* c-decl.c (warn_if_shadowing): Don't warn if shadowed

[pf3gnuchains/gcc-fork.git] / gcc / c-decl.c

/* Process declarations and variables for C compiler.
   Copyright (C) 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
   2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
   Free Software Foundation, Inc.

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/>.  */

/* Process declarations and symbol lookup for C front end.
   Also constructs types; the standard scalar types at initialization,
   and structure, union, array and enum types when they are declared.  */

/* ??? not all decl nodes are given the most useful possible
   line numbers.  For example, the CONST_DECLs for enum values.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "input.h"
#include "tm.h"
#include "intl.h"
#include "tree.h"
#include "tree-inline.h"
#include "flags.h"
#include "function.h"
#include "output.h"
#include "c-tree.h"
#include "toplev.h"
#include "tm_p.h"
#include "cpplib.h"
#include "target.h"
#include "debug.h"
#include "opts.h"
#include "timevar.h"
#include "c-family/c-common.h"
#include "c-family/c-objc.h"
#include "c-family/c-pragma.h"
#include "c-lang.h"
#include "langhooks.h"
#include "tree-mudflap.h"
#include "tree-iterator.h"
#include "diagnostic-core.h"
#include "tree-dump.h"
#include "cgraph.h"
#include "hashtab.h"
#include "langhooks-def.h"
#include "pointer-set.h"
#include "plugin.h"
#include "c-family/c-ada-spec.h"

/* In grokdeclarator, distinguish syntactic contexts of declarators.  */
enum decl_context
{ NORMAL,                       /* Ordinary declaration */
  FUNCDEF,                      /* Function definition */
  PARM,                         /* Declaration of parm before function body */
  FIELD,                        /* Declaration inside struct or union */
  TYPENAME};                    /* Typename (inside cast or sizeof)  */

/* States indicating how grokdeclarator() should handle declspecs marked
   with __attribute__((deprecated)).  An object declared as
   __attribute__((deprecated)) suppresses warnings of uses of other
   deprecated items.  */

enum deprecated_states {
  DEPRECATED_NORMAL,
  DEPRECATED_SUPPRESS
};

\f
/* Nonzero if we have seen an invalid cross reference
   to a struct, union, or enum, but not yet printed the message.  */
tree pending_invalid_xref;

/* File and line to appear in the eventual error message.  */
location_t pending_invalid_xref_location;

/* The file and line that the prototype came from if this is an
   old-style definition; used for diagnostics in
   store_parm_decls_oldstyle.  */

static location_t current_function_prototype_locus;

/* Whether this prototype was built-in.  */

static bool current_function_prototype_built_in;

/* The argument type information of this prototype.  */

static tree current_function_prototype_arg_types;

/* The argument information structure for the function currently being
   defined.  */

static struct c_arg_info *current_function_arg_info;

/* The obstack on which parser and related data structures, which are
   not live beyond their top-level declaration or definition, are
   allocated.  */
struct obstack parser_obstack;

/* The current statement tree.  */

static GTY(()) struct stmt_tree_s c_stmt_tree;

/* State saving variables.  */
tree c_break_label;
tree c_cont_label;

/* A list of decls to be made automatically visible in each file scope.  */
static GTY(()) tree visible_builtins;

/* Set to 0 at beginning of a function definition, set to 1 if
   a return statement that specifies a return value is seen.  */

int current_function_returns_value;

/* Set to 0 at beginning of a function definition, set to 1 if
   a return statement with no argument is seen.  */

int current_function_returns_null;

/* Set to 0 at beginning of a function definition, set to 1 if
   a call to a noreturn function is seen.  */

int current_function_returns_abnormally;

/* Set to nonzero by `grokdeclarator' for a function
   whose return type is defaulted, if warnings for this are desired.  */

static int warn_about_return_type;

/* Nonzero when the current toplevel function contains a declaration
   of a nested function which is never defined.  */

static bool undef_nested_function;

\f
/* Each c_binding structure describes one binding of an identifier to
   a decl.  All the decls in a scope - irrespective of namespace - are
   chained together by the ->prev field, which (as the name implies)
   runs in reverse order.  All the decls in a given namespace bound to
   a given identifier are chained by the ->shadowed field, which runs
   from inner to outer scopes.

   The ->decl field usually points to a DECL node, but there are two
   exceptions.  In the namespace of type tags, the bound entity is a
   RECORD_TYPE, UNION_TYPE, or ENUMERAL_TYPE node.  If an undeclared
   identifier is encountered, it is bound to error_mark_node to
   suppress further errors about that identifier in the current
   function.

   The ->u.type field stores the type of the declaration in this scope;
   if NULL, the type is the type of the ->decl field.  This is only of
   relevance for objects with external or internal linkage which may
   be redeclared in inner scopes, forming composite types that only
   persist for the duration of those scopes.  In the external scope,
   this stores the composite of all the types declared for this
   object, visible or not.  The ->inner_comp field (used only at file
   scope) stores whether an incomplete array type at file scope was
   completed at an inner scope to an array size other than 1.

   The ->u.label field is used for labels.  It points to a structure
   which stores additional information used for warnings.

   The depth field is copied from the scope structure that holds this
   decl.  It is used to preserve the proper ordering of the ->shadowed
   field (see bind()) and also for a handful of special-case checks.
   Finally, the invisible bit is true for a decl which should be
   ignored for purposes of normal name lookup, and the nested bit is
   true for a decl that's been bound a second time in an inner scope;
   in all such cases, the binding in the outer scope will have its
   invisible bit true.  */

struct GTY((chain_next ("%h.prev"))) c_binding {
  union GTY(()) {               /* first so GTY desc can use decl */
    tree GTY((tag ("0"))) type; /* the type in this scope */
    struct c_label_vars * GTY((tag ("1"))) label; /* for warnings */
  } GTY((desc ("TREE_CODE (%0.decl) == LABEL_DECL"))) u;
  tree decl;                    /* the decl bound */
  tree id;                      /* the identifier it's bound to */
  struct c_binding *prev;       /* the previous decl in this scope */
  struct c_binding *shadowed;   /* the innermost decl shadowed by this one */
  unsigned int depth : 28;      /* depth of this scope */
  BOOL_BITFIELD invisible : 1;  /* normal lookup should ignore this binding */
  BOOL_BITFIELD nested : 1;     /* do not set DECL_CONTEXT when popping */
  BOOL_BITFIELD inner_comp : 1; /* incomplete array completed in inner scope */
  BOOL_BITFIELD in_struct : 1;  /* currently defined as struct field */
  location_t locus;             /* location for nested bindings */
};
#define B_IN_SCOPE(b1, b2) ((b1)->depth == (b2)->depth)
#define B_IN_CURRENT_SCOPE(b) ((b)->depth == current_scope->depth)
#define B_IN_FILE_SCOPE(b) ((b)->depth == 1 /*file_scope->depth*/)
#define B_IN_EXTERNAL_SCOPE(b) ((b)->depth == 0 /*external_scope->depth*/)

#define I_SYMBOL_BINDING(node) \
  (((struct lang_identifier *) IDENTIFIER_NODE_CHECK(node))->symbol_binding)
#define I_SYMBOL_DECL(node) \
 (I_SYMBOL_BINDING(node) ? I_SYMBOL_BINDING(node)->decl : 0)

#define I_TAG_BINDING(node) \
  (((struct lang_identifier *) IDENTIFIER_NODE_CHECK(node))->tag_binding)
#define I_TAG_DECL(node) \
 (I_TAG_BINDING(node) ? I_TAG_BINDING(node)->decl : 0)

#define I_LABEL_BINDING(node) \
  (((struct lang_identifier *) IDENTIFIER_NODE_CHECK(node))->label_binding)
#define I_LABEL_DECL(node) \
 (I_LABEL_BINDING(node) ? I_LABEL_BINDING(node)->decl : 0)

/* Each C symbol points to three linked lists of c_binding structures.
   These describe the values of the identifier in the three different
   namespaces defined by the language.  */

struct GTY(()) lang_identifier {
  struct c_common_identifier common_id;
  struct c_binding *symbol_binding; /* vars, funcs, constants, typedefs */
  struct c_binding *tag_binding;    /* struct/union/enum tags */
  struct c_binding *label_binding;  /* labels */
};

/* Validate c-lang.c's assumptions.  */
extern char C_SIZEOF_STRUCT_LANG_IDENTIFIER_isnt_accurate
[(sizeof(struct lang_identifier) == C_SIZEOF_STRUCT_LANG_IDENTIFIER) ? 1 : -1];

/* The resulting tree type.  */

union GTY((desc ("TREE_CODE (&%h.generic) == IDENTIFIER_NODE"),
       chain_next ("(union lang_tree_node *) c_tree_chain_next (&%h.generic)"))) lang_tree_node
 {
  union tree_node GTY ((tag ("0"),
                        desc ("tree_node_structure (&%h)")))
    generic;
  struct lang_identifier GTY ((tag ("1"))) identifier;
};

/* Track bindings and other things that matter for goto warnings.  For
   efficiency, we do not gather all the decls at the point of
   definition.  Instead, we point into the bindings structure.  As
   scopes are popped, we update these structures and gather the decls
   that matter at that time.  */

struct GTY(()) c_spot_bindings {
  /* The currently open scope which holds bindings defined when the
     label was defined or the goto statement was found.  */
  struct c_scope *scope;
  /* The bindings in the scope field which were defined at the point
     of the label or goto.  This lets us look at older or newer
     bindings in the scope, as appropriate.  */
  struct c_binding *bindings_in_scope;
  /* The number of statement expressions that have started since this
     label or goto statement was defined.  This is zero if we are at
     the same statement expression level.  It is positive if we are in
     a statement expression started since this spot.  It is negative
     if this spot was in a statement expression and we have left
     it.  */
  int stmt_exprs;
  /* Whether we started in a statement expression but are no longer in
     it.  This is set to true if stmt_exprs ever goes negative.  */
  bool left_stmt_expr;
};

/* This structure is used to keep track of bindings seen when a goto
   statement is defined.  This is only used if we see the goto
   statement before we see the label.  */

struct GTY(()) c_goto_bindings {
  /* The location of the goto statement.  */
  location_t loc;
  /* The bindings of the goto statement.  */
  struct c_spot_bindings goto_bindings;
};

typedef struct c_goto_bindings *c_goto_bindings_p;
DEF_VEC_P(c_goto_bindings_p);
DEF_VEC_ALLOC_P(c_goto_bindings_p,gc);

/* The additional information we keep track of for a label binding.
   These fields are updated as scopes are popped.  */

struct GTY(()) c_label_vars {
  /* The shadowed c_label_vars, when one label shadows another (which
     can only happen using a __label__ declaration).  */
  struct c_label_vars *shadowed;
  /* The bindings when the label was defined.  */
  struct c_spot_bindings label_bindings;
  /* A list of decls that we care about: decls about which we should
     warn if a goto branches to this label from later in the function.
     Decls are added to this list as scopes are popped.  We only add
     the decls that matter.  */
  VEC(tree,gc) *decls_in_scope;
  /* A list of goto statements to this label.  This is only used for
     goto statements seen before the label was defined, so that we can
     issue appropriate warnings for them.  */
  VEC(c_goto_bindings_p,gc) *gotos;
};

/* Each c_scope structure describes the complete contents of one
   scope.  Four scopes are distinguished specially: the innermost or
   current scope, the innermost function scope, the file scope (always
   the second to outermost) and the outermost or external scope.

   Most declarations are recorded in the current scope.

   All normal label declarations are recorded in the innermost
   function scope, as are bindings of undeclared identifiers to
   error_mark_node.  (GCC permits nested functions as an extension,
   hence the 'innermost' qualifier.)  Explicitly declared labels
   (using the __label__ extension) appear in the current scope.

   Being in the file scope (current_scope == file_scope) causes
   special behavior in several places below.  Also, under some
   conditions the Objective-C front end records declarations in the
   file scope even though that isn't the current scope.

   All declarations with external linkage are recorded in the external
   scope, even if they aren't visible there; this models the fact that
   such declarations are visible to the entire program, and (with a
   bit of cleverness, see pushdecl) allows diagnosis of some violations
   of C99 6.2.2p7 and 6.2.7p2:

     If, within the same translation unit, the same identifier appears
     with both internal and external linkage, the behavior is
     undefined.

     All declarations that refer to the same object or function shall
     have compatible type; otherwise, the behavior is undefined.

   Initially only the built-in declarations, which describe compiler
   intrinsic functions plus a subset of the standard library, are in
   this scope.

   The order of the blocks list matters, and it is frequently appended
   to.  To avoid having to walk all the way to the end of the list on
   each insertion, or reverse the list later, we maintain a pointer to
   the last list entry.  (FIXME: It should be feasible to use a reversed
   list here.)

   The bindings list is strictly in reverse order of declarations;
   pop_scope relies on this.  */


struct GTY((chain_next ("%h.outer"))) c_scope {
  /* The scope containing this one.  */
  struct c_scope *outer;

  /* The next outermost function scope.  */
  struct c_scope *outer_function;

  /* All bindings in this scope.  */
  struct c_binding *bindings;

  /* For each scope (except the global one), a chain of BLOCK nodes
     for all the scopes that were entered and exited one level down.  */
  tree blocks;
  tree blocks_last;

  /* The depth of this scope.  Used to keep the ->shadowed chain of
     bindings sorted innermost to outermost.  */
  unsigned int depth : 28;

  /* True if we are currently filling this scope with parameter
     declarations.  */
  BOOL_BITFIELD parm_flag : 1;

  /* True if we saw [*] in this scope.  Used to give an error messages
     if these appears in a function definition.  */
  BOOL_BITFIELD had_vla_unspec : 1;

  /* True if we already complained about forward parameter decls
     in this scope.  This prevents double warnings on
     foo (int a; int b; ...)  */
  BOOL_BITFIELD warned_forward_parm_decls : 1;

  /* True if this is the outermost block scope of a function body.
     This scope contains the parameters, the local variables declared
     in the outermost block, and all the labels (except those in
     nested functions, or declared at block scope with __label__).  */
  BOOL_BITFIELD function_body : 1;

  /* True means make a BLOCK for this scope no matter what.  */
  BOOL_BITFIELD keep : 1;

  /* True means that an unsuffixed float constant is _Decimal64.  */
  BOOL_BITFIELD float_const_decimal64 : 1;

  /* True if this scope has any label bindings.  This is used to speed
     up searching for labels when popping scopes, particularly since
     labels are normally only found at function scope.  */
  BOOL_BITFIELD has_label_bindings : 1;

  /* True if we should issue a warning if a goto statement crosses any
     of the bindings.  We still need to check the list of bindings to
     find the specific ones we need to warn about.  This is true if
     decl_jump_unsafe would return true for any of the bindings.  This
     is used to avoid looping over all the bindings unnecessarily.  */
  BOOL_BITFIELD has_jump_unsafe_decl : 1;
};

/* The scope currently in effect.  */

static GTY(()) struct c_scope *current_scope;

/* The innermost function scope.  Ordinary (not explicitly declared)
   labels, bindings to error_mark_node, and the lazily-created
   bindings of __func__ and its friends get this scope.  */

static GTY(()) struct c_scope *current_function_scope;

/* The C file scope.  This is reset for each input translation unit.  */

static GTY(()) struct c_scope *file_scope;

/* The outermost scope.  This is used for all declarations with
   external linkage, and only these, hence the name.  */

static GTY(()) struct c_scope *external_scope;

/* A chain of c_scope structures awaiting reuse.  */

static GTY((deletable)) struct c_scope *scope_freelist;

/* A chain of c_binding structures awaiting reuse.  */

static GTY((deletable)) struct c_binding *binding_freelist;

/* Append VAR to LIST in scope SCOPE.  */
#define SCOPE_LIST_APPEND(scope, list, decl) do {       \
  struct c_scope *s_ = (scope);                         \
  tree d_ = (decl);                                     \
  if (s_->list##_last)                                  \
    BLOCK_CHAIN (s_->list##_last) = d_;                 \
  else                                                  \
    s_->list = d_;                                      \
  s_->list##_last = d_;                                 \
} while (0)

/* Concatenate FROM in scope FSCOPE onto TO in scope TSCOPE.  */
#define SCOPE_LIST_CONCAT(tscope, to, fscope, from) do {        \
  struct c_scope *t_ = (tscope);                                \
  struct c_scope *f_ = (fscope);                                \
  if (t_->to##_last)                                            \
    BLOCK_CHAIN (t_->to##_last) = f_->from;                     \
  else                                                          \
    t_->to = f_->from;                                          \
  t_->to##_last = f_->from##_last;                              \
} while (0)

/* A c_inline_static structure stores details of a static identifier
   referenced in a definition of a function that may be an inline
   definition if no subsequent declaration of that function uses
   "extern" or does not use "inline".  */

struct GTY((chain_next ("%h.next"))) c_inline_static {
  /* The location for a diagnostic.  */
  location_t location;

  /* The function that may be an inline definition.  */
  tree function;

  /* The object or function referenced.  */
  tree static_decl;

  /* What sort of reference this is.  */
  enum c_inline_static_type type;

  /* The next such structure or NULL.  */
  struct c_inline_static *next;
};

/* List of static identifiers used or referenced in functions that may
   be inline definitions.  */
static GTY(()) struct c_inline_static *c_inline_statics;

/* True means unconditionally make a BLOCK for the next scope pushed.  */

static bool keep_next_level_flag;

/* True means the next call to push_scope will be the outermost scope
   of a function body, so do not push a new scope, merely cease
   expecting parameter decls.  */

static bool next_is_function_body;

/* A VEC of pointers to c_binding structures.  */

typedef struct c_binding *c_binding_ptr;
DEF_VEC_P(c_binding_ptr);
DEF_VEC_ALLOC_P(c_binding_ptr,heap);

/* Information that we keep for a struct or union while it is being
   parsed.  */

struct c_struct_parse_info
{
  /* If warn_cxx_compat, a list of types defined within this
     struct.  */
  VEC(tree,heap) *struct_types;
  /* If warn_cxx_compat, a list of field names which have bindings,
     and which are defined in this struct, but which are not defined
     in any enclosing struct.  This is used to clear the in_struct
     field of the c_bindings structure.  */
  VEC(c_binding_ptr,heap) *fields;
  /* If warn_cxx_compat, a list of typedef names used when defining
     fields in this struct.  */
  VEC(tree,heap) *typedefs_seen;
};

/* Information for the struct or union currently being parsed, or
   NULL if not parsing a struct or union.  */
static struct c_struct_parse_info *struct_parse_info;

/* Forward declarations.  */
static tree lookup_name_in_scope (tree, struct c_scope *);
static tree c_make_fname_decl (location_t, tree, int);
static tree grokdeclarator (const struct c_declarator *,
                            struct c_declspecs *,
                            enum decl_context, bool, tree *, tree *, tree *,
                            bool *, enum deprecated_states);
static tree grokparms (struct c_arg_info *, bool);
static void layout_array_type (tree);
\f
/* T is a statement.  Add it to the statement-tree.  This is the
   C/ObjC version--C++ has a slightly different version of this
   function.  */

tree
add_stmt (tree t)
{
  enum tree_code code = TREE_CODE (t);

  if (CAN_HAVE_LOCATION_P (t) && code != LABEL_EXPR)
    {
      if (!EXPR_HAS_LOCATION (t))
        SET_EXPR_LOCATION (t, input_location);
    }

  if (code == LABEL_EXPR || code == CASE_LABEL_EXPR)
    STATEMENT_LIST_HAS_LABEL (cur_stmt_list) = 1;

  /* Add T to the statement-tree.  Non-side-effect statements need to be
     recorded during statement expressions.  */
  if (!building_stmt_list_p ())
    push_stmt_list ();
  append_to_statement_list_force (t, &cur_stmt_list);

  return t;
}
\f
/* Return true if we will want to say something if a goto statement
   crosses DECL.  */

static bool
decl_jump_unsafe (tree decl)
{
  if (error_operand_p (decl))
    return false;

  /* Always warn about crossing variably modified types.  */
  if ((TREE_CODE (decl) == VAR_DECL || TREE_CODE (decl) == TYPE_DECL)
      && variably_modified_type_p (TREE_TYPE (decl), NULL_TREE))
    return true;

  /* Otherwise, only warn if -Wgoto-misses-init and this is an
     initialized automatic decl.  */
  if (warn_jump_misses_init
      && TREE_CODE (decl) == VAR_DECL
      && !TREE_STATIC (decl)
      && DECL_INITIAL (decl) != NULL_TREE)
    return true;

  return false;
}
\f

void
c_print_identifier (FILE *file, tree node, int indent)
{
  print_node (file, "symbol", I_SYMBOL_DECL (node), indent + 4);
  print_node (file, "tag", I_TAG_DECL (node), indent + 4);
  print_node (file, "label", I_LABEL_DECL (node), indent + 4);
  if (C_IS_RESERVED_WORD (node) && C_RID_CODE (node) != RID_CXX_COMPAT_WARN)
    {
      tree rid = ridpointers[C_RID_CODE (node)];
      indent_to (file, indent + 4);
      fprintf (file, "rid " HOST_PTR_PRINTF " \"%s\"",
               (void *) rid, IDENTIFIER_POINTER (rid));
    }
}

/* Establish a binding between NAME, an IDENTIFIER_NODE, and DECL,
   which may be any of several kinds of DECL or TYPE or error_mark_node,
   in the scope SCOPE.  */
static void
bind (tree name, tree decl, struct c_scope *scope, bool invisible,
      bool nested, location_t locus)
{
  struct c_binding *b, **here;

  if (binding_freelist)
    {
      b = binding_freelist;
      binding_freelist = b->prev;
    }
  else
    b = ggc_alloc_c_binding ();

  b->shadowed = 0;
  b->decl = decl;
  b->id = name;
  b->depth = scope->depth;
  b->invisible = invisible;
  b->nested = nested;
  b->inner_comp = 0;
  b->in_struct = 0;
  b->locus = locus;

  b->u.type = NULL;

  b->prev = scope->bindings;
  scope->bindings = b;

  if (decl_jump_unsafe (decl))
    scope->has_jump_unsafe_decl = 1;

  if (!name)
    return;

  switch (TREE_CODE (decl))
    {
    case LABEL_DECL:     here = &I_LABEL_BINDING (name);   break;
    case ENUMERAL_TYPE:
    case UNION_TYPE:
    case RECORD_TYPE:    here = &I_TAG_BINDING (name);     break;
    case VAR_DECL:
    case FUNCTION_DECL:
    case TYPE_DECL:
    case CONST_DECL:
    case PARM_DECL:
    case ERROR_MARK:     here = &I_SYMBOL_BINDING (name);  break;

    default:
      gcc_unreachable ();
    }

  /* Locate the appropriate place in the chain of shadowed decls
     to insert this binding.  Normally, scope == current_scope and
     this does nothing.  */
  while (*here && (*here)->depth > scope->depth)
    here = &(*here)->shadowed;

  b->shadowed = *here;
  *here = b;
}

/* Clear the binding structure B, stick it on the binding_freelist,
   and return the former value of b->prev.  This is used by pop_scope
   and get_parm_info to iterate destructively over all the bindings
   from a given scope.  */
static struct c_binding *
free_binding_and_advance (struct c_binding *b)
{
  struct c_binding *prev = b->prev;

  memset (b, 0, sizeof (struct c_binding));
  b->prev = binding_freelist;
  binding_freelist = b;

  return prev;
}

/* Bind a label.  Like bind, but skip fields which aren't used for
   labels, and add the LABEL_VARS value.  */
static void
bind_label (tree name, tree label, struct c_scope *scope,
            struct c_label_vars *label_vars)
{
  struct c_binding *b;

  bind (name, label, scope, /*invisible=*/false, /*nested=*/false,
        UNKNOWN_LOCATION);

  scope->has_label_bindings = true;

  b = scope->bindings;
  gcc_assert (b->decl == label);
  label_vars->shadowed = b->u.label;
  b->u.label = label_vars;
}
\f
/* Hook called at end of compilation to assume 1 elt
   for a file-scope tentative array defn that wasn't complete before.  */

void
c_finish_incomplete_decl (tree decl)
{
  if (TREE_CODE (decl) == VAR_DECL)
    {
      tree type = TREE_TYPE (decl);
      if (type != error_mark_node
          && TREE_CODE (type) == ARRAY_TYPE
          && !DECL_EXTERNAL (decl)
          && TYPE_DOMAIN (type) == 0)
        {
          warning_at (DECL_SOURCE_LOCATION (decl),
                      0, "array %q+D assumed to have one element", decl);

          complete_array_type (&TREE_TYPE (decl), NULL_TREE, true);

          layout_decl (decl, 0);
        }
    }
}
\f
/* Record that inline function FUNC contains a reference (location
   LOC) to static DECL (file-scope or function-local according to
   TYPE).  */

void
record_inline_static (location_t loc, tree func, tree decl,
                      enum c_inline_static_type type)
{
  struct c_inline_static *csi = ggc_alloc_c_inline_static ();
  csi->location = loc;
  csi->function = func;
  csi->static_decl = decl;
  csi->type = type;
  csi->next = c_inline_statics;
  c_inline_statics = csi;
}

/* Check for references to static declarations in inline functions at
   the end of the translation unit and diagnose them if the functions
   are still inline definitions.  */

static void
check_inline_statics (void)
{
  struct c_inline_static *csi;
  for (csi = c_inline_statics; csi; csi = csi->next)
    {
      if (DECL_EXTERNAL (csi->function))
        switch (csi->type)
          {
          case csi_internal:
            pedwarn (csi->location, 0,
                     "%qD is static but used in inline function %qD "
                     "which is not static", csi->static_decl, csi->function);
            break;
          case csi_modifiable:
            pedwarn (csi->location, 0,
                     "%q+D is static but declared in inline function %qD "
                     "which is not static", csi->static_decl, csi->function);
            break;
          default:
            gcc_unreachable ();
          }
    }
  c_inline_statics = NULL;
}
\f
/* Fill in a c_spot_bindings structure.  If DEFINING is true, set it
   for the current state, otherwise set it to uninitialized.  */

static void
set_spot_bindings (struct c_spot_bindings *p, bool defining)
{
  if (defining)
    {
      p->scope = current_scope;
      p->bindings_in_scope = current_scope->bindings;
    }
  else
    {
      p->scope = NULL;
      p->bindings_in_scope = NULL;
    }
  p->stmt_exprs = 0;
  p->left_stmt_expr = false;
}

/* Update spot bindings P as we pop out of SCOPE.  Return true if we
   should push decls for a label.  */

static bool
update_spot_bindings (struct c_scope *scope, struct c_spot_bindings *p)
{
  if (p->scope != scope)
    {
      /* This label or goto is defined in some other scope, or it is a
         label which is not yet defined.  There is nothing to
         update.  */
      return false;
    }

  /* Adjust the spot bindings to refer to the bindings already defined
     in the enclosing scope.  */
  p->scope = scope->outer;
  p->bindings_in_scope = p->scope->bindings;

  return true;
}
\f
/* The Objective-C front-end often needs to determine the current scope.  */

void *
objc_get_current_scope (void)
{
  return current_scope;
}

/* The following function is used only by Objective-C.  It needs to live here
   because it accesses the innards of c_scope.  */

void
objc_mark_locals_volatile (void *enclosing_blk)
{
  struct c_scope *scope;
  struct c_binding *b;

  for (scope = current_scope;
       scope && scope != enclosing_blk;
       scope = scope->outer)
    {
      for (b = scope->bindings; b; b = b->prev)
        objc_volatilize_decl (b->decl);

      /* Do not climb up past the current function.  */
      if (scope->function_body)
        break;
    }
}

/* Return true if we are in the global binding level.  */

bool
global_bindings_p (void)
{
  return current_scope == file_scope;
}

void
keep_next_level (void)
{
  keep_next_level_flag = true;
}

/* Set the flag for the FLOAT_CONST_DECIMAL64 pragma being ON.  */

void
set_float_const_decimal64 (void)
{
  current_scope->float_const_decimal64 = true;
}

/* Clear the flag for the FLOAT_CONST_DECIMAL64 pragma.  */

void
clear_float_const_decimal64 (void)
{
  current_scope->float_const_decimal64 = false;
}

/* Return nonzero if an unsuffixed float constant is _Decimal64.  */

bool
float_const_decimal64_p (void)
{
  return current_scope->float_const_decimal64;
}

/* Identify this scope as currently being filled with parameters.  */

void
declare_parm_level (void)
{
  current_scope->parm_flag = true;
}

void
push_scope (void)
{
  if (next_is_function_body)
    {
      /* This is the transition from the parameters to the top level
         of the function body.  These are the same scope
         (C99 6.2.1p4,6) so we do not push another scope structure.
         next_is_function_body is set only by store_parm_decls, which
         in turn is called when and only when we are about to
         encounter the opening curly brace for the function body.

         The outermost block of a function always gets a BLOCK node,
         because the debugging output routines expect that each
         function has at least one BLOCK.  */
      current_scope->parm_flag         = false;
      current_scope->function_body     = true;
      current_scope->keep              = true;
      current_scope->outer_function    = current_function_scope;
      current_function_scope           = current_scope;

      keep_next_level_flag = false;
      next_is_function_body = false;

      /* The FLOAT_CONST_DECIMAL64 pragma applies to nested scopes.  */
      if (current_scope->outer)
        current_scope->float_const_decimal64
          = current_scope->outer->float_const_decimal64;
      else
        current_scope->float_const_decimal64 = false;
    }
  else
    {
      struct c_scope *scope;
      if (scope_freelist)
        {
          scope = scope_freelist;
          scope_freelist = scope->outer;
        }
      else
        scope = ggc_alloc_cleared_c_scope ();

      /* The FLOAT_CONST_DECIMAL64 pragma applies to nested scopes.  */
      if (current_scope)
        scope->float_const_decimal64 = current_scope->float_const_decimal64;
      else
        scope->float_const_decimal64 = false;

      scope->keep          = keep_next_level_flag;
      scope->outer         = current_scope;
      scope->depth         = current_scope ? (current_scope->depth + 1) : 0;

      /* Check for scope depth overflow.  Unlikely (2^28 == 268,435,456) but
         possible.  */
      if (current_scope && scope->depth == 0)
        {
          scope->depth--;
          sorry ("GCC supports only %u nested scopes", scope->depth);
        }

      current_scope        = scope;
      keep_next_level_flag = false;
    }
}

/* This is called when we are leaving SCOPE.  For each label defined
   in SCOPE, add any appropriate decls to its decls_in_scope fields.
   These are the decls whose initialization will be skipped by a goto
   later in the function.  */

static void
update_label_decls (struct c_scope *scope)
{
  struct c_scope *s;

  s = scope;
  while (s != NULL)
    {
      if (s->has_label_bindings)
        {
          struct c_binding *b;

          for (b = s->bindings; b != NULL; b = b->prev)
            {
              struct c_label_vars *label_vars;
              struct c_binding *b1;
              bool hjud;
              unsigned int ix;
              struct c_goto_bindings *g;

              if (TREE_CODE (b->decl) != LABEL_DECL)
                continue;
              label_vars = b->u.label;

              b1 = label_vars->label_bindings.bindings_in_scope;
              if (label_vars->label_bindings.scope == NULL)
                hjud = false;
              else
                hjud = label_vars->label_bindings.scope->has_jump_unsafe_decl;
              if (update_spot_bindings (scope, &label_vars->label_bindings))
                {
                  /* This label is defined in this scope.  */
                  if (hjud)
                    {
                      for (; b1 != NULL; b1 = b1->prev)
                        {
                          /* A goto from later in the function to this
                             label will never see the initialization
                             of B1, if any.  Save it to issue a
                             warning if needed.  */
                          if (decl_jump_unsafe (b1->decl))
                            VEC_safe_push (tree, gc,
                                           label_vars->decls_in_scope,
                                           b1->decl);
                        }
                    }
                }

              /* Update the bindings of any goto statements associated
                 with this label.  */
              FOR_EACH_VEC_ELT (c_goto_bindings_p, label_vars->gotos, ix, g)
                update_spot_bindings (scope, &g->goto_bindings);
            }
        }

      /* Don't search beyond the current function.  */
      if (s == current_function_scope)
        break;

      s = s->outer;
    }
}

/* Set the TYPE_CONTEXT of all of TYPE's variants to CONTEXT.  */

static void
set_type_context (tree type, tree context)
{
  for (type = TYPE_MAIN_VARIANT (type); type;
       type = TYPE_NEXT_VARIANT (type))
    TYPE_CONTEXT (type) = context;
}

/* Exit a scope.  Restore the state of the identifier-decl mappings
   that were in effect when this scope was entered.  Return a BLOCK
   node containing all the DECLs in this scope that are of interest
   to debug info generation.  */

tree
pop_scope (void)
{
  struct c_scope *scope = current_scope;
  tree block, context, p;
  struct c_binding *b;

  bool functionbody = scope->function_body;
  bool keep = functionbody || scope->keep || scope->bindings;

  update_label_decls (scope);

  /* If appropriate, create a BLOCK to record the decls for the life
     of this function.  */
  block = 0;
  if (keep)
    {
      block = make_node (BLOCK);
      BLOCK_SUBBLOCKS (block) = scope->blocks;
      TREE_USED (block) = 1;

      /* In each subblock, record that this is its superior.  */
      for (p = scope->blocks; p; p = BLOCK_CHAIN (p))
        BLOCK_SUPERCONTEXT (p) = block;

      BLOCK_VARS (block) = 0;
    }

  /* The TYPE_CONTEXTs for all of the tagged types belonging to this
     scope must be set so that they point to the appropriate
     construct, i.e.  either to the current FUNCTION_DECL node, or
     else to the BLOCK node we just constructed.

     Note that for tagged types whose scope is just the formal
     parameter list for some function type specification, we can't
     properly set their TYPE_CONTEXTs here, because we don't have a
     pointer to the appropriate FUNCTION_TYPE node readily available
     to us.  For those cases, the TYPE_CONTEXTs of the relevant tagged
     type nodes get set in `grokdeclarator' as soon as we have created
     the FUNCTION_TYPE node which will represent the "scope" for these
     "parameter list local" tagged types.  */
  if (scope->function_body)
    context = current_function_decl;
  else if (scope == file_scope)
    {
      tree file_decl = build_translation_unit_decl (NULL_TREE);
      context = file_decl;
    }
  else
    context = block;

  /* Clear all bindings in this scope.  */
  for (b = scope->bindings; b; b = free_binding_and_advance (b))
    {
      p = b->decl;
      switch (TREE_CODE (p))
        {
        case LABEL_DECL:
          /* Warnings for unused labels, errors for undefined labels.  */
          if (TREE_USED (p) && !DECL_INITIAL (p))
            {
              error ("label %q+D used but not defined", p);
              DECL_INITIAL (p) = error_mark_node;
            }
          else
            warn_for_unused_label (p);

          /* Labels go in BLOCK_VARS.  */
          DECL_CHAIN (p) = BLOCK_VARS (block);
          BLOCK_VARS (block) = p;
          gcc_assert (I_LABEL_BINDING (b->id) == b);
          I_LABEL_BINDING (b->id) = b->shadowed;

          /* Also pop back to the shadowed label_vars.  */
          release_tree_vector (b->u.label->decls_in_scope);
          b->u.label = b->u.label->shadowed;
          break;

        case ENUMERAL_TYPE:
        case UNION_TYPE:
        case RECORD_TYPE:
          set_type_context (p, context);

          /* Types may not have tag-names, in which case the type
             appears in the bindings list with b->id NULL.  */
          if (b->id)
            {
              gcc_assert (I_TAG_BINDING (b->id) == b);
              I_TAG_BINDING (b->id) = b->shadowed;
            }
          break;

        case FUNCTION_DECL:
          /* Propagate TREE_ADDRESSABLE from nested functions to their
             containing functions.  */
          if (!TREE_ASM_WRITTEN (p)
              && DECL_INITIAL (p) != 0
              && TREE_ADDRESSABLE (p)
              && DECL_ABSTRACT_ORIGIN (p) != 0
              && DECL_ABSTRACT_ORIGIN (p) != p)
            TREE_ADDRESSABLE (DECL_ABSTRACT_ORIGIN (p)) = 1;
          if (!DECL_EXTERNAL (p)
              && !DECL_INITIAL (p)
              && scope != file_scope
              && scope != external_scope)
            {
              error ("nested function %q+D declared but never defined", p);
              undef_nested_function = true;
            }
          else if (DECL_DECLARED_INLINE_P (p)
                   && TREE_PUBLIC (p)
                   && !DECL_INITIAL (p))
            {
              /* C99 6.7.4p6: "a function with external linkage... declared
                 with an inline function specifier ... shall also be defined
                 in the same translation unit."  */
              if (!flag_gnu89_inline)
                pedwarn (input_location, 0,
                         "inline function %q+D declared but never defined", p);
              DECL_EXTERNAL (p) = 1;
            }

          goto common_symbol;

        case VAR_DECL:
          /* Warnings for unused variables.  */
          if ((!TREE_USED (p) || !DECL_READ_P (p))
              && !TREE_NO_WARNING (p)
              && !DECL_IN_SYSTEM_HEADER (p)
              && DECL_NAME (p)
              && !DECL_ARTIFICIAL (p)
              && scope != file_scope
              && scope != external_scope)
            {
              if (!TREE_USED (p))
                warning (OPT_Wunused_variable, "unused variable %q+D", p);
              else if (DECL_CONTEXT (p) == current_function_decl)
                warning_at (DECL_SOURCE_LOCATION (p),
                            OPT_Wunused_but_set_variable,
                            "variable %qD set but not used", p);
            }

          if (b->inner_comp)
            {
              error ("type of array %q+D completed incompatibly with"
                     " implicit initialization", p);
            }

          /* Fall through.  */
        case TYPE_DECL:
        case CONST_DECL:
        common_symbol:
          /* All of these go in BLOCK_VARS, but only if this is the
             binding in the home scope.  */
          if (!b->nested)
            {
              DECL_CHAIN (p) = BLOCK_VARS (block);
              BLOCK_VARS (block) = p;
            }
          else if (VAR_OR_FUNCTION_DECL_P (p))
            {
              /* For block local externs add a special
                 DECL_EXTERNAL decl for debug info generation.  */
              tree extp = copy_node (p);

              DECL_EXTERNAL (extp) = 1;
              TREE_STATIC (extp) = 0;
              TREE_PUBLIC (extp) = 1;
              DECL_INITIAL (extp) = NULL_TREE;
              DECL_LANG_SPECIFIC (extp) = NULL;
              DECL_CONTEXT (extp) = current_function_decl;
              if (TREE_CODE (p) == FUNCTION_DECL)
                {
                  DECL_RESULT (extp) = NULL_TREE;
                  DECL_SAVED_TREE (extp) = NULL_TREE;
                  DECL_STRUCT_FUNCTION (extp) = NULL;
                }
              if (b->locus != UNKNOWN_LOCATION)
                DECL_SOURCE_LOCATION (extp) = b->locus;
              DECL_CHAIN (extp) = BLOCK_VARS (block);
              BLOCK_VARS (block) = extp;
            }
          /* If this is the file scope set DECL_CONTEXT of each decl to
             the TRANSLATION_UNIT_DECL.  This makes same_translation_unit_p
             work.  */
          if (scope == file_scope)
            {
              DECL_CONTEXT (p) = context;
              if (TREE_CODE (p) == TYPE_DECL
                  && TREE_TYPE (p) != error_mark_node)
                set_type_context (TREE_TYPE (p), context);
            }

          /* Fall through.  */
          /* Parameters go in DECL_ARGUMENTS, not BLOCK_VARS, and have
             already been put there by store_parm_decls.  Unused-
             parameter warnings are handled by function.c.
             error_mark_node obviously does not go in BLOCK_VARS and
             does not get unused-variable warnings.  */
        case PARM_DECL:
        case ERROR_MARK:
          /* It is possible for a decl not to have a name.  We get
             here with b->id NULL in this case.  */
          if (b->id)
            {
              gcc_assert (I_SYMBOL_BINDING (b->id) == b);
              I_SYMBOL_BINDING (b->id) = b->shadowed;
              if (b->shadowed && b->shadowed->u.type)
                TREE_TYPE (b->shadowed->decl) = b->shadowed->u.type;
            }
          break;

        default:
          gcc_unreachable ();
        }
    }


  /* Dispose of the block that we just made inside some higher level.  */
  if ((scope->function_body || scope == file_scope) && context)
    {
      DECL_INITIAL (context) = block;
      BLOCK_SUPERCONTEXT (block) = context;
    }
  else if (scope->outer)
    {
      if (block)
        SCOPE_LIST_APPEND (scope->outer, blocks, block);
      /* If we did not make a block for the scope just exited, any
         blocks made for inner scopes must be carried forward so they
         will later become subblocks of something else.  */
      else if (scope->blocks)
        SCOPE_LIST_CONCAT (scope->outer, blocks, scope, blocks);
    }

  /* Pop the current scope, and free the structure for reuse.  */
  current_scope = scope->outer;
  if (scope->function_body)
    current_function_scope = scope->outer_function;

  memset (scope, 0, sizeof (struct c_scope));
  scope->outer = scope_freelist;
  scope_freelist = scope;

  return block;
}

void
push_file_scope (void)
{
  tree decl;

  if (file_scope)
    return;

  push_scope ();
  file_scope = current_scope;

  start_fname_decls ();

  for (decl = visible_builtins; decl; decl = DECL_CHAIN (decl))
    bind (DECL_NAME (decl), decl, file_scope,
          /*invisible=*/false, /*nested=*/true, DECL_SOURCE_LOCATION (decl));
}

void
pop_file_scope (void)
{
  /* In case there were missing closebraces, get us back to the global
     binding level.  */
  while (current_scope != file_scope)
    pop_scope ();

  /* __FUNCTION__ is defined at file scope ("").  This
     call may not be necessary as my tests indicate it
     still works without it.  */
  finish_fname_decls ();

  check_inline_statics ();

  /* This is the point to write out a PCH if we're doing that.
     In that case we do not want to do anything else.  */
  if (pch_file)
    {
      c_common_write_pch ();
      return;
    }

  /* Pop off the file scope and close this translation unit.  */
  pop_scope ();
  file_scope = 0;

  maybe_apply_pending_pragma_weaks ();
}
\f
/* Adjust the bindings for the start of a statement expression.  */

void
c_bindings_start_stmt_expr (struct c_spot_bindings* switch_bindings)
{
  struct c_scope *scope;

  for (scope = current_scope; scope != NULL; scope = scope->outer)
    {
      struct c_binding *b;

      if (!scope->has_label_bindings)
        continue;

      for (b = scope->bindings; b != NULL; b = b->prev)
        {
          struct c_label_vars *label_vars;
          unsigned int ix;
          struct c_goto_bindings *g;

          if (TREE_CODE (b->decl) != LABEL_DECL)
            continue;
          label_vars = b->u.label;
          ++label_vars->label_bindings.stmt_exprs;
          FOR_EACH_VEC_ELT (c_goto_bindings_p, label_vars->gotos, ix, g)
            ++g->goto_bindings.stmt_exprs;
        }
    }

  if (switch_bindings != NULL)
    ++switch_bindings->stmt_exprs;
}

/* Adjust the bindings for the end of a statement expression.  */

void
c_bindings_end_stmt_expr (struct c_spot_bindings *switch_bindings)
{
  struct c_scope *scope;

  for (scope = current_scope; scope != NULL; scope = scope->outer)
    {
      struct c_binding *b;

      if (!scope->has_label_bindings)
        continue;

      for (b = scope->bindings; b != NULL; b = b->prev)
        {
          struct c_label_vars *label_vars;
          unsigned int ix;
          struct c_goto_bindings *g;

          if (TREE_CODE (b->decl) != LABEL_DECL)
            continue;
          label_vars = b->u.label;
          --label_vars->label_bindings.stmt_exprs;
          if (label_vars->label_bindings.stmt_exprs < 0)
            {
              label_vars->label_bindings.left_stmt_expr = true;
              label_vars->label_bindings.stmt_exprs = 0;
            }
          FOR_EACH_VEC_ELT (c_goto_bindings_p, label_vars->gotos, ix, g)
            {
              --g->goto_bindings.stmt_exprs;
              if (g->goto_bindings.stmt_exprs < 0)
                {
                  g->goto_bindings.left_stmt_expr = true;
                  g->goto_bindings.stmt_exprs = 0;
                }
            }
        }
    }

  if (switch_bindings != NULL)
    {
      --switch_bindings->stmt_exprs;
      gcc_assert (switch_bindings->stmt_exprs >= 0);
    }
}
\f
/* Push a definition or a declaration of struct, union or enum tag "name".
   "type" should be the type node.
   We assume that the tag "name" is not already defined, and has a location
   of LOC.

   Note that the definition may really be just a forward reference.
   In that case, the TYPE_SIZE will be zero.  */

static void
pushtag (location_t loc, tree name, tree type)
{
  /* Record the identifier as the type's name if it has none.  */
  if (name && !TYPE_NAME (type))
    TYPE_NAME (type) = name;
  bind (name, type, current_scope, /*invisible=*/false, /*nested=*/false, loc);

  /* Create a fake NULL-named TYPE_DECL node whose TREE_TYPE will be the
     tagged type we just added to the current scope.  This fake
     NULL-named TYPE_DECL node helps dwarfout.c to know when it needs
     to output a representation of a tagged type, and it also gives
     us a convenient place to record the "scope start" address for the
     tagged type.  */

  TYPE_STUB_DECL (type) = pushdecl (build_decl (loc,
                                                TYPE_DECL, NULL_TREE, type));

  /* An approximation for now, so we can tell this is a function-scope tag.
     This will be updated in pop_scope.  */
  TYPE_CONTEXT (type) = DECL_CONTEXT (TYPE_STUB_DECL (type));

  if (warn_cxx_compat && name != NULL_TREE)
    {
      struct c_binding *b = I_SYMBOL_BINDING (name);

      if (b != NULL
          && b->decl != NULL_TREE
          && TREE_CODE (b->decl) == TYPE_DECL
          && (B_IN_CURRENT_SCOPE (b)
              || (current_scope == file_scope && B_IN_EXTERNAL_SCOPE (b)))
          && (TYPE_MAIN_VARIANT (TREE_TYPE (b->decl))
              != TYPE_MAIN_VARIANT (type)))
        {
          warning_at (loc, OPT_Wc___compat,
                      ("using %qD as both a typedef and a tag is "
                       "invalid in C++"),
                      b->decl);
          if (b->locus != UNKNOWN_LOCATION)
            inform (b->locus, "originally defined here");
        }
    }
}
\f
/* Subroutine of compare_decls.  Allow harmless mismatches in return
   and argument types provided that the type modes match.  This function
   return a unified type given a suitable match, and 0 otherwise.  */

static tree
match_builtin_function_types (tree newtype, tree oldtype)
{
  tree newrettype, oldrettype;
  tree newargs, oldargs;
  tree trytype, tryargs;

  /* Accept the return type of the new declaration if same modes.  */
  oldrettype = TREE_TYPE (oldtype);
  newrettype = TREE_TYPE (newtype);

  if (TYPE_MODE (oldrettype) != TYPE_MODE (newrettype))
    return 0;

  oldargs = TYPE_ARG_TYPES (oldtype);
  newargs = TYPE_ARG_TYPES (newtype);
  tryargs = newargs;

  while (oldargs || newargs)
    {
      if (!oldargs
          || !newargs
          || !TREE_VALUE (oldargs)
          || !TREE_VALUE (newargs)
          || TYPE_MODE (TREE_VALUE (oldargs))
             != TYPE_MODE (TREE_VALUE (newargs)))
        return 0;

      oldargs = TREE_CHAIN (oldargs);
      newargs = TREE_CHAIN (newargs);
    }

  trytype = build_function_type (newrettype, tryargs);
  return build_type_attribute_variant (trytype, TYPE_ATTRIBUTES (oldtype));
}

/* Subroutine of diagnose_mismatched_decls.  Check for function type
   mismatch involving an empty arglist vs a nonempty one and give clearer
   diagnostics.  */
static void
diagnose_arglist_conflict (tree newdecl, tree olddecl,
                           tree newtype, tree oldtype)
{
  tree t;

  if (TREE_CODE (olddecl) != FUNCTION_DECL
      || !comptypes (TREE_TYPE (oldtype), TREE_TYPE (newtype))
      || !((!prototype_p (oldtype) && DECL_INITIAL (olddecl) == 0)
           || (!prototype_p (newtype) && DECL_INITIAL (newdecl) == 0)))
    return;

  t = TYPE_ARG_TYPES (oldtype);
  if (t == 0)
    t = TYPE_ARG_TYPES (newtype);
  for (; t; t = TREE_CHAIN (t))
    {
      tree type = TREE_VALUE (t);

      if (TREE_CHAIN (t) == 0
          && TYPE_MAIN_VARIANT (type) != void_type_node)
        {
          inform (input_location, "a parameter list with an ellipsis can%'t match "
                  "an empty parameter name list declaration");
          break;
        }

      if (c_type_promotes_to (type) != type)
        {
          inform (input_location, "an argument type that has a default promotion can%'t match "
                  "an empty parameter name list declaration");
          break;
        }
    }
}

/* Another subroutine of diagnose_mismatched_decls.  OLDDECL is an
   old-style function definition, NEWDECL is a prototype declaration.
   Diagnose inconsistencies in the argument list.  Returns TRUE if
   the prototype is compatible, FALSE if not.  */
static bool
validate_proto_after_old_defn (tree newdecl, tree newtype, tree oldtype)
{
  tree newargs, oldargs;
  int i;

#define END_OF_ARGLIST(t) ((t) == void_type_node)

  oldargs = TYPE_ACTUAL_ARG_TYPES (oldtype);
  newargs = TYPE_ARG_TYPES (newtype);
  i = 1;

  for (;;)
    {
      tree oldargtype = TREE_VALUE (oldargs);
      tree newargtype = TREE_VALUE (newargs);

      if (oldargtype == error_mark_node || newargtype == error_mark_node)
        return false;

      oldargtype = TYPE_MAIN_VARIANT (oldargtype);
      newargtype = TYPE_MAIN_VARIANT (newargtype);

      if (END_OF_ARGLIST (oldargtype) && END_OF_ARGLIST (newargtype))
        break;

      /* Reaching the end of just one list means the two decls don't
         agree on the number of arguments.  */
      if (END_OF_ARGLIST (oldargtype))
        {
          error ("prototype for %q+D declares more arguments "
                 "than previous old-style definition", newdecl);
          return false;
        }
      else if (END_OF_ARGLIST (newargtype))
        {
          error ("prototype for %q+D declares fewer arguments "
                 "than previous old-style definition", newdecl);
          return false;
        }

      /* Type for passing arg must be consistent with that declared
         for the arg.  */
      else if (!comptypes (oldargtype, newargtype))
        {
          error ("prototype for %q+D declares argument %d"
                 " with incompatible type",
                 newdecl, i);
          return false;
        }

      oldargs = TREE_CHAIN (oldargs);
      newargs = TREE_CHAIN (newargs);
      i++;
    }

  /* If we get here, no errors were found, but do issue a warning
     for this poor-style construct.  */
  warning (0, "prototype for %q+D follows non-prototype definition",
           newdecl);
  return true;
#undef END_OF_ARGLIST
}

/* Subroutine of diagnose_mismatched_decls.  Report the location of DECL,
   first in a pair of mismatched declarations, using the diagnostic
   function DIAG.  */
static void
locate_old_decl (tree decl)
{
  if (TREE_CODE (decl) == FUNCTION_DECL && DECL_BUILT_IN (decl))
    ;
  else if (DECL_INITIAL (decl))
    inform (input_location, "previous definition of %q+D was here", decl);
  else if (C_DECL_IMPLICIT (decl))
    inform (input_location, "previous implicit declaration of %q+D was here", decl);
  else
    inform (input_location, "previous declaration of %q+D was here", decl);
}

/* Subroutine of duplicate_decls.  Compare NEWDECL to OLDDECL.
   Returns true if the caller should proceed to merge the two, false
   if OLDDECL should simply be discarded.  As a side effect, issues
   all necessary diagnostics for invalid or poor-style combinations.
   If it returns true, writes the types of NEWDECL and OLDDECL to
   *NEWTYPEP and *OLDTYPEP - these may have been adjusted from
   TREE_TYPE (NEWDECL, OLDDECL) respectively.  */

static bool
diagnose_mismatched_decls (tree newdecl, tree olddecl,
                           tree *newtypep, tree *oldtypep)
{
  tree newtype, oldtype;
  bool pedwarned = false;
  bool warned = false;
  bool retval = true;

#define DECL_EXTERN_INLINE(DECL) (DECL_DECLARED_INLINE_P (DECL)  \
                                  && DECL_EXTERNAL (DECL))

  /* If we have error_mark_node for either decl or type, just discard
     the previous decl - we're in an error cascade already.  */
  if (olddecl == error_mark_node || newdecl == error_mark_node)
    return false;
  *oldtypep = oldtype = TREE_TYPE (olddecl);
  *newtypep = newtype = TREE_TYPE (newdecl);
  if (oldtype == error_mark_node || newtype == error_mark_node)
    return false;

  /* Two different categories of symbol altogether.  This is an error
     unless OLDDECL is a builtin.  OLDDECL will be discarded in any case.  */
  if (TREE_CODE (olddecl) != TREE_CODE (newdecl))
    {
      if (!(TREE_CODE (olddecl) == FUNCTION_DECL
            && DECL_BUILT_IN (olddecl)
            && !C_DECL_DECLARED_BUILTIN (olddecl)))
        {
          error ("%q+D redeclared as different kind of symbol", newdecl);
          locate_old_decl (olddecl);
        }
      else if (TREE_PUBLIC (newdecl))
        warning (0, "built-in function %q+D declared as non-function",
                 newdecl);
      else
        warning (OPT_Wshadow, "declaration of %q+D shadows "
                 "a built-in function", newdecl);
      return false;
    }

  /* Enumerators have no linkage, so may only be declared once in a
     given scope.  */
  if (TREE_CODE (olddecl) == CONST_DECL)
    {
      error ("redeclaration of enumerator %q+D", newdecl);
      locate_old_decl (olddecl);
      return false;
    }

  if (!comptypes (oldtype, newtype))
    {
      if (TREE_CODE (olddecl) == FUNCTION_DECL
          && DECL_BUILT_IN (olddecl) && !C_DECL_DECLARED_BUILTIN (olddecl))
        {
          /* Accept harmless mismatch in function types.
             This is for the ffs and fprintf builtins.  */
          tree trytype = match_builtin_function_types (newtype, oldtype);

          if (trytype && comptypes (newtype, trytype))
            *oldtypep = oldtype = trytype;
          else
            {
              /* If types don't match for a built-in, throw away the
                 built-in.  No point in calling locate_old_decl here, it
                 won't print anything.  */
              warning (0, "conflicting types for built-in function %q+D",
                       newdecl);
              return false;
            }
        }
      else if (TREE_CODE (olddecl) == FUNCTION_DECL
               && DECL_IS_BUILTIN (olddecl))
        {
          /* A conflicting function declaration for a predeclared
             function that isn't actually built in.  Objective C uses
             these.  The new declaration silently overrides everything
             but the volatility (i.e. noreturn) indication.  See also
             below.  FIXME: Make Objective C use normal builtins.  */
          TREE_THIS_VOLATILE (newdecl) |= TREE_THIS_VOLATILE (olddecl);
          return false;
        }
      /* Permit void foo (...) to match int foo (...) if the latter is
         the definition and implicit int was used.  See
         c-torture/compile/920625-2.c.  */
      else if (TREE_CODE (newdecl) == FUNCTION_DECL && DECL_INITIAL (newdecl)
               && TYPE_MAIN_VARIANT (TREE_TYPE (oldtype)) == void_type_node
               && TYPE_MAIN_VARIANT (TREE_TYPE (newtype)) == integer_type_node
               && C_FUNCTION_IMPLICIT_INT (newdecl) && !DECL_INITIAL (olddecl))
        {
          pedwarned = pedwarn (input_location, 0,
                               "conflicting types for %q+D", newdecl);
          /* Make sure we keep void as the return type.  */
          TREE_TYPE (newdecl) = *newtypep = newtype = oldtype;
          C_FUNCTION_IMPLICIT_INT (newdecl) = 0;
        }
      /* Permit void foo (...) to match an earlier call to foo (...) with
         no declared type (thus, implicitly int).  */
      else if (TREE_CODE (newdecl) == FUNCTION_DECL
               && TYPE_MAIN_VARIANT (TREE_TYPE (newtype)) == void_type_node
               && TYPE_MAIN_VARIANT (TREE_TYPE (oldtype)) == integer_type_node
               && C_DECL_IMPLICIT (olddecl) && !DECL_INITIAL (olddecl))
        {
          pedwarned = pedwarn (input_location, 0,
                               "conflicting types for %q+D", newdecl);
          /* Make sure we keep void as the return type.  */
          TREE_TYPE (olddecl) = *oldtypep = oldtype = newtype;
        }
      else
        {
          int new_quals = TYPE_QUALS (newtype);
          int old_quals = TYPE_QUALS (oldtype);

          if (new_quals != old_quals)
            {
              addr_space_t new_addr = DECODE_QUAL_ADDR_SPACE (new_quals);
              addr_space_t old_addr = DECODE_QUAL_ADDR_SPACE (old_quals);
              if (new_addr != old_addr)
                {
                  if (ADDR_SPACE_GENERIC_P (new_addr))
                    error ("conflicting named address spaces (generic vs %s) "
                           "for %q+D",
                           c_addr_space_name (old_addr), newdecl);
                  else if (ADDR_SPACE_GENERIC_P (old_addr))
                    error ("conflicting named address spaces (%s vs generic) "
                           "for %q+D",
                           c_addr_space_name (new_addr), newdecl);
                  else
                    error ("conflicting named address spaces (%s vs %s) "
                           "for %q+D",
                           c_addr_space_name (new_addr),
                           c_addr_space_name (old_addr),
                           newdecl);
                }

              if (CLEAR_QUAL_ADDR_SPACE (new_quals)
                  != CLEAR_QUAL_ADDR_SPACE (old_quals))
                error ("conflicting type qualifiers for %q+D", newdecl);
            }
          else
            error ("conflicting types for %q+D", newdecl);
          diagnose_arglist_conflict (newdecl, olddecl, newtype, oldtype);
          locate_old_decl (olddecl);
          return false;
        }
    }

  /* Redeclaration of a type is a constraint violation (6.7.2.3p1),
     but silently ignore the redeclaration if either is in a system
     header.  (Conflicting redeclarations were handled above.)  This
     is allowed for C1X if the types are the same, not just
     compatible.  */
  if (TREE_CODE (newdecl) == TYPE_DECL)
    {
      bool types_different = false;
      int comptypes_result;

      comptypes_result
        = comptypes_check_different_types (oldtype, newtype, &types_different);

      if (comptypes_result != 1 || types_different)
        {
          error ("redefinition of typedef %q+D with different type", newdecl);
          locate_old_decl (olddecl);
          return false;
        }

      if (DECL_IN_SYSTEM_HEADER (newdecl)
          || DECL_IN_SYSTEM_HEADER (olddecl)
          || TREE_NO_WARNING (newdecl)
          || TREE_NO_WARNING (olddecl))
        return true;  /* Allow OLDDECL to continue in use.  */

      if (variably_modified_type_p (newtype, NULL))
        {
          error ("redefinition of typedef %q+D with variably modified type",
                 newdecl);
          locate_old_decl (olddecl);
        }
      else if (pedantic && !flag_isoc1x)
        {
          pedwarn (input_location, OPT_pedantic,
                   "redefinition of typedef %q+D", newdecl);
          locate_old_decl (olddecl);
        }

      return true;
    }

  /* Function declarations can either be 'static' or 'extern' (no
     qualifier is equivalent to 'extern' - C99 6.2.2p5) and therefore
     can never conflict with each other on account of linkage
     (6.2.2p4).  Multiple definitions are not allowed (6.9p3,5) but
     gnu89 mode permits two definitions if one is 'extern inline' and
     one is not.  The non- extern-inline definition supersedes the
     extern-inline definition.  */

  else if (TREE_CODE (newdecl) == FUNCTION_DECL)
    {
      /* If you declare a built-in function name as static, or
         define the built-in with an old-style definition (so we
         can't validate the argument list) the built-in definition is
         overridden, but optionally warn this was a bad choice of name.  */
      if (DECL_BUILT_IN (olddecl)
          && !C_DECL_DECLARED_BUILTIN (olddecl)
          && (!TREE_PUBLIC (newdecl)
              || (DECL_INITIAL (newdecl)
                  && !prototype_p (TREE_TYPE (newdecl)))))
        {
          warning (OPT_Wshadow, "declaration of %q+D shadows "
                   "a built-in function", newdecl);
          /* Discard the old built-in function.  */
          return false;
        }

      if (DECL_INITIAL (newdecl))
        {
          if (DECL_INITIAL (olddecl))
            {
              /* If both decls are in the same TU and the new declaration
                 isn't overriding an extern inline reject the new decl.
                 In c99, no overriding is allowed in the same translation
                 unit.  */
              if ((!DECL_EXTERN_INLINE (olddecl)
                   || DECL_EXTERN_INLINE (newdecl)
                   || (!flag_gnu89_inline
                       && (!DECL_DECLARED_INLINE_P (olddecl)
                           || !lookup_attribute ("gnu_inline",
                                                 DECL_ATTRIBUTES (olddecl)))
                       && (!DECL_DECLARED_INLINE_P (newdecl)
                           || !lookup_attribute ("gnu_inline",
                                                 DECL_ATTRIBUTES (newdecl))))
                  )
                  && same_translation_unit_p (newdecl, olddecl))
                {
                  error ("redefinition of %q+D", newdecl);
                  locate_old_decl (olddecl);
                  return false;
                }
            }
        }
      /* If we have a prototype after an old-style function definition,
         the argument types must be checked specially.  */
      else if (DECL_INITIAL (olddecl)
               && !prototype_p (oldtype) && prototype_p (newtype)
               && TYPE_ACTUAL_ARG_TYPES (oldtype)
               && !validate_proto_after_old_defn (newdecl, newtype, oldtype))
        {
          locate_old_decl (olddecl);
          return false;
        }
      /* A non-static declaration (even an "extern") followed by a
         static declaration is undefined behavior per C99 6.2.2p3-5,7.
         The same is true for a static forward declaration at block
         scope followed by a non-static declaration/definition at file
         scope.  Static followed by non-static at the same scope is
         not undefined behavior, and is the most convenient way to get
         some effects (see e.g.  what unwind-dw2-fde-glibc.c does to
         the definition of _Unwind_Find_FDE in unwind-dw2-fde.c), but
         we do diagnose it if -Wtraditional.  */
      if (TREE_PUBLIC (olddecl) && !TREE_PUBLIC (newdecl))
        {
          /* Two exceptions to the rule.  If olddecl is an extern
             inline, or a predeclared function that isn't actually
             built in, newdecl silently overrides olddecl.  The latter
             occur only in Objective C; see also above.  (FIXME: Make
             Objective C use normal builtins.)  */
          if (!DECL_IS_BUILTIN (olddecl)
              && !DECL_EXTERN_INLINE (olddecl))
            {
              error ("static declaration of %q+D follows "
                     "non-static declaration", newdecl);
              locate_old_decl (olddecl);
            }
          return false;
        }
      else if (TREE_PUBLIC (newdecl) && !TREE_PUBLIC (olddecl))
        {
          if (DECL_CONTEXT (olddecl))
            {
              error ("non-static declaration of %q+D follows "
                     "static declaration", newdecl);
              locate_old_decl (olddecl);
              return false;
            }
          else if (warn_traditional)
            {
              warned |= warning (OPT_Wtraditional,
                                 "non-static declaration of %q+D "
                                 "follows static declaration", newdecl);
            }
        }

      /* Make sure gnu_inline attribute is either not present, or
         present on all inline decls.  */
      if (DECL_DECLARED_INLINE_P (olddecl)
          && DECL_DECLARED_INLINE_P (newdecl))
        {
          bool newa = lookup_attribute ("gnu_inline",
                                        DECL_ATTRIBUTES (newdecl)) != NULL;
          bool olda = lookup_attribute ("gnu_inline",
                                        DECL_ATTRIBUTES (olddecl)) != NULL;
          if (newa != olda)
            {
              error_at (input_location, "%<gnu_inline%> attribute present on %q+D",
                        newa ? newdecl : olddecl);
              error_at (DECL_SOURCE_LOCATION (newa ? olddecl : newdecl),
                        "but not here");
            }
        }
    }
  else if (TREE_CODE (newdecl) == VAR_DECL)
    {
      /* Only variables can be thread-local, and all declarations must
         agree on this property.  */
      if (C_DECL_THREADPRIVATE_P (olddecl) && !DECL_THREAD_LOCAL_P (newdecl))
        {
          /* Nothing to check.  Since OLDDECL is marked threadprivate
             and NEWDECL does not have a thread-local attribute, we
             will merge the threadprivate attribute into NEWDECL.  */
          ;
        }
      else if (DECL_THREAD_LOCAL_P (newdecl) != DECL_THREAD_LOCAL_P (olddecl))
        {
          if (DECL_THREAD_LOCAL_P (newdecl))
            error ("thread-local declaration of %q+D follows "
                   "non-thread-local declaration", newdecl);
          else
            error ("non-thread-local declaration of %q+D follows "
                   "thread-local declaration", newdecl);

          locate_old_decl (olddecl);
          return false;
        }

      /* Multiple initialized definitions are not allowed (6.9p3,5).  */
      if (DECL_INITIAL (newdecl) && DECL_INITIAL (olddecl))
        {
          error ("redefinition of %q+D", newdecl);
          locate_old_decl (olddecl);
          return false;
        }

      /* Objects declared at file scope: if the first declaration had
         external linkage (even if it was an external reference) the
         second must have external linkage as well, or the behavior is
         undefined.  If the first declaration had internal linkage, then
         the second must too, or else be an external reference (in which
         case the composite declaration still has internal linkage).
         As for function declarations, we warn about the static-then-
         extern case only for -Wtraditional.  See generally 6.2.2p3-5,7.  */
      if (DECL_FILE_SCOPE_P (newdecl)
          && TREE_PUBLIC (newdecl) != TREE_PUBLIC (olddecl))
        {
          if (DECL_EXTERNAL (newdecl))
            {
              if (!DECL_FILE_SCOPE_P (olddecl))
                {
                  error ("extern declaration of %q+D follows "
                         "declaration with no linkage", newdecl);
                  locate_old_decl (olddecl);
                  return false;
                }
              else if (warn_traditional)
                {
                  warned |= warning (OPT_Wtraditional,
                                     "non-static declaration of %q+D "
                                     "follows static declaration", newdecl);
                }
            }
          else
            {
              if (TREE_PUBLIC (newdecl))
                error ("non-static declaration of %q+D follows "
                       "static declaration", newdecl);
              else
                error ("static declaration of %q+D follows "
                       "non-static declaration", newdecl);

              locate_old_decl (olddecl);
              return false;
            }
        }
      /* Two objects with the same name declared at the same block
         scope must both be external references (6.7p3).  */
      else if (!DECL_FILE_SCOPE_P (newdecl))
        {
          if (DECL_EXTERNAL (newdecl))
            {
              /* Extern with initializer at block scope, which will
                 already have received an error.  */
            }
          else if (DECL_EXTERNAL (olddecl))
            {
              error ("declaration of %q+D with no linkage follows "
                     "extern declaration", newdecl);
              locate_old_decl (olddecl);
            }
          else
            {
              error ("redeclaration of %q+D with no linkage", newdecl);
              locate_old_decl (olddecl);
            }

          return false;
        }

      /* C++ does not permit a decl to appear multiple times at file
         scope.  */
      if (warn_cxx_compat
          && DECL_FILE_SCOPE_P (newdecl)
          && !DECL_EXTERNAL (newdecl)
          && !DECL_EXTERNAL (olddecl))
        warned |= warning_at (DECL_SOURCE_LOCATION (newdecl),
                              OPT_Wc___compat,
                              ("duplicate declaration of %qD is "
                               "invalid in C++"),
                              newdecl);
    }

  /* warnings */
  /* All decls must agree on a visibility.  */
  if (CODE_CONTAINS_STRUCT (TREE_CODE (newdecl), TS_DECL_WITH_VIS)
      && DECL_VISIBILITY_SPECIFIED (newdecl) && DECL_VISIBILITY_SPECIFIED (olddecl)
      && DECL_VISIBILITY (newdecl) != DECL_VISIBILITY (olddecl))
    {
      warned |= warning (0, "redeclaration of %q+D with different visibility "
                         "(old visibility preserved)", newdecl);
    }

  if (TREE_CODE (newdecl) == FUNCTION_DECL)
    {
      /* Diagnose inline __attribute__ ((noinline)) which is silly.  */
      if (DECL_DECLARED_INLINE_P (newdecl)
          && lookup_attribute ("noinline", DECL_ATTRIBUTES (olddecl)))
        {
          warned |= warning (OPT_Wattributes,
                             "inline declaration of %qD follows "
                             "declaration with attribute noinline", newdecl);
        }
      else if (DECL_DECLARED_INLINE_P (olddecl)
               && lookup_attribute ("noinline", DECL_ATTRIBUTES (newdecl)))
        {
          warned |= warning (OPT_Wattributes,
                             "declaration of %q+D with attribute "
                             "noinline follows inline declaration ", newdecl);
        }
    }
  else /* PARM_DECL, VAR_DECL */
    {
      /* Redeclaration of a parameter is a constraint violation (this is
         not explicitly stated, but follows from C99 6.7p3 [no more than
         one declaration of the same identifier with no linkage in the
         same scope, except type tags] and 6.2.2p6 [parameters have no
         linkage]).  We must check for a forward parameter declaration,
         indicated by TREE_ASM_WRITTEN on the old declaration - this is
         an extension, the mandatory diagnostic for which is handled by
         mark_forward_parm_decls.  */

      if (TREE_CODE (newdecl) == PARM_DECL
          && (!TREE_ASM_WRITTEN (olddecl) || TREE_ASM_WRITTEN (newdecl)))
        {
          error ("redefinition of parameter %q+D", newdecl);
          locate_old_decl (olddecl);
          return false;
        }
    }

  /* Optional warning for completely redundant decls.  */
  if (!warned && !pedwarned
      && warn_redundant_decls
      /* Don't warn about a function declaration followed by a
         definition.  */
      && !(TREE_CODE (newdecl) == FUNCTION_DECL
           && DECL_INITIAL (newdecl) && !DECL_INITIAL (olddecl))
      /* Don't warn about redundant redeclarations of builtins.  */
      && !(TREE_CODE (newdecl) == FUNCTION_DECL
           && !DECL_BUILT_IN (newdecl)
           && DECL_BUILT_IN (olddecl)
           && !C_DECL_DECLARED_BUILTIN (olddecl))
      /* Don't warn about an extern followed by a definition.  */
      && !(DECL_EXTERNAL (olddecl) && !DECL_EXTERNAL (newdecl))
      /* Don't warn about forward parameter decls.  */
      && !(TREE_CODE (newdecl) == PARM_DECL
           && TREE_ASM_WRITTEN (olddecl) && !TREE_ASM_WRITTEN (newdecl))
      /* Don't warn about a variable definition following a declaration.  */
      && !(TREE_CODE (newdecl) == VAR_DECL
           && DECL_INITIAL (newdecl) && !DECL_INITIAL (olddecl)))
    {
      warned = warning (OPT_Wredundant_decls, "redundant redeclaration of %q+D",
                        newdecl);
    }

  /* Report location of previous decl/defn.  */
  if (warned || pedwarned)
    locate_old_decl (olddecl);

#undef DECL_EXTERN_INLINE

  return retval;
}

/* Subroutine of duplicate_decls.  NEWDECL has been found to be
   consistent with OLDDECL, but carries new information.  Merge the
   new information into OLDDECL.  This function issues no
   diagnostics.  */

static void
merge_decls (tree newdecl, tree olddecl, tree newtype, tree oldtype)
{
  bool new_is_definition = (TREE_CODE (newdecl) == FUNCTION_DECL
                            && DECL_INITIAL (newdecl) != 0);
  bool new_is_prototype = (TREE_CODE (newdecl) == FUNCTION_DECL
                           && prototype_p (TREE_TYPE (newdecl)));
  bool old_is_prototype = (TREE_CODE (olddecl) == FUNCTION_DECL
                           && prototype_p (TREE_TYPE (olddecl)));
  bool extern_changed = false;

  /* For real parm decl following a forward decl, rechain the old decl
     in its new location and clear TREE_ASM_WRITTEN (it's not a
     forward decl anymore).  */
  if (TREE_CODE (newdecl) == PARM_DECL
      && TREE_ASM_WRITTEN (olddecl) && !TREE_ASM_WRITTEN (newdecl))
    {
      struct c_binding *b, **here;

      for (here = &current_scope->bindings; *here; here = &(*here)->prev)
        if ((*here)->decl == olddecl)
          goto found;
      gcc_unreachable ();

    found:
      b = *here;
      *here = b->prev;
      b->prev = current_scope->bindings;
      current_scope->bindings = b;

      TREE_ASM_WRITTEN (olddecl) = 0;
    }

  DECL_ATTRIBUTES (newdecl)
    = targetm.merge_decl_attributes (olddecl, newdecl);

  /* Merge the data types specified in the two decls.  */
  TREE_TYPE (newdecl)
    = TREE_TYPE (olddecl)
    = composite_type (newtype, oldtype);

  /* Lay the type out, unless already done.  */
  if (!comptypes (oldtype, TREE_TYPE (newdecl)))
    {
      if (TREE_TYPE (newdecl) != error_mark_node)
        layout_type (TREE_TYPE (newdecl));
      if (TREE_CODE (newdecl) != FUNCTION_DECL
          && TREE_CODE (newdecl) != TYPE_DECL
          && TREE_CODE (newdecl) != CONST_DECL)
        layout_decl (newdecl, 0);
    }
  else
    {
      /* Since the type is OLDDECL's, make OLDDECL's size go with.  */
      DECL_SIZE (newdecl) = DECL_SIZE (olddecl);
      DECL_SIZE_UNIT (newdecl) = DECL_SIZE_UNIT (olddecl);
      DECL_MODE (newdecl) = DECL_MODE (olddecl);
      if (DECL_ALIGN (olddecl) > DECL_ALIGN (newdecl))
        {
          DECL_ALIGN (newdecl) = DECL_ALIGN (olddecl);
          DECL_USER_ALIGN (newdecl) |= DECL_USER_ALIGN (olddecl);
        }
    }

  /* Keep the old rtl since we can safely use it.  */
  if (HAS_RTL_P (olddecl))
    COPY_DECL_RTL (olddecl, newdecl);

  /* Merge the type qualifiers.  */
  if (TREE_READONLY (newdecl))
    TREE_READONLY (olddecl) = 1;

  if (TREE_THIS_VOLATILE (newdecl))
    TREE_THIS_VOLATILE (olddecl) = 1;

  /* Merge deprecatedness.  */
  if (TREE_DEPRECATED (newdecl))
    TREE_DEPRECATED (olddecl) = 1;

  /* If a decl is in a system header and the other isn't, keep the one on the
     system header. Otherwise, keep source location of definition rather than
     declaration and of prototype rather than non-prototype unless that
     prototype is built-in.  */
  if (CODE_CONTAINS_STRUCT (TREE_CODE (olddecl), TS_DECL_WITH_VIS)
      && DECL_IN_SYSTEM_HEADER (olddecl)
      && !DECL_IN_SYSTEM_HEADER (newdecl) )
    DECL_SOURCE_LOCATION (newdecl) = DECL_SOURCE_LOCATION (olddecl);
  else if (CODE_CONTAINS_STRUCT (TREE_CODE (olddecl), TS_DECL_WITH_VIS)
           && DECL_IN_SYSTEM_HEADER (newdecl)
           && !DECL_IN_SYSTEM_HEADER (olddecl))
    DECL_SOURCE_LOCATION (olddecl) = DECL_SOURCE_LOCATION (newdecl);
  else if ((DECL_INITIAL (newdecl) == 0 && DECL_INITIAL (olddecl) != 0)
           || (old_is_prototype && !new_is_prototype
               && !C_DECL_BUILTIN_PROTOTYPE (olddecl)))
    DECL_SOURCE_LOCATION (newdecl) = DECL_SOURCE_LOCATION (olddecl);

  /* Merge the initialization information.  */
   if (DECL_INITIAL (newdecl) == 0)
    DECL_INITIAL (newdecl) = DECL_INITIAL (olddecl);

  /* Merge the threadprivate attribute.  */
  if (TREE_CODE (olddecl) == VAR_DECL && C_DECL_THREADPRIVATE_P (olddecl))
    {
      DECL_TLS_MODEL (newdecl) = DECL_TLS_MODEL (olddecl);
      C_DECL_THREADPRIVATE_P (newdecl) = 1;
    }

  if (CODE_CONTAINS_STRUCT (TREE_CODE (olddecl), TS_DECL_WITH_VIS))
    {
      /* Merge the section attribute.
         We want to issue an error if the sections conflict but that
         must be done later in decl_attributes since we are called
         before attributes are assigned.  */
      if (DECL_SECTION_NAME (newdecl) == NULL_TREE)
        DECL_SECTION_NAME (newdecl) = DECL_SECTION_NAME (olddecl);

      /* Copy the assembler name.
         Currently, it can only be defined in the prototype.  */
      COPY_DECL_ASSEMBLER_NAME (olddecl, newdecl);

      /* Use visibility of whichever declaration had it specified */
      if (DECL_VISIBILITY_SPECIFIED (olddecl))
        {
          DECL_VISIBILITY (newdecl) = DECL_VISIBILITY (olddecl);
          DECL_VISIBILITY_SPECIFIED (newdecl) = 1;
        }

      if (TREE_CODE (newdecl) == FUNCTION_DECL)
        {
          DECL_STATIC_CONSTRUCTOR(newdecl) |= DECL_STATIC_CONSTRUCTOR(olddecl);
          DECL_STATIC_DESTRUCTOR (newdecl) |= DECL_STATIC_DESTRUCTOR (olddecl);
          DECL_NO_LIMIT_STACK (newdecl) |= DECL_NO_LIMIT_STACK (olddecl);
          DECL_NO_INSTRUMENT_FUNCTION_ENTRY_EXIT (newdecl)
            |= DECL_NO_INSTRUMENT_FUNCTION_ENTRY_EXIT (olddecl);
          TREE_THIS_VOLATILE (newdecl) |= TREE_THIS_VOLATILE (olddecl);
          DECL_IS_MALLOC (newdecl) |= DECL_IS_MALLOC (olddecl);
          DECL_IS_OPERATOR_NEW (newdecl) |= DECL_IS_OPERATOR_NEW (olddecl);
          TREE_READONLY (newdecl) |= TREE_READONLY (olddecl);
          DECL_PURE_P (newdecl) |= DECL_PURE_P (olddecl);
          DECL_IS_NOVOPS (newdecl) |= DECL_IS_NOVOPS (olddecl);
        }

      /* Merge the storage class information.  */
      merge_weak (newdecl, olddecl);

      /* For functions, static overrides non-static.  */
      if (TREE_CODE (newdecl) == FUNCTION_DECL)
        {
          TREE_PUBLIC (newdecl) &= TREE_PUBLIC (olddecl);
          /* This is since we don't automatically
             copy the attributes of NEWDECL into OLDDECL.  */
          TREE_PUBLIC (olddecl) = TREE_PUBLIC (newdecl);
          /* If this clears `static', clear it in the identifier too.  */
          if (!TREE_PUBLIC (olddecl))
            TREE_PUBLIC (DECL_NAME (olddecl)) = 0;
        }
    }

  /* In c99, 'extern' declaration before (or after) 'inline' means this
     function is not DECL_EXTERNAL, unless 'gnu_inline' attribute
     is present.  */
  if (TREE_CODE (newdecl) == FUNCTION_DECL
      && !flag_gnu89_inline
      && (DECL_DECLARED_INLINE_P (newdecl)
          || DECL_DECLARED_INLINE_P (olddecl))
      && (!DECL_DECLARED_INLINE_P (newdecl)
          || !DECL_DECLARED_INLINE_P (olddecl)
          || !DECL_EXTERNAL (olddecl))
      && DECL_EXTERNAL (newdecl)
      && !lookup_attribute ("gnu_inline", DECL_ATTRIBUTES (newdecl))
      && !current_function_decl)
    DECL_EXTERNAL (newdecl) = 0;

  if (DECL_EXTERNAL (newdecl))
    {
      TREE_STATIC (newdecl) = TREE_STATIC (olddecl);
      DECL_EXTERNAL (newdecl) = DECL_EXTERNAL (olddecl);

      /* An extern decl does not override previous storage class.  */
      TREE_PUBLIC (newdecl) = TREE_PUBLIC (olddecl);
      if (!DECL_EXTERNAL (newdecl))
        {
          DECL_CONTEXT (newdecl) = DECL_CONTEXT (olddecl);
          DECL_COMMON (newdecl) = DECL_COMMON (olddecl);
        }
    }
  else
    {
      TREE_STATIC (olddecl) = TREE_STATIC (newdecl);
      TREE_PUBLIC (olddecl) = TREE_PUBLIC (newdecl);
    }

  if (TREE_CODE (newdecl) == FUNCTION_DECL)
    {
      /* If we're redefining a function previously defined as extern
         inline, make sure we emit debug info for the inline before we
         throw it away, in case it was inlined into a function that
         hasn't been written out yet.  */
      if (new_is_definition && DECL_INITIAL (olddecl))
        /* The new defn must not be inline.  */
        DECL_UNINLINABLE (newdecl) = 1;
      else
        {
          /* If either decl says `inline', this fn is inline, unless
             its definition was passed already.  */
          if (DECL_DECLARED_INLINE_P (newdecl)
              || DECL_DECLARED_INLINE_P (olddecl))
            DECL_DECLARED_INLINE_P (newdecl) = 1;

          DECL_UNINLINABLE (newdecl) = DECL_UNINLINABLE (olddecl)
            = (DECL_UNINLINABLE (newdecl) || DECL_UNINLINABLE (olddecl));

          DECL_DISREGARD_INLINE_LIMITS (newdecl)
            = DECL_DISREGARD_INLINE_LIMITS (olddecl)
            = (DECL_DISREGARD_INLINE_LIMITS (newdecl)
               || DECL_DISREGARD_INLINE_LIMITS (olddecl));
        }

      if (DECL_BUILT_IN (olddecl))
        {
          /* If redeclaring a builtin function, it stays built in.
             But it gets tagged as having been declared.  */
          DECL_BUILT_IN_CLASS (newdecl) = DECL_BUILT_IN_CLASS (olddecl);
          DECL_FUNCTION_CODE (newdecl) = DECL_FUNCTION_CODE (olddecl);
          C_DECL_DECLARED_BUILTIN (newdecl) = 1;
          if (new_is_prototype)
            {
              C_DECL_BUILTIN_PROTOTYPE (newdecl) = 0;
              if (DECL_BUILT_IN_CLASS (newdecl) == BUILT_IN_NORMAL)
                {
                  enum built_in_function fncode = DECL_FUNCTION_CODE (newdecl);
                  switch (fncode)
                    {
                      /* If a compatible prototype of these builtin functions
                         is seen, assume the runtime implements it with the
                         expected semantics.  */
                    case BUILT_IN_STPCPY:
                      if (builtin_decl_explicit_p (fncode))
                        set_builtin_decl_implicit_p (fncode, true);
                      break;
                    default:
                      break;
                    }
                }
            }
          else
            C_DECL_BUILTIN_PROTOTYPE (newdecl)
              = C_DECL_BUILTIN_PROTOTYPE (olddecl);
        }

      /* Preserve function specific target and optimization options */
      if (DECL_FUNCTION_SPECIFIC_TARGET (olddecl)
          && !DECL_FUNCTION_SPECIFIC_TARGET (newdecl))
        DECL_FUNCTION_SPECIFIC_TARGET (newdecl)
          = DECL_FUNCTION_SPECIFIC_TARGET (olddecl);

      if (DECL_FUNCTION_SPECIFIC_OPTIMIZATION (olddecl)
          && !DECL_FUNCTION_SPECIFIC_OPTIMIZATION (newdecl))
        DECL_FUNCTION_SPECIFIC_OPTIMIZATION (newdecl)
          = DECL_FUNCTION_SPECIFIC_OPTIMIZATION (olddecl);

      /* Also preserve various other info from the definition.  */
      if (!new_is_definition)
        {
          tree t;
          DECL_RESULT (newdecl) = DECL_RESULT (olddecl);
          DECL_INITIAL (newdecl) = DECL_INITIAL (olddecl);
          DECL_STRUCT_FUNCTION (newdecl) = DECL_STRUCT_FUNCTION (olddecl);
          DECL_SAVED_TREE (newdecl) = DECL_SAVED_TREE (olddecl);
          DECL_ARGUMENTS (newdecl) = copy_list (DECL_ARGUMENTS (olddecl));
          for (t = DECL_ARGUMENTS (newdecl); t ; t = DECL_CHAIN (t))
            DECL_CONTEXT (t) = newdecl;

          /* See if we've got a function to instantiate from.  */
          if (DECL_SAVED_TREE (olddecl))
            DECL_ABSTRACT_ORIGIN (newdecl)
              = DECL_ABSTRACT_ORIGIN (olddecl);
        }
    }

  extern_changed = DECL_EXTERNAL (olddecl) && !DECL_EXTERNAL (newdecl);

  /* Merge the USED information.  */
  if (TREE_USED (olddecl))
    TREE_USED (newdecl) = 1;
  else if (TREE_USED (newdecl))
    TREE_USED (olddecl) = 1;
  if (TREE_CODE (olddecl) == VAR_DECL || TREE_CODE (olddecl) == PARM_DECL)
    DECL_READ_P (newdecl) |= DECL_READ_P (olddecl);
  if (DECL_PRESERVE_P (olddecl))
    DECL_PRESERVE_P (newdecl) = 1;
  else if (DECL_PRESERVE_P (newdecl))
    DECL_PRESERVE_P (olddecl) = 1;

  /* Copy most of the decl-specific fields of NEWDECL into OLDDECL.
     But preserve OLDDECL's DECL_UID, DECL_CONTEXT and
     DECL_ARGUMENTS (if appropriate).  */
  {
    unsigned olddecl_uid = DECL_UID (olddecl);
    tree olddecl_context = DECL_CONTEXT (olddecl);
    tree olddecl_arguments = NULL;
    if (TREE_CODE (olddecl) == FUNCTION_DECL)
      olddecl_arguments = DECL_ARGUMENTS (olddecl);

    memcpy ((char *) olddecl + sizeof (struct tree_common),
            (char *) newdecl + sizeof (struct tree_common),
            sizeof (struct tree_decl_common) - sizeof (struct tree_common));
    switch (TREE_CODE (olddecl))
      {
      case FUNCTION_DECL:
      case FIELD_DECL:
      case VAR_DECL:
      case PARM_DECL:
      case LABEL_DECL:
      case RESULT_DECL:
      case CONST_DECL:
      case TYPE_DECL:
        memcpy ((char *) olddecl + sizeof (struct tree_decl_common),
                (char *) newdecl + sizeof (struct tree_decl_common),
                tree_code_size (TREE_CODE (olddecl)) - sizeof (struct tree_decl_common));
        break;

      default:

        memcpy ((char *) olddecl + sizeof (struct tree_decl_common),
                (char *) newdecl + sizeof (struct tree_decl_common),
                sizeof (struct tree_decl_non_common) - sizeof (struct tree_decl_common));
      }
    DECL_UID (olddecl) = olddecl_uid;
    DECL_CONTEXT (olddecl) = olddecl_context;
    if (TREE_CODE (olddecl) == FUNCTION_DECL)
      DECL_ARGUMENTS (olddecl) = olddecl_arguments;
  }

  /* If OLDDECL had its DECL_RTL instantiated, re-invoke make_decl_rtl
     so that encode_section_info has a chance to look at the new decl
     flags and attributes.  */
  if (DECL_RTL_SET_P (olddecl)
      && (TREE_CODE (olddecl) == FUNCTION_DECL
          || (TREE_CODE (olddecl) == VAR_DECL
              && TREE_STATIC (olddecl))))
    make_decl_rtl (olddecl);

  /* If we changed a function from DECL_EXTERNAL to !DECL_EXTERNAL,
     and the definition is coming from the old version, cgraph needs
     to be called again.  */
  if (extern_changed && !new_is_definition
      && TREE_CODE (olddecl) == FUNCTION_DECL && DECL_INITIAL (olddecl))
    cgraph_mark_if_needed (olddecl);
}

/* Handle when a new declaration NEWDECL has the same name as an old
   one OLDDECL in the same binding contour.  Prints an error message
   if appropriate.

   If safely possible, alter OLDDECL to look like NEWDECL, and return
   true.  Otherwise, return false.  */

static bool
duplicate_decls (tree newdecl, tree olddecl)
{
  tree newtype = NULL, oldtype = NULL;

  if (!diagnose_mismatched_decls (newdecl, olddecl, &newtype, &oldtype))
    {
      /* Avoid `unused variable' and other warnings for OLDDECL.  */
      TREE_NO_WARNING (olddecl) = 1;
      return false;
    }

  merge_decls (newdecl, olddecl, newtype, oldtype);
  return true;
}

\f
/* Check whether decl-node NEW_DECL shadows an existing declaration.  */
static void
warn_if_shadowing (tree new_decl)
{
  struct c_binding *b;

  /* Shadow warnings wanted?  */
  if (!warn_shadow
      /* No shadow warnings for internally generated vars.  */
      || DECL_IS_BUILTIN (new_decl)
      /* No shadow warnings for vars made for inlining.  */
      || DECL_FROM_INLINE (new_decl))
    return;

  /* Is anything being shadowed?  Invisible decls do not count.  */
  for (b = I_SYMBOL_BINDING (DECL_NAME (new_decl)); b; b = b->shadowed)
    if (b->decl && b->decl != new_decl && !b->invisible
        && (b->decl == error_mark_node
            || diagnostic_report_warnings_p (global_dc,
                                             DECL_SOURCE_LOCATION (b->decl))))
      {
        tree old_decl = b->decl;

        if (old_decl == error_mark_node)
          {
            warning (OPT_Wshadow, "declaration of %q+D shadows previous "
                     "non-variable", new_decl);
            break;
          }
        else if (TREE_CODE (old_decl) == PARM_DECL)
          warning (OPT_Wshadow, "declaration of %q+D shadows a parameter",
                   new_decl);
        else if (DECL_FILE_SCOPE_P (old_decl))
          warning (OPT_Wshadow, "declaration of %q+D shadows a global "
                   "declaration", new_decl);
        else if (TREE_CODE (old_decl) == FUNCTION_DECL
                 && DECL_BUILT_IN (old_decl))
          {
            warning (OPT_Wshadow, "declaration of %q+D shadows "
                     "a built-in function", new_decl);
            break;
          }
        else
          warning (OPT_Wshadow, "declaration of %q+D shadows a previous local",
                   new_decl);

        warning_at (DECL_SOURCE_LOCATION (old_decl), OPT_Wshadow,
                    "shadowed declaration is here");

        break;
      }
}

/* Record a decl-node X as belonging to the current lexical scope.
   Check for errors (such as an incompatible declaration for the same
   name already seen in the same scope).

   Returns either X or an old decl for the same name.
   If an old decl is returned, it may have been smashed
   to agree with what X says.  */

tree
pushdecl (tree x)
{
  tree name = DECL_NAME (x);
  struct c_scope *scope = current_scope;
  struct c_binding *b;
  bool nested = false;
  location_t locus = DECL_SOURCE_LOCATION (x);

  /* Must set DECL_CONTEXT for everything not at file scope or
     DECL_FILE_SCOPE_P won't work.  Local externs don't count
     unless they have initializers (which generate code).  */
  if (current_function_decl
      && ((TREE_CODE (x) != FUNCTION_DECL && TREE_CODE (x) != VAR_DECL)
          || DECL_INITIAL (x) || !DECL_EXTERNAL (x)))
    DECL_CONTEXT (x) = current_function_decl;

  /* Anonymous decls are just inserted in the scope.  */
  if (!name)
    {
      bind (name, x, scope, /*invisible=*/false, /*nested=*/false,
            locus);
      return x;
    }

  /* First, see if there is another declaration with the same name in
     the current scope.  If there is, duplicate_decls may do all the
     work for us.  If duplicate_decls returns false, that indicates
     two incompatible decls in the same scope; we are to silently
     replace the old one (duplicate_decls has issued all appropriate
     diagnostics).  In particular, we should not consider possible
     duplicates in the external scope, or shadowing.  */
  b = I_SYMBOL_BINDING (name);
  if (b && B_IN_SCOPE (b, scope))
    {
      struct c_binding *b_ext, *b_use;
      tree type = TREE_TYPE (x);
      tree visdecl = b->decl;
      tree vistype = TREE_TYPE (visdecl);
      if (TREE_CODE (TREE_TYPE (x)) == ARRAY_TYPE
          && COMPLETE_TYPE_P (TREE_TYPE (x)))
        b->inner_comp = false;
      b_use = b;
      b_ext = b;
      /* If this is an external linkage declaration, we should check
         for compatibility with the type in the external scope before
         setting the type at this scope based on the visible
         information only.  */
      if (TREE_PUBLIC (x) && TREE_PUBLIC (visdecl))
        {
          while (b_ext && !B_IN_EXTERNAL_SCOPE (b_ext))
            b_ext = b_ext->shadowed;
          if (b_ext)
            {
              b_use = b_ext;
              if (b_use->u.type)
                TREE_TYPE (b_use->decl) = b_use->u.type;
            }
        }
      if (duplicate_decls (x, b_use->decl))
        {
          if (b_use != b)
            {
              /* Save the updated type in the external scope and
                 restore the proper type for this scope.  */
              tree thistype;
              if (comptypes (vistype, type))
                thistype = composite_type (vistype, type);
              else
                thistype = TREE_TYPE (b_use->decl);
              b_use->u.type = TREE_TYPE (b_use->decl);
              if (TREE_CODE (b_use->decl) == FUNCTION_DECL
                  && DECL_BUILT_IN (b_use->decl))
                thistype
                  = build_type_attribute_variant (thistype,
                                                  TYPE_ATTRIBUTES
                                                  (b_use->u.type));
              TREE_TYPE (b_use->decl) = thistype;
            }
          return b_use->decl;
        }
      else
        goto skip_external_and_shadow_checks;
    }

  /* All declarations with external linkage, and all external
     references, go in the external scope, no matter what scope is
     current.  However, the binding in that scope is ignored for
     purposes of normal name lookup.  A separate binding structure is
     created in the requested scope; this governs the normal
     visibility of the symbol.

     The binding in the externals scope is used exclusively for
     detecting duplicate declarations of the same object, no matter
     what scope they are in; this is what we do here.  (C99 6.2.7p2:
     All declarations that refer to the same object or function shall
     have compatible type; otherwise, the behavior is undefined.)  */
  if (DECL_EXTERNAL (x) || scope == file_scope)
    {
      tree type = TREE_TYPE (x);
      tree vistype = 0;
      tree visdecl = 0;
      bool type_saved = false;
      if (b && !B_IN_EXTERNAL_SCOPE (b)
          && (TREE_CODE (b->decl) == FUNCTION_DECL
              || TREE_CODE (b->decl) == VAR_DECL)
          && DECL_FILE_SCOPE_P (b->decl))
        {
          visdecl = b->decl;
          vistype = TREE_TYPE (visdecl);
        }
      if (scope != file_scope
          && !DECL_IN_SYSTEM_HEADER (x))
        warning (OPT_Wnested_externs, "nested extern declaration of %qD", x);

      while (b && !B_IN_EXTERNAL_SCOPE (b))
        {
          /* If this decl might be modified, save its type.  This is
             done here rather than when the decl is first bound
             because the type may change after first binding, through
             being completed or through attributes being added.  If we
             encounter multiple such decls, only the first should have
             its type saved; the others will already have had their
             proper types saved and the types will not have changed as
             their scopes will not have been re-entered.  */
          if (DECL_P (b->decl) && DECL_FILE_SCOPE_P (b->decl) && !type_saved)
            {
              b->u.type = TREE_TYPE (b->decl);
              type_saved = true;
            }
          if (B_IN_FILE_SCOPE (b)
              && TREE_CODE (b->decl) == VAR_DECL
              && TREE_STATIC (b->decl)
              && TREE_CODE (TREE_TYPE (b->decl)) == ARRAY_TYPE
              && !TYPE_DOMAIN (TREE_TYPE (b->decl))
              && TREE_CODE (type) == ARRAY_TYPE
              && TYPE_DOMAIN (type)
              && TYPE_MAX_VALUE (TYPE_DOMAIN (type))
              && !integer_zerop (TYPE_MAX_VALUE (TYPE_DOMAIN (type))))
            {
              /* Array type completed in inner scope, which should be
                 diagnosed if the completion does not have size 1 and
                 it does not get completed in the file scope.  */
              b->inner_comp = true;
            }
          b = b->shadowed;
        }

      /* If a matching external declaration has been found, set its
         type to the composite of all the types of that declaration.
         After the consistency checks, it will be reset to the
         composite of the visible types only.  */
      if (b && (TREE_PUBLIC (x) || same_translation_unit_p (x, b->decl))
          && b->u.type)
        TREE_TYPE (b->decl) = b->u.type;

      /* The point of the same_translation_unit_p check here is,
         we want to detect a duplicate decl for a construct like
         foo() { extern bar(); } ... static bar();  but not if
         they are in different translation units.  In any case,
         the static does not go in the externals scope.  */
      if (b
          && (TREE_PUBLIC (x) || same_translation_unit_p (x, b->decl))
          && duplicate_decls (x, b->decl))
        {
          tree thistype;
          if (vistype)
            {
              if (comptypes (vistype, type))
                thistype = composite_type (vistype, type);
              else
                thistype = TREE_TYPE (b->decl);
            }
          else
            thistype = type;
          b->u.type = TREE_TYPE (b->decl);
          if (TREE_CODE (b->decl) == FUNCTION_DECL && DECL_BUILT_IN (b->decl))
            thistype
              = build_type_attribute_variant (thistype,
                                              TYPE_ATTRIBUTES (b->u.type));
          TREE_TYPE (b->decl) = thistype;
          bind (name, b->decl, scope, /*invisible=*/false, /*nested=*/true,
                locus);
          return b->decl;
        }
      else if (TREE_PUBLIC (x))
        {
          if (visdecl && !b && duplicate_decls (x, visdecl))
            {
              /* An external declaration at block scope referring to a
                 visible entity with internal linkage.  The composite
                 type will already be correct for this scope, so we
                 just need to fall through to make the declaration in
                 this scope.  */
              nested = true;
              x = visdecl;
            }
          else
            {
              bind (name, x, external_scope, /*invisible=*/true,
                    /*nested=*/false, locus);
              nested = true;
            }
        }
    }

  if (TREE_CODE (x) != PARM_DECL)
    warn_if_shadowing (x);

 skip_external_and_shadow_checks:
  if (TREE_CODE (x) == TYPE_DECL)
    {
      /* So this is a typedef, set its underlying type.  */
      set_underlying_type (x);

      /* If X is a typedef defined in the current function, record it
         for the purpose of implementing the -Wunused-local-typedefs
         warning.  */
      record_locally_defined_typedef (x);
    }

  bind (name, x, scope, /*invisible=*/false, nested, locus);

  /* If x's type is incomplete because it's based on a
     structure or union which has not yet been fully declared,
     attach it to that structure or union type, so we can go
     back and complete the variable declaration later, if the
     structure or union gets fully declared.

     If the input is erroneous, we can have error_mark in the type
     slot (e.g. "f(void a, ...)") - that doesn't count as an
     incomplete type.  */
  if (TREE_TYPE (x) != error_mark_node
      && !COMPLETE_TYPE_P (TREE_TYPE (x)))
    {
      tree element = TREE_TYPE (x);

      while (TREE_CODE (element) == ARRAY_TYPE)
        element = TREE_TYPE (element);
      element = TYPE_MAIN_VARIANT (element);

      if ((TREE_CODE (element) == RECORD_TYPE
           || TREE_CODE (element) == UNION_TYPE)
          && (TREE_CODE (x) != TYPE_DECL
              || TREE_CODE (TREE_TYPE (x)) == ARRAY_TYPE)
          && !COMPLETE_TYPE_P (element))
        C_TYPE_INCOMPLETE_VARS (element)
          = tree_cons (NULL_TREE, x, C_TYPE_INCOMPLETE_VARS (element));
    }
  return x;
}

/* Record X as belonging to file scope.
   This is used only internally by the Objective-C front end,
   and is limited to its needs.  duplicate_decls is not called;
   if there is any preexisting decl for this identifier, it is an ICE.  */

tree
pushdecl_top_level (tree x)
{
  tree name;
  bool nested = false;
  gcc_assert (TREE_CODE (x) == VAR_DECL || TREE_CODE (x) == CONST_DECL);

  name = DECL_NAME (x);

 gcc_assert (TREE_CODE (x) == CONST_DECL || !I_SYMBOL_BINDING (name));

  if (TREE_PUBLIC (x))
    {
      bind (name, x, external_scope, /*invisible=*/true, /*nested=*/false,
            UNKNOWN_LOCATION);
      nested = true;
    }
  if (file_scope)
    bind (name, x, file_scope, /*invisible=*/false, nested, UNKNOWN_LOCATION);

  return x;
}
\f
static void
implicit_decl_warning (tree id, tree olddecl)
{
  if (warn_implicit_function_declaration)
    {
      bool warned;

      if (flag_isoc99)
        warned = pedwarn (input_location, OPT_Wimplicit_function_declaration,
                          "implicit declaration of function %qE", id);
      else
        warned = warning (OPT_Wimplicit_function_declaration,
                          G_("implicit declaration of function %qE"), id);
      if (olddecl && warned)
        locate_old_decl (olddecl);
    }
}

/* Generate an implicit declaration for identifier FUNCTIONID at LOC as a
   function of type int ().  */

tree
implicitly_declare (location_t loc, tree functionid)
{
  struct c_binding *b;
  tree decl = 0;
  tree asmspec_tree;

  for (b = I_SYMBOL_BINDING (functionid); b; b = b->shadowed)
    {
      if (B_IN_SCOPE (b, external_scope))
        {
          decl = b->decl;
          break;
        }
    }

  if (decl)
    {
      if (decl == error_mark_node)
        return decl;

      /* FIXME: Objective-C has weird not-really-builtin functions
         which are supposed to be visible automatically.  They wind up
         in the external scope because they're pushed before the file
         scope gets created.  Catch this here and rebind them into the
         file scope.  */
      if (!DECL_BUILT_IN (decl) && DECL_IS_BUILTIN (decl))
        {
          bind (functionid, decl, file_scope,
                /*invisible=*/false, /*nested=*/true,
                DECL_SOURCE_LOCATION (decl));
          return decl;
        }
      else
        {
          tree newtype = default_function_type;
          if (b->u.type)
            TREE_TYPE (decl) = b->u.type;
          /* Implicit declaration of a function already declared
             (somehow) in a different scope, or as a built-in.
             If this is the first time this has happened, warn;
             then recycle the old declaration but with the new type.  */
          if (!C_DECL_IMPLICIT (decl))
            {
              implicit_decl_warning (functionid, decl);
              C_DECL_IMPLICIT (decl) = 1;
            }
          if (DECL_BUILT_IN (decl))
            {
              newtype = build_type_attribute_variant (newtype,
                                                      TYPE_ATTRIBUTES
                                                      (TREE_TYPE (decl)));
              if (!comptypes (newtype, TREE_TYPE (decl)))
                {
                  warning_at (loc, 0, "incompatible implicit declaration of "
                              "built-in function %qD", decl);
                  newtype = TREE_TYPE (decl);
                }
            }
          else
            {
              if (!comptypes (newtype, TREE_TYPE (decl)))
                {
                  error_at (loc, "incompatible implicit declaration of function %qD", decl);
                  locate_old_decl (decl);
                }
            }
          b->u.type = TREE_TYPE (decl);
          TREE_TYPE (decl) = newtype;
          bind (functionid, decl, current_scope,
                /*invisible=*/false, /*nested=*/true,
                DECL_SOURCE_LOCATION (decl));
          return decl;
        }
    }

  /* Not seen before.  */
  decl = build_decl (loc, FUNCTION_DECL, functionid, default_function_type);
  DECL_EXTERNAL (decl) = 1;
  TREE_PUBLIC (decl) = 1;
  C_DECL_IMPLICIT (decl) = 1;
  implicit_decl_warning (functionid, 0);
  asmspec_tree = maybe_apply_renaming_pragma (decl, /*asmname=*/NULL);
  if (asmspec_tree)
    set_user_assembler_name (decl, TREE_STRING_POINTER (asmspec_tree));

  /* C89 says implicit declarations are in the innermost block.
     So we record the decl in the standard fashion.  */
  decl = pushdecl (decl);

  /* No need to call objc_check_decl here - it's a function type.  */
  rest_of_decl_compilation (decl, 0, 0);

  /* Write a record describing this implicit function declaration
     to the prototypes file (if requested).  */
  gen_aux_info_record (decl, 0, 1, 0);

  /* Possibly apply some default attributes to this implicit declaration.  */
  decl_attributes (&decl, NULL_TREE, 0);

  return decl;
}

/* Issue an error message for a reference to an undeclared variable
   ID, including a reference to a builtin outside of function-call
   context.  Establish a binding of the identifier to error_mark_node
   in an appropriate scope, which will suppress further errors for the
   same identifier.  The error message should be given location LOC.  */
void
undeclared_variable (location_t loc, tree id)
{
  static bool already = false;
  struct c_scope *scope;

  if (current_function_decl == 0)
    {
      error_at (loc, "%qE undeclared here (not in a function)", id);
      scope = current_scope;
    }
  else
    {
      if (!objc_diagnose_private_ivar (id))
        error_at (loc, "%qE undeclared (first use in this function)", id);
      if (!already)
        {
          inform (loc, "each undeclared identifier is reported only"
                  " once for each function it appears in");
          already = true;
        }

      /* If we are parsing old-style parameter decls, current_function_decl
         will be nonnull but current_function_scope will be null.  */
      scope = current_function_scope ? current_function_scope : current_scope;
    }
  bind (id, error_mark_node, scope, /*invisible=*/false, /*nested=*/false,
        UNKNOWN_LOCATION);
}
\f
/* Subroutine of lookup_label, declare_label, define_label: construct a
   LABEL_DECL with all the proper frills.  Also create a struct
   c_label_vars initialized for the current scope.  */

static tree
make_label (location_t location, tree name, bool defining,
            struct c_label_vars **p_label_vars)
{
  tree label = build_decl (location, LABEL_DECL, name, void_type_node);
  struct c_label_vars *label_vars;

  DECL_CONTEXT (label) = current_function_decl;
  DECL_MODE (label) = VOIDmode;

  label_vars = ggc_alloc_c_label_vars ();
  label_vars->shadowed = NULL;
  set_spot_bindings (&label_vars->label_bindings, defining);
  label_vars->decls_in_scope = make_tree_vector ();
  label_vars->gotos = VEC_alloc (c_goto_bindings_p, gc, 0);
  *p_label_vars = label_vars;

  return label;
}

/* Get the LABEL_DECL corresponding to identifier NAME as a label.
   Create one if none exists so far for the current function.
   This is called when a label is used in a goto expression or
   has its address taken.  */

tree
lookup_label (tree name)
{
  tree label;
  struct c_label_vars *label_vars;

  if (current_function_scope == 0)
    {
      error ("label %qE referenced outside of any function", name);
      return 0;
    }

  /* Use a label already defined or ref'd with this name, but not if
     it is inherited from a containing function and wasn't declared
     using __label__.  */
  label = I_LABEL_DECL (name);
  if (label && (DECL_CONTEXT (label) == current_function_decl
                || C_DECLARED_LABEL_FLAG (label)))
    {
      /* If the label has only been declared, update its apparent
         location to point here, for better diagnostics if it
         turns out not to have been defined.  */
      if (DECL_INITIAL (label) == NULL_TREE)
        DECL_SOURCE_LOCATION (label) = input_location;
      return label;
    }

  /* No label binding for that identifier; make one.  */
  label = make_label (input_location, name, false, &label_vars);

  /* Ordinary labels go in the current function scope.  */
  bind_label (name, label, current_function_scope, label_vars);

  return label;
}

/* Issue a warning about DECL for a goto statement at GOTO_LOC going
   to LABEL.  */

static void
warn_about_goto (location_t goto_loc, tree label, tree decl)
{
  if (variably_modified_type_p (TREE_TYPE (decl), NULL_TREE))
    error_at (goto_loc,
              "jump into scope of identifier with variably modified type");
  else
    warning_at (goto_loc, OPT_Wjump_misses_init,
                "jump skips variable initialization");
  inform (DECL_SOURCE_LOCATION (label), "label %qD defined here", label);
  inform (DECL_SOURCE_LOCATION (decl), "%qD declared here", decl);
}

/* Look up a label because of a goto statement.  This is like
   lookup_label, but also issues any appropriate warnings.  */

tree
lookup_label_for_goto (location_t loc, tree name)
{
  tree label;
  struct c_label_vars *label_vars;
  unsigned int ix;
  tree decl;

  label = lookup_label (name);
  if (label == NULL_TREE)
    return NULL_TREE;

  /* If we are jumping to a different function, we can't issue any
     useful warnings.  */
  if (DECL_CONTEXT (label) != current_function_decl)
    {
      gcc_assert (C_DECLARED_LABEL_FLAG (label));
      return label;
    }

  label_vars = I_LABEL_BINDING (name)->u.label;

  /* If the label has not yet been defined, then push this goto on a
     list for possible later warnings.  */
  if (label_vars->label_bindings.scope == NULL)
    {
      struct c_goto_bindings *g;

      g = ggc_alloc_c_goto_bindings ();
      g->loc = loc;
      set_spot_bindings (&g->goto_bindings, true);
      VEC_safe_push (c_goto_bindings_p, gc, label_vars->gotos, g);
      return label;
    }

  /* If there are any decls in label_vars->decls_in_scope, then this
     goto has missed the declaration of the decl.  This happens for a
     case like
       int i = 1;
      lab:
       ...
       goto lab;
     Issue a warning or error.  */
  FOR_EACH_VEC_ELT (tree, label_vars->decls_in_scope, ix, decl)
    warn_about_goto (loc, label, decl);

  if (label_vars->label_bindings.left_stmt_expr)
    {
      error_at (loc, "jump into statement expression");
      inform (DECL_SOURCE_LOCATION (label), "label %qD defined here", label);
    }

  return label;
}

/* Make a label named NAME in the current function, shadowing silently
   any that may be inherited from containing functions or containing
   scopes.  This is called for __label__ declarations.  */

tree
declare_label (tree name)
{
  struct c_binding *b = I_LABEL_BINDING (name);
  tree label;
  struct c_label_vars *label_vars;

  /* Check to make sure that the label hasn't already been declared
     at this scope */
  if (b && B_IN_CURRENT_SCOPE (b))
    {
      error ("duplicate label declaration %qE", name);
      locate_old_decl (b->decl);

      /* Just use the previous declaration.  */
      return b->decl;
    }

  label = make_label (input_location, name, false, &label_vars);
  C_DECLARED_LABEL_FLAG (label) = 1;

  /* Declared labels go in the current scope.  */
  bind_label (name, label, current_scope, label_vars);

  return label;
}

/* When we define a label, issue any appropriate warnings if there are
   any gotos earlier in the function which jump to this label.  */

static void
check_earlier_gotos (tree label, struct c_label_vars* label_vars)
{
  unsigned int ix;
  struct c_goto_bindings *g;

  FOR_EACH_VEC_ELT (c_goto_bindings_p, label_vars->gotos, ix, g)
    {
      struct c_binding *b;
      struct c_scope *scope;

      /* We have a goto to this label.  The goto is going forward.  In
         g->scope, the goto is going to skip any binding which was
         defined after g->bindings_in_scope.  */
      if (g->goto_bindings.scope->has_jump_unsafe_decl)
        {
          for (b = g->goto_bindings.scope->bindings;
               b != g->goto_bindings.bindings_in_scope;
               b = b->prev)
            {
              if (decl_jump_unsafe (b->decl))
                warn_about_goto (g->loc, label, b->decl);
            }
        }

      /* We also need to warn about decls defined in any scopes
         between the scope of the label and the scope of the goto.  */
      for (scope = label_vars->label_bindings.scope;
           scope != g->goto_bindings.scope;
           scope = scope->outer)
        {
          gcc_assert (scope != NULL);
          if (scope->has_jump_unsafe_decl)
            {
              if (scope == label_vars->label_bindings.scope)
                b = label_vars->label_bindings.bindings_in_scope;
              else
                b = scope->bindings;
              for (; b != NULL; b = b->prev)
                {
                  if (decl_jump_unsafe (b->decl))
                    warn_about_goto (g->loc, label, b->decl);
                }
            }
        }

      if (g->goto_bindings.stmt_exprs > 0)
        {
          error_at (g->loc, "jump into statement expression");
          inform (DECL_SOURCE_LOCATION (label), "label %qD defined here",
                  label);
        }
    }

  /* Now that the label is defined, we will issue warnings about
     subsequent gotos to this label when we see them.  */
  VEC_truncate (c_goto_bindings_p, label_vars->gotos, 0);
  label_vars->gotos = NULL;
}

/* Define a label, specifying the location in the source file.
   Return the LABEL_DECL node for the label, if the definition is valid.
   Otherwise return 0.  */

tree
define_label (location_t location, tree name)
{
  /* Find any preexisting label with this name.  It is an error
     if that label has already been defined in this function, or
     if there is a containing function with a declared label with
     the same name.  */
  tree label = I_LABEL_DECL (name);

  if (label
      && ((DECL_CONTEXT (label) == current_function_decl
           && DECL_INITIAL (label) != 0)
          || (DECL_CONTEXT (label) != current_function_decl
              && C_DECLARED_LABEL_FLAG (label))))
    {
      error_at (location, "duplicate label %qD", label);
      locate_old_decl (label);
      return 0;
    }
  else if (label && DECL_CONTEXT (label) == current_function_decl)
    {
      struct c_label_vars *label_vars = I_LABEL_BINDING (name)->u.label;

      /* The label has been used or declared already in this function,
         but not defined.  Update its location to point to this
         definition.  */
      DECL_SOURCE_LOCATION (label) = location;
      set_spot_bindings (&label_vars->label_bindings, true);

      /* Issue warnings as required about any goto statements from
         earlier in the function.  */
      check_earlier_gotos (label, label_vars);
    }
  else
    {
      struct c_label_vars *label_vars;

      /* No label binding for that identifier; make one.  */
      label = make_label (location, name, true, &label_vars);

      /* Ordinary labels go in the current function scope.  */
      bind_label (name, label, current_function_scope, label_vars);
    }

  if (!in_system_header && lookup_name (name))
    warning_at (location, OPT_Wtraditional,
                "traditional C lacks a separate namespace "
                "for labels, identifier %qE conflicts", name);

  /* Mark label as having been defined.  */
  DECL_INITIAL (label) = error_mark_node;
  return label;
}
\f
/* Get the bindings for a new switch statement.  This is used to issue
   warnings as appropriate for jumps from the switch to case or
   default labels.  */

struct c_spot_bindings *
c_get_switch_bindings (void)
{
  struct c_spot_bindings *switch_bindings;

  switch_bindings = XNEW (struct c_spot_bindings);
  set_spot_bindings (switch_bindings, true);
  return switch_bindings;
}

void
c_release_switch_bindings (struct c_spot_bindings *bindings)
{
  gcc_assert (bindings->stmt_exprs == 0 && !bindings->left_stmt_expr);
  XDELETE (bindings);
}

/* This is called at the point of a case or default label to issue
   warnings about decls as needed.  It returns true if it found an
   error, not just a warning.  */

bool
c_check_switch_jump_warnings (struct c_spot_bindings *switch_bindings,
                              location_t switch_loc, location_t case_loc)
{
  bool saw_error;
  struct c_scope *scope;

  saw_error = false;
  for (scope = current_scope;
       scope != switch_bindings->scope;
       scope = scope->outer)
    {
      struct c_binding *b;

      gcc_assert (scope != NULL);

      if (!scope->has_jump_unsafe_decl)
        continue;

      for (b = scope->bindings; b != NULL; b = b->prev)
        {
          if (decl_jump_unsafe (b->decl))
            {
              if (variably_modified_type_p (TREE_TYPE (b->decl), NULL_TREE))
                {
                  saw_error = true;
                  error_at (case_loc,
                            ("switch jumps into scope of identifier with "
                             "variably modified type"));
                }
              else
                warning_at (case_loc, OPT_Wjump_misses_init,
                            "switch jumps over variable initialization");
              inform (switch_loc, "switch starts here");
              inform (DECL_SOURCE_LOCATION (b->decl), "%qD declared here",
                      b->decl);
            }
        }
    }

  if (switch_bindings->stmt_exprs > 0)
    {
      saw_error = true;
      error_at (case_loc, "switch jumps into statement expression");
      inform (switch_loc, "switch starts here");
    }

  return saw_error;
}
\f
/* Given NAME, an IDENTIFIER_NODE,
   return the structure (or union or enum) definition for that name.
   If THISLEVEL_ONLY is nonzero, searches only the current_scope.
   CODE says which kind of type the caller wants;
   it is RECORD_TYPE or UNION_TYPE or ENUMERAL_TYPE.
   If PLOC is not NULL and this returns non-null, it sets *PLOC to the
   location where the tag was defined.
   If the wrong kind of type is found, an error is reported.  */

static tree
lookup_tag (enum tree_code code, tree name, int thislevel_only,
            location_t *ploc)
{
  struct c_binding *b = I_TAG_BINDING (name);
  int thislevel = 0;

  if (!b || !b->decl)
    return 0;

  /* We only care about whether it's in this level if
     thislevel_only was set or it might be a type clash.  */
  if (thislevel_only || TREE_CODE (b->decl) != code)
    {
      /* For our purposes, a tag in the external scope is the same as
         a tag in the file scope.  (Primarily relevant to Objective-C
         and its builtin structure tags, which get pushed before the
         file scope is created.)  */
      if (B_IN_CURRENT_SCOPE (b)
          || (current_scope == file_scope && B_IN_EXTERNAL_SCOPE (b)))
        thislevel = 1;
    }

  if (thislevel_only && !thislevel)
    return 0;

  if (TREE_CODE (b->decl) != code)
    {
      /* Definition isn't the kind we were looking for.  */
      pending_invalid_xref = name;
      pending_invalid_xref_location = input_location;

      /* If in the same binding level as a declaration as a tag
         of a different type, this must not be allowed to
         shadow that tag, so give the error immediately.
         (For example, "struct foo; union foo;" is invalid.)  */
      if (thislevel)
        pending_xref_error ();
    }

  if (ploc != NULL)
    *ploc = b->locus;

  return b->decl;
}

/* Print an error message now
   for a recent invalid struct, union or enum cross reference.
   We don't print them immediately because they are not invalid
   when used in the `struct foo;' construct for shadowing.  */

void
pending_xref_error (void)
{
  if (pending_invalid_xref != 0)
    error_at (pending_invalid_xref_location, "%qE defined as wrong kind of tag",
              pending_invalid_xref);
  pending_invalid_xref = 0;
}

\f
/* Look up NAME in the current scope and its superiors
   in the namespace of variables, functions and typedefs.
   Return a ..._DECL node of some kind representing its definition,
   or return 0 if it is undefined.  */

tree
lookup_name (tree name)
{
  struct c_binding *b = I_SYMBOL_BINDING (name);
  if (b && !b->invisible)
    {
      maybe_record_typedef_use (b->decl);
      return b->decl;
    }
  return 0;
}

/* Similar to `lookup_name' but look only at the indicated scope.  */

static tree
lookup_name_in_scope (tree name, struct c_scope *scope)
{
  struct c_binding *b;