store all constructed constant strings in a hash table so that
   they get uniqued properly.  */

struct GTY(()) string_descriptor {
  /* The literal argument .  */
  tree literal;

  /* The resulting constant string.  */
  tree constructor;
};

static GTY((param_is (struct string_descriptor))) htab_t string_htab;

FILE *gen_declaration_file;

/* Tells "encode_pointer/encode_aggregate" whether we are generating
   type descriptors for instance variables (as opposed to methods).
   Type descriptors for instance variables contain more information
   than methods (for static typing and embedded structures).  */

static int generating_instance_variables = 0;

/* For building an objc struct.  These may not be used when this file
   is compiled as part of obj-c++.  */

static bool objc_building_struct;
static struct c_struct_parse_info *objc_struct_info ATTRIBUTE_UNUSED;

/* Start building a struct for objc.  */

static tree
objc_start_struct (tree name)
{
  gcc_assert (!objc_building_struct);
  objc_building_struct = true;
  return start_struct (input_location, RECORD_TYPE, name, &objc_struct_info);
}

/* Finish building a struct for objc.  */

static tree
objc_finish_struct (tree type, tree fieldlist)
{
  gcc_assert (objc_building_struct);
  objc_building_struct = false;
  return finish_struct (input_location, type, fieldlist, NULL_TREE,
                        objc_struct_info);
}

static tree
build_sized_array_type (tree base_type, int size)
{
  tree index_type = build_index_type (build_int_cst (NULL_TREE, size - 1));
  return build_array_type (base_type, index_type);
}

static tree
add_field_decl (tree type, const char *name, tree **chain)
{
  tree field = create_field_decl (type, name);

  if (*chain != NULL)
    **chain = field;
  *chain = &DECL_CHAIN (field);

  return field;
}

/* Create a temporary variable of type 'type'.  If 'name' is set, uses
   the specified name, else use no name.  Returns the declaration of
   the type.  The 'name' is mostly useful for debugging.
*/
static tree
objc_create_temporary_var (tree type, const char *name)
{
  tree decl;

  if (name != NULL)
    {
      decl = build_decl (input_location,
                         VAR_DECL, get_identifier (name), type);
    }
  else
    {
      decl = build_decl (input_location,
                         VAR_DECL, NULL_TREE, type);
    }
  TREE_USED (decl) = 1;
  DECL_ARTIFICIAL (decl) = 1;
  DECL_IGNORED_P (decl) = 1;
  DECL_CONTEXT (decl) = current_function_decl;

  return decl;
}

/* Some platforms pass small structures through registers versus
   through an invisible pointer.  Determine at what size structure is
   the transition point between the two possibilities.  */

static void
generate_struct_by_value_array (void)
{
  tree type;
  tree decls;
  int i, j;
  int aggregate_in_mem[32];
  int found = 0;

  /* Presumably no platform passes 32 byte structures in a register.  */
  for (i = 1; i < 32; i++)
    {
      char buffer[5];
      tree *chain = NULL;

      /* Create an unnamed struct that has `i' character components */
      type = objc_start_struct (NULL_TREE);

      strcpy (buffer, "c1");
      decls = add_field_decl (char_type_node, buffer, &chain);

      for (j = 1; j < i; j++)
        {
          sprintf (buffer, "c%d", j + 1);
          add_field_decl (char_type_node, buffer, &chain);
        }
      objc_finish_struct (type, decls);

      aggregate_in_mem[i] = aggregate_value_p (type, 0);
      if (!aggregate_in_mem[i])
        found = 1;
    }

  /* We found some structures that are returned in registers instead of memory
     so output the necessary data.  */
  if (found)
    {
      for (i = 31; i >= 0;  i--)
        if (!aggregate_in_mem[i])
          break;
      printf ("#define OBJC_MAX_STRUCT_BY_VALUE %d\n\n", i);

      /* The first member of the structure is always 0 because we don't handle
         structures with 0 members */
      printf ("static int struct_forward_array[] = {\n  0");

      for (j = 1; j <= i; j++)
        printf (", %d", aggregate_in_mem[j]);
      printf ("\n};\n");
    }

  exit (0);
}

bool
objc_init (void)
{
#ifdef OBJCPLUS
  if (cxx_init () == false)
#else
  if (c_objc_common_init () == false)
#endif
    return false;

  /* If gen_declaration desired, open the output file.  */
  if (flag_gen_declaration)
    {
      register char * const dumpname = concat (dump_base_name, ".decl", NULL);
      gen_declaration_file = fopen (dumpname, "w");
      if (gen_declaration_file == 0)
        fatal_error ("can%'t open %s: %m", dumpname);
      free (dumpname);
    }

  if (flag_next_runtime)
    {
      TAG_GETCLASS = "objc_getClass";
      TAG_GETMETACLASS = "objc_getMetaClass";
      TAG_MSGSEND = "objc_msgSend";
      TAG_MSGSENDSUPER = "objc_msgSendSuper";
      TAG_MSGSEND_STRET = "objc_msgSend_stret";
      TAG_MSGSENDSUPER_STRET = "objc_msgSendSuper_stret";
      default_constant_string_class_name = "NSConstantString";
    }
  else
    {
      TAG_GETCLASS = "objc_get_class";
      TAG_GETMETACLASS = "objc_get_meta_class";
      TAG_MSGSEND = "objc_msg_lookup";
      TAG_MSGSENDSUPER = "objc_msg_lookup_super";
      /* GNU runtime does not provide special functions to support
         structure-returning methods.  */
      default_constant_string_class_name = "NXConstantString";
      flag_typed_selectors = 1;
      /* GNU runtime does not need the compiler to change code
         in order to do GC. */
      if (flag_objc_gc)
        {
          warning_at (0, 0, "%<-fobjc-gc%> is ignored for %<-fgnu-runtime%>");
          flag_objc_gc=0;
        }
    }

  init_objc ();

  if (print_struct_values && !flag_compare_debug)
    generate_struct_by_value_array ();

  return true;
}

/* This is called automatically (at the very end of compilation) by
   c_write_global_declarations and cp_write_global_declarations.  */
void
objc_write_global_declarations (void)
{
  mark_referenced_methods ();

  /* Finalize Objective-C runtime data.  */
  finish_objc ();

  if (gen_declaration_file)
    fclose (gen_declaration_file);
}
\f
/* Return the first occurrence of a method declaration corresponding
   to sel_name in rproto_list.  Search rproto_list recursively.
   If is_class is 0, search for instance methods, otherwise for class
   methods.  */
static tree
lookup_method_in_protocol_list (tree rproto_list, tree sel_name,
                                int is_class)
{
  tree rproto, p, m;

   for (rproto = rproto_list; rproto; rproto = TREE_CHAIN (rproto))
     {
       p = TREE_VALUE (rproto);
       m = NULL_TREE;

        if (TREE_CODE (p) == PROTOCOL_INTERFACE_TYPE)
          {
            /* First, search the @required protocol methods.  */
            if (is_class)
              m = lookup_method (PROTOCOL_CLS_METHODS (p),  sel_name);
            else
              m = lookup_method (PROTOCOL_NST_METHODS (p), sel_name);

            if (m)
              return m;

            /* If still not found, search the @optional protocol methods.  */
            if (is_class)
              m = lookup_method (PROTOCOL_OPTIONAL_CLS_METHODS (p), sel_name);
            else
              m = lookup_method (PROTOCOL_OPTIONAL_NST_METHODS (p), sel_name);

            if (m)
              return m;

            /* If still not found, search the attached protocols.  */
            if (PROTOCOL_LIST (p))
              m = lookup_method_in_protocol_list (PROTOCOL_LIST (p),
                                                  sel_name, is_class);
            if (m)
              return m;
          }
        else
          {
            ; /* An identifier...if we could not find a protocol.  */
          }
     }

   return 0;
}

static tree
lookup_protocol_in_reflist (tree rproto_list, tree lproto)
{
  tree rproto, p;

  /* Make sure the protocol is supported by the object on the rhs.  */
  if (TREE_CODE (lproto) == PROTOCOL_INTERFACE_TYPE)
    {
      tree fnd = 0;
      for (rproto = rproto_list; rproto; rproto = TREE_CHAIN (rproto))
        {
          p = TREE_VALUE (rproto);

          if (TREE_CODE (p) == PROTOCOL_INTERFACE_TYPE)
            {
              if (lproto == p)
                fnd = lproto;

              else if (PROTOCOL_LIST (p))
                fnd = lookup_protocol_in_reflist (PROTOCOL_LIST (p), lproto);
            }

          if (fnd)
            return fnd;
        }
    }
  else
    {
      ; /* An identifier...if we could not find a protocol.  */
    }

  return 0;
}

void
objc_start_class_interface (tree klass, tree super_class,
                            tree protos, tree attributes)
{
  if (flag_objc1_only && attributes)
    error_at (input_location, "class attributes are not available in Objective-C 1.0"); 

  objc_interface_context
    = objc_ivar_context
    = start_class (CLASS_INTERFACE_TYPE, klass, super_class, protos, attributes);
  objc_ivar_visibility = OBJC_IVAR_VIS_PROTECTED;
}

void
objc_start_category_interface (tree klass, tree categ,
                               tree protos, tree attributes)
{
  if (attributes)
    {
      if (flag_objc1_only)
        error_at (input_location, "category attributes are not available in Objective-C 1.0");
      else
        warning_at (input_location, OPT_Wattributes, 
                    "category attributes are not available in this version"
                    " of the compiler, (ignored)");
    }
  objc_interface_context
    = start_class (CATEGORY_INTERFACE_TYPE, klass, categ, protos, NULL_TREE);
  objc_ivar_chain
    = continue_class (objc_interface_context);
}

void
objc_start_protocol (tree name, tree protos, tree attributes)
{
  if (flag_objc1_only && attributes)
    error_at (input_location, "protocol attributes are not available in Objective-C 1.0");      

  objc_interface_context
    = start_protocol (PROTOCOL_INTERFACE_TYPE, name, protos, attributes);
  objc_method_optional_flag = false;
}

void
objc_continue_interface (void)
{
  objc_ivar_chain
    = continue_class (objc_interface_context);
}

void
objc_finish_interface (void)
{
  finish_class (objc_interface_context);
  objc_interface_context = NULL_TREE;
  objc_method_optional_flag = false;
}

void
objc_start_class_implementation (tree klass, tree super_class)
{
  objc_implementation_context
    = objc_ivar_context
    = start_class (CLASS_IMPLEMENTATION_TYPE, klass, super_class, NULL_TREE,
                   NULL_TREE);
  objc_ivar_visibility = OBJC_IVAR_VIS_PROTECTED;
}

void
objc_start_category_implementation (tree klass, tree categ)
{
  objc_implementation_context
    = start_class (CATEGORY_IMPLEMENTATION_TYPE, klass, categ, NULL_TREE,
                   NULL_TREE);
  objc_ivar_chain
    = continue_class (objc_implementation_context);
}

void
objc_continue_implementation (void)
{
  objc_ivar_chain
    = continue_class (objc_implementation_context);
}

void
objc_finish_implementation (void)
{
#ifdef OBJCPLUS
  if (flag_objc_call_cxx_cdtors)
    objc_generate_cxx_cdtors ();
#endif

  if (objc_implementation_context)
    {
      finish_class (objc_implementation_context);
      objc_ivar_chain = NULL_TREE;
      objc_implementation_context = NULL_TREE;
    }
  else
    warning (0, "%<@end%> must appear in an @implementation context");
}

void
objc_set_visibility (objc_ivar_visibility_kind visibility)
{
  if (visibility == OBJC_IVAR_VIS_PACKAGE)
    {
      if (flag_objc1_only)
        error ("%<@package%> is not available in Objective-C 1.0");
      else
        warning (0, "%<@package%> presently has the same effect as %<@public%>");
    }
  objc_ivar_visibility = visibility;
}

void
objc_set_method_opt (bool optional)
{
  if (flag_objc1_only)
    error_at (input_location, "@optional/@required are not available in Objective-C 1.0");      

  objc_method_optional_flag = optional;
  if (!objc_interface_context 
      || TREE_CODE (objc_interface_context) != PROTOCOL_INTERFACE_TYPE)
    {
      error ("@optional/@required is allowed in @protocol context only");
      objc_method_optional_flag = false;
    }
}

/* This routine looks for a given PROPERTY in a list of CLASS, CATEGORY, or
   PROTOCOL.  */
static tree
lookup_property_in_list (tree chain, tree property)
{
  tree x;
  for (x = CLASS_PROPERTY_DECL (chain); x; x = TREE_CHAIN (x))
    if (PROPERTY_NAME (x) == property)
      return x;
  return NULL_TREE;
}

/* This routine looks for a given PROPERTY in the tree chain of RPROTO_LIST. */
static tree lookup_property_in_protocol_list (tree rproto_list, tree property)
{
  tree rproto, x;
  for (rproto = rproto_list; rproto; rproto = TREE_CHAIN (rproto))
    {
      tree p = TREE_VALUE (rproto);
      if (TREE_CODE (p) == PROTOCOL_INTERFACE_TYPE)
        {
          if ((x = lookup_property_in_list (p, property)))
            return x;
          if (PROTOCOL_LIST (p))
            return lookup_property_in_protocol_list (PROTOCOL_LIST (p), property);
        }
      else
        {
          ; /* An identifier...if we could not find a protocol.  */
        }
    }
  return NULL_TREE;
}

/* This routine looks up the PROPERTY in current INTERFACE, its categories and up the
   chain of interface hierarchy.  */
static tree
lookup_property (tree interface_type, tree property)
{
  tree inter = interface_type;
  while (inter)
    {
      tree x, category;
      if ((x = lookup_property_in_list (inter, property)))
        return x;
      /* Failing that, look for the property in each category of the class.  */
      category = inter;
      while ((category = CLASS_CATEGORY_LIST (category)))
        {
          if ((x = lookup_property_in_list (category, property)))
            return x;

          /* When checking a category, also check the protocols
             attached with the category itself.  */
          if (CLASS_PROTOCOL_LIST (category)
              && (x = lookup_property_in_protocol_list
                  (CLASS_PROTOCOL_LIST (category), property)))
            return x;
        }

      /*  Failing to find in categories, look for property in protocol list. */
      if (CLASS_PROTOCOL_LIST (inter) 
          && (x = lookup_property_in_protocol_list
              (CLASS_PROTOCOL_LIST (inter), property)))
        return x;
      
      /* Failing that, climb up the inheritance hierarchy.  */
      inter = lookup_interface (CLASS_SUPER_NAME (inter));
    }
  return inter;
}

/* This routine is called by the parser when a
   @property... declaration is found.  'decl' is the declaration of
   the property (type/identifier), and the other arguments represent
   property attributes that may have been specified in the Objective-C
   declaration.  'parsed_property_readonly' is 'true' if the attribute
   'readonly' was specified, and 'false' if not; similarly for the
   other bool parameters.  'parsed_property_getter_ident' is NULL_TREE
   if the attribute 'getter' was not specified, and is the identifier
   corresponding to the specified getter if it was; similarly for
   'parsed_property_setter_ident'.  */
void
objc_add_property_declaration (location_t location, tree decl,
                               bool parsed_property_readonly, bool parsed_property_readwrite,
                               bool parsed_property_assign, bool parsed_property_retain,
                               bool parsed_property_copy, bool parsed_property_nonatomic,
                               tree parsed_property_getter_ident, tree parsed_property_setter_ident)
{
  tree property_decl;
  tree x;
  /* 'property_readonly' and 'property_assign_semantics' are the final
     attributes of the property after all parsed attributes have been
     considered (eg, if we parsed no 'readonly' and no 'readwrite', ie
     parsed_property_readonly = false and parsed_property_readwrite =
     false, then property_readonly will be false because the default
     is readwrite).  */
  bool property_readonly = false;
  objc_property_assign_semantics property_assign_semantics = OBJC_PROPERTY_ASSIGN;

  if (flag_objc1_only)
    error_at (input_location, "%<@property%> is not available in Objective-C 1.0");

  if (parsed_property_readonly && parsed_property_readwrite)
    {
      error_at (location, "%<readonly%> attribute conflicts with %<readwrite%> attribute");
      /* In case of conflicting attributes (here and below), after
         producing an error, we pick one of the attributes and keep
         going.  */
      property_readonly = false;
    }
  else
    {
      if (parsed_property_readonly)
        property_readonly = true;
  
      if (parsed_property_readwrite)
        property_readonly = false;
    }

  if (parsed_property_readonly && parsed_property_setter_ident)
    {
      error_at (location, "%<readonly%> attribute conflicts with %<setter%> attribute");
      property_readonly = false;
    }

  if (parsed_property_assign && parsed_property_retain)
    {
      error_at (location, "%<assign%> attribute conflicts with %<retain%> attribute");
      property_assign_semantics = OBJC_PROPERTY_RETAIN;
    }
  else if (parsed_property_assign && parsed_property_copy)
    {
      error_at (location, "%<assign%> attribute conflicts with %<copy%> attribute");
      property_assign_semantics = OBJC_PROPERTY_COPY;
    }
  else if (parsed_property_retain && parsed_property_copy)
    {
      error_at (location, "%<retain%> attribute conflicts with %<copy%> attribute");
      property_assign_semantics = OBJC_PROPERTY_COPY;
    }
  else
    {
      if (parsed_property_assign)
        property_assign_semantics = OBJC_PROPERTY_ASSIGN;

      if (parsed_property_retain)
        property_assign_semantics = OBJC_PROPERTY_RETAIN;

      if (parsed_property_copy)
        property_assign_semantics = OBJC_PROPERTY_COPY;
    }

  if (!objc_interface_context)
    {
      error_at (location, "property declaration not in @interface or @protocol context");
      return;
    }

  /* At this point we know that we are either in an interface, a
     category, or a protocol.  */

  /* We expect a FIELD_DECL from the parser.  Make sure we didn't get
     something else, as that would confuse the checks below.  */
  if (TREE_CODE (decl) != FIELD_DECL)
    {
      error_at (location, "invalid property declaration");
      return;      
    }

  /* Do some spot-checks for the most obvious invalid types.  */

  if (TREE_CODE (TREE_TYPE (decl)) == ARRAY_TYPE)
    {
      error_at (location, "property can not be an array");
      return;
    }

  /* The C++/ObjC++ parser seems to reject the ':' for a bitfield when
     parsing, while the C/ObjC parser accepts it and gives us a
     FIELD_DECL with a DECL_INITIAL set.  So we use the DECL_INITIAL
     to check for a bitfield when doing ObjC.  */
#ifndef OBJCPLUS
  if (DECL_INITIAL (decl))
    {
      /* A @property is not an actual variable, but it is a way to
         describe a pair of accessor methods, so its type (which is
         the type of the return value of the getter and the first
         argument of the setter) can't be a bitfield (as return values
         and arguments of functions can not be bitfields).  The
         underlying instance variable could be a bitfield, but that is
         a different matter.  */
      error_at (location, "property can not be a bit-field");
      return;      
    }
#endif

  /* TODO: Check that the property type is an Objective-C object or a
     "POD".  */

  /* Implement -Wproperty-assign-default (which is enabled by default).  */
  if (warn_property_assign_default
      /* If garbage collection is not being used, then 'assign' is
         valid for objects (and typically used for delegates) but it
         is wrong in most cases (since most objects need to be
         retained or copied in setters).  Warn users when 'assign' is
         used implicitly.  */
      && property_assign_semantics == OBJC_PROPERTY_ASSIGN
      /* Read-only properties are never assigned, so the assignment
         semantics do not matter in that case.  */
      && !property_readonly
      && !flag_objc_gc)
    {
      /* Please note that it would make sense to default to 'assign'
         for non-{Objective-C objects}, and to 'retain' for
         Objective-C objects.  But that would break compatibility with
         other compilers.  */
      if (!parsed_property_assign && !parsed_property_retain && !parsed_property_copy)
        {
          /* Use 'false' so we do not warn for Class objects.  */
          if (objc_type_valid_for_messaging (TREE_TYPE (decl), false))
            {
              warning_at (location, 
                          0,
                          "object property %qD has no %<assign%>, %<retain%> or %<copy%> attribute; assuming %<assign%>", 
                          decl);
              inform (location, 
                      "%<assign%> can be unsafe for Objective-C objects; please state explicitly if you need it");
            }
        }
    }
  
  if (property_assign_semantics == OBJC_PROPERTY_RETAIN
      && !objc_type_valid_for_messaging (TREE_TYPE (decl), true))
    error_at (location, "%<retain%> attribute is only valid for Objective-C objects");
  
  if (property_assign_semantics == OBJC_PROPERTY_COPY
      && !objc_type_valid_for_messaging (TREE_TYPE (decl), true))
    error_at (location, "%<copy%> attribute is only valid for Objective-C objects");

  /* Now determine the final property getter and setter names.  They
     will be stored in the PROPERTY_DECL, from which they'll always be
     extracted and used.  */

  /* Adjust, or fill in, setter and getter names.  We overwrite the
     parsed_property_setter_ident and parsed_property_getter_ident
     with the final setter and getter identifiers that will be
     used.  */
  if (parsed_property_setter_ident)
    {
      /* The setter should be terminated by ':', but the parser only
         gives us an identifier without ':'.  So, we need to add ':'
         at the end.  */
      const char *parsed_setter = IDENTIFIER_POINTER (parsed_property_setter_ident);
      size_t length = strlen (parsed_setter);
      char *final_setter = (char *)alloca (length + 2);

      sprintf (final_setter, "%s:", parsed_setter);
      parsed_property_setter_ident = get_identifier (final_setter);
    }
  else
    {
      if (!property_readonly)
        parsed_property_setter_ident = get_identifier (objc_build_property_setter_name 
                                                       (DECL_NAME (decl)));
    }

  if (!parsed_property_getter_ident)
    parsed_property_getter_ident = DECL_NAME (decl);

  /* Check for duplicate property declarations.  We first check the
     immediate context for a property with the same name.  Any such
     declarations are an error.  */
  for (x = CLASS_PROPERTY_DECL (objc_interface_context); x; x = TREE_CHAIN (x))
    {
      if (PROPERTY_NAME (x) == DECL_NAME (decl))
        {
          location_t original_location = DECL_SOURCE_LOCATION (x);
          
          error_at (location, "redeclaration of property %qD", decl);

          if (original_location != UNKNOWN_LOCATION)
            inform (original_location, "originally specified here");
          return;
      }
    }

  /* We now need to check for existing property declarations (in the
     superclass, other categories or protocols) and check that the new
     declaration is not in conflict with existing ones.  */

  /* Search for a previous, existing declaration of a property with
     the same name in superclasses, protocols etc.  If one is found,
     it will be in the 'x' variable.  */
  x = NULL_TREE;

  /* Note that, for simplicity, the following may search again the
     local context.  That's Ok as nothing will be found (else we'd
     have thrown an error above); it's only a little inefficient, but
     the code is simpler.  */
  switch (TREE_CODE (objc_interface_context))
    {
    case CLASS_INTERFACE_TYPE:
      /* Look up the property in the current @interface (which will
         find nothing), then its protocols and categories and
         superclasses.  */
      x = lookup_property (objc_interface_context, DECL_NAME (decl));
      break;
    case CATEGORY_INTERFACE_TYPE:
      /* Look up the property in the main @interface, then protocols
         and categories (one of them is ours, and will find nothing)
         and superclasses.  */
      x = lookup_property (lookup_interface (CLASS_NAME (objc_interface_context)),
                           DECL_NAME (decl));
      break;
    case PROTOCOL_INTERFACE_TYPE:
      /* Looks up the property in any protocols attached to the
         current protocol.  */
      if (PROTOCOL_LIST (objc_interface_context))
        {
          x = lookup_property_in_protocol_list (PROTOCOL_LIST (objc_interface_context),
                                                DECL_NAME (decl));
        }
      break;
    default:
      gcc_unreachable ();
    }

  if (x != NULL_TREE)
    {
      /* An existing property was found; check that it has the same
         types, or it is compatible.  */
      location_t original_location = DECL_SOURCE_LOCATION (x);

      if (PROPERTY_NONATOMIC (x) != parsed_property_nonatomic)
        {
          warning_at (location, 0,
                      "'nonatomic' attribute of property %qD conflicts with previous declaration", decl);
      
          if (original_location != UNKNOWN_LOCATION)
            inform (original_location, "originally specified here");
          return;
        }

      if (PROPERTY_GETTER_NAME (x) != parsed_property_getter_ident)
        {
          warning_at (location, 0,
                      "'getter' attribute of property %qD conflicts with previous declaration", decl);
      
          if (original_location != UNKNOWN_LOCATION)
            inform (original_location, "originally specified here");
          return;
        }

      /* We can only compare the setter names if both the old and new property have a setter.  */
      if (!property_readonly  &&  !PROPERTY_READONLY(x))
        {
          if (PROPERTY_SETTER_NAME (x) != parsed_property_setter_ident)
            {
              warning_at (location, 0,
                          "'setter' attribute of property %qD conflicts with previous declaration", decl);
              
              if (original_location != UNKNOWN_LOCATION)
                inform (original_location, "originally specified here");
              return;
            }
        }

      if (PROPERTY_ASSIGN_SEMANTICS (x) != property_assign_semantics)
        {
          warning_at (location, 0,
                      "assign semantics attributes of property %qD conflict with previous declaration", decl);
      
          if (original_location != UNKNOWN_LOCATION)
            inform (original_location, "originally specified here");
          return;
        }

      /* It's ok to have a readonly property that becomes a readwrite, but not vice versa.  */
      if (PROPERTY_READONLY (x) == 0  &&  property_readonly == 1)
        {
          warning_at (location, 0,
                      "'readonly' attribute of property %qD conflicts with previous declaration", decl);
      
          if (original_location != UNKNOWN_LOCATION)
            inform (original_location, "originally specified here");
          return;
        }

      /* We now check that the new and old property declarations have
         the same types (or compatible one).  In the Objective-C
         tradition of loose type checking, we do type-checking but
         only generate warnings (not errors) if they do not match.
         For non-readonly properties, the types must match exactly;
         for readonly properties, it is allowed to use a "more
         specialized" type in the new property declaration.  Eg, the
         superclass has a getter returning (NSArray *) and the
         subclass a getter returning (NSMutableArray *).  The object's
         getter returns an (NSMutableArray *); but if you cast the
         object to the superclass, which is allowed, you'd still
         expect the getter to return an (NSArray *), which works since
         an (NSMutableArray *) is an (NSArray *) too.  So, the set of
         objects belonging to the type of the new @property should be
         a subset of the set of objects belonging to the type of the
         old @property.  This is what "specialization" means.  And the
         reason it only applies to readonly properties is that for a
         readwrite property the setter would have the opposite
         requirement - ie that the superclass type is more specialized
         then the subclass one; hence the only way to satisfy both
         constraints is that the types match.  */

      /* If the types are not the same in the C sense, we warn ...  */
      if (!comptypes (TREE_TYPE (x), TREE_TYPE (decl))
          /* ... unless the property is readonly, in which case we
             allow a new, more specialized, declaration.  */
          && (!property_readonly 
              || !objc_compare_types (TREE_TYPE (x),
                                      TREE_TYPE (decl), -5, NULL_TREE)))
        {
          warning_at (location, 0,
                      "type of property %qD conflicts with previous declaration", decl);
          if (original_location != UNKNOWN_LOCATION)
            inform (original_location, "originally specified here");
          return;
        }
    }

  /* Create a PROPERTY_DECL node.  */
  property_decl = make_node (PROPERTY_DECL);

  /* Copy the basic information from the original decl.  */
  TREE_TYPE (property_decl) = TREE_TYPE (decl);
  DECL_SOURCE_LOCATION (property_decl) = DECL_SOURCE_LOCATION (decl);
  TREE_DEPRECATED (property_decl) = TREE_DEPRECATED (decl);
  
  /* Add property-specific information.  */
  PROPERTY_NAME (property_decl) = DECL_NAME (decl);
  PROPERTY_GETTER_NAME (property_decl) = parsed_property_getter_ident;
  PROPERTY_SETTER_NAME (property_decl) = parsed_property_setter_ident;
  PROPERTY_READONLY (property_decl) = property_readonly;
  PROPERTY_NONATOMIC (property_decl) = parsed_property_nonatomic;
  PROPERTY_ASSIGN_SEMANTICS (property_decl) = property_assign_semantics;
  PROPERTY_IVAR_NAME (property_decl) = NULL_TREE;
  PROPERTY_DYNAMIC (property_decl) = 0;

  /* Remember the fact that the property was found in the @optional
     section in a @protocol, or not.  */
  if (objc_method_optional_flag)
    PROPERTY_OPTIONAL (property_decl) = 1;
  else
    PROPERTY_OPTIONAL (property_decl) = 0;

  /* Note that PROPERTY_GETTER_NAME is always set for all
     PROPERTY_DECLs, and PROPERTY_SETTER_NAME is always set for all
     PROPERTY_DECLs where PROPERTY_READONLY == 0.  Any time we deal
     with a getter or setter, we should get the PROPERTY_DECL and use
     PROPERTY_GETTER_NAME and PROPERTY_SETTER_NAME to know the correct
     names.  */

  /* Add the PROPERTY_DECL to the list of properties for the class.  */
  TREE_CHAIN (property_decl) = CLASS_PROPERTY_DECL (objc_interface_context);
  CLASS_PROPERTY_DECL (objc_interface_context) = property_decl;
}

/* This is a subroutine of objc_maybe_build_component_ref.  Search the
   list of methods in the interface (and, failing that, the local list
   in the implementation, and failing that, the protocol list)
   provided for a 'setter' or 'getter' for 'component' with default
   names (ie, if 'component' is "name", then search for "name" and
   "setName:").  It is also possible to specify a different
   'getter_name' (this is used for @optional readonly properties).  If
   any is found, then create an artificial property that uses them.
   Return NULL_TREE if 'getter' or 'setter' could not be found.  */
static tree
maybe_make_artificial_property_decl (tree interface, tree implementation, 
                                     tree protocol_list, tree component, bool is_class,
                                     tree getter_name)
{
  tree setter_name = get_identifier (objc_build_property_setter_name (component));
  tree getter = NULL_TREE;
  tree setter = NULL_TREE;

  if (getter_name == NULL_TREE)
    getter_name = component;

  /* First, check the @interface and all superclasses.  */
  if (interface)
    {
      int flags = 0;

      /* Using instance methods of the root class as accessors is most
         likely unwanted and can be extremely confusing (and, most
         importantly, other Objective-C 2.0 compilers do not do it).
         Turn it off.  */
      if (is_class)
        flags = OBJC_LOOKUP_CLASS | OBJC_LOOKUP_NO_INSTANCE_METHODS_OF_ROOT_CLASS;
      
      getter = lookup_method_static (interface, getter_name, flags);
      setter = lookup_method_static (interface, setter_name, flags);
    }

  /* Second, check the local @implementation context.  */
  if (!getter && !setter)
    {
      if (implementation)
        {
          if (is_class)
            {
              getter = lookup_method (CLASS_CLS_METHODS (implementation), getter_name);
              setter = lookup_method (CLASS_CLS_METHODS (implementation), setter_name);
            }
          else
            {
              getter = lookup_method (CLASS_NST_METHODS (implementation), getter_name);
              setter = lookup_method (CLASS_NST_METHODS (implementation), setter_name);       
            }
        }
    }

  /* Try the protocol_list if we didn't find anything in the
     @interface and in the @implementation.  */
  if (!getter && !setter)
    {
      getter = lookup_method_in_protocol_list (protocol_list, getter_name, is_class);
      setter = lookup_method_in_protocol_list (protocol_list, setter_name, is_class);
    }

  /* There needs to be at least a getter or setter for this to be a
     valid 'object.component' syntax.  */
  if (getter || setter)
    {
      /* Yes ... determine the type of the expression.  */
      tree property_decl;
      tree type;
      
      if (getter)
        type = TREE_VALUE (TREE_TYPE (getter));
      else
        type = TREE_VALUE (TREE_TYPE (METHOD_SEL_ARGS (setter)));
      
      /* Create an artificial property declaration with the
         information we collected on the type and getter/setter
         names.  */
      property_decl = make_node (PROPERTY_DECL);
      
      TREE_TYPE (property_decl) = type;
      DECL_SOURCE_LOCATION (property_decl) = input_location;
      TREE_DEPRECATED (property_decl) = 0;
      DECL_ARTIFICIAL (property_decl) = 1;
              
      /* Add property-specific information.  Note that one of
         PROPERTY_GETTER_NAME or PROPERTY_SETTER_NAME may refer to a
         non-existing method; this will generate an error when the
         expression is later compiled.  At this stage we don't know if
         the getter or setter will be used, so we can't generate an
         error.  */
      PROPERTY_NAME (property_decl) = component;
      PROPERTY_GETTER_NAME (property_decl) = getter_name;
      PROPERTY_SETTER_NAME (property_decl) = setter_name;
      PROPERTY_READONLY (property_decl) = 0;
      PROPERTY_NONATOMIC (property_decl) = 0;
      PROPERTY_ASSIGN_SEMANTICS (property_decl) = 0;
      PROPERTY_IVAR_NAME (property_decl) = NULL_TREE;
      PROPERTY_DYNAMIC (property_decl) = 0;
      PROPERTY_OPTIONAL (property_decl) = 0;

      if (!getter)
        PROPERTY_HAS_NO_GETTER (property_decl) = 1;

      /* The following is currently unused, but it's nice to have
         there.  We may use it if we need in the future.  */
      if (!setter)
        PROPERTY_HAS_NO_SETTER (property_decl) = 1;

      return property_decl;
    }

  return NULL_TREE;
}

/* This hook routine is invoked by the parser when an expression such
   as 'xxx.yyy' is parsed.  We get a chance to process these
   expressions in a way that is specified to Objective-C (to implement
   the Objective-C 2.0 dot-syntax, properties, or non-fragile ivars).
   If the expression is not an Objective-C specified expression, we
   should return NULL_TREE; else we return the expression.

   At the moment this only implements dot-syntax and properties (not
   non-fragile ivars yet), ie 'object.property' or 'object.component'
   where 'component' is not a declared property, but a valid getter or
   setter for it could be found.  */
tree
objc_maybe_build_component_ref (tree object, tree property_ident)
{
  tree x = NULL_TREE;
  tree rtype;

  /* If we are in Objective-C 1.0 mode, dot-syntax and properties are
     not available.  */
  if (flag_objc1_only)
    return NULL_TREE;

  /* Try to determine if 'object' is an Objective-C object or not.  If
     not, return.  */
  if (object == NULL_TREE || object == error_mark_node 
      || (rtype = TREE_TYPE (object)) == NULL_TREE)
    return NULL_TREE;
  
  if (property_ident == NULL_TREE || property_ident == error_mark_node
      || TREE_CODE (property_ident) != IDENTIFIER_NODE)
    return NULL_TREE;

  /* The following analysis of 'object' is similar to the one used for
     the 'receiver' of a method invocation.  We need to determine what
     'object' is and find the appropriate property (either declared,
     or artificial) for it (in the same way as we need to find the
     appropriate method prototype for a method invocation).  There are
     some simplifications here though: "object.property" is invalid if
     "object" has a type of "id" or "Class"; it must at least have a
     protocol attached to it, and "object" is never a class name as
     that is done by objc_build_class_component_ref.  Finally, we
     don't know if this really is a dot-syntax expression, so we want
     to make a quick exit if it is not; for this reason, we try to
     postpone checks after determining that 'object' looks like an
     Objective-C object.  */

  if (objc_is_id (rtype))
    {
      /* This is the case that the 'object' is of type 'id' or
         'Class'.  */

      /* Check if at least it is of type 'id <Protocol>' or 'Class
         <Protocol>'; if so, look the property up in the
         protocols.  */
      if (TYPE_HAS_OBJC_INFO (TREE_TYPE (rtype)))
        {
          tree rprotos = TYPE_OBJC_PROTOCOL_LIST (TREE_TYPE (rtype));
          
          if (rprotos)
            {
              /* No point looking up declared @properties if we are
                 dealing with a class.  Classes have no declared
                 properties.  */
              if (!IS_CLASS (rtype))
                x = lookup_property_in_protocol_list (rprotos, property_ident);

              if (x == NULL_TREE)
                {
                  /* Ok, no property.  Maybe it was an
                     object.component dot-syntax without a declared
                     property (this is valid for classes too).  Look
                     for getter/setter methods and internally declare
                     an artifical property based on them if found.  */
                  x = maybe_make_artificial_property_decl (NULL_TREE,
                                                           NULL_TREE,
                                                           rprotos, 
                                                           property_ident,
                                                           IS_CLASS (rtype),
                                                           NULL_TREE);
                }
              else if (PROPERTY_OPTIONAL (x) && PROPERTY_READONLY (x))
                {
                  /* This is a special, complicated case.  If the
                     property is optional, and is read-only, then the
                     property is always used for reading, but an
                     eventual existing non-property setter can be used
                     for writing.  We create an artificial property
                     decl copying the getter from the optional
                     property, and looking up the setter in the
                     interface.  */
                  x = maybe_make_artificial_property_decl (NULL_TREE,
                                                           NULL_TREE,
                                                           rprotos,
                                                           property_ident,
                                                           false,
                                                           PROPERTY_GETTER_NAME (x));             
                }
            }
        }
      else if (objc_method_context)
        {
          /* Else, if we are inside a method it could be the case of
             'super' or 'self'.  */
          tree interface_type = NULL_TREE;
          tree t = object;
          while (TREE_CODE (t) == COMPOUND_EXPR
                 || TREE_CODE (t) == MODIFY_EXPR
                 || CONVERT_EXPR_P (t)
                 || TREE_CODE (t) == COMPONENT_REF)
            t = TREE_OPERAND (t, 0);
          
          if (t == UOBJC_SUPER_decl)    
            interface_type = lookup_interface (CLASS_SUPER_NAME (implementation_template));
          else if (t == self_decl)
            interface_type = lookup_interface (CLASS_NAME (implementation_template));

          if (interface_type)
            {
              if (TREE_CODE (objc_method_context) != CLASS_METHOD_DECL)
                x = lookup_property (interface_type, property_ident);
        
              if (x == NULL_TREE)
                {
                  /* Try the dot-syntax without a declared property.
                     If this is an access to 'self', it is possible
                     that they may refer to a setter/getter that is
                     not declared in the interface, but exists locally
                     in the implementation.  In that case, get the
                     implementation context and use it.  */
                  tree implementation = NULL_TREE;

                  if (t == self_decl)
                    implementation = objc_implementation_context;
                  
                  x = maybe_make_artificial_property_decl 
                    (interface_type, implementation, NULL_TREE,
                     property_ident,
                     (TREE_CODE (objc_method_context) == CLASS_METHOD_DECL),
                     NULL_TREE);
                }
              else if (PROPERTY_OPTIONAL (x) && PROPERTY_READONLY (x))
                {
                  tree implementation = NULL_TREE;
                  
                  if (t == self_decl)
                    implementation = objc_implementation_context;
                  
                  x = maybe_make_artificial_property_decl (interface_type,
                                                           implementation,
                                                           NULL_TREE,
                                                           property_ident,
                                                           false,
                                                           PROPERTY_GETTER_NAME (x));             
                }
            }
        }
    }
  else
    {
      /* This is the case where we have more information on 'rtype'.  */
      tree basetype = TYPE_MAIN_VARIANT (rtype);

      /* Skip the pointer - if none, it's not an Objective-C object or
         class.  */
      if (basetype != NULL_TREE && TREE_CODE (basetype) == POINTER_TYPE)
        basetype = TREE_TYPE (basetype);
      else
        return NULL_TREE;

      /* Traverse typedefs.  */
      while (basetype != NULL_TREE
             && TREE_CODE (basetype) == RECORD_TYPE 
             && OBJC_TYPE_NAME (basetype)
             && TREE_CODE (OBJC_TYPE_NAME (basetype)) == TYPE_DECL
             && DECL_ORIGINAL_TYPE (OBJC_TYPE_NAME (basetype)))
        basetype = DECL_ORIGINAL_TYPE (OBJC_TYPE_NAME (basetype));

      if (basetype != NULL_TREE && TYPED_OBJECT (basetype))
        {
          tree interface_type = TYPE_OBJC_INTERFACE (basetype);
          tree protocol_list = TYPE_OBJC_PROTOCOL_LIST (basetype);

          if (interface_type 
              && (TREE_CODE (interface_type) == CLASS_INTERFACE_TYPE
                  || TREE_CODE (interface_type) == CATEGORY_INTERFACE_TYPE
                  || TREE_CODE (interface_type) == PROTOCOL_INTERFACE_TYPE))
            {
              /* Not sure 'rtype' could ever be a class here!  Just
                 for safety we keep the checks.  */
              if (!IS_CLASS (rtype))
                {
                  x = lookup_property (interface_type, property_ident);
                  
                  if (x == NULL_TREE)
                    x = lookup_property_in_protocol_list (protocol_list, 
                                                          property_ident);
                }
              
              if (x == NULL_TREE)
                {
                  /* Try the dot-syntax without a declared property.
                     If we are inside a method implementation, it is
                     possible that they may refer to a setter/getter
                     that is not declared in the interface, but exists
                     locally in the implementation.  In that case, get
                     the implementation context and use it.  */
                  tree implementation = NULL_TREE;

                  if (objc_implementation_context
                      && CLASS_NAME (objc_implementation_context) 
                      == OBJC_TYPE_NAME (interface_type))
                    implementation = objc_implementation_context;
                  
                  x = maybe_make_artificial_property_decl (interface_type,
                                                           implementation,
                                                           protocol_list, 
                                                           property_ident,
                                                           IS_CLASS (rtype),
                                                           NULL_TREE);
                }
              else if (PROPERTY_OPTIONAL (x) && PROPERTY_READONLY (x))
                {
                  tree implementation = NULL_TREE;

                  if (objc_implementation_context
                      && CLASS_NAME (objc_implementation_context) 
                      == OBJC_TYPE_NAME (interface_type))
                    implementation = objc_implementation_context;
                  
                  x = maybe_make_artificial_property_decl (interface_type,
                                                           implementation,
                                                           protocol_list,
                                                           property_ident,
                                                           false,
                                                           PROPERTY_GETTER_NAME (x));             
                }             
            }
        }
    }

  if (x)
    {
      tree expression;
      tree getter_call;

      /* We have an additional nasty problem here; if this
         PROPERTY_REF needs to become a 'getter', then the conversion
         from PROPERTY_REF into a getter call happens in gimplify,
         after the selector table has already been generated and when
         it is too late to add another selector to it.  To work around
         the problem, we always create the getter call at this stage,
         which puts the selector in the table.  Note that if the
         PROPERTY_REF becomes a 'setter' instead of a 'getter', then
         we have added a selector too many to the selector table.
         This is a little inefficient.

         Also note that method calls to 'self' and 'super' require the
         context (self_decl, UOBJS_SUPER_decl,
         objc_implementation_context etc) to be built correctly; this
         is yet another reason why building the call at the gimplify
         stage (when this context has been lost) is not very
         practical.  If we build it at this stage, we know it will
         always be built correctly.

         If the PROPERTY_HAS_NO_GETTER() (ie, it is an artificial
         property decl created to deal with a dotsyntax not really
         referring to an existing property) then do not try to build a
         call to the getter as there is no getter.  */
      if (PROPERTY_HAS_NO_GETTER (x))
        getter_call = NULL_TREE;
      else
        getter_call = objc_finish_message_expr (object,
                                                PROPERTY_GETTER_NAME (x),
                                                NULL_TREE);

      if (TREE_DEPRECATED (x))
        warn_deprecated_use (x, NULL_TREE);

      expression = build3 (PROPERTY_REF, TREE_TYPE(x), object, x, getter_call);
      SET_EXPR_LOCATION (expression, input_location);
      TREE_SIDE_EFFECTS (expression) = 1;
      
      return expression;
    }

  return NULL_TREE;
}

/* This hook routine is invoked by the parser when an expression such
   as 'xxx.yyy' is parsed, and 'xxx' is a class name.  This is the
   Objective-C 2.0 dot-syntax applied to classes, so we need to
   convert it into a setter/getter call on the class.  */
tree
objc_build_class_component_ref (tree class_name, tree property_ident)
{
  tree x = NULL_TREE;
  tree object, rtype;
  
  if (flag_objc1_only)
    error_at (input_location, "the dot syntax is not available in Objective-C 1.0");
  
  if (class_name == NULL_TREE || class_name == error_mark_node
      || TREE_CODE (class_name) != IDENTIFIER_NODE)
    return error_mark_node;
  
  if (property_ident == NULL_TREE || property_ident == error_mark_node
      || TREE_CODE (property_ident) != IDENTIFIER_NODE)
    return NULL_TREE;
  
  object = objc_get_class_reference (class_name);
  if (!object)
    {
      /* We know that 'class_name' is an Objective-C class name as the
         parser won't call this function if it is not.  This is only a
         double-check for safety.  */
      error_at (input_location, "could not find class %qE", class_name); 
      return error_mark_node;
    }

  rtype = lookup_interface (class_name);
  if (!rtype)
    {
      /* Again, this should never happen, but we do check.  */
      error_at (input_location, "could not find interface for class %qE", class_name); 
      return error_mark_node;
    }
  else
    {
      if (TREE_DEPRECATED (rtype))
        warning (OPT_Wdeprecated_declarations, "class %qE is deprecated", class_name);    
    }

  x = maybe_make_artificial_property_decl (rtype, NULL_TREE, NULL_TREE,
                                           property_ident,
                                           true, NULL_TREE);
  
  if (x)
    {
      tree expression;
      tree getter_call;

      if (PROPERTY_HAS_NO_GETTER (x))
        getter_call = NULL_TREE;
      else
        getter_call = objc_finish_message_expr (object,
                                                PROPERTY_GETTER_NAME (x),
                                                NULL_TREE);
      if (TREE_DEPRECATED (x))
        warn_deprecated_use (x, NULL_TREE);

      expression = build3 (PROPERTY_REF, TREE_TYPE(x), object, x, getter_call);
      SET_EXPR_LOCATION (expression, input_location);
      TREE_SIDE_EFFECTS (expression) = 1;

      return expression;
    }
  else
    {
      error_at (input_location, "could not find setter/getter for %qE in class %qE", 
                property_ident, class_name); 
      return error_mark_node;
    }

  return NULL_TREE;
}



/* This is used because we don't want to expose PROPERTY_REF to the
   C/C++ frontends.  Maybe we should!  */
bool
objc_is_property_ref (tree node)
{
  if (node  &&  TREE_CODE (node) == PROPERTY_REF)
    return true;
  else
    return false;
}

/* This function builds a setter call for a PROPERTY_REF (real, for a
   declared property, or artificial, for a dot-syntax accessor which
   is not corresponding to a property).  'lhs' must be a PROPERTY_REF
   (the caller must check this beforehand).  'rhs' is the value to
   assign to the property.  A plain setter call is returned, or
   error_mark_node if the property is readonly.  */

static tree
objc_build_setter_call (tree lhs, tree rhs)
{
  tree object_expr = PROPERTY_REF_OBJECT (lhs);
  tree property_decl = PROPERTY_REF_PROPERTY_DECL (lhs);
  
  if (PROPERTY_READONLY (property_decl))
    {
      error ("readonly property can not be set");         
      return error_mark_node;
    }
  else
    {
      tree setter_argument = build_tree_list (NULL_TREE, rhs);
      tree setter;
      
      /* TODO: Check that the setter return type is 'void'.  */

      /* TODO: Decay arguments in C.  */
      setter = objc_finish_message_expr (object_expr, 
                                         PROPERTY_SETTER_NAME (property_decl),
                                         setter_argument);
      return setter;
    }

  /* Unreachable, but the compiler may not realize.  */
  return error_mark_node;
}

/* This hook routine is called when a MODIFY_EXPR is being built.  We
   check what is being modified; if it is a PROPERTY_REF, we need to
   generate a 'setter' function call for the property.  If this is not
   a PROPERTY_REF, we return NULL_TREE and the C/C++ frontend will go
   on creating their MODIFY_EXPR.

   This is used for example if you write

   object.count = 1;

   where 'count' is a property.  The left-hand side creates a
   PROPERTY_REF, and then the compiler tries to generate a MODIFY_EXPR
   to assign something to it.  We intercept that here, and generate a
   call to the 'setter' method instead.  */
tree
objc_maybe_build_modify_expr (tree lhs, tree rhs)
{
  if (lhs && TREE_CODE (lhs) == PROPERTY_REF)
    {
      /* Building a simple call to the setter method would work for cases such as

      object.count = 1;

      but wouldn't work for cases such as

      count = object2.count = 1;

      to get these to work with very little effort, we build a
      compound statement which does the setter call (to set the
      property to 'rhs'), but which can also be evaluated returning
      the 'rhs'.  So, we want to create the following:

      (temp = rhs; [object setProperty: temp]; temp)
      */
      tree temp_variable_decl, bind;
      /* s1, s2 and s3 are the tree statements that we need in the
         compound expression.  */
      tree s1, s2, s3, compound_expr;
      
      /* TODO: If 'rhs' is a constant, we could maybe do without the
         'temp' variable ? */

      /* Declare __objc_property_temp in a local bind.  */
      temp_variable_decl = objc_create_temporary_var (TREE_TYPE (rhs), "__objc_property_temp");
      DECL_SOURCE_LOCATION (temp_variable_decl) = input_location;
      bind = build3 (BIND_EXPR, void_type_node, temp_variable_decl, NULL, NULL);
      SET_EXPR_LOCATION (bind, input_location);
      TREE_SIDE_EFFECTS (bind) = 1;
      add_stmt (bind);
      
      /* Now build the compound statement.  */
      
      /* s1: __objc_property_temp = rhs */
      s1 = build_modify_expr (input_location, temp_variable_decl, NULL_TREE,
                              NOP_EXPR,
                              input_location, rhs, NULL_TREE);
      SET_EXPR_LOCATION (s1, input_location);
  
      /* s2: [object setProperty: __objc_property_temp] */
      s2 = objc_build_setter_call (lhs, temp_variable_decl);

      /* This happens if building the setter failed because the property
         is readonly.  */
      if (s2 == error_mark_node)
        return error_mark_node;

      SET_EXPR_LOCATION (s2, input_location);
  
      /* s3: __objc_property_temp */
      s3 = convert (TREE_TYPE (lhs), temp_variable_decl);

      /* Now build the compound statement (s1, s2, s3) */
      compound_expr = build_compound_expr (input_location, build_compound_expr (input_location, s1, s2), s3);

      /* Without this, with -Wall you get a 'valued computed is not
         used' every time there is a "object.property = x" where the
         value of the resulting MODIFY_EXPR is not used.  That is
         correct (maybe a more sophisticated implementation could
         avoid generating the compound expression if not needed), but
         we need to turn it off.  */
      TREE_NO_WARNING (compound_expr) = 1;
      return compound_expr;
    }
  else
    return NULL_TREE;
}

/* This hook is called by the frontend when one of the four unary
   expressions PREINCREMENT_EXPR, POSTINCREMENT_EXPR,
   PREDECREMENT_EXPR and POSTDECREMENT_EXPR is being built with an
   argument which is a PROPERTY_REF.  For example, this happens if you have

   object.count++;

   where 'count' is a property.  We need to use the 'getter' and
   'setter' for the property in an appropriate way to build the
   appropriate expression.  'code' is the code for the expression (one
   of the four mentioned above); 'argument' is the PROPERTY_REF, and
   'increment' is how much we need to add or subtract.  */   
tree
objc_build_incr_expr_for_property_ref (location_t location,
                                       enum tree_code code, 
                                       tree argument, tree increment)
{
  /* Here are the expressions that we want to build:

     For PREINCREMENT_EXPR / PREDECREMENT_EXPR:
    (temp = [object property] +/- increment, [object setProperty: temp], temp)
    
    For POSTINCREMENT_EXPR / POSTECREMENT_EXPR:
    (temp = [object property], [object setProperty: temp +/- increment], temp) */
  
  tree temp_variable_decl, bind;
  /* s1, s2 and s3 are the tree statements that we need in the
     compound expression.  */
  tree s1, s2, s3, compound_expr;
  
  /* Safety check.  */
  if (!argument || TREE_CODE (argument) != PROPERTY_REF)
    return error_mark_node;

  /* Declare __objc_property_temp in a local bind.  */
  temp_variable_decl = objc_create_temporary_var (TREE_TYPE (argument), "__objc_property_temp");
  DECL_SOURCE_LOCATION (temp_variable_decl) = location;
  bind = build3 (BIND_EXPR, void_type_node, temp_variable_decl, NULL, NULL);
  SET_EXPR_LOCATION (bind, location);
  TREE_SIDE_EFFECTS (bind) = 1;
  add_stmt (bind);
  
  /* Now build the compound statement.  */
  
  /* Note that the 'getter' is generated at gimplify time; at this
     time, we can simply put the property_ref (ie, argument) wherever
     we want the getter ultimately to be.  */
  
  /* s1: __objc_property_temp = [object property] <+/- increment> */
  switch (code)
    {
    case PREINCREMENT_EXPR:      
      /* __objc_property_temp = [object property] + increment */
      s1 = build_modify_expr (location, temp_variable_decl, NULL_TREE,
                              NOP_EXPR,
                              location, build2 (PLUS_EXPR, TREE_TYPE (argument), 
                                                argument, increment), NULL_TREE);
      break;
    case PREDECREMENT_EXPR:
      /* __objc_property_temp = [object property] - increment */
      s1 = build_modify_expr (location, temp_variable_decl, NULL_TREE,
                              NOP_EXPR,
                              location, build2 (MINUS_EXPR, TREE_TYPE (argument), 
                                                argument, increment), NULL_TREE);
      break;
    case POSTINCREMENT_EXPR:
    case POSTDECREMENT_EXPR:
      /* __objc_property_temp = [object property] */
      s1 = build_modify_expr (location, temp_variable_decl, NULL_TREE,
                              NOP_EXPR,
                              location, argument, NULL_TREE);
      break;
    default:
      gcc_unreachable ();
    }
  
  /* s2: [object setProperty: __objc_property_temp <+/- increment>] */
  switch (code)
    {
    case PREINCREMENT_EXPR:      
    case PREDECREMENT_EXPR:
      /* [object setProperty: __objc_property_temp] */
      s2 = objc_build_setter_call (argument, temp_variable_decl);
      break;
    case POSTINCREMENT_EXPR:
      /* [object setProperty: __objc_property_temp + increment] */
      s2 = objc_build_setter_call (argument,
                                   build2 (PLUS_EXPR, TREE_TYPE (argument), 
                                           temp_variable_decl, increment));
      break;
    case POSTDECREMENT_EXPR:
      /* [object setProperty: __objc_property_temp - increment] */
      s2 = objc_build_setter_call (argument,
                                   build2 (MINUS_EXPR, TREE_TYPE (argument), 
                                           temp_variable_decl, increment));
      break;
    default:
      gcc_unreachable ();
    }

  /* This happens if building the setter failed because the property
     is readonly.  */
  if (s2 == error_mark_node)
    return error_mark_node;

  SET_EXPR_LOCATION (s2, location); 
  
  /* s3: __objc_property_temp */
  s3 = convert (TREE_TYPE (argument), temp_variable_decl);
  
  /* Now build the compound statement (s1, s2, s3) */
  compound_expr = build_compound_expr (location, build_compound_expr (location, s1, s2), s3);

  /* Prevent C++ from warning with -Wall that "right operand of comma
     operator has no effect".  */
  TREE_NO_WARNING (compound_expr) = 1;
  return compound_expr;
}

tree
objc_build_method_signature (bool is_class_method, tree rettype, tree selector,
                             tree optparms, bool ellipsis)
{
  if (is_class_method)
    return build_method_decl (CLASS_METHOD_DECL, rettype, selector,
                              optparms, ellipsis);
  else
    return build_method_decl (INSTANCE_METHOD_DECL, rettype, selector,
                              optparms, ellipsis);
}

void
objc_add_method_declaration (bool is_class_method, tree decl, tree attributes)
{
  if (!objc_interface_context)
    {
      /* PS: At the moment, due to how the parser works, it should be
         impossible to get here.  But it's good to have the check in
         case the parser changes.
      */
      fatal_error ("method declaration not in @interface context");
    }

  if (flag_objc1_only && attributes)
    error_at (input_location, "method attributes are not available in Objective-C 1.0");

  objc_decl_method_attributes (&decl, attributes, 0);
  objc_add_method (objc_interface_context,
                   decl,
                   is_class_method,
                   objc_method_optional_flag);
}

/* Return 'true' if the method definition could be started, and
   'false' if not (because we are outside an @implementation context).
*/
bool
objc_start_method_definition (bool is_class_method, tree decl, tree attributes)
{
  if (!objc_implementation_context)
    {
      error ("method definition not in @implementation context");
      return false;
    }

  if (decl != NULL_TREE  && METHOD_SEL_NAME (decl) == error_mark_node)
    return false;

#ifndef OBJCPLUS
  /* Indicate no valid break/continue context by setting these variables
     to some non-null, non-label value.  We'll notice and emit the proper
     error message in c_finish_bc_stmt.  */
  c_break_label = c_cont_label = size_zero_node;
#endif

  if (attributes)
    warning_at (input_location, 0, "method attributes can not be specified in @implementation context");
  else
    objc_decl_method_attributes (&decl, attributes, 0);

  objc_add_method (objc_implementation_context,
                   decl,
                   is_class_method,
                   /* is optional */ false);
  start_method_def (decl);
  return true;
}

void
objc_add_instance_variable (tree decl)
{
  (void) add_instance_variable (objc_ivar_context,
                                objc_ivar_visibility,
                                decl);
}

/* Return true if TYPE is 'id'.  */

static bool
objc_is_object_id (tree type)
{
  return OBJC_TYPE_NAME (type) == objc_object_id;
}

static bool
objc_is_class_id (tree type)
{
  return OBJC_TYPE_NAME (type) == objc_class_id;
}

/* Construct a C struct with same name as KLASS, a base struct with tag
   SUPER_NAME (if any), and FIELDS indicated.  */

static tree
objc_build_struct (tree klass, tree fields, tree super_name)
{
  tree name = CLASS_NAME (klass);
  tree s = objc_start_struct (name);
  tree super = (super_name ? xref_tag (RECORD_TYPE, super_name) : NULL_TREE);
  tree t;
  VEC(tree,heap) *objc_info = NULL;
  int i;

  if (super)
    {
      /* Prepend a packed variant of the base class into the layout.  This
         is necessary to preserve ObjC ABI compatibility.  */
      tree base = build_decl (input_location,
                              FIELD_DECL, NULL_TREE, super);
      tree field = TYPE_FIELDS (super);

      while (field && DECL_CHAIN (field)
             && TREE_CODE (DECL_CHAIN (field)) == FIELD_DECL)
        field = DECL_CHAIN (field);

      /* For ObjC ABI purposes, the "packed" size of a base class is
         the sum of the offset and the size (in bits) of the last field
         in the class.  */
      DECL_SIZE (base)
        = (field && TREE_CODE (field) == FIELD_DECL
           ? size_binop (PLUS_EXPR,
                         size_binop (PLUS_EXPR,
                                     size_binop
                                     (MULT_EXPR,
                                      convert (bitsizetype,
                                               DECL_FIELD_OFFSET (field)),
                                      bitsize_int (BITS_PER_UNIT)),
                                     DECL_FIELD_BIT_OFFSET (field)),
                         DECL_SIZE (field))
           : bitsize_zero_node);
      DECL_SIZE_UNIT (base)
        = size_binop (FLOOR_DIV_EXPR, convert (sizetype, DECL_SIZE (base)),
                      size_int (BITS_PER_UNIT));
      DECL_ARTIFICIAL (base) = 1;
      DECL_ALIGN (base) = 1;
      DECL_FIELD_CONTEXT (base) = s;
#ifdef OBJCPLUS
      DECL_FIELD_IS_BASE (base) = 1;

      if (fields)
        TREE_NO_WARNING (fields) = 1;   /* Suppress C++ ABI warnings -- we   */
#endif                                  /* are following the ObjC ABI here.  */
      DECL_CHAIN (base) = fields;
      fields = base;
    }

  /* NB: Calling finish_struct() may cause type TYPE_OBJC_INFO
     information in all variants of this RECORD_TYPE to be destroyed
     (this is because the C frontend manipulates TYPE_LANG_SPECIFIC
     for something else and then will change all variants to use the
     same resulting TYPE_LANG_SPECIFIC, ignoring the fact that we use
     it for ObjC protocols and that such propagation will make all
     variants use the same objc_info), but it is therein that we store
     protocol conformance info (e.g., 'NSObject <MyProtocol>').
     Hence, we must save the ObjC-specific information before calling
     finish_struct(), and then reinstate it afterwards.  */

  for (t = TYPE_MAIN_VARIANT (s); t; t = TYPE_NEXT_VARIANT (t))
    {
      INIT_TYPE_OBJC_INFO (t);
      VEC_safe_push (tree, heap, objc_info, TYPE_OBJC_INFO (t));
    }

  s = objc_finish_struct (s, fields);

  for (i = 0, t = TYPE_MAIN_VARIANT (s); t; t = TYPE_NEXT_VARIANT (t), i++)
    {
      /* We now want to restore the different TYPE_OBJC_INFO, but we
         have the additional problem that the C frontend doesn't just
         copy TYPE_LANG_SPECIFIC from one variant to the other; it
         actually makes all of them the *same* TYPE_LANG_SPECIFIC.  As
         we need a different TYPE_OBJC_INFO for each (and
         TYPE_OBJC_INFO is a field in TYPE_LANG_SPECIFIC), we need to
         make a copy of each TYPE_LANG_SPECIFIC before we modify
         TYPE_OBJC_INFO.  */
      if (TYPE_LANG_SPECIFIC (t))
        {
          /* Create a copy of TYPE_LANG_SPECIFIC.  */
          struct lang_type *old_lang_type = TYPE_LANG_SPECIFIC (t);
          ALLOC_OBJC_TYPE_LANG_SPECIFIC (t);
          memcpy (TYPE_LANG_SPECIFIC (t), old_lang_type,
                  SIZEOF_OBJC_TYPE_LANG_SPECIFIC);
        }
      else
        {
          /* Just create a new one.  */
          ALLOC_OBJC_TYPE_LANG_SPECIFIC (t);
        }
      /* Replace TYPE_OBJC_INFO with the saved one.  This restores any
         protocol information that may have been associated with the
         type.  */
      TYPE_OBJC_INFO (t) = VEC_index (tree, objc_info, i);
      /* Replace the IDENTIFIER_NODE with an actual @interface now
         that we have it.  */
      TYPE_OBJC_INTERFACE (t) = klass;
    }
  VEC_free (tree, heap, objc_info);

  /* Use TYPE_BINFO structures to point at the super class, if any.  */
  objc_xref_basetypes (s, super);

  /* Mark this struct as a class template.  */
  CLASS_STATIC_TEMPLATE (klass) = s;

  return s;
}

/* Mark DECL as being 'volatile' for purposes of Darwin
   _setjmp()/_longjmp() exception handling.  Called from
   objc_mark_locals_volatile().  */
void
objc_volatilize_decl (tree decl)
{
  /* Do not mess with variables that are 'static' or (already)
     'volatile'.  */
  if (!TREE_THIS_VOLATILE (decl) && !TREE_STATIC (decl)
      && (TREE_CODE (decl) == VAR_DECL
          || TREE_CODE (decl) == PARM_DECL))
    {
      if (local_variables_to_volatilize == NULL)
        local_variables_to_volatilize = VEC_alloc (tree, gc, 8);

      VEC_safe_push (tree, gc, local_variables_to_volatilize, decl);
    }
}

/* Called when parsing of a function completes; if any local variables
   in the function were marked as variables to volatilize, change them
   to volatile.  We do this at the end of the function when the
   warnings about discarding 'volatile' have already been produced.
   We are making the variables as volatile just to force the compiler
   to preserve them between setjmp/longjmp, but we don't want warnings
   for them as they aren't really volatile.  */
void
objc_finish_function (void)
{
  /* If there are any local variables to volatilize, volatilize them.  */
  if (local_variables_to_volatilize)
    {
      int i;
      tree decl;
      FOR_EACH_VEC_ELT (tree, local_variables_to_volatilize, i, decl)
        {
          tree t = TREE_TYPE (decl);

          t = build_qualified_type (t, TYPE_QUALS (t) | TYPE_QUAL_VOLATILE);
          TREE_TYPE (decl) = t;
          TREE_THIS_VOLATILE (decl) = 1;
          TREE_SIDE_EFFECTS (decl) = 1;
          DECL_REGISTER (decl) = 0;
#ifndef OBJCPLUS
          C_DECL_REGISTER (decl) = 0;
#endif
        }

      /* Now we delete the vector.  This sets it to NULL as well.  */
      VEC_free (tree, gc, local_variables_to_volatilize);
    }
}

/* Check if protocol PROTO is adopted (directly or indirectly) by class CLS
   (including its categories and superclasses) or by object type TYP.
   Issue a warning if PROTO is not adopted anywhere and WARN is set.  */

static bool
objc_lookup_protocol (tree proto, tree cls, tree typ, bool warn)
{
  bool class_type = (cls != NULL_TREE);

  while (cls)
    {
      tree c;

      /* Check protocols adopted by the class and its categories.  */
      for (c = cls; c; c = CLASS_CATEGORY_LIST (c))
        {
          if (lookup_protocol_in_reflist (CLASS_PROTOCOL_LIST (c), proto))
            return true;
        }

      /* Repeat for superclasses.  */
      cls = lookup_interface (CLASS_SUPER_NAME (cls));
    }

  /* Check for any protocols attached directly to the object type.  */
  if (TYPE_HAS_OBJC_INFO (typ))
    {
      if (lookup_protocol_in_reflist (TYPE_OBJC_PROTOCOL_LIST (typ), proto))
        return true;
    }

  if (warn)
    {
      *errbuf = 0;
      gen_type_name_0 (class_type ? typ : TYPE_POINTER_TO (typ));
      /* NB: Types 'id' and 'Class' cannot reasonably be described as
         "implementing" a given protocol, since they do not have an
         implementation.  */
      if (class_type)
        warning (0, "class %qs does not implement the %qE protocol",
                 identifier_to_locale (errbuf), PROTOCOL_NAME (proto));
      else
        warning (0, "type %qs does not conform to the %qE protocol",
                 identifier_to_locale (errbuf), PROTOCOL_NAME (proto));
    }

  return false;
}

/* Check if class RCLS and instance struct type RTYP conform to at least the
   same protocols that LCLS and LTYP conform to.  */

static bool
objc_compare_protocols (tree lcls, tree ltyp, tree rcls, tree rtyp, bool warn)
{
  tree p;
  bool have_lproto = false;

  while (lcls)
    {
      /* NB: We do _not_ look at categories defined for LCLS; these may or
         may not get loaded in, and therefore it is unreasonable to require
         that RCLS/RTYP must implement any of their protocols.  */
      for (p = CLASS_PROTOCOL_LIST (lcls); p; p = TREE_CHAIN (p))
        {
          have_lproto = true;

          if (!objc_lookup_protocol (TREE_VALUE (p), rcls, rtyp, warn))
            return warn;
        }

      /* Repeat for superclasses.  */
      lcls = lookup_interface (CLASS_SUPER_NAME (lcls));
    }

  /* Check for any protocols attached directly to the object type.  */
  if (TYPE_HAS_OBJC_INFO (ltyp))
    {
      for (p = TYPE_OBJC_PROTOCOL_LIST (ltyp); p; p = TREE_CHAIN (p))
        {
          have_lproto = true;

          if (!objc_lookup_protocol (TREE_VALUE (p), rcls, rtyp, warn))
            return warn;
        }
    }

  /* NB: If LTYP and LCLS have no protocols to search for, return 'true'
     vacuously, _unless_ RTYP is a protocol-qualified 'id'.  We can get
     away with simply checking for 'id' or 'Class' (!RCLS), since this
     routine will not get called in other cases.  */
  return have_lproto || (rcls != NULL_TREE);
}

/* Given two types TYPE1 and TYPE2, return their least common ancestor.
   Both TYPE1 and TYPE2 must be pointers, and already determined to be
   compatible by objc_compare_types() below.  */

tree
objc_common_type (tree type1, tree type2)
{
  tree inner1 = TREE_TYPE (type1), inner2 = TREE_TYPE (type2);

  while (POINTER_TYPE_P (inner1))
    {
      inner1 = TREE_TYPE (inner1);
      inner2 = TREE_TYPE (inner2);
    }

  /* If one type is derived from another, return the base type.  */
  if (DERIVED_FROM_P (inner1, inner2))
    return type1;
  else if (DERIVED_FROM_P (inner2, inner1))
    return type2;

  /* If both types are 'Class', return 'Class'.  */
  if (objc_is_class_id (inner1) && objc_is_class_id (inner2))
    return objc_class_type;

  /* Otherwise, return 'id'.  */
  return objc_object_type;
}

/* Determine if it is permissible to assign (if ARGNO is greater than -3)
   an instance of RTYP to an instance of LTYP or to compare the two
   (if ARGNO is equal to -3), per ObjC type system rules.  Before
   returning 'true', this routine may issue warnings related to, e.g.,
   protocol conformance.  When returning 'false', the routine must
   produce absolutely no warnings; the C or C++ front-end will do so
   instead, if needed.  If either LTYP or RTYP is not an Objective-C
   type, the routine must return 'false'.

   The ARGNO parameter is encoded as follows:
     >= 1       Parameter number (CALLEE contains function being called);
     0          Return value;
     -1         Assignment;
     -2         Initialization;
     -3         Comparison (LTYP and RTYP may match in either direction);
     -4         Silent comparison (for C++ overload resolution);
     -5         Silent "specialization" comparison for RTYP to be a "specialization" 
                of LTYP (a specialization means that RTYP is LTYP plus some constraints, 
                so that each object of type RTYP is also of type LTYP).  This is used
                when comparing property types.  */

bool
objc_compare_types (tree ltyp, tree rtyp, int argno, tree callee)
{
  tree lcls, rcls, lproto, rproto;
  bool pointers_compatible;

  /* We must be dealing with pointer types */
  if (!POINTER_TYPE_P (ltyp) || !POINTER_TYPE_P (rtyp))
    return false;

  do
    {
      ltyp = TREE_TYPE (ltyp);  /* Remove indirections.  */
      rtyp = TREE_TYPE (rtyp);
    }
  while (POINTER_TYPE_P (ltyp) && POINTER_TYPE_P (rtyp));

  /* We must also handle function pointers, since ObjC is a bit more
     lenient than C or C++ on this.  */
  if (TREE_CODE (ltyp) == FUNCTION_TYPE && TREE_CODE (rtyp) == FUNCTION_TYPE)
    {
      /* Return types must be covariant.  */
      if (!comptypes (TREE_TYPE (ltyp), TREE_TYPE (rtyp))
          && !objc_compare_types (TREE_TYPE (ltyp), TREE_TYPE (rtyp),
                                  argno, callee))
      return false;

      /* Argument types must be contravariant.  */
      for (ltyp = TYPE_ARG_TYPES (ltyp), rtyp = TYPE_ARG_TYPES (rtyp);
           ltyp && rtyp; ltyp = TREE_CHAIN (ltyp), rtyp = TREE_CHAIN (rtyp))
        {
          if (!comptypes (TREE_VALUE (rtyp), TREE_VALUE (ltyp))
              && !objc_compare_types (TREE_VALUE (rtyp), TREE_VALUE (ltyp),
                                      argno, callee))
            return false;
      }

      return (ltyp == rtyp);
    }

  /* Past this point, we are only interested in ObjC class instances,
     or 'id' or 'Class'.  */
  if (TREE_CODE (ltyp) != RECORD_TYPE || TREE_CODE (rtyp) != RECORD_TYPE)
    return false;

  if (!objc_is_object_id (ltyp) && !objc_is_class_id (ltyp)
      && !TYPE_HAS_OBJC_INFO (ltyp))
    return false;

  if (!objc_is_object_id (rtyp) && !objc_is_class_id (rtyp)
      && !TYPE_HAS_OBJC_INFO (rtyp))
    return false;

  /* Past this point, we are committed to returning 'true' to the caller
     (unless performing a silent comparison; see below).  However, we can
     still warn about type and/or protocol mismatches.  */

  if (TYPE_HAS_OBJC_INFO (ltyp))
    {
      lcls = TYPE_OBJC_INTERFACE (ltyp);
      lproto = TYPE_OBJC_PROTOCOL_LIST (ltyp);
    }
  else
    lcls = lproto = NULL_TREE;

  if (TYPE_HAS_OBJC_INFO (rtyp))
    {
      rcls = TYPE_OBJC_INTERFACE (rtyp);
      rproto = TYPE_OBJC_PROTOCOL_LIST (rtyp);
    }
  else
    rcls = rproto = NULL_TREE;

  /* If we could not find an @interface declaration, we must have
     only seen a @class declaration; for purposes of type comparison,
     treat it as a stand-alone (root) class.  */

  if (lcls && TREE_CODE (lcls) == IDENTIFIER_NODE)
    lcls = NULL_TREE;

  if (rcls && TREE_CODE (rcls) == IDENTIFIER_NODE)
    rcls = NULL_TREE;

  /* If either type is an unqualified 'id', we're done.  This is because
     an 'id' can be assigned to or from any type with no warnings.  */
  if (argno != -5)
    {
      if ((!lproto && objc_is_object_id (ltyp))
          || (!rproto && objc_is_object_id (rtyp)))
        return true;
    }
  else
    {
      /* For property checks, though, an 'id' is considered the most
         general type of object, hence if you try to specialize an
         'NSArray *' (ltyp) property with an 'id' (rtyp) one, we need
         to warn.  */
      if (!lproto && objc_is_object_id (ltyp))
        return true;
    }
  
  pointers_compatible = (TYPE_MAIN_VARIANT (ltyp) == TYPE_MAIN_VARIANT (rtyp));

  /* If the underlying types are the same, and at most one of them has
     a protocol list, we do not need to issue any diagnostics.  */
  if (pointers_compatible && (!lproto || !rproto))
    return true;

  /* If exactly one of the types is 'Class', issue a diagnostic; any
     exceptions of this rule have already been handled.  */
  if (objc_is_class_id (ltyp) ^ objc_is_class_id (rtyp))
    pointers_compatible = false;
  /* Otherwise, check for inheritance relations.  */
  else
    {
      if (!pointers_compatible)
        {
          /* Again, if any of the two is an 'id', we're satisfied,
             unless we're comparing properties, in which case only an
             'id' on the left-hand side (old property) is good
             enough.  */
          if (argno != -5)
            pointers_compatible
              = (objc_is_object_id (ltyp) || objc_is_object_id (rtyp));
          else
            pointers_compatible = objc_is_object_id (ltyp);         
        }

      if (!pointers_compatible)
        pointers_compatible = DERIVED_FROM_P (ltyp, rtyp);

      if (!pointers_compatible && (argno == -3 || argno == -4))
        pointers_compatible = DERIVED_FROM_P (rtyp, ltyp);
    }

  /* If the pointers match modulo protocols, check for protocol conformance
     mismatches.  */
  if (pointers_compatible)
    {
      pointers_compatible = objc_compare_protocols (lcls, ltyp, rcls, rtyp,
                                                    argno != -3);

      if (!pointers_compatible && argno == -3)
        pointers_compatible = objc_compare_protocols (rcls, rtyp, lcls, ltyp,
                                                      argno != -3);
    }

  if (!pointers_compatible)
    {
      /* The two pointers are not exactly compatible.  Issue a warning, unless
         we are performing a silent comparison, in which case return 'false'
         instead.  */
      /* NB: For the time being, we shall make our warnings look like their
         C counterparts.  In the future, we may wish to make them more
         ObjC-specific.  */
      switch (argno)
        {
        case -5:
        case -4:
          return false;

        case -3:
          warning (0, "comparison of distinct Objective-C types lacks a cast");
          break;

        case -2:
          warning (0, "initialization from distinct Objective-C type");
          break;

        case -1:
          warning (0, "assignment from distinct Objective-C type");
          break;

        case 0:
          warning (0, "distinct Objective-C type in return");
          break;

        default:
          warning (0, "passing argument %d of %qE from distinct "
                   "Objective-C type", argno, callee);
          break;
        }
    }

  return true;
}

/* This routine is similar to objc_compare_types except that function-pointers are
   excluded. This is because, caller assumes that common types are of (id, Object*)
   variety and calls objc_common_type to obtain a common type. There is no commonolty
   between two function-pointers in this regard. */

bool 
objc_have_common_type (tree ltyp, tree rtyp, int argno, tree callee)
{
  if (objc_compare_types (ltyp, rtyp, argno, callee))
    {
      /* exclude function-pointer types. */
      do
        {
          ltyp = TREE_TYPE (ltyp);  /* Remove indirections.  */
          rtyp = TREE_TYPE (rtyp);
        }
      while (POINTER_TYPE_P (ltyp) && POINTER_TYPE_P (rtyp));
      return !(TREE_CODE (ltyp) == FUNCTION_TYPE && TREE_CODE (rtyp) == FUNCTION_TYPE);
    }
  return false;
}

#ifndef OBJCPLUS
/* Determine if CHILD is derived from PARENT.  The routine assumes that
   both parameters are RECORD_TYPEs, and is non-reflexive.  */

static bool
objc_derived_from_p (tree parent, tree child)
{
  parent = TYPE_MAIN_VARIANT (parent);

  for (child = TYPE_MAIN_VARIANT (child);
       TYPE_BINFO (child) && BINFO_N_BASE_BINFOS (TYPE_BINFO (child));)
    {
      child = TYPE_MAIN_VARIANT (BINFO_TYPE (BINFO_BASE_BINFO
                                             (TYPE_BINFO (child),
                                              0)));

      if (child == parent)
        return true;
    }

  return false;
}
#endif

static tree
objc_build_component_ref (tree datum, tree component)
{
  /* If COMPONENT is NULL, the caller is referring to the anonymous
     base class field.  */
  if (!component)
    {
      tree base = TYPE_FIELDS (TREE_TYPE (datum));

      return build3 (COMPONENT_REF, TREE_TYPE (base), datum, base, NULL_TREE);
    }

  /* The 'build_component_ref' routine has been removed from the C++
     front-end, but 'finish_class_member_access_expr' seems to be
     a worthy substitute.  */
#ifdef OBJCPLUS
  return finish_class_member_access_expr (datum, component, false,
                                          tf_warning_or_error);
#else
  return build_component_ref (input_location, datum, component);
#endif
}

/* Recursively copy inheritance information rooted at BINFO.  To do this,
   we emulate the song and dance performed by cp/tree.c:copy_binfo().  */

static tree
objc_copy_binfo (tree binfo)
{
  tree btype = BINFO_TYPE (binfo);
  tree binfo2 = make_tree_binfo (BINFO_N_BASE_BINFOS (binfo));
  tree base_binfo;
  int ix;

  BINFO_TYPE (binfo2) = btype;
  BINFO_OFFSET (binfo2) = BINFO_OFFSET (binfo);
  BINFO_BASE_ACCESSES (binfo2) = BINFO_BASE_ACCESSES (binfo);

  /* Recursively copy base binfos of BINFO.  */
  for (ix = 0; BINFO_BASE_ITERATE (binfo, ix, base_binfo); ix++)
    {
      tree base_binfo2 = objc_copy_binfo (base_binfo);

      BINFO_INHERITANCE_CHAIN (base_binfo2) = binfo2;
      BINFO_BASE_APPEND (binfo2, base_binfo2);
    }

  return binfo2;
}

/* Record superclass information provided in BASETYPE for ObjC class REF.
   This is loosely based on cp/decl.c:xref_basetypes().  */

static void
objc_xref_basetypes (tree ref, tree basetype)
{
  tree binfo = make_tree_binfo (basetype ? 1 : 0);

  TYPE_BINFO (ref) = binfo;
  BINFO_OFFSET (binfo) = size_zero_node;
  BINFO_TYPE (binfo) = ref;

  if (basetype)
    {
      tree base_binfo = objc_copy_binfo (TYPE_BINFO (basetype));

      BINFO_INHERITANCE_CHAIN (base_binfo) = binfo;
      BINFO_BASE_ACCESSES (binfo) = VEC_alloc (tree, gc, 1);
      BINFO_BASE_APPEND (binfo, base_binfo);
      BINFO_BASE_ACCESS_APPEND (binfo, access_public_node);
    }
}

/* Called from finish_decl.  */

void
objc_check_decl (tree decl)
{
  tree type = TREE_TYPE (decl);

  if (TREE_CODE (type) != RECORD_TYPE)
    return;
  if (OBJC_TYPE_NAME (type) && (type = objc_is_class_name (OBJC_TYPE_NAME (type))))
    error ("statically allocated instance of Objective-C class %qE",
           type);
}

void
objc_check_global_decl (tree decl)
{
  tree id = DECL_NAME (decl);
  if (objc_is_class_name (id) && global_bindings_p())
    error ("redeclaration of Objective-C class %qs", IDENTIFIER_POINTER (id));
}

/* Construct a PROTOCOLS-qualified variant of INTERFACE, where
   INTERFACE may either name an Objective-C class, or refer to the
   special 'id' or 'Class' types.  If INTERFACE is not a valid ObjC
   type, just return it unchanged.  This function is often called when
   PROTOCOLS is NULL_TREE, in which case we simply look up the
   appropriate INTERFACE.  */

tree
objc_get_protocol_qualified_type (tree interface, tree protocols)
{
  /* If INTERFACE is not provided, default to 'id'.  */
  tree type = (interface ? objc_is_id (interface) : objc_object_type);
  bool is_ptr = (type != NULL_TREE);

  if (!is_ptr)
    {
      type = objc_is_class_name (interface);

      if (type)
        {
          /* If looking at a typedef, retrieve the precise type it
             describes.  */
          if (TREE_CODE (interface) == IDENTIFIER_NODE)
            interface = identifier_global_value (interface);

          type = ((interface && TREE_CODE (interface) == TYPE_DECL
                   && DECL_ORIGINAL_TYPE (interface))
                  ? DECL_ORIGINAL_TYPE (interface)
                  : xref_tag (RECORD_TYPE, type));
        }
      else
        {
          /* This case happens when we are given an 'interface' which
             is not a valid class name.  For example if a typedef was
             used, and 'interface' really is the identifier of the
             typedef, but when you resolve it you don't get an
             Objective-C class, but something else, such as 'int'.
             This is an error; protocols make no sense unless you use
             them with Objective-C objects.  */
          error_at (input_location, "only Objective-C object types can be qualified with a protocol");

          /* Try to recover.  Ignore the invalid class name, and treat
             the object as an 'id' to silence further warnings about
             the class.  */
          type = objc_object_type;
          is_ptr = true;
        }
    }

  if (protocols)
    {
      type = build_variant_type_copy (type);

      /* For pointers (i.e., 'id' or 'Class'), attach the protocol(s)
         to the pointee.  */
      if (is_ptr)
        {
          tree orig_pointee_type = TREE_TYPE (type);
          TREE_TYPE (type) = build_variant_type_copy (orig_pointee_type);

          /* Set up the canonical type information. */
          TYPE_CANONICAL (type) 
            = TYPE_CANONICAL (TYPE_POINTER_TO (orig_pointee_type));

          TYPE_POINTER_TO (TREE_TYPE (type)) = type;
          type = TREE_TYPE (type);
        }

      /* Look up protocols and install in lang specific list.  */
      DUP_TYPE_OBJC_INFO (type, TYPE_MAIN_VARIANT (type));
      TYPE_OBJC_PROTOCOL_LIST (type) = lookup_and_install_protocols (protocols);

      /* For RECORD_TYPEs, point to the @interface; for 'id' and 'Class',
         return the pointer to the new pointee variant.  */
      if (is_ptr)
        type = TYPE_POINTER_TO (type);
      else
        TYPE_OBJC_INTERFACE (type)
          = TYPE_OBJC_INTERFACE (TYPE_MAIN_VARIANT (type));
    }

  return type;
}

/* Check for circular dependencies in protocols.  The arguments are
   PROTO, the protocol to check, and LIST, a list of protocol it
   conforms to.  */

static void
check_protocol_recursively (tree proto, tree list)
{
  tree p;

  for (p = list; p; p = TREE_CHAIN (p))
    {
      tree pp = TREE_VALUE (p);

      if (TREE_CODE (pp) == IDENTIFIER_NODE)
        pp = lookup_protocol (pp, /* warn if deprecated */ false);

      if (pp == proto)
        fatal_error ("protocol %qE has circular dependency",
                     PROTOCOL_NAME (pp));
      if (pp)
        check_protocol_recursively (proto, PROTOCOL_LIST (pp));
    }
}

/* Look up PROTOCOLS, and return a list of those that are found.  If
   none are found, return NULL.  Note that this function will emit a
   warning if a protocol is found and is deprecated.  */

static tree
lookup_and_install_protocols (tree protocols)
{
  tree proto;
  tree return_value = NULL_TREE;

  if (protocols == error_mark_node)
    return NULL;

  for (proto = protocols; proto; proto = TREE_CHAIN (proto))
    {
      tree ident = TREE_VALUE (proto);
      tree p = lookup_protocol (ident, /* warn_if_deprecated */ true);

      if (p)
        return_value = chainon (return_value,
                                build_tree_list (NULL_TREE, p));
      else if (ident != error_mark_node)
        error ("cannot find protocol declaration for %qE",
               ident);
    }

  return return_value;
}

/* Create a declaration for field NAME of a given TYPE.  */

static tree
create_field_decl (tree type, const char *name)
{
  return build_decl (input_location,
                     FIELD_DECL, get_identifier (name), type);
}

/* Create a global, static declaration for variable NAME of a given TYPE.  The
   finish_var_decl() routine will need to be called on it afterwards.  */

static tree
start_var_decl (tree type, const char *name)
{
  tree var = build_decl (input_location,
                         VAR_DECL, get_identifier (name), type);

  TREE_STATIC (var) = 1;
  DECL_INITIAL (var) = error_mark_node;  /* A real initializer is coming... */
  DECL_IGNORED_P (var) = 1;
  DECL_ARTIFICIAL (var) = 1;
  DECL_CONTEXT (var) = NULL_TREE;
#ifdef OBJCPLUS
  DECL_THIS_STATIC (var) = 1; /* squash redeclaration errors */
#endif

  return var;
}

/* Finish off the variable declaration created by start_var_decl().  */

static void
finish_var_decl (tree var, tree initializer)
{
  finish_decl (var, input_location, initializer, NULL_TREE, NULL_TREE);
}

/* Find the decl for the constant string class reference.  This is only
   used for the NeXT runtime.  */

static tree
setup_string_decl (void)
{
  char *name;
  size_t length;

  /* %s in format will provide room for terminating null */
  length = strlen (STRING_OBJECT_GLOBAL_FORMAT)
           + strlen (constant_string_class_name);
  name = XNEWVEC (char, length);
  sprintf (name, STRING_OBJECT_GLOBAL_FORMAT,
           constant_string_class_name);
  constant_string_global_id = get_identifier (name);
  string_class_decl = lookup_name (constant_string_global_id);

  return string_class_decl;
}

/* Purpose: "play" parser, creating/installing representations
   of the declarations that are required by Objective-C.

   Model:

        type_spec--------->sc_spec
        (tree_list)        (tree_list)
            |                  |
            |                  |
        identifier_node    identifier_node  */

static void
synth_module_prologue (void)
{
  tree type;
  enum debug_info_type save_write_symbols = write_symbols;
  const struct gcc_debug_hooks *const save_hooks = debug_hooks;

  /* Suppress outputting debug symbols, because
     dbxout_init hasn't been called yet.  */
  write_symbols = NO_DEBUG;
  debug_hooks = &do_nothing_debug_hooks;

#ifdef OBJCPLUS
  push_lang_context (lang_name_c); /* extern "C" */
#endif

  /* The following are also defined in <objc/objc.h> and friends.  */

  objc_object_id = get_identifier (TAG_OBJECT);
  objc_class_id = get_identifier (TAG_CLASS);

  objc_object_reference = xref_tag (RECORD_TYPE, objc_object_id);
  objc_class_reference = xref_tag (RECORD_TYPE, objc_class_id);

  objc_object_type = build_pointer_type (objc_object_reference);
  objc_class_type = build_pointer_type (objc_class_reference);

  objc_object_name = get_identifier (OBJECT_TYPEDEF_NAME);
  objc_class_name = get_identifier (CLASS_TYPEDEF_NAME);

  /* Declare the 'id' and 'Class' typedefs.  */

  type = lang_hooks.decls.pushdecl (build_decl (input_location,
                                                TYPE_DECL,
                                                objc_object_name,
                                                objc_object_type));
  TREE_NO_WARNING (type) = 1;
  type = lang_hooks.decls.pushdecl (build_decl (input_location,
                                                TYPE_DECL,
                                                objc_class_name,
                                                objc_class_type));
  TREE_NO_WARNING (type) = 1;

  /* Forward-declare '@interface Protocol'.  */

  type = get_identifier (PROTOCOL_OBJECT_CLASS_NAME);
  objc_declare_class (tree_cons (NULL_TREE, type, NULL_TREE));
  objc_protocol_type = build_pointer_type (xref_tag (RECORD_TYPE,
                                type));

  /* Declare type of selector-objects that represent an operation name.  */

  if (flag_next_runtime)
    /* `struct objc_selector *' */
    objc_selector_type
      = build_pointer_type (xref_tag (RECORD_TYPE,
                                      get_identifier (TAG_SELECTOR)));
  else
    /* `const struct objc_selector *' */
    objc_selector_type
      = build_pointer_type
        (build_qualified_type (xref_tag (RECORD_TYPE,
                                         get_identifier (TAG_SELECTOR)),
                               TYPE_QUAL_CONST));

  /* Declare receiver type used for dispatching messages to 'super'.  */

  /* `struct objc_super *' */
  objc_super_type = build_pointer_type (xref_tag (RECORD_TYPE,
                                                  get_identifier (TAG_SUPER)));

  /* Declare pointers to method and ivar lists.  */
  objc_method_list_ptr = build_pointer_type
                         (xref_tag (RECORD_TYPE,
                                    get_identifier (UTAG_METHOD_LIST)));
  objc_method_proto_list_ptr
    = build_pointer_type (xref_tag (RECORD_TYPE,
                                    get_identifier (UTAG_METHOD_PROTOTYPE_LIST)));
  objc_ivar_list_ptr = build_pointer_type
                       (xref_tag (RECORD_TYPE,
                                  get_identifier (UTAG_IVAR_LIST)));

  /* TREE_NOTHROW is cleared for the message-sending functions,
     because the function that gets called can throw in Obj-C++, or
     could itself call something that can throw even in Obj-C.  */

  if (flag_next_runtime)
    {
      /* NB: In order to call one of the ..._stret (struct-returning)
      functions, the function *MUST* first be cast to a signature that
      corresponds to the actual ObjC method being invoked.  This is
      what is done by the build_objc_method_call() routine below.  */

      /* id objc_msgSend (id, SEL, ...); */
      /* id objc_msgSendNonNil (id, SEL, ...); */
      /* id objc_msgSend_stret (id, SEL, ...); */
      /* id objc_msgSendNonNil_stret (id, SEL, ...); */
      type
        = build_varargs_function_type_list (objc_object_type,
                                            objc_object_type,
                                            objc_selector_type,
                                            NULL_TREE);
      umsg_decl = add_builtin_function (TAG_MSGSEND,
                                        type, 0, NOT_BUILT_IN,
                                        NULL, NULL_TREE);
      umsg_nonnil_decl = add_builtin_function (TAG_MSGSEND_NONNIL,
                                               type, 0, NOT_BUILT_IN,
                                               NULL, NULL_TREE);
      umsg_stret_decl = add_builtin_function (TAG_MSGSEND_STRET,
                                              type, 0, NOT_BUILT_IN,
                                              NULL, NULL_TREE);
      umsg_nonnil_stret_decl = add_builtin_function (TAG_MSGSEND_NONNIL_STRET,
                                                     type, 0, NOT_BUILT_IN,
                                                     NULL, NULL_TREE);

      /* These can throw, because the function that gets called can throw
         in Obj-C++, or could itself call something that can throw even
         in Obj-C.  */
      TREE_NOTHROW (umsg_decl) = 0;
      TREE_NOTHROW (umsg_nonnil_decl) = 0;
      TREE_NOTHROW (umsg_stret_decl) = 0;
      TREE_NOTHROW (umsg_nonnil_stret_decl) = 0;

      /* id objc_msgSend_Fast (id, SEL, ...)
           __attribute__ ((hard_coded_address (OFFS_MSGSEND_FAST))); */
#ifdef OFFS_MSGSEND_FAST
      umsg_fast_decl = add_builtin_function (TAG_MSGSEND_FAST,
                                             type, 0, NOT_BUILT_IN,
                                             NULL, NULL_TREE);
      TREE_NOTHROW (umsg_fast_decl) = 0;
      DECL_ATTRIBUTES (umsg_fast_decl)
        = tree_cons (get_identifier ("hard_coded_address"),
                     build_int_cst (NULL_TREE, OFFS_MSGSEND_FAST),
                     NULL_TREE);
#else
      /* No direct dispatch available.  */
      umsg_fast_decl = umsg_decl;
#endif

      /* id objc_msgSendSuper (struct objc_super *, SEL, ...); */
      /* id objc_msgSendSuper_stret (struct objc_super *, SEL, ...); */
      type
        = build_varargs_function_type_list (objc_object_type,
                                            objc_super_type,
                                            objc_selector_type,
                                            NULL_TREE);
      umsg_super_decl = add_builtin_function (TAG_MSGSENDSUPER,
                                              type, 0, NOT_BUILT_IN,
                                              NULL, NULL_TREE);
      umsg_super_stret_decl = add_builtin_function (TAG_MSGSENDSUPER_STRET,
                                                    type, 0, NOT_BUILT_IN, 0,
                                                    NULL_TREE);
      TREE_NOTHROW (umsg_super_decl) = 0;
      TREE_NOTHROW (umsg_super_stret_decl) = 0;
    }
  else
    {
      /* GNU runtime messenger entry points.  */

      /* typedef id (*IMP)(id, SEL, ...); */
      tree ftype =
        build_varargs_function_type_list (objc_object_type,
                                          objc_object_type,
                                          objc_selector_type,
                                          NULL_TREE);
      tree IMP_type = build_pointer_type (ftype);

      /* IMP objc_msg_lookup (id, SEL); */
      type = build_function_type_list (IMP_type,
                                       objc_object_type,
                                       objc_selector_type,
                                       NULL_TREE);
      umsg_decl = add_builtin_function (TAG_MSGSEND,
                                        type, 0, NOT_BUILT_IN,
                                        NULL, NULL_TREE);
      TREE_NOTHROW (umsg_decl) = 0;

      /* IMP objc_msg_lookup_super (struct objc_super *, SEL); */
      type
        = build_function_type_list (IMP_type,
                                    objc_super_type,
                                    objc_selector_type,
                                    NULL_TREE);
      umsg_super_decl = add_builtin_function (TAG_MSGSENDSUPER,
                                              type, 0, NOT_BUILT_IN,
                                              NULL, NULL_TREE);
      TREE_NOTHROW (umsg_super_decl) = 0;

      /* The following GNU runtime entry point is called to initialize
         each module:

         __objc_exec_class (void *); */
      type
        = build_function_type_list (void_type_node,
                                    ptr_type_node,
                                    NULL_TREE);
      execclass_decl = add_builtin_function (TAG_EXECCLASS,
                                             type, 0, NOT_BUILT_IN,
                                             NULL, NULL_TREE);
    }

  /* id objc_getClass (const char *); */

  type = build_function_type_list (objc_object_type,
                                   const_string_type_node,
                                   NULL_TREE);

  objc_get_class_decl
    = add_builtin_function (TAG_GETCLASS, type, 0, NOT_BUILT_IN,
                            NULL, NULL_TREE);

  /* id objc_getMetaClass (const char *); */

  objc_get_meta_class_decl
    = add_builtin_function (TAG_GETMETACLASS, type, 0, NOT_BUILT_IN, NULL, NULL_TREE);

  build_class_template ();
  build_super_template ();
  build_protocol_template ();
  build_category_template ();
  build_objc_exception_stuff ();

  /* Declare objc_getProperty, object_setProperty and other property
     accessor helpers.  */
  build_objc_property_accessor_helpers ();

  if (flag_next_runtime)
    build_next_objc_exception_stuff ();

  /* static SEL _OBJC_SELECTOR_TABLE[]; */

  if (! flag_next_runtime)
    build_selector_table_decl ();

  /* Forward declare constant_string_id and constant_string_type.  */
  if (!constant_string_class_name)
    constant_string_class_name = default_constant_string_class_name;

  constant_string_id = get_identifier (constant_string_class_name);
  objc_declare_class (tree_cons (NULL_TREE, constant_string_id, NULL_TREE));

  /* Pre-build the following entities - for speed/convenience.  */
  self_id = get_identifier ("self");
  ucmd_id = get_identifier ("_cmd");

  /* Declare struct _objc_fast_enumeration_state { ... };  */
  build_fast_enumeration_state_template ();
  
  /* void objc_enumeration_mutation (id) */
  type = build_function_type (void_type_node,
                              tree_cons (NULL_TREE, objc_object_type, NULL_TREE));
  objc_enumeration_mutation_decl 
    = add_builtin_function (TAG_ENUMERATION_MUTATION, type, 0, NOT_BUILT_IN, 
                            NULL, NULL_TREE);
  TREE_NOTHROW (objc_enumeration_mutation_decl) = 0;

#ifdef OBJCPLUS
  pop_lang_context ();
#endif

  write_symbols = save_write_symbols;
  debug_hooks = save_hooks;
}

/* Ensure that the ivar list for NSConstantString/NXConstantString
   (or whatever was specified via `-fconstant-string-class')
   contains fields at least as large as the following three, so that
   the runtime can stomp on them with confidence:

   struct STRING_OBJECT_CLASS_NAME
   {
     Object isa;
     char *cString;
     unsigned int length;
   }; */

static int
check_string_class_template (void)
{
  tree field_decl = objc_get_class_ivars (constant_string_id);

#define AT_LEAST_AS_LARGE_AS(F, T) \
  (F && TREE_CODE (F) == FIELD_DECL \
     && (TREE_INT_CST_LOW (TYPE_SIZE (TREE_TYPE (F))) \
         >= TREE_INT_CST_LOW (TYPE_SIZE (T))))

  if (!AT_LEAST_AS_LARGE_AS (field_decl, ptr_type_node))
    return 0;

  field_decl = DECL_CHAIN (field_decl);
  if (!AT_LEAST_AS_LARGE_AS (field_decl, ptr_type_node))
    return 0;

  field_decl = DECL_CHAIN (field_decl);
  return AT_LEAST_AS_LARGE_AS (field_decl, unsigned_type_node);

#undef AT_LEAST_AS_LARGE_AS
}

/* Avoid calling `check_string_class_template ()' more than once.  */
static GTY(()) int string_layout_checked;

/* Construct an internal string layout to be used as a template for
   creating NSConstantString/NXConstantString instances.  */

static tree
objc_build_internal_const_str_type (void)
{
  tree type = (*lang_hooks.types.make_type) (RECORD_TYPE);
  tree fields = build_decl (input_location,
                            FIELD_DECL, NULL_TREE, ptr_type_node);
  tree field = build_decl (input_location,
                           FIELD_DECL, NULL_TREE, ptr_type_node);

  DECL_CHAIN (field) = fields; fields = field;
  field = build_decl (input_location,
                      FIELD_DECL, NULL_TREE, unsigned_type_node);
  DECL_CHAIN (field) = fields; fields = field;
  /* NB: The finish_builtin_struct() routine expects FIELD_DECLs in
     reverse order!  */
  finish_builtin_struct (type, "__builtin_ObjCString",
                         fields, NULL_TREE);

  return type;
}

/* Custom build_string which sets TREE_TYPE!  */

static tree
my_build_string (int len, const char *str)
{
  return fix_string_type (build_string (len, str));
}

/* Build a string with contents STR and length LEN and convert it to a
   pointer.  */

static tree
my_build_string_pointer (int len, const char *str)
{
  tree string = my_build_string (len, str);
  tree ptrtype = build_pointer_type (TREE_TYPE (TREE_TYPE (string)));
  return build1 (ADDR_EXPR, ptrtype, string);
}

static hashval_t
string_hash (const void *ptr)
{
  const_tree const str = ((const struct string_descriptor *)ptr)->literal;
  const unsigned char *p = (const unsigned char *) TREE_STRING_POINTER (str);
  int i, len = TREE_STRING_LENGTH (str);
  hashval_t h = len;

  for (i = 0; i < len; i++)
    h = ((h * 613) + p[i]);

  return h;
}

static int
string_eq (const void *ptr1, const void *ptr2)
{
  const_tree const str1 = ((const struct string_descriptor *)ptr1)->literal;
  const_tree const str2 = ((const struct string_descriptor *)ptr2)->literal;
  int len1 = TREE_STRING_LENGTH (str1);

  return (len1 == TREE_STRING_LENGTH (str2)
          && !memcmp (TREE_STRING_POINTER (str1), TREE_STRING_POINTER (str2),
                      len1));
}

/* Given a chain of STRING_CST's, build a static instance of
   NXConstantString which points at the concatenation of those
   strings.  We place the string object in the __string_objects
   section of the __OBJC segment.  The Objective-C runtime will
   initialize the isa pointers of the string objects to point at the
   NXConstantString class object.  */

tree
objc_build_string_object (tree string)
{
  tree constant_string_class;
  int length;
  tree fields, addr;
  struct string_descriptor *desc, key;
  void **loc;

  /* Prep the string argument.  */
  string = fix_string_type (string);
  TREE_SET_CODE (string, STRING_CST);
  length = TREE_STRING_LENGTH (string) - 1;

  /* The target may have different ideas on how to construct an ObjC string 
     literal.  On Darwin (Mac OS X), for example, we may wish to obtain a 
     constant CFString reference instead.
     At present, this is only supported for the NeXT runtime.  */
  if (flag_next_runtime && targetcm.objc_construct_string_object)
    {
      tree constructor = (*targetcm.objc_construct_string_object) (string);
      if (constructor)
        return build1 (NOP_EXPR, objc_object_type, constructor);
    }

  /* Check whether the string class being used actually exists and has the
     correct ivar layout.  */
  if (!string_layout_checked)
    {
      string_layout_checked = -1;
      constant_string_class = lookup_interface (constant_string_id);
      internal_const_str_type = objc_build_internal_const_str_type ();

      if (!constant_string_class
          || !(constant_string_type
               = CLASS_STATIC_TEMPLATE (constant_string_class)))
        error ("cannot find interface declaration for %qE",
               constant_string_id);
      /* The NSConstantString/NXConstantString ivar layout is now known.  */
      else if (!check_string_class_template ())
        error ("interface %qE does not have valid constant string layout",
               constant_string_id);
      /* For the NeXT runtime, we can generate a literal reference
         to the string class, don't need to run a constructor.  */
      else if (flag_next_runtime && !setup_string_decl ())
        error ("cannot find reference tag for class %qE",
               constant_string_id);
      else
        {
          string_layout_checked = 1;  /* Success!  */
          add_class_reference (constant_string_id);
        }
    }

  if (string_layout_checked == -1)
    return error_mark_node;

  /* Perhaps we already constructed a constant string just like this one? */
  key.literal = string;
  loc = htab_find_slot (string_htab, &key, INSERT);
  desc = (struct string_descriptor *) *loc;

  if (!desc)
    {
      tree var, constructor;
      VEC(constructor_elt,gc) *v = NULL;
      *loc = desc = ggc_alloc_string_descriptor ();
      desc->literal = string;

      /* GNU:    (NXConstantString *) & ((__builtin_ObjCString) { NULL, string, length })  */
      /* NeXT:   (NSConstantString *) & ((__builtin_ObjCString) { isa, string, length })   */
      fields = TYPE_FIELDS (internal_const_str_type);
      CONSTRUCTOR_APPEND_ELT (v, fields,
                              flag_next_runtime
                              ? build_unary_op (input_location,
                                                ADDR_EXPR, string_class_decl, 0)
                              : build_int_cst (NULL_TREE, 0));
      fields = DECL_CHAIN (fields);
      CONSTRUCTOR_APPEND_ELT (v, fields,
                              build_unary_op (input_location,
                                              ADDR_EXPR, string, 1));
      fields = DECL_CHAIN (fields);
      CONSTRUCTOR_APPEND_ELT (v, fields, build_int_cst (NULL_TREE, length));
      constructor = objc_build_constructor (internal_const_str_type, v);

      if (!flag_next_runtime)
        constructor
          = objc_add_static_instance (constructor, constant_string_type);
      else
        {
          var = build_decl (input_location,
                            CONST_DECL, NULL, TREE_TYPE (constructor));
          DECL_INITIAL (var) = constructor;
          TREE_STATIC (var) = 1;
          pushdecl_top_level (var);
          constructor = var;
        }
      desc->constructor = constructor;
    }

  addr = convert (build_pointer_type (constant_string_type),
                  build_unary_op (input_location,
                                  ADDR_EXPR, desc->constructor, 1));

  return addr;
}

/* Declare a static instance of CLASS_DECL initialized by CONSTRUCTOR.  */

static GTY(()) int num_static_inst;

static tree
objc_add_static_instance (tree constructor, tree class_decl)
{
  tree *chain, decl;
  char buf[256];

  /* Find the list of static instances for the CLASS_DECL.  Create one if
     not found.  */
  for (chain = &objc_static_instances;
       *chain && TREE_VALUE (*chain) != class_decl;
       chain = &TREE_CHAIN (*chain));
  if (!*chain)
    {
      *chain = tree_cons (NULL_TREE, class_decl, NULL_TREE);
      add_objc_string (OBJC_TYPE_NAME (class_decl), class_names);
    }

  sprintf (buf, "_OBJC_INSTANCE_%d", num_static_inst++);
  decl = build_decl (input_location,
                     VAR_DECL, get_identifier (buf), class_decl);
  TREE_STATIC (decl) = 1;
  DECL_ARTIFICIAL (decl) = 1;
  TREE_USED (decl) = 1;
  DECL_INITIAL (decl) = constructor;

  /* We may be writing something else just now.
     Postpone till end of input.  */
  DECL_DEFER_OUTPUT (decl) = 1;
  pushdecl_top_level (decl);
  rest_of_decl_compilation (decl, 1, 0);

  /* Add the DECL to the head of this CLASS' list.  */
  TREE_PURPOSE (*chain) = tree_cons (NULL_TREE, decl, TREE_PURPOSE (*chain));

  return decl;
}

/* Build a static constant CONSTRUCTOR
   with type TYPE and elements ELTS.  */

static tree
objc_build_constructor (tree type, VEC(constructor_elt,gc) *elts)
{
  tree constructor = build_constructor (type, elts);

  TREE_CONSTANT (constructor) = 1;
  TREE_STATIC (constructor) = 1;
  TREE_READONLY (constructor) = 1;

#ifdef OBJCPLUS
  /* Adjust for impedance mismatch.  We should figure out how to build
     CONSTRUCTORs that consistently please both the C and C++ gods.  */
  if (!VEC_index (constructor_elt, elts, 0)->index)
    TREE_TYPE (constructor) = init_list_type_node;
#endif

  return constructor;
}
\f
/* Take care of defining and initializing _OBJC_SYMBOLS.  */

/* Predefine the following data type:

   struct _objc_symtab
   {
     long sel_ref_cnt;
     SEL *refs;
     short cls_def_cnt;
     short cat_def_cnt;
     void *defs[cls_def_cnt + cat_def_cnt];
   }; */

static void
build_objc_symtab_template (void)
{
  tree fields, *chain = NULL;

  objc_symtab_template = objc_start_struct (get_identifier (UTAG_SYMTAB));

  /* long sel_ref_cnt; */
  fields = add_field_decl (long_integer_type_node, "sel_ref_cnt", &chain);

  /* SEL *refs; */
  add_field_decl (build_pointer_type (objc_selector_type), "refs", &chain);

  /* short cls_def_cnt; */
  add_field_decl (short_integer_type_node, "cls_def_cnt", &chain);

  /* short cat_def_cnt; */
  add_field_decl (short_integer_type_node, "cat_def_cnt", &chain);

  if (imp_count || cat_count || !flag_next_runtime)
    {
      /* void *defs[imp_count + cat_count (+ 1)]; */
      /* NB: The index is one less than the size of the array.  */
      int index = imp_count + cat_count + (flag_next_runtime ? -1: 0);
      tree array_type = build_sized_array_type (ptr_type_node, index + 1);
      add_field_decl (array_type, "defs", &chain);
    }

  objc_finish_struct (objc_symtab_template, fields);
}

/* Create the initial value for the `defs' field of _objc_symtab.
   This is a CONSTRUCTOR.  */

static tree
init_def_list (tree type)
{
  tree expr;
  struct imp_entry *impent;
  VEC(constructor_elt,gc) *v = NULL;

  if (imp_count)
    for (impent = imp_list; impent; impent = impent->next)
      {
        if (TREE_CODE (impent->imp_context) == CLASS_IMPLEMENTATION_TYPE)
          {
            expr = build_unary_op (input_location,
                                   ADDR_EXPR, impent->class_decl, 0);
            CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, expr);
          }
      }

  if (cat_count)
    for (impent = imp_list; impent; impent = impent->next)
      {
        if (TREE_CODE (impent->imp_context) == CATEGORY_IMPLEMENTATION_TYPE)
          {
            expr = build_unary_op (input_location,
                                   ADDR_EXPR, impent->class_decl, 0);
            CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, expr);
          }
      }

  if (!flag_next_runtime)
    {
      /* statics = { ..., _OBJC_STATIC_INSTANCES, ... }  */
      if (static_instances_decl)
        expr = build_unary_op (input_location,
                               ADDR_EXPR, static_instances_decl, 0);
      else
        expr = integer_zero_node;

      CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, expr);
    }

  return objc_build_constructor (type, v);
}

/* Construct the initial value for all of _objc_symtab.  */

static tree
init_objc_symtab (tree type)
{
  VEC(constructor_elt,gc) *v = NULL;

  /* sel_ref_cnt = { ..., 5, ... } */

  CONSTRUCTOR_APPEND_ELT (v, NULL_TREE,
                          build_int_cst (long_integer_type_node, 0));

  /* refs = { ..., _OBJC_SELECTOR_TABLE, ... } */

  if (flag_next_runtime || ! sel_ref_chain)
    CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, convert (
                                        build_pointer_type (objc_selector_type),
                                                        integer_zero_node));
  else
    {
      tree expr = build_unary_op (input_location, ADDR_EXPR,
                                  UOBJC_SELECTOR_TABLE_decl, 1);

      CONSTRUCTOR_APPEND_ELT (v, NULL_TREE,
                              convert (build_pointer_type (objc_selector_type),
                                       expr));
    }

  /* cls_def_cnt = { ..., 5, ... } */

  CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, 
                          build_int_cst (short_integer_type_node, imp_count));

  /* cat_def_cnt = { ..., 5, ... } */

  CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, 
                          build_int_cst (short_integer_type_node, cat_count));

  /* cls_def = { ..., { &Foo, &Bar, ...}, ... } */

  if (imp_count || cat_count || !flag_next_runtime)
    {

      tree field = TYPE_FIELDS (type);
      field = DECL_CHAIN (DECL_CHAIN (DECL_CHAIN (DECL_CHAIN (field))));

      CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, init_def_list (TREE_TYPE (field)));
    }

  return objc_build_constructor (type, v);
}

/* Generate forward declarations for metadata such as
  'OBJC_CLASS_...'.  */

static tree
build_metadata_decl (const char *name, tree type)
{
  tree decl;

  /* struct TYPE NAME_<name>; */
  decl = start_var_decl (type, synth_id_with_class_suffix
                               (name,
                                objc_implementation_context));

  return decl;
}

/* Push forward-declarations of all the categories so that
   init_def_list can use them in a CONSTRUCTOR.  */

static void
forward_declare_categories (void)
{
  struct imp_entry *impent;
  tree sav = objc_implementation_context;

  for (impent = imp_list; impent; impent = impent->next)
    {
      if (TREE_CODE (impent->imp_context) == CATEGORY_IMPLEMENTATION_TYPE)
        {
          /* Set an invisible arg to synth_id_with_class_suffix.  */
          objc_implementation_context = impent->imp_context;
          /* extern struct objc_category _OBJC_CATEGORY_<name>; */
          impent->class_decl = build_metadata_decl ("_OBJC_CATEGORY",
                                                    objc_category_template);
        }
    }
  objc_implementation_context = sav;
}

/* Create the declaration of _OBJC_SYMBOLS, with type `struct _objc_symtab'
   and initialized appropriately.  */

static void
generate_objc_symtab_decl (void)
{
 
  build_objc_symtab_template ();
  UOBJC_SYMBOLS_decl = start_var_decl (objc_symtab_template, "_OBJC_SYMBOLS");
  finish_var_decl (UOBJC_SYMBOLS_decl,
                   init_objc_symtab (TREE_TYPE (UOBJC_SYMBOLS_decl)));
}
\f
static tree
init_module_descriptor (tree type)
{
  tree expr;
  VEC(constructor_elt,gc) *v = NULL;

  /* version = { 1, ... } */

  expr = build_int_cst (long_integer_type_node, OBJC_VERSION);
  CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, expr);

  /* size = { ..., sizeof (struct _objc_module), ... } */

  expr = convert (long_integer_type_node,
                  size_in_bytes (objc_module_template));
  CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, expr);

  /* Don't provide any file name for security reasons. */
  /* name = { ..., "", ... } */

  expr = add_objc_string (get_identifier (""), class_names);
  CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, expr);

  /* symtab = { ..., _OBJC_SYMBOLS, ... } */

  if (UOBJC_SYMBOLS_decl)
    expr = build_unary_op (input_location,
                           ADDR_EXPR, UOBJC_SYMBOLS_decl, 0);
  else
    expr = null_pointer_node;
  CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, expr);

  return objc_build_constructor (type, v);
}

/* Write out the data structures to describe Objective C classes defined.

   struct _objc_module { ... } _OBJC_MODULE = { ... };   */

static void
build_module_descriptor (void)
{
  tree decls, *chain = NULL;

#ifdef OBJCPLUS
  push_lang_context (lang_name_c); /* extern "C" */
#endif

  objc_module_template = objc_start_struct (get_identifier (UTAG_MODULE));

  /* long version; */
  decls = add_field_decl (long_integer_type_node, "version", &chain);

  /* long size; */
  add_field_decl (long_integer_type_node, "size", &chain);

  /* char *name; */
  add_field_decl (string_type_node, "name", &chain);

  /* struct _objc_symtab *symtab; */
  add_field_decl (build_pointer_type (xref_tag (RECORD_TYPE,
                                                get_identifier (UTAG_SYMTAB))),
                  "symtab", &chain);

  objc_finish_struct (objc_module_template, decls);

  /* Create an instance of "_objc_module".  */
  UOBJC_MODULES_decl = start_var_decl (objc_module_template, "_OBJC_MODULES");
  /* This is the root of the metadata for defined classes and categories, it
     is referenced by the runtime and, therefore, needed.  */
  DECL_PRESERVE_P (UOBJC_MODULES_decl) = 1;
  finish_var_decl (UOBJC_MODULES_decl,
                   init_module_descriptor (TREE_TYPE (UOBJC_MODULES_decl)));

#ifdef OBJCPLUS
  pop_lang_context ();
#endif
}

/* The GNU runtime requires us to provide a static initializer function
   for each module:

   static void __objc_gnu_init (void) {
     __objc_exec_class (&L_OBJC_MODULES);
   }  */

static void
build_module_initializer_routine (void)
{
  tree body;

#ifdef OBJCPLUS
  push_lang_context (lang_name_c); /* extern "C" */
#endif

  objc_push_parm (build_decl (input_location,
                              PARM_DECL, NULL_TREE, void_type_node));
#ifdef OBJCPLUS
  objc_start_function (get_identifier (TAG_GNUINIT),
                       build_function_type_list (void_type_node, NULL_TREE),
                       NULL_TREE, NULL_TREE);
#else
  objc_start_function (get_identifier (TAG_GNUINIT),
                       build_function_type_list (void_type_node, NULL_TREE),
                       NULL_TREE, objc_get_parm_info (0));
#endif
  body = c_begin_compound_stmt (true);
  add_stmt (build_function_call
            (input_location,
             execclass_decl,
             build_tree_list
             (NULL_TREE,
              build_unary_op (input_location, ADDR_EXPR,
                              UOBJC_MODULES_decl, 0))));
  add_stmt (c_end_compound_stmt (input_location, body, true));

  TREE_PUBLIC (current_function_decl) = 0;

#ifndef OBJCPLUS
  /* For Objective-C++, we will need to call __objc_gnu_init
     from objc_generate_static_init_call() below.  */
  DECL_STATIC_CONSTRUCTOR (current_function_decl) = 1;
#endif

  GNU_INIT_decl = current_function_decl;
  finish_function ();

#ifdef OBJCPLUS
    pop_lang_context ();
#endif
}

#ifdef OBJCPLUS
/* Return 1 if the __objc_gnu_init function has been synthesized and needs
   to be called by the module initializer routine.  */

int
objc_static_init_needed_p (void)
{
  return (GNU_INIT_decl != NULL_TREE);
}

/* Generate a call to the __objc_gnu_init initializer function.  */

tree
objc_generate_static_init_call (tree ctors ATTRIBUTE_UNUSED)
{
  add_stmt (build_stmt (input_location, EXPR_STMT,
                        build_function_call (input_location,
                                             GNU_INIT_decl, NULL_TREE)));

  return ctors;
}
#endif /* OBJCPLUS */

/* Return the DECL of the string IDENT in the SECTION.  */

static tree
get_objc_string_decl (tree ident, enum string_section section)
{
  tree chain;

  switch (section)
    {
    case class_names:
      chain = class_names_chain;
      break;
    case meth_var_names:
      chain = meth_var_names_chain;
      break;
    case meth_var_types:
      chain = meth_var_types_chain;
      break;
    default:
      gcc_unreachable ();
    }

  for (; chain != 0; chain = TREE_CHAIN (chain))
    if (TREE_VALUE (chain) == ident)
      return (TREE_PURPOSE (chain));

  gcc_unreachable ();
  return NULL_TREE;
}

/* Output references to all statically allocated objects.  Return the DECL
   for the array built.  */

static void
generate_static_references (void)
{
  tree expr = NULL_TREE;
  tree class_name, klass, decl;
  tree cl_chain, in_chain, type
    = build_array_type (build_pointer_type (void_type_node), NULL_TREE);
  int num_inst, num_class;
  char buf[256];
  VEC(constructor_elt,gc) *decls = NULL;

  if (flag_next_runtime)
    gcc_unreachable ();

  for (cl_chain = objc_static_instances, num_class = 0;
       cl_chain; cl_chain = TREE_CHAIN (cl_chain), num_class++)
    {
      VEC(constructor_elt,gc) *v = NULL;

      for (num_inst = 0, in_chain = TREE_PURPOSE (cl_chain);
           in_chain; num_inst++, in_chain = TREE_CHAIN (in_chain));

      sprintf (buf, "_OBJC_STATIC_INSTANCES_%d", num_class);
      decl = start_var_decl (type, buf);

      /* Output {class_name, ...}.  */
      klass = TREE_VALUE (cl_chain);
      class_name = get_objc_string_decl (OBJC_TYPE_NAME (klass), class_names);
      CONSTRUCTOR_APPEND_ELT (v, NULL_TREE,
                              build_unary_op (input_location, 
                                              ADDR_EXPR, class_name, 1));

      /* Output {..., instance, ...}.  */
      for (in_chain = TREE_PURPOSE (cl_chain);
           in_chain; in_chain = TREE_CHAIN (in_chain))
        {
          expr = build_unary_op (input_location,
                                 ADDR_EXPR, TREE_VALUE (in_chain), 1);
          CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, expr);
        }

      /* Output {..., NULL}.  */
      CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, build_int_cst (NULL_TREE, 0));

      expr = objc_build_constructor (TREE_TYPE (decl), v);
      finish_var_decl (decl, expr);
      CONSTRUCTOR_APPEND_ELT (decls, NULL_TREE,
                              build_unary_op (input_location,
                                              ADDR_EXPR, decl, 1));
    }

  CONSTRUCTOR_APPEND_ELT (decls, NULL_TREE, build_int_cst (NULL_TREE, 0));
  expr = objc_build_constructor (type, decls);
  static_instances_decl = start_var_decl (type, "_OBJC_STATIC_INSTANCES");
  finish_var_decl (static_instances_decl, expr);
}

static GTY(()) int selector_reference_idx;

static tree
build_selector_reference_decl (void)
{
  tree decl;
  char buf[256];

  sprintf (buf, "_OBJC_SELECTOR_REFERENCES_%d", selector_reference_idx++);
  decl = start_var_decl (objc_selector_type, buf);

  return decl;
}

static void
build_selector_table_decl (void)
{
  tree temp;

  if (flag_typed_selectors)
    {
      build_selector_template ();
      temp = build_array_type (objc_selector_template, NULL_TREE);
    }
  else
    temp = build_array_type (objc_selector_type, NULL_TREE);

  UOBJC_SELECTOR_TABLE_decl = start_var_decl (temp, "_OBJC_SELECTOR_TABLE");
}

/* Just a handy wrapper for add_objc_string.  */

static tree
build_selector (tree ident)
{
  return convert (objc_selector_type,
                  add_objc_string (ident, meth_var_names));
}