gcc/c-typeck.c

/* Build expressions with type checking for C compiler.
   Copyright (C) 1987, 1988, 1991, 1992, 1993, 1994, 1995, 1996, 1997,
   1998, 1999, 2000, 2001, 2002, 2003, 2004 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 2, 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 COPYING.  If not, write to the Free
Software Foundation, 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.  */


/* This file is part of the C front end.
   It contains routines to build C expressions given their operands,
   including computing the types of the result, C-specific error checks,
   and some optimization.

   There are also routines to build RETURN_STMT nodes and CASE_STMT nodes,
   and to process initializations in declarations (since they work
   like a strange sort of assignment).  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "rtl.h"
#include "tree.h"
#include "c-tree.h"
#include "tm_p.h"
#include "flags.h"
#include "output.h"
#include "expr.h"
#include "toplev.h"
#include "intl.h"
#include "ggc.h"
#include "target.h"

/* Nonzero if we've already printed a "missing braces around initializer"
   message within this initializer.  */
static int missing_braces_mentioned;

static int require_constant_value;
static int require_constant_elements;

static tree qualify_type (tree, tree);
static int same_translation_unit_p (tree, tree);
static int tagged_types_tu_compatible_p (tree, tree, int);
static int comp_target_types (tree, tree, int);
static int function_types_compatible_p (tree, tree, int);
static int type_lists_compatible_p (tree, tree, int);
static tree decl_constant_value_for_broken_optimization (tree);
static tree default_function_array_conversion (tree);
static tree lookup_field (tree, tree);
static tree convert_arguments (tree, tree, tree, tree);
static tree pointer_diff (tree, tree);
static tree unary_complex_lvalue (enum tree_code, tree, int);
static void pedantic_lvalue_warning (enum tree_code);
static tree internal_build_compound_expr (tree, int);
static tree convert_for_assignment (tree, tree, const char *, tree, tree,
				    int);
static void warn_for_assignment (const char *, const char *, tree, int);
static tree valid_compound_expr_initializer (tree, tree);
static void push_string (const char *);
static void push_member_name (tree);
static void push_array_bounds (int);
static int spelling_length (void);
static char *print_spelling (char *);
static void warning_init (const char *);
static tree digest_init (tree, tree, int);
static void output_init_element (tree, tree, tree, int);
static void output_pending_init_elements (int);
static int set_designator (int);
static void push_range_stack (tree);
static void add_pending_init (tree, tree);
static void set_nonincremental_init (void);
static void set_nonincremental_init_from_string (tree);
static tree find_init_member (tree);

/* Do `exp = require_complete_type (exp);' to make sure exp
   does not have an incomplete type.  (That includes void types.)  */

tree
require_complete_type (tree value)
{
  tree type = TREE_TYPE (value);

  if (value == error_mark_node || type == error_mark_node)
    return error_mark_node;

  /* First, detect a valid value with a complete type.  */
  if (COMPLETE_TYPE_P (type))
    return value;

  c_incomplete_type_error (value, type);
  return error_mark_node;
}

/* Print an error message for invalid use of an incomplete type.
   VALUE is the expression that was used (or 0 if that isn't known)
   and TYPE is the type that was invalid.  */

void
c_incomplete_type_error (tree value, tree type)
{
  const char *type_code_string;

  /* Avoid duplicate error message.  */
  if (TREE_CODE (type) == ERROR_MARK)
    return;

  if (value != 0 && (TREE_CODE (value) == VAR_DECL
		     || TREE_CODE (value) == PARM_DECL))
    error ("`%s' has an incomplete type",
	   IDENTIFIER_POINTER (DECL_NAME (value)));
  else
    {
    retry:
      /* We must print an error message.  Be clever about what it says.  */

      switch (TREE_CODE (type))
	{
	case RECORD_TYPE:
	  type_code_string = "struct";
	  break;

	case UNION_TYPE:
	  type_code_string = "union";
	  break;

	case ENUMERAL_TYPE:
	  type_code_string = "enum";
	  break;

	case VOID_TYPE:
	  error ("invalid use of void expression");
	  return;

	case ARRAY_TYPE:
	  if (TYPE_DOMAIN (type))
	    {
	      if (TYPE_MAX_VALUE (TYPE_DOMAIN (type)) == NULL)
		{
		  error ("invalid use of flexible array member");
		  return;
		}
	      type = TREE_TYPE (type);
	      goto retry;
	    }
	  error ("invalid use of array with unspecified bounds");
	  return;

	default:
	  abort ();
	}

      if (TREE_CODE (TYPE_NAME (type)) == IDENTIFIER_NODE)
	error ("invalid use of undefined type `%s %s'",
	       type_code_string, IDENTIFIER_POINTER (TYPE_NAME (type)));
      else
	/* If this type has a typedef-name, the TYPE_NAME is a TYPE_DECL.  */
	error ("invalid use of incomplete typedef `%s'",
	       IDENTIFIER_POINTER (DECL_NAME (TYPE_NAME (type))));
    }
}

/* Given a type, apply default promotions wrt unnamed function
   arguments and return the new type.  */

tree
c_type_promotes_to (tree type)
{
  if (TYPE_MAIN_VARIANT (type) == float_type_node)
    return double_type_node;

  if (c_promoting_integer_type_p (type))
    {
      /* Preserve unsignedness if not really getting any wider.  */
      if (TREE_UNSIGNED (type)
          && (TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node)))
        return unsigned_type_node;
      return integer_type_node;
    }

  return type;
}

/* Return a variant of TYPE which has all the type qualifiers of LIKE
   as well as those of TYPE.  */

static tree
qualify_type (tree type, tree like)
{
  return c_build_qualified_type (type,
				 TYPE_QUALS (type) | TYPE_QUALS (like));
}

/* Return the common type of two types.
   We assume that comptypes has already been done and returned 1;
   if that isn't so, this may crash.  In particular, we assume that qualifiers
   match.

   This is the type for the result of most arithmetic operations
   if the operands have the given two types.  */

tree
common_type (tree t1, tree t2)
{
  enum tree_code code1;
  enum tree_code code2;
  tree attributes;

  /* Save time if the two types are the same.  */

  if (t1 == t2) return t1;

  /* If one type is nonsense, use the other.  */
  if (t1 == error_mark_node)
    return t2;
  if (t2 == error_mark_node)
    return t1;

  /* Merge the attributes.  */
  attributes = (*targetm.merge_type_attributes) (t1, t2);

  /* Treat an enum type as the unsigned integer type of the same width.  */

  if (TREE_CODE (t1) == ENUMERAL_TYPE)
    t1 = c_common_type_for_size (TYPE_PRECISION (t1), 1);
  if (TREE_CODE (t2) == ENUMERAL_TYPE)
    t2 = c_common_type_for_size (TYPE_PRECISION (t2), 1);

  code1 = TREE_CODE (t1);
  code2 = TREE_CODE (t2);

  /* If one type is complex, form the common type of the non-complex
     components, then make that complex.  Use T1 or T2 if it is the
     required type.  */
  if (code1 == COMPLEX_TYPE || code2 == COMPLEX_TYPE)
    {
      tree subtype1 = code1 == COMPLEX_TYPE ? TREE_TYPE (t1) : t1;
      tree subtype2 = code2 == COMPLEX_TYPE ? TREE_TYPE (t2) : t2;
      tree subtype = common_type (subtype1, subtype2);

      if (code1 == COMPLEX_TYPE && TREE_TYPE (t1) == subtype)
	return build_type_attribute_variant (t1, attributes);
      else if (code2 == COMPLEX_TYPE && TREE_TYPE (t2) == subtype)
	return build_type_attribute_variant (t2, attributes);
      else
	return build_type_attribute_variant (build_complex_type (subtype),
					     attributes);
    }

  switch (code1)
    {
    case INTEGER_TYPE:
    case REAL_TYPE:
      /* If only one is real, use it as the result.  */

      if (code1 == REAL_TYPE && code2 != REAL_TYPE)
	return build_type_attribute_variant (t1, attributes);

      if (code2 == REAL_TYPE && code1 != REAL_TYPE)
	return build_type_attribute_variant (t2, attributes);

      /* Both real or both integers; use the one with greater precision.  */

      if (TYPE_PRECISION (t1) > TYPE_PRECISION (t2))
	return build_type_attribute_variant (t1, attributes);
      else if (TYPE_PRECISION (t2) > TYPE_PRECISION (t1))
	return build_type_attribute_variant (t2, attributes);

      /* Same precision.  Prefer longs to ints even when same size.  */

      if (TYPE_MAIN_VARIANT (t1) == long_unsigned_type_node
	  || TYPE_MAIN_VARIANT (t2) == long_unsigned_type_node)
	{
	  t1 = build_qualified_type (long_unsigned_type_node,
				     TYPE_QUALS (t1));
	  return build_type_attribute_variant (t1, attributes);
	}

      if (TYPE_MAIN_VARIANT (t1) == long_integer_type_node
	  || TYPE_MAIN_VARIANT (t2) == long_integer_type_node)
	{
	  tree ntype;

	  /* But preserve unsignedness from the other type,
	     since long cannot hold all the values of an unsigned int.  */
	  if (TREE_UNSIGNED (t1) || TREE_UNSIGNED (t2))
	     ntype = long_unsigned_type_node;
	  else
	     ntype = long_integer_type_node;

	  ntype = build_qualified_type (ntype, TYPE_QUALS (t1));
	  return build_type_attribute_variant (ntype, attributes);
	}

      /* Likewise, prefer long double to double even if same size.  */
      if (TYPE_MAIN_VARIANT (t1) == long_double_type_node
	  || TYPE_MAIN_VARIANT (t2) == long_double_type_node)
	{
	  t1 = build_qualified_type (long_double_type_node,
				     TYPE_QUALS (t1));
	  return build_type_attribute_variant (t1, attributes);
	}

      /* Otherwise prefer the unsigned one.  */

      if (TREE_UNSIGNED (t1))
	return build_type_attribute_variant (t1, attributes);
      else
	return build_type_attribute_variant (t2, attributes);

    case POINTER_TYPE:
      /* For two pointers, do this recursively on the target type,
	 and combine the qualifiers of the two types' targets.  */
      /* This code was turned off; I don't know why.
	 But ANSI C specifies doing this with the qualifiers.
	 So I turned it on again.  */
      {
	tree pointed_to_1 = TREE_TYPE (t1);
	tree pointed_to_2 = TREE_TYPE (t2);
	tree target = common_type (TYPE_MAIN_VARIANT (pointed_to_1),
				   TYPE_MAIN_VARIANT (pointed_to_2));
	t1 = build_pointer_type (c_build_qualified_type
				 (target,
				  TYPE_QUALS (pointed_to_1) |
				  TYPE_QUALS (pointed_to_2)));
	return build_type_attribute_variant (t1, attributes);
      }

    case ARRAY_TYPE:
      {
	tree elt = common_type (TREE_TYPE (t1), TREE_TYPE (t2));
	/* Save space: see if the result is identical to one of the args.  */
	if (elt == TREE_TYPE (t1) && TYPE_DOMAIN (t1))
	  return build_type_attribute_variant (t1, attributes);
	if (elt == TREE_TYPE (t2) && TYPE_DOMAIN (t2))
	  return build_type_attribute_variant (t2, attributes);
	/* Merge the element types, and have a size if either arg has one.  */
	t1 = build_array_type (elt, TYPE_DOMAIN (TYPE_DOMAIN (t1) ? t1 : t2));
	return build_type_attribute_variant (t1, attributes);
      }

    case FUNCTION_TYPE:
      /* Function types: prefer the one that specified arg types.
	 If both do, merge the arg types.  Also merge the return types.  */
      {
	tree valtype = common_type (TREE_TYPE (t1), TREE_TYPE (t2));
	tree p1 = TYPE_ARG_TYPES (t1);
	tree p2 = TYPE_ARG_TYPES (t2);
	int len;
	tree newargs, n;
	int i;

	/* Save space: see if the result is identical to one of the args.  */
	if (valtype == TREE_TYPE (t1) && ! TYPE_ARG_TYPES (t2))
	  return build_type_attribute_variant (t1, attributes);
	if (valtype == TREE_TYPE (t2) && ! TYPE_ARG_TYPES (t1))
	  return build_type_attribute_variant (t2, attributes);

	/* Simple way if one arg fails to specify argument types.  */
	if (TYPE_ARG_TYPES (t1) == 0)
	 {
	   t1 = build_function_type (valtype, TYPE_ARG_TYPES (t2));
	   return build_type_attribute_variant (t1, attributes);
	 }
	if (TYPE_ARG_TYPES (t2) == 0)
	 {
	   t1 = build_function_type (valtype, TYPE_ARG_TYPES (t1));
	   return build_type_attribute_variant (t1, attributes);
	 }

	/* If both args specify argument types, we must merge the two
	   lists, argument by argument.  */

	pushlevel (0);
	declare_parm_level ();

	len = list_length (p1);
	newargs = 0;

	for (i = 0; i < len; i++)
	  newargs = tree_cons (NULL_TREE, NULL_TREE, newargs);

	n = newargs;

	for (; p1;
	     p1 = TREE_CHAIN (p1), p2 = TREE_CHAIN (p2), n = TREE_CHAIN (n))
	  {
	    /* A null type means arg type is not specified.
	       Take whatever the other function type has.  */
	    if (TREE_VALUE (p1) == 0)
	      {
		TREE_VALUE (n) = TREE_VALUE (p2);
		goto parm_done;
	      }
	    if (TREE_VALUE (p2) == 0)
	      {
		TREE_VALUE (n) = TREE_VALUE (p1);
		goto parm_done;
	      }

	    /* Given  wait (union {union wait *u; int *i} *)
	       and  wait (union wait *),
	       prefer  union wait *  as type of parm.  */
	    if (TREE_CODE (TREE_VALUE (p1)) == UNION_TYPE
		&& TREE_VALUE (p1) != TREE_VALUE (p2))
	      {
		tree memb;
		for (memb = TYPE_FIELDS (TREE_VALUE (p1));
		     memb; memb = TREE_CHAIN (memb))
		  if (comptypes (TREE_TYPE (memb), TREE_VALUE (p2),
				 COMPARE_STRICT))
		    {
		      TREE_VALUE (n) = TREE_VALUE (p2);
		      if (pedantic)
			pedwarn ("function types not truly compatible in ISO C");
		      goto parm_done;
		    }
	      }
	    if (TREE_CODE (TREE_VALUE (p2)) == UNION_TYPE
		&& TREE_VALUE (p2) != TREE_VALUE (p1))
	      {
		tree memb;
		for (memb = TYPE_FIELDS (TREE_VALUE (p2));
		     memb; memb = TREE_CHAIN (memb))
		  if (comptypes (TREE_TYPE (memb), TREE_VALUE (p1),
				 COMPARE_STRICT))
		    {
		      TREE_VALUE (n) = TREE_VALUE (p1);
		      if (pedantic)
			pedwarn ("function types not truly compatible in ISO C");
		      goto parm_done;
		    }
	      }
	    TREE_VALUE (n) = common_type (TREE_VALUE (p1), TREE_VALUE (p2));
	  parm_done: ;
	  }

	poplevel (0, 0, 0);

	t1 = build_function_type (valtype, newargs);
	/* ... falls through ...  */
      }

    default:
      return build_type_attribute_variant (t1, attributes);
    }

}

/* Return 1 if TYPE1 and TYPE2 are compatible types for assignment
   or various other operations.  Return 2 if they are compatible
   but a warning may be needed if you use them together.  */

int
comptypes (tree type1, tree type2, int flags)
{
  tree t1 = type1;
  tree t2 = type2;
  int attrval, val;

  /* Suppress errors caused by previously reported errors.  */

  if (t1 == t2 || !t1 || !t2
      || TREE_CODE (t1) == ERROR_MARK || TREE_CODE (t2) == ERROR_MARK)
    return 1;

  /* If either type is the internal version of sizetype, return the
     language version.  */
  if (TREE_CODE (t1) == INTEGER_TYPE && TYPE_IS_SIZETYPE (t1)
      && TYPE_DOMAIN (t1) != 0)
    t1 = TYPE_DOMAIN (t1);

  if (TREE_CODE (t2) == INTEGER_TYPE && TYPE_IS_SIZETYPE (t2)
      && TYPE_DOMAIN (t2) != 0)
    t2 = TYPE_DOMAIN (t2);

  /* Enumerated types are compatible with integer types, but this is
     not transitive: two enumerated types in the same translation unit
     are compatible with each other only if they are the same type.  */

  if (TREE_CODE (t1) == ENUMERAL_TYPE && TREE_CODE (t2) != ENUMERAL_TYPE)
    t1 = c_common_type_for_size (TYPE_PRECISION (t1), TREE_UNSIGNED (t1));
  else if (TREE_CODE (t2) == ENUMERAL_TYPE && TREE_CODE (t1) != ENUMERAL_TYPE)
    t2 = c_common_type_for_size (TYPE_PRECISION (t2), TREE_UNSIGNED (t2));

  if (t1 == t2)
    return 1;

  /* Different classes of types can't be compatible.  */

  if (TREE_CODE (t1) != TREE_CODE (t2))
    return 0;

  /* Qualifiers must match.  */

  if (TYPE_QUALS (t1) != TYPE_QUALS (t2))
    return 0;

  /* Allow for two different type nodes which have essentially the same
     definition.  Note that we already checked for equality of the type
     qualifiers (just above).  */

  if (TYPE_MAIN_VARIANT (t1) == TYPE_MAIN_VARIANT (t2))
    return 1;

  /* 1 if no need for warning yet, 2 if warning cause has been seen.  */
  if (! (attrval = (*targetm.comp_type_attributes) (t1, t2)))
     return 0;

  /* 1 if no need for warning yet, 2 if warning cause has been seen.  */
  val = 0;

  switch (TREE_CODE (t1))
    {
    case POINTER_TYPE:
      /* We must give ObjC the first crack at comparing pointers, since
	   protocol qualifiers may be involved.  */
      if (c_dialect_objc () && (val = objc_comptypes (t1, t2, 0)) >= 0)
	break;
      val = (TREE_TYPE (t1) == TREE_TYPE (t2)
	     ? 1 : comptypes (TREE_TYPE (t1), TREE_TYPE (t2), flags));
      break;

    case FUNCTION_TYPE:
      val = function_types_compatible_p (t1, t2, flags);
      break;

    case ARRAY_TYPE:
      {
	tree d1 = TYPE_DOMAIN (t1);
	tree d2 = TYPE_DOMAIN (t2);
	bool d1_variable, d2_variable;
	bool d1_zero, d2_zero;
	val = 1;

	/* Target types must match incl. qualifiers.  */
	if (TREE_TYPE (t1) != TREE_TYPE (t2)
	    && 0 == (val = comptypes (TREE_TYPE (t1), TREE_TYPE (t2),
				      flags)))
	  return 0;

	/* Sizes must match unless one is missing or variable.  */
	if (d1 == 0 || d2 == 0 || d1 == d2)
	  break;

	d1_zero = ! TYPE_MAX_VALUE (d1);
	d2_zero = ! TYPE_MAX_VALUE (d2);

	d1_variable = (! d1_zero
		       && (TREE_CODE (TYPE_MIN_VALUE (d1)) != INTEGER_CST
			   || TREE_CODE (TYPE_MAX_VALUE (d1)) != INTEGER_CST));
	d2_variable = (! d2_zero
		       && (TREE_CODE (TYPE_MIN_VALUE (d2)) != INTEGER_CST
			   || TREE_CODE (TYPE_MAX_VALUE (d2)) != INTEGER_CST));

	if (d1_variable || d2_variable)
	  break;
	if (d1_zero && d2_zero)
	  break;
	if (d1_zero || d2_zero
	    || ! tree_int_cst_equal (TYPE_MIN_VALUE (d1), TYPE_MIN_VALUE (d2))
	    || ! tree_int_cst_equal (TYPE_MAX_VALUE (d1), TYPE_MAX_VALUE (d2)))
	  val = 0;

        break;
      }

    case RECORD_TYPE:
      /* We are dealing with two distinct structs.  In assorted Objective-C
	 corner cases, however, these can still be deemed equivalent.  */
      if (c_dialect_objc () && objc_comptypes (t1, t2, 0) == 1)
	val = 1;

    case ENUMERAL_TYPE:
    case UNION_TYPE:
      if (val != 1 && !same_translation_unit_p (t1, t2))
	val = tagged_types_tu_compatible_p (t1, t2, flags);
      break;

    case VECTOR_TYPE:
      /* The target might allow certain vector types to be compatible.  */
      val = (*targetm.vector_opaque_p) (t1)
	|| (*targetm.vector_opaque_p) (t2);
      break;

    default:
      break;
    }
  return attrval == 2 && val == 1 ? 2 : val;
}

/* Return 1 if TTL and TTR are pointers to types that are equivalent,
   ignoring their qualifiers.  REFLEXIVE is only used by ObjC - set it
   to 1 or 0 depending if the check of the pointer types is meant to
   be reflexive or not (typically, assignments are not reflexive,
   while comparisons are reflexive).
*/

static int
comp_target_types (tree ttl, tree ttr, int reflexive)
{
  int val;

  /* Give objc_comptypes a crack at letting these types through.  */
  if ((val = objc_comptypes (ttl, ttr, reflexive)) >= 0)
    return val;

  val = comptypes (TYPE_MAIN_VARIANT (TREE_TYPE (ttl)),
		   TYPE_MAIN_VARIANT (TREE_TYPE (ttr)), COMPARE_STRICT);

  if (val == 2 && pedantic)
    pedwarn ("types are not quite compatible");
  return val;
}

/* Subroutines of `comptypes'.  */

/* Determine whether two types derive from the same translation unit.
   If the CONTEXT chain ends in a null, that type's context is still
   being parsed, so if two types have context chains ending in null,
   they're in the same translation unit.  */
static int
same_translation_unit_p (tree t1, tree t2)
{
  while (t1 && TREE_CODE (t1) != TRANSLATION_UNIT_DECL)
    switch (TREE_CODE_CLASS (TREE_CODE (t1)))
      {
      case 'd': t1 = DECL_CONTEXT (t1); break;
      case 't': t1 = TYPE_CONTEXT (t1); break;
      case 'b': t1 = BLOCK_SUPERCONTEXT (t1); break;
      default: abort ();
      }

  while (t2 && TREE_CODE (t2) != TRANSLATION_UNIT_DECL)
    switch (TREE_CODE_CLASS (TREE_CODE (t2)))
      {
      case 'd': t2 = DECL_CONTEXT (t1); break;
      case 't': t2 = TYPE_CONTEXT (t2); break;
      case 'b': t2 = BLOCK_SUPERCONTEXT (t2); break;
      default: abort ();
      }

  return t1 == t2;
}

/* The C standard says that two structures in different translation
   units are compatible with each other only if the types of their
   fields are compatible (among other things).  So, consider two copies
   of this structure:  */

struct tagged_tu_seen {
  const struct tagged_tu_seen * next;
  tree t1;
  tree t2;
};

/* Can they be compatible with each other?  We choose to break the
   recursion by allowing those types to be compatible.  */

static const struct tagged_tu_seen * tagged_tu_seen_base;

/* Return 1 if two 'struct', 'union', or 'enum' types T1 and T2 are
   compatible.  If the two types are not the same (which has been
   checked earlier), this can only happen when multiple translation
   units are being compiled.  See C99 6.2.7 paragraph 1 for the exact
   rules.  */

static int
tagged_types_tu_compatible_p (tree t1, tree t2, int flags)
{
  tree s1, s2;
  bool needs_warning = false;

  /* We have to verify that the tags of the types are the same.  This
     is harder than it looks because this may be a typedef, so we have
     to go look at the original type.  It may even be a typedef of a
     typedef...  */
  while (TYPE_NAME (t1)
	 && TREE_CODE (TYPE_NAME (t1)) == TYPE_DECL
	 && DECL_ORIGINAL_TYPE (TYPE_NAME (t1)))
    t1 = DECL_ORIGINAL_TYPE (TYPE_NAME (t1));

  while (TYPE_NAME (t2)
	 && TREE_CODE (TYPE_NAME (t2)) == TYPE_DECL
	 && DECL_ORIGINAL_TYPE (TYPE_NAME (t2)))
    t2 = DECL_ORIGINAL_TYPE (TYPE_NAME (t2));

  /* C90 didn't have the requirement that the two tags be the same.  */
  if (flag_isoc99 && TYPE_NAME (t1) != TYPE_NAME (t2))
    return 0;

  /* C90 didn't say what happened if one or both of the types were
     incomplete; we choose to follow C99 rules here, which is that they
     are compatible.  */
  if (TYPE_SIZE (t1) == NULL
      || TYPE_SIZE (t2) == NULL)
    return 1;

  {
    const struct tagged_tu_seen * tts_i;
    for (tts_i = tagged_tu_seen_base; tts_i != NULL; tts_i = tts_i->next)
      if (tts_i->t1 == t1 && tts_i->t2 == t2)
	return 1;
  }

  switch (TREE_CODE (t1))
    {
    case ENUMERAL_TYPE:
      {
	if (list_length (TYPE_VALUES (t1)) != list_length (TYPE_VALUES (t2)))
	  return 0;

	for (s1 = TYPE_VALUES (t1); s1; s1 = TREE_CHAIN (s1))
	  {
	    s2 = purpose_member (TREE_PURPOSE (s1), TYPE_VALUES (t2));
	    if (s2 == NULL
		|| simple_cst_equal (TREE_VALUE (s1), TREE_VALUE (s2)) != 1)
	      return 0;
	  }
	return 1;
      }

    case UNION_TYPE:
      {
	if (list_length (TYPE_FIELDS (t1)) != list_length (TYPE_FIELDS (t2)))
	  return 0;

	for (s1 = TYPE_FIELDS (t1); s1; s1 = TREE_CHAIN (s1))
	  {
	    bool ok = false;
	    struct tagged_tu_seen tts;

	    tts.next = tagged_tu_seen_base;
	    tts.t1 = t1;
	    tts.t2 = t2;
	    tagged_tu_seen_base = &tts;

	    if (DECL_NAME (s1) != NULL)
	      for (s2 = TYPE_VALUES (t2); s2; s2 = TREE_CHAIN (s2))
		if (DECL_NAME (s1) == DECL_NAME (s2))
		  {
		    int result;
		    result = comptypes (TREE_TYPE (s1), TREE_TYPE (s2), flags);
		    if (result == 0)
		      break;
		    if (result == 2)
		      needs_warning = true;

		    if (TREE_CODE (s1) == FIELD_DECL
			&& simple_cst_equal (DECL_FIELD_BIT_OFFSET (s1),
					     DECL_FIELD_BIT_OFFSET (s2)) != 1)
		      break;

		    ok = true;
		    break;
		  }
	    tagged_tu_seen_base = tts.next;
	    if (! ok)
	      return 0;
	  }
	return needs_warning ? 2 : 1;
      }

    case RECORD_TYPE:
      {
	struct tagged_tu_seen tts;

	tts.next = tagged_tu_seen_base;
	tts.t1 = t1;
	tts.t2 = t2;
	tagged_tu_seen_base = &tts;

	for (s1 = TYPE_FIELDS (t1), s2 = TYPE_FIELDS (t2);
	     s1 && s2;
	     s1 = TREE_CHAIN (s1), s2 = TREE_CHAIN (s2))
	  {
	    int result;
	    if (TREE_CODE (s1) != TREE_CODE (s2)
		|| DECL_NAME (s1) != DECL_NAME (s2))
	      break;
	    result = comptypes (TREE_TYPE (s1), TREE_TYPE (s2), flags);
	    if (result == 0)
	      break;
	    if (result == 2)
	      needs_warning = true;

	    if (TREE_CODE (s1) == FIELD_DECL
		&& simple_cst_equal (DECL_FIELD_BIT_OFFSET (s1),
				     DECL_FIELD_BIT_OFFSET (s2)) != 1)
	      break;
	  }
	tagged_tu_seen_base = tts.next;
	if (s1 && s2)
	  return 0;
	return needs_warning ? 2 : 1;
      }

    default:
      abort ();
    }
}

/* Return 1 if two function types F1 and F2 are compatible.
   If either type specifies no argument types,
   the other must specify a fixed number of self-promoting arg types.
   Otherwise, if one type specifies only the number of arguments,
   the other must specify that number of self-promoting arg types.
   Otherwise, the argument types must match.  */

static int
function_types_compatible_p (tree f1, tree f2, int flags)
{
  tree args1, args2;
  /* 1 if no need for warning yet, 2 if warning cause has been seen.  */
  int val = 1;
  int val1;
  tree ret1, ret2;

  ret1 = TREE_TYPE (f1);
  ret2 = TREE_TYPE (f2);

  /* 'volatile' qualifiers on a function's return type mean the function
     is noreturn.  */
  if (pedantic && TYPE_VOLATILE (ret1) != TYPE_VOLATILE (ret2))
    pedwarn ("function return types not compatible due to `volatile'");
  if (TYPE_VOLATILE (ret1))
    ret1 = build_qualified_type (TYPE_MAIN_VARIANT (ret1),
				 TYPE_QUALS (ret1) & ~TYPE_QUAL_VOLATILE);
  if (TYPE_VOLATILE (ret2))
    ret2 = build_qualified_type (TYPE_MAIN_VARIANT (ret2),
				 TYPE_QUALS (ret2) & ~TYPE_QUAL_VOLATILE);
  val = comptypes (ret1, ret2, flags);
  if (val == 0)
    return 0;

  args1 = TYPE_ARG_TYPES (f1);
  args2 = TYPE_ARG_TYPES (f2);

  /* An unspecified parmlist matches any specified parmlist
     whose argument types don't need default promotions.  */

  if (args1 == 0)
    {
      if (!self_promoting_args_p (args2))
	return 0;
      /* If one of these types comes from a non-prototype fn definition,
	 compare that with the other type's arglist.
	 If they don't match, ask for a warning (but no error).  */
      if (TYPE_ACTUAL_ARG_TYPES (f1)
	  && 1 != type_lists_compatible_p (args2, TYPE_ACTUAL_ARG_TYPES (f1),
					   flags))
	val = 2;
      return val;
    }
  if (args2 == 0)
    {
      if (!self_promoting_args_p (args1))
	return 0;
      if (TYPE_ACTUAL_ARG_TYPES (f2)
	  && 1 != type_lists_compatible_p (args1, TYPE_ACTUAL_ARG_TYPES (f2),
					   flags))
	val = 2;
      return val;
    }

  /* Both types have argument lists: compare them and propagate results.  */
  val1 = type_lists_compatible_p (args1, args2, flags);
  return val1 != 1 ? val1 : val;
}

/* Check two lists of types for compatibility,
   returning 0 for incompatible, 1 for compatible,
   or 2 for compatible with warning.  */

static int
type_lists_compatible_p (tree args1, tree args2, int flags)
{
  /* 1 if no need for warning yet, 2 if warning cause has been seen.  */
  int val = 1;
  int newval = 0;

  while (1)
    {
      if (args1 == 0 && args2 == 0)
	return val;
      /* If one list is shorter than the other,
	 they fail to match.  */
      if (args1 == 0 || args2 == 0)
	return 0;
      /* A null pointer instead of a type
	 means there is supposed to be an argument
	 but nothing is specified about what type it has.
	 So match anything that self-promotes.  */
      if (TREE_VALUE (args1) == 0)
	{
	  if (c_type_promotes_to (TREE_VALUE (args2)) != TREE_VALUE (args2))
	    return 0;
	}
      else if (TREE_VALUE (args2) == 0)
	{
	  if (c_type_promotes_to (TREE_VALUE (args1)) != TREE_VALUE (args1))
	    return 0;
	}
      /* If one of the lists has an error marker, ignore this arg.  */
      else if (TREE_CODE (TREE_VALUE (args1)) == ERROR_MARK
	       || TREE_CODE (TREE_VALUE (args2)) == ERROR_MARK)
	;
      else if (! (newval = comptypes (TYPE_MAIN_VARIANT (TREE_VALUE (args1)),
				      TYPE_MAIN_VARIANT (TREE_VALUE (args2)),
				      flags)))
	{
	  /* Allow  wait (union {union wait *u; int *i} *)
	     and  wait (union wait *)  to be compatible.  */
	  if (TREE_CODE (TREE_VALUE (args1)) == UNION_TYPE
	      && (TYPE_NAME (TREE_VALUE (args1)) == 0
		  || TYPE_TRANSPARENT_UNION (TREE_VALUE (args1)))
	      && TREE_CODE (TYPE_SIZE (TREE_VALUE (args1))) == INTEGER_CST
	      && tree_int_cst_equal (TYPE_SIZE (TREE_VALUE (args1)),
				     TYPE_SIZE (TREE_VALUE (args2))))
	    {
	      tree memb;
	      for (memb = TYPE_FIELDS (TREE_VALUE (args1));
		   memb; memb = TREE_CHAIN (memb))
		if (comptypes (TREE_TYPE (memb), TREE_VALUE (args2),
			       flags))
		  break;
	      if (memb == 0)
		return 0;
	    }
	  else if (TREE_CODE (TREE_VALUE (args2)) == UNION_TYPE
		   && (TYPE_NAME (TREE_VALUE (args2)) == 0
		       || TYPE_TRANSPARENT_UNION (TREE_VALUE (args2)))
		   && TREE_CODE (TYPE_SIZE (TREE_VALUE (args2))) == INTEGER_CST
		   && tree_int_cst_equal (TYPE_SIZE (TREE_VALUE (args2)),
					  TYPE_SIZE (TREE_VALUE (args1))))
	    {
	      tree memb;
	      for (memb = TYPE_FIELDS (TREE_VALUE (args2));
		   memb; memb = TREE_CHAIN (memb))
		if (comptypes (TREE_TYPE (memb), TREE_VALUE (args1),
			       flags))
		  break;
	      if (memb == 0)
		return 0;
	    }
	  else
	    return 0;
	}

      /* comptypes said ok, but record if it said to warn.  */
      if (newval > val)
	val = newval;

      args1 = TREE_CHAIN (args1);
      args2 = TREE_CHAIN (args2);
    }
}

/* Compute the size to increment a pointer by.  */

tree
c_size_in_bytes (tree type)
{
  enum tree_code code = TREE_CODE (type);

  if (code == FUNCTION_TYPE || code == VOID_TYPE || code == ERROR_MARK)
    return size_one_node;

  if (!COMPLETE_OR_VOID_TYPE_P (type))
    {
      error ("arithmetic on pointer to an incomplete type");
      return size_one_node;
    }

  /* Convert in case a char is more than one unit.  */
  return size_binop (CEIL_DIV_EXPR, TYPE_SIZE_UNIT (type),
		     size_int (TYPE_PRECISION (char_type_node)
			       / BITS_PER_UNIT));
}

/* Return either DECL or its known constant value (if it has one).  */

tree
decl_constant_value (tree decl)
{
  if (/* Don't change a variable array bound or initial value to a constant
	 in a place where a variable is invalid.  */
      current_function_decl != 0
      && ! TREE_THIS_VOLATILE (decl)
      && TREE_READONLY (decl)
      && DECL_INITIAL (decl) != 0
      && TREE_CODE (DECL_INITIAL (decl)) != ERROR_MARK
      /* This is invalid if initial value is not constant.
	 If it has either a function call, a memory reference,
	 or a variable, then re-evaluating it could give different results.  */
      && TREE_CONSTANT (DECL_INITIAL (decl))
      /* Check for cases where this is sub-optimal, even though valid.  */
      && TREE_CODE (DECL_INITIAL (decl)) != CONSTRUCTOR)
    return DECL_INITIAL (decl);
  return decl;
}

/* Return either DECL or its known constant value (if it has one), but
   return DECL if pedantic or DECL has mode BLKmode.  This is for
   bug-compatibility with the old behavior of decl_constant_value
   (before GCC 3.0); every use of this function is a bug and it should
   be removed before GCC 3.1.  It is not appropriate to use pedantic
   in a way that affects optimization, and BLKmode is probably not the
   right test for avoiding misoptimizations either.  */

static tree
decl_constant_value_for_broken_optimization (tree decl)
{
  if (pedantic || DECL_MODE (decl) == BLKmode)
    return decl;
  else
    return decl_constant_value (decl);
}


/* Perform the default conversion of arrays and functions to pointers.
   Return the result of converting EXP.  For any other expression, just
   return EXP.  */

static tree
default_function_array_conversion (tree exp)
{
  tree orig_exp;
  tree type = TREE_TYPE (exp);
  enum tree_code code = TREE_CODE (type);
  int not_lvalue = 0;

  /* Strip NON_LVALUE_EXPRs and no-op conversions, since we aren't using as
     an lvalue.

     Do not use STRIP_NOPS here!  It will remove conversions from pointer
     to integer and cause infinite recursion.  */
  orig_exp = exp;
  while (TREE_CODE (exp) == NON_LVALUE_EXPR
	 || (TREE_CODE (exp) == NOP_EXPR
	     && TREE_TYPE (TREE_OPERAND (exp, 0)) == TREE_TYPE (exp)))
    {
      if (TREE_CODE (exp) == NON_LVALUE_EXPR)
	not_lvalue = 1;
      exp = TREE_OPERAND (exp, 0);
    }

  /* Preserve the original expression code.  */
  if (IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (TREE_CODE (exp))))
    C_SET_EXP_ORIGINAL_CODE (exp, C_EXP_ORIGINAL_CODE (orig_exp));

  if (code == FUNCTION_TYPE)
    {
      return build_unary_op (ADDR_EXPR, exp, 0);
    }
  if (code == ARRAY_TYPE)
    {
      tree adr;
      tree restype = TREE_TYPE (type);
      tree ptrtype;
      int constp = 0;
      int volatilep = 0;
      int lvalue_array_p;

      if (TREE_CODE_CLASS (TREE_CODE (exp)) == 'r' || DECL_P (exp))
	{
	  constp = TREE_READONLY (exp);
	  volatilep = TREE_THIS_VOLATILE (exp);
	}

      if (TYPE_QUALS (type) || constp || volatilep)
	restype
	  = c_build_qualified_type (restype,
				    TYPE_QUALS (type)
				    | (constp * TYPE_QUAL_CONST)
				    | (volatilep * TYPE_QUAL_VOLATILE));

      if (TREE_CODE (exp) == INDIRECT_REF)
	return convert (TYPE_POINTER_TO (restype),
			TREE_OPERAND (exp, 0));

      if (TREE_CODE (exp) == COMPOUND_EXPR)
	{
	  tree op1 = default_conversion (TREE_OPERAND (exp, 1));
	  return build (COMPOUND_EXPR, TREE_TYPE (op1),
			TREE_OPERAND (exp, 0), op1);
	}

      lvalue_array_p = !not_lvalue && lvalue_p (exp);
      if (!flag_isoc99 && !lvalue_array_p)
	{
	  /* Before C99, non-lvalue arrays do not decay to pointers.
	     Normally, using such an array would be invalid; but it can
	     be used correctly inside sizeof or as a statement expression.
	     Thus, do not give an error here; an error will result later.  */
	  return exp;
	}

      ptrtype = build_pointer_type (restype);

      if (TREE_CODE (exp) == VAR_DECL)
	{
	  /* ??? This is not really quite correct
	     in that the type of the operand of ADDR_EXPR
	     is not the target type of the type of the ADDR_EXPR itself.
	     Question is, can this lossage be avoided?  */
	  adr = build1 (ADDR_EXPR, ptrtype, exp);
	  if (!c_mark_addressable (exp))
	    return error_mark_node;
	  TREE_CONSTANT (adr) = staticp (exp);
	  TREE_SIDE_EFFECTS (adr) = 0;   /* Default would be, same as EXP.  */
	  return adr;
	}
      /* This way is better for a COMPONENT_REF since it can
	 simplify the offset for a component.  */
      adr = build_unary_op (ADDR_EXPR, exp, 1);
      return convert (ptrtype, adr);
    }
  return exp;
}

/* Perform default promotions for C data used in expressions.
   Arrays and functions are converted to pointers;
   enumeral types or short or char, to int.
   In addition, manifest constants symbols are replaced by their values.  */

tree
default_conversion (tree exp)
{
  tree orig_exp;
  tree type = TREE_TYPE (exp);
  enum tree_code code = TREE_CODE (type);

  if (code == FUNCTION_TYPE || code == ARRAY_TYPE)
    return default_function_array_conversion (exp);

  /* Constants can be used directly unless they're not loadable.  */
  if (TREE_CODE (exp) == CONST_DECL)
    exp = DECL_INITIAL (exp);

  /* Replace a nonvolatile const static variable with its value unless
     it is an array, in which case we must be sure that taking the
     address of the array produces consistent results.  */
  else if (optimize && TREE_CODE (exp) == VAR_DECL && code != ARRAY_TYPE)
    {
      exp = decl_constant_value_for_broken_optimization (exp);
      type = TREE_TYPE (exp);
    }

  /* Strip NON_LVALUE_EXPRs and no-op conversions, since we aren't using as
     an lvalue.

     Do not use STRIP_NOPS here!  It will remove conversions from pointer
     to integer and cause infinite recursion.  */
  orig_exp = exp;
  while (TREE_CODE (exp) == NON_LVALUE_EXPR
	 || (TREE_CODE (exp) == NOP_EXPR
	     && TREE_TYPE (TREE_OPERAND (exp, 0)) == TREE_TYPE (exp)))
    exp = TREE_OPERAND (exp, 0);

  /* Preserve the original expression code.  */
  if (IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (TREE_CODE (exp))))
    C_SET_EXP_ORIGINAL_CODE (exp, C_EXP_ORIGINAL_CODE (orig_exp));

  /* Normally convert enums to int,
     but convert wide enums to something wider.  */
  if (code == ENUMERAL_TYPE)
    {
      type = c_common_type_for_size (MAX (TYPE_PRECISION (type),
					  TYPE_PRECISION (integer_type_node)),
				     ((TYPE_PRECISION (type)
				       >= TYPE_PRECISION (integer_type_node))
				      && TREE_UNSIGNED (type)));

      return convert (type, exp);
    }

  if (TREE_CODE (exp) == COMPONENT_REF
      && DECL_C_BIT_FIELD (TREE_OPERAND (exp, 1))
      /* If it's thinner than an int, promote it like a
	 c_promoting_integer_type_p, otherwise leave it alone.  */
      && 0 > compare_tree_int (DECL_SIZE (TREE_OPERAND (exp, 1)),
			       TYPE_PRECISION (integer_type_node)))
    return convert (integer_type_node, exp);

  if (c_promoting_integer_type_p (type))
    {
      /* Preserve unsignedness if not really getting any wider.  */
      if (TREE_UNSIGNED (type)
	  && TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node))
	return convert (unsigned_type_node, exp);

      return convert (integer_type_node, exp);
    }

  if (code == VOID_TYPE)
    {
      error ("void value not ignored as it ought to be");
      return error_mark_node;
    }
  return exp;
}

/* Look up COMPONENT in a structure or union DECL.

   If the component name is not found, returns NULL_TREE.  Otherwise,
   the return value is a TREE_LIST, with each TREE_VALUE a FIELD_DECL
   stepping down the chain to the component, which is in the last
   TREE_VALUE of the list.  Normally the list is of length one, but if
   the component is embedded within (nested) anonymous structures or
   unions, the list steps down the chain to the component.  */

static tree
lookup_field (tree decl, tree component)
{
  tree type = TREE_TYPE (decl);
  tree field;

  /* If TYPE_LANG_SPECIFIC is set, then it is a sorted array of pointers
     to the field elements.  Use a binary search on this array to quickly
     find the element.  Otherwise, do a linear search.  TYPE_LANG_SPECIFIC
     will always be set for structures which have many elements.  */

  if (TYPE_LANG_SPECIFIC (type))
    {
      int bot, top, half;
      tree *field_array = &TYPE_LANG_SPECIFIC (type)->s->elts[0];

      field = TYPE_FIELDS (type);
      bot = 0;
      top = TYPE_LANG_SPECIFIC (type)->s->len;
      while (top - bot > 1)
	{
	  half = (top - bot + 1) >> 1;
	  field = field_array[bot+half];

	  if (DECL_NAME (field) == NULL_TREE)
	    {
	      /* Step through all anon unions in linear fashion.  */
	      while (DECL_NAME (field_array[bot]) == NULL_TREE)
		{
		  field = field_array[bot++];
		  if (TREE_CODE (TREE_TYPE (field)) == RECORD_TYPE
		      || TREE_CODE (TREE_TYPE (field)) == UNION_TYPE)
		    {
		      tree anon = lookup_field (field, component);

		      if (anon)
			return tree_cons (NULL_TREE, field, anon);
		    }
		}

	      /* Entire record is only anon unions.  */
	      if (bot > top)
		return NULL_TREE;

	      /* Restart the binary search, with new lower bound.  */
	      continue;
	    }

	  if (DECL_NAME (field) == component)
	    break;
	  if (DECL_NAME (field) < component)
	    bot += half;
	  else
	    top = bot + half;
	}

      if (DECL_NAME (field_array[bot]) == component)
	field = field_array[bot];
      else if (DECL_NAME (field) != component)
	return NULL_TREE;
    }
  else
    {
      for (field = TYPE_FIELDS (type); field; field = TREE_CHAIN (field))
	{
	  if (DECL_NAME (field) == NULL_TREE
	      && (TREE_CODE (TREE_TYPE (field)) == RECORD_TYPE
		  || TREE_CODE (TREE_TYPE (field)) == UNION_TYPE))
	    {
	      tree anon = lookup_field (field, component);

	      if (anon)
		return tree_cons (NULL_TREE, field, anon);
	    }

	  if (DECL_NAME (field) == component)
	    break;
	}

      if (field == NULL_TREE)
	return NULL_TREE;
    }

  return tree_cons (NULL_TREE, field, NULL_TREE);
}

/* Make an expression to refer to the COMPONENT field of
   structure or union value DATUM.  COMPONENT is an IDENTIFIER_NODE.  */

tree
build_component_ref (tree datum, tree component)
{
  tree type = TREE_TYPE (datum);
  enum tree_code code = TREE_CODE (type);
  tree field = NULL;
  tree ref;

  /* See if there is a field or component with name COMPONENT.  */

  if (code == RECORD_TYPE || code == UNION_TYPE)
    {
      if (!COMPLETE_TYPE_P (type))
	{
	  c_incomplete_type_error (NULL_TREE, type);
	  return error_mark_node;
	}

      field = lookup_field (datum, component);

      if (!field)
	{
	  error ("%s has no member named `%s'",
		 code == RECORD_TYPE ? "structure" : "union",
		 IDENTIFIER_POINTER (component));
	  return error_mark_node;
	}

      /* Chain the COMPONENT_REFs if necessary down to the FIELD.
	 This might be better solved in future the way the C++ front
	 end does it - by giving the anonymous entities each a
	 separate name and type, and then have build_component_ref
	 recursively call itself.  We can't do that here.  */
      do
	{
	  tree subdatum = TREE_VALUE (field);

	  if (TREE_TYPE (subdatum) == error_mark_node)
	    return error_mark_node;

	  ref = build (COMPONENT_REF, TREE_TYPE (subdatum), datum, subdatum);
	  if (TREE_READONLY (datum) || TREE_READONLY (subdatum))
	    TREE_READONLY (ref) = 1;
	  if (TREE_THIS_VOLATILE (datum) || TREE_THIS_VOLATILE (subdatum))
	    TREE_THIS_VOLATILE (ref) = 1;

	  if (TREE_DEPRECATED (subdatum))
	    warn_deprecated_use (subdatum);

	  datum = ref;

	  field = TREE_CHAIN (field);
	}
      while (field);

      return ref;
    }
  else if (code != ERROR_MARK)
    error ("request for member `%s' in something not a structure or union",
	    IDENTIFIER_POINTER (component));

  return error_mark_node;
}

/* Given an expression PTR for a pointer, return an expression
   for the value pointed to.
   ERRORSTRING is the name of the operator to appear in error messages.  */

tree
build_indirect_ref (tree ptr, const char *errorstring)
{
  tree pointer = default_conversion (ptr);
  tree type = TREE_TYPE (pointer);

  if (TREE_CODE (type) == POINTER_TYPE)
    {
      if (TREE_CODE (pointer) == ADDR_EXPR
	  && (TREE_TYPE (TREE_OPERAND (pointer, 0))
	      == TREE_TYPE (type)))
	return TREE_OPERAND (pointer, 0);
      else
	{
	  tree t = TREE_TYPE (type);
	  tree ref = build1 (INDIRECT_REF, TYPE_MAIN_VARIANT (t), pointer);

	  if (!COMPLETE_OR_VOID_TYPE_P (t) && TREE_CODE (t) != ARRAY_TYPE)
	    {
	      error ("dereferencing pointer to incomplete type");
	      return error_mark_node;
	    }
	  if (VOID_TYPE_P (t) && skip_evaluation == 0)
	    warning ("dereferencing `void *' pointer");

	  /* We *must* set TREE_READONLY when dereferencing a pointer to const,
	     so that we get the proper error message if the result is used
	     to assign to.  Also, &* is supposed to be a no-op.
	     And ANSI C seems to specify that the type of the result
	     should be the const type.  */
	  /* A de-reference of a pointer to const is not a const.  It is valid
	     to change it via some other pointer.  */
	  TREE_READONLY (ref) = TYPE_READONLY (t);
	  TREE_SIDE_EFFECTS (ref)
	    = TYPE_VOLATILE (t) || TREE_SIDE_EFFECTS (pointer);
	  TREE_THIS_VOLATILE (ref) = TYPE_VOLATILE (t);
	  return ref;
	}
    }
  else if (TREE_CODE (pointer) != ERROR_MARK)
    error ("invalid type argument of `%s'", errorstring);
  return error_mark_node;
}

/* This handles expressions of the form "a[i]", which denotes
   an array reference.

   This is logically equivalent in C to *(a+i), but we may do it differently.
   If A is a variable or a member, we generate a primitive ARRAY_REF.
   This avoids forcing the array out of registers, and can work on
   arrays that are not lvalues (for example, members of structures returned
   by functions).  */

tree
build_array_ref (tree array, tree index)
{
  if (index == 0)
    {
      error ("subscript missing in array reference");
      return error_mark_node;
    }

  if (TREE_TYPE (array) == error_mark_node
      || TREE_TYPE (index) == error_mark_node)
    return error_mark_node;

  if (TREE_CODE (TREE_TYPE (array)) == ARRAY_TYPE
      && TREE_CODE (array) != INDIRECT_REF)
    {
      tree rval, type;

      /* Subscripting with type char is likely to lose
	 on a machine where chars are signed.
	 So warn on any machine, but optionally.
	 Don't warn for unsigned char since that type is safe.
	 Don't warn for signed char because anyone who uses that
	 must have done so deliberately.  */
      if (warn_char_subscripts
	  && TYPE_MAIN_VARIANT (TREE_TYPE (index)) == char_type_node)
	warning ("array subscript has type `char'");

      /* Apply default promotions *after* noticing character types.  */
      index = default_conversion (index);

      /* Require integer *after* promotion, for sake of enums.  */
      if (TREE_CODE (TREE_TYPE (index)) != INTEGER_TYPE)
	{
	  error ("array subscript is not an integer");
	  return error_mark_node;
	}

      /* An array that is indexed by a non-constant
	 cannot be stored in a register; we must be able to do
	 address arithmetic on its address.
	 Likewise an array of elements of variable size.  */
      if (TREE_CODE (index) != INTEGER_CST
	  || (COMPLETE_TYPE_P (TREE_TYPE (TREE_TYPE (array)))
	      && TREE_CODE (TYPE_SIZE (TREE_TYPE (TREE_TYPE (array)))) != INTEGER_CST))
	{
	  if (!c_mark_addressable (array))
	    return error_mark_node;
	}
      /* An array that is indexed by a constant value which is not within
	 the array bounds cannot be stored in a register either; because we
	 would get a crash in store_bit_field/extract_bit_field when trying
	 to access a non-existent part of the register.  */
      if (TREE_CODE (index) == INTEGER_CST
	  && TYPE_VALUES (TREE_TYPE (array))
	  && ! int_fits_type_p (index, TYPE_VALUES (TREE_TYPE (array))))
	{
	  if (!c_mark_addressable (array))
	    return error_mark_node;
	}

      if (pedantic)
	{
	  tree foo = array;
	  while (TREE_CODE (foo) == COMPONENT_REF)
	    foo = TREE_OPERAND (foo, 0);
	  if (TREE_CODE (foo) == VAR_DECL && DECL_REGISTER (foo))
	    pedwarn ("ISO C forbids subscripting `register' array");
	  else if (! flag_isoc99 && ! lvalue_p (foo))
	    pedwarn ("ISO C90 forbids subscripting non-lvalue array");
	}

      type = TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (array)));
      rval = build (ARRAY_REF, type, array, index);
      /* Array ref is const/volatile if the array elements are
         or if the array is.  */
      TREE_READONLY (rval)
	|= (TYPE_READONLY (TREE_TYPE (TREE_TYPE (array)))
	    | TREE_READONLY (array));
      TREE_SIDE_EFFECTS (rval)
	|= (TYPE_VOLATILE (TREE_TYPE (TREE_TYPE (array)))
	    | TREE_SIDE_EFFECTS (array));
      TREE_THIS_VOLATILE (rval)
	|= (TYPE_VOLATILE (TREE_TYPE (TREE_TYPE (array)))
	    /* This was added by rms on 16 Nov 91.
	       It fixes  vol struct foo *a;  a->elts[1]
	       in an inline function.
	       Hope it doesn't break something else.  */
	    | TREE_THIS_VOLATILE (array));
      return require_complete_type (fold (rval));
    }

  {
    tree ar = default_conversion (array);
    tree ind = default_conversion (index);

    /* Do the same warning check as above, but only on the part that's
       syntactically the index and only if it is also semantically
       the index.  */
    if (warn_char_subscripts
	&& TREE_CODE (TREE_TYPE (index)) == INTEGER_TYPE
	&& TYPE_MAIN_VARIANT (TREE_TYPE (index)) == char_type_node)
      warning ("subscript has type `char'");

    /* Put the integer in IND to simplify error checking.  */
    if (TREE_CODE (TREE_TYPE (ar)) == INTEGER_TYPE)
      {
	tree temp = ar;
	ar = ind;
	ind = temp;
      }

    if (ar == error_mark_node)
      return ar;

    if (TREE_CODE (TREE_TYPE (ar)) != POINTER_TYPE
	|| TREE_CODE (TREE_TYPE (TREE_TYPE (ar))) == FUNCTION_TYPE)
      {
	error ("subscripted value is neither array nor pointer");
	return error_mark_node;
      }
    if (TREE_CODE (TREE_TYPE (ind)) != INTEGER_TYPE)
      {
	error ("array subscript is not an integer");
	return error_mark_node;
      }

    return build_indirect_ref (build_binary_op (PLUS_EXPR, ar, ind, 0),
			       "array indexing");
  }
}

/* Build an external reference to identifier ID.  FUN indicates
   whether this will be used for a function call.  */
tree
build_external_ref (tree id, int fun)
{
  tree ref;
  tree decl = lookup_name (id);
  tree objc_ivar = lookup_objc_ivar (id);

  if (decl && decl != error_mark_node)
    {
      /* Properly declared variable or function reference.  */
      if (!objc_ivar)
	ref = decl;
      else if (decl != objc_ivar && !DECL_FILE_SCOPE_P (decl))
	{
	  warning ("local declaration of `%s' hides instance variable",
		   IDENTIFIER_POINTER (id));
	  ref = decl;
	}
      else
	ref = objc_ivar;
    }
  else if (objc_ivar)
    ref = objc_ivar;
  else if (fun)
    /* Implicit function declaration.  */
    ref = implicitly_declare (id);
  else if (decl == error_mark_node)
    /* Don't complain about something that's already been
       complained about.  */
    return error_mark_node;
  else
    {
      undeclared_variable (id);
      return error_mark_node;
    }

  if (TREE_TYPE (ref) == error_mark_node)
    return error_mark_node;

  if (TREE_DEPRECATED (ref))
    warn_deprecated_use (ref);

  if (!skip_evaluation)
    assemble_external (ref);
  TREE_USED (ref) = 1;

  if (TREE_CODE (ref) == CONST_DECL)
    {
      ref = DECL_INITIAL (ref);
      TREE_CONSTANT (ref) = 1;
    }
  else if (current_function_decl != 0
	   && !DECL_FILE_SCOPE_P (current_function_decl)
	   && (TREE_CODE (ref) == VAR_DECL
	       || TREE_CODE (ref) == PARM_DECL
	       || TREE_CODE (ref) == FUNCTION_DECL))
    {
      tree context = decl_function_context (ref);

      if (context != 0 && context != current_function_decl)
	DECL_NONLOCAL (ref) = 1;
    }

  return ref;
}

/* Build a function call to function FUNCTION with parameters PARAMS.
   PARAMS is a list--a chain of TREE_LIST nodes--in which the
   TREE_VALUE of each node is a parameter-expression.
   FUNCTION's data type may be a function type or a pointer-to-function.  */

tree
build_function_call (tree function, tree params)
{
  tree fntype, fundecl = 0;
  tree coerced_params;
  tree name = NULL_TREE, result;
  tree tem;

  /* Strip NON_LVALUE_EXPRs, etc., since we aren't using as an lvalue.  */
  STRIP_TYPE_NOPS (function);

  /* Convert anything with function type to a pointer-to-function.  */
  if (TREE_CODE (function) == FUNCTION_DECL)
    {
      name = DECL_NAME (function);

      /* Differs from default_conversion by not setting TREE_ADDRESSABLE
	 (because calling an inline function does not mean the function
	 needs to be separately compiled).  */
      fntype = build_type_variant (TREE_TYPE (function),
				   TREE_READONLY (function),
				   TREE_THIS_VOLATILE (function));
      fundecl = function;
      function = build1 (ADDR_EXPR, build_pointer_type (fntype), function);
    }
  else
    function = default_conversion (function);

  fntype = TREE_TYPE (function);

  if (TREE_CODE (fntype) == ERROR_MARK)
    return error_mark_node;

  if (!(TREE_CODE (fntype) == POINTER_TYPE
	&& TREE_CODE (TREE_TYPE (fntype)) == FUNCTION_TYPE))
    {
      error ("called object is not a function");
      return error_mark_node;
    }

  if (fundecl && TREE_THIS_VOLATILE (fundecl))
    current_function_returns_abnormally = 1;

  /* fntype now gets the type of function pointed to.  */
  fntype = TREE_TYPE (fntype);

  /* Check that the function is called through a compatible prototype.
     If it is not, replace the call by a trap, wrapped up in a compound
     expression if necessary.  This has the nice side-effect to prevent
     the tree-inliner from generating invalid assignment trees which may
     blow up in the RTL expander later.

     ??? This doesn't work for Objective-C because objc_comptypes
     refuses to compare function prototypes, yet the compiler appears
     to build calls that are flagged as invalid by C's comptypes.  */
  if (! c_dialect_objc ()
      && TREE_CODE (function) == NOP_EXPR
      && TREE_CODE (tem = TREE_OPERAND (function, 0)) == ADDR_EXPR
      && TREE_CODE (tem = TREE_OPERAND (tem, 0)) == FUNCTION_DECL
      && ! comptypes (fntype, TREE_TYPE (tem), COMPARE_STRICT))
    {
      tree return_type = TREE_TYPE (fntype);
      tree trap = build_function_call (built_in_decls[BUILT_IN_TRAP],
				       NULL_TREE);

      /* This situation leads to run-time undefined behavior.  We can't,
	 therefore, simply error unless we can prove that all possible
	 executions of the program must execute the code.  */
      warning ("function called through a non-compatible type");

      /* We can, however, treat "undefined" any way we please.
	 Call abort to encourage the user to fix the program.  */
      inform ("if this code is reached, the program will abort");

      if (VOID_TYPE_P (return_type))
	return trap;
      else
	{
	  tree rhs;

	  if (AGGREGATE_TYPE_P (return_type))
	    rhs = build_compound_literal (return_type,
					  build_constructor (return_type,
							     NULL_TREE));
	  else
	    rhs = fold (build1 (NOP_EXPR, return_type, integer_zero_node));

	  return build (COMPOUND_EXPR, return_type, trap, rhs);
	}
    }

  /* Convert the parameters to the types declared in the
     function prototype, or apply default promotions.  */

  coerced_params
    = convert_arguments (TYPE_ARG_TYPES (fntype), params, name, fundecl);

  /* Check that the arguments to the function are valid.  */

  check_function_arguments (TYPE_ATTRIBUTES (fntype), coerced_params);

  /* Recognize certain built-in functions so we can make tree-codes
     other than CALL_EXPR.  We do this when it enables fold-const.c
     to do something useful.  */

  if (TREE_CODE (function) == ADDR_EXPR
      && TREE_CODE (TREE_OPERAND (function, 0)) == FUNCTION_DECL
      && DECL_BUILT_IN (TREE_OPERAND (function, 0)))
    {
      result = expand_tree_builtin (TREE_OPERAND (function, 0),
				    params, coerced_params);
      if (result)
	return result;
    }

  result = build (CALL_EXPR, TREE_TYPE (fntype),
		  function, coerced_params, NULL_TREE);
  TREE_SIDE_EFFECTS (result) = 1;

  if (require_constant_value)
    {
      result = fold_initializer (result);

      if (TREE_CONSTANT (result)
	  && (name == NULL_TREE
	      || strncmp (IDENTIFIER_POINTER (name), "__builtin_", 10) != 0))
	pedwarn_init ("initializer element is not constant");
    }
  else
    result = fold (result);

  if (VOID_TYPE_P (TREE_TYPE (result)))
    return result;
  return require_complete_type (result);
}

/* Convert the argument expressions in the list VALUES
   to the types in the list TYPELIST.  The result is a list of converted
   argument expressions.

   If TYPELIST is exhausted, or when an element has NULL as its type,
   perform the default conversions.

   PARMLIST is the chain of parm decls for the function being called.
   It may be 0, if that info is not available.
   It is used only for generating error messages.

   NAME is an IDENTIFIER_NODE or 0.  It is used only for error messages.

   This is also where warnings about wrong number of args are generated.

   Both VALUES and the returned value are chains of TREE_LIST nodes
   with the elements of the list in the TREE_VALUE slots of those nodes.  */

static tree
convert_arguments (tree typelist, tree values, tree name, tree fundecl)
{
  tree typetail, valtail;
  tree result = NULL;
  int parmnum;

  /* Scan the given expressions and types, producing individual
     converted arguments and pushing them on RESULT in reverse order.  */

  for (valtail = values, typetail = typelist, parmnum = 0;
       valtail;
       valtail = TREE_CHAIN (valtail), parmnum++)
    {
      tree type = typetail ? TREE_VALUE (typetail) : 0;
      tree val = TREE_VALUE (valtail);

      if (type == void_type_node)
	{
	  if (name)
	    error ("too many arguments to function `%s'",
		   IDENTIFIER_POINTER (name));
	  else
	    error ("too many arguments to function");
	  break;
	}

      /* Strip NON_LVALUE_EXPRs since we aren't using as an lvalue.  */
      /* Do not use STRIP_NOPS here!  We do not want an enumerator with value 0
	 to convert automatically to a pointer.  */
      if (TREE_CODE (val) == NON_LVALUE_EXPR)
	val = TREE_OPERAND (val, 0);

      val = default_function_array_conversion (val);

      val = require_complete_type (val);

      if (type != 0)
	{
	  /* Formal parm type is specified by a function prototype.  */
	  tree parmval;

	  if (!COMPLETE_TYPE_P (type))
	    {
	      error ("type of formal parameter %d is incomplete", parmnum + 1);
	      parmval = val;
	    }
	  else
	    {
	      /* Optionally warn about conversions that
		 differ from the default conversions.  */
	      if (warn_conversion || warn_traditional)
		{
		  int formal_prec = TYPE_PRECISION (type);

		  if (INTEGRAL_TYPE_P (type)
		      && TREE_CODE (TREE_TYPE (val)) == REAL_TYPE)
		    warn_for_assignment ("%s as integer rather than floating due to prototype", (char *) 0, name, parmnum + 1);
		  if (INTEGRAL_TYPE_P (type)
		      && TREE_CODE (TREE_TYPE (val)) == COMPLEX_TYPE)
		    warn_for_assignment ("%s as integer rather than complex due to prototype", (char *) 0, name, parmnum + 1);
		  else if (TREE_CODE (type) == COMPLEX_TYPE
			   && TREE_CODE (TREE_TYPE (val)) == REAL_TYPE)
		    warn_for_assignment ("%s as complex rather than floating due to prototype", (char *) 0, name, parmnum + 1);
		  else if (TREE_CODE (type) == REAL_TYPE
			   && INTEGRAL_TYPE_P (TREE_TYPE (val)))
		    warn_for_assignment ("%s as floating rather than integer due to prototype", (char *) 0, name, parmnum + 1);
		  else if (TREE_CODE (type) == COMPLEX_TYPE
			   && INTEGRAL_TYPE_P (TREE_TYPE (val)))
		    warn_for_assignment ("%s as complex rather than integer due to prototype", (char *) 0, name, parmnum + 1);
		  else if (TREE_CODE (type) == REAL_TYPE
			   && TREE_CODE (TREE_TYPE (val)) == COMPLEX_TYPE)
		    warn_for_assignment ("%s as floating rather than complex due to prototype", (char *) 0, name, parmnum + 1);
		  /* ??? At some point, messages should be written about
		     conversions between complex types, but that's too messy
		     to do now.  */
		  else if (TREE_CODE (type) == REAL_TYPE
			   && TREE_CODE (TREE_TYPE (val)) == REAL_TYPE)
		    {
		      /* Warn if any argument is passed as `float',
			 since without a prototype it would be `double'.  */
		      if (formal_prec == TYPE_PRECISION (float_type_node))
			warn_for_assignment ("%s as `float' rather than `double' due to prototype", (char *) 0, name, parmnum + 1);
		    }
		  /* Detect integer changing in width or signedness.
		     These warnings are only activated with
		     -Wconversion, not with -Wtraditional.  */
		  else if (warn_conversion && INTEGRAL_TYPE_P (type)
			   && INTEGRAL_TYPE_P (TREE_TYPE (val)))
		    {
		      tree would_have_been = default_conversion (val);
		      tree type1 = TREE_TYPE (would_have_been);

		      if (TREE_CODE (type) == ENUMERAL_TYPE
			  && (TYPE_MAIN_VARIANT (type)
			      == TYPE_MAIN_VARIANT (TREE_TYPE (val))))
			/* No warning if function asks for enum
			   and the actual arg is that enum type.  */
			;
		      else if (formal_prec != TYPE_PRECISION (type1))
			warn_for_assignment ("%s with different width due to prototype", (char *) 0, name, parmnum + 1);
		      else if (TREE_UNSIGNED (type) == TREE_UNSIGNED (type1))
			;
		      /* Don't complain if the formal parameter type
			 is an enum, because we can't tell now whether
			 the value was an enum--even the same enum.  */
		      else if (TREE_CODE (type) == ENUMERAL_TYPE)
			;
		      else if (TREE_CODE (val) == INTEGER_CST
			       && int_fits_type_p (val, type))
			/* Change in signedness doesn't matter
			   if a constant value is unaffected.  */
			;
		      /* Likewise for a constant in a NOP_EXPR.  */
		      else if (TREE_CODE (val) == NOP_EXPR
			       && TREE_CODE (TREE_OPERAND (val, 0)) == INTEGER_CST
			       && int_fits_type_p (TREE_OPERAND (val, 0), type))
			;
		      /* If the value is extended from a narrower
			 unsigned type, it doesn't matter whether we
			 pass it as signed or unsigned; the value
			 certainly is the same either way.  */
		      else if (TYPE_PRECISION (TREE_TYPE (val)) < TYPE_PRECISION (type)
			       && TREE_UNSIGNED (TREE_TYPE (val)))
			;
		      else if (TREE_UNSIGNED (type))
			warn_for_assignment ("%s as unsigned due to prototype", (char *) 0, name, parmnum + 1);
		      else
			warn_for_assignment ("%s as signed due to prototype", (char *) 0, name, parmnum + 1);
		    }
		}

	      parmval = convert_for_assignment (type, val,
					        (char *) 0, /* arg passing  */
						fundecl, name, parmnum + 1);

	      if (targetm.calls.promote_prototypes (fundecl ? TREE_TYPE (fundecl) : 0)
		  && INTEGRAL_TYPE_P (type)
		  && (TYPE_PRECISION (type) < TYPE_PRECISION (integer_type_node)))
		parmval = default_conversion (parmval);
	    }
	  result = tree_cons (NULL_TREE, parmval, result);
	}
      else if (TREE_CODE (TREE_TYPE (val)) == REAL_TYPE
               && (TYPE_PRECISION (TREE_TYPE (val))
	           < TYPE_PRECISION (double_type_node)))
	/* Convert `float' to `double'.  */
	result = tree_cons (NULL_TREE, convert (double_type_node, val), result);
      else
	/* Convert `short' and `char' to full-size `int'.  */
	result = tree_cons (NULL_TREE, default_conversion (val), result);

      if (typetail)
	typetail = TREE_CHAIN (typetail);
    }

  if (typetail != 0 && TREE_VALUE (typetail) != void_type_node)
    {
      if (name)
	error ("too few arguments to function `%s'",
	       IDENTIFIER_POINTER (name));
      else
	error ("too few arguments to function");
    }

  return nreverse (result);
}

/* This is the entry point used by the parser
   for binary operators in the input.
   In addition to constructing the expression,
   we check for operands that were written with other binary operators
   in a way that is likely to confuse the user.  */

tree
parser_build_binary_op (enum tree_code code, tree arg1, tree arg2)
{
  tree result = build_binary_op (code, arg1, arg2, 1);

  char class;
  char class1 = TREE_CODE_CLASS (TREE_CODE (arg1));
  char class2 = TREE_CODE_CLASS (TREE_CODE (arg2));
  enum tree_code code1 = ERROR_MARK;
  enum tree_code code2 = ERROR_MARK;

  if (TREE_CODE (result) == ERROR_MARK)
    return error_mark_node;

  if (IS_EXPR_CODE_CLASS (class1))
    code1 = C_EXP_ORIGINAL_CODE (arg1);
  if (IS_EXPR_CODE_CLASS (class2))
    code2 = C_EXP_ORIGINAL_CODE (arg2);

  /* Check for cases such as x+y<<z which users are likely
     to misinterpret.  If parens are used, C_EXP_ORIGINAL_CODE
     is cleared to prevent these warnings.  */
  if (warn_parentheses)
    {
      if (code == LSHIFT_EXPR || code == RSHIFT_EXPR)
	{
	  if (code1 == PLUS_EXPR || code1 == MINUS_EXPR
	      || code2 == PLUS_EXPR || code2 == MINUS_EXPR)
	    warning ("suggest parentheses around + or - inside shift");
	}

      if (code == TRUTH_ORIF_EXPR)
	{
	  if (code1 == TRUTH_ANDIF_EXPR
	      || code2 == TRUTH_ANDIF_EXPR)
	    warning ("suggest parentheses around && within ||");
	}

      if (code == BIT_IOR_EXPR)
	{
	  if (code1 == BIT_AND_EXPR || code1 == BIT_XOR_EXPR
	      || code1 == PLUS_EXPR || code1 == MINUS_EXPR
	      || code2 == BIT_AND_EXPR || code2 == BIT_XOR_EXPR
	      || code2 == PLUS_EXPR || code2 == MINUS_EXPR)
	    warning ("suggest parentheses around arithmetic in operand of |");
	  /* Check cases like x|y==z */
	  if (TREE_CODE_CLASS (code1) == '<' || TREE_CODE_CLASS (code2) == '<')
	    warning ("suggest parentheses around comparison in operand of |");
	}

      if (code == BIT_XOR_EXPR)
	{
	  if (code1 == BIT_AND_EXPR
	      || code1 == PLUS_EXPR || code1 == MINUS_EXPR
	      || code2 == BIT_AND_EXPR
	      || code2 == PLUS_EXPR || code2 == MINUS_EXPR)
	    warning ("suggest parentheses around arithmetic in operand of ^");
	  /* Check cases like x^y==z */
	  if (TREE_CODE_CLASS (code1) == '<' || TREE_CODE_CLASS (code2) == '<')
	    warning ("suggest parentheses around comparison in operand of ^");
	}

      if (code == BIT_AND_EXPR)
	{
	  if (code1 == PLUS_EXPR || code1 == MINUS_EXPR
	      || code2 == PLUS_EXPR || code2 == MINUS_EXPR)
	    warning ("suggest parentheses around + or - in operand of &");
	  /* Check cases like x&y==z */
	  if (TREE_CODE_CLASS (code1) == '<' || TREE_CODE_CLASS (code2) == '<')
	    warning ("suggest parentheses around comparison in operand of &");
	}
    }

  /* Similarly, check for cases like 1<=i<=10 that are probably errors.  */
  if (TREE_CODE_CLASS (code) == '<' && extra_warnings
      && (TREE_CODE_CLASS (code1) == '<' || TREE_CODE_CLASS (code2) == '<'))
    warning ("comparisons like X<=Y<=Z do not have their mathematical meaning");

  unsigned_conversion_warning (result, arg1);
  unsigned_conversion_warning (result, arg2);
  overflow_warning (result);

  class = TREE_CODE_CLASS (TREE_CODE (result));

  /* Record the code that was specified in the source,
     for the sake of warnings about confusing nesting.  */
  if (IS_EXPR_CODE_CLASS (class))
    C_SET_EXP_ORIGINAL_CODE (result, code);
  else
    {
      int flag = TREE_CONSTANT (result);
      /* We used to use NOP_EXPR rather than NON_LVALUE_EXPR
	 so that convert_for_assignment wouldn't strip it.
	 That way, we got warnings for things like p = (1 - 1).
	 But it turns out we should not get those warnings.  */
      result = build1 (NON_LVALUE_EXPR, TREE_TYPE (result), result);
      C_SET_EXP_ORIGINAL_CODE (result, code);
      TREE_CONSTANT (result) = flag;
    }

  return result;
}


/* Return true if `t' is known to be non-negative.  */

int
c_tree_expr_nonnegative_p (tree t)
{
  if (TREE_CODE (t) == STMT_EXPR)
    {
      t = COMPOUND_BODY (STMT_EXPR_STMT (t));

      /* Find the last statement in the chain, ignoring the final
	     * scope statement */
      while (TREE_CHAIN (t) != NULL_TREE
             && TREE_CODE (TREE_CHAIN (t)) != SCOPE_STMT)
        t = TREE_CHAIN (t);
      return tree_expr_nonnegative_p (TREE_OPERAND (t, 0));
    }
  return tree_expr_nonnegative_p (t);
}

/* Return a tree for the difference of pointers OP0 and OP1.
   The resulting tree has type int.  */

static tree
pointer_diff (tree op0, tree op1)
{
  tree result, folded;
  tree restype = ptrdiff_type_node;

  tree target_type = TREE_TYPE (TREE_TYPE (op0));
  tree con0, con1, lit0, lit1;
  tree orig_op1 = op1;

  if (pedantic || warn_pointer_arith)
    {
      if (TREE_CODE (target_type) == VOID_TYPE)
	pedwarn ("pointer of type `void *' used in subtraction");
      if (TREE_CODE (target_type) == FUNCTION_TYPE)
	pedwarn ("pointer to a function used in subtraction");
    }

  /* If the conversion to ptrdiff_type does anything like widening or
     converting a partial to an integral mode, we get a convert_expression
     that is in the way to do any simplifications.
     (fold-const.c doesn't know that the extra bits won't be needed.
     split_tree uses STRIP_SIGN_NOPS, which leaves conversions to a
     different mode in place.)
     So first try to find a common term here 'by hand'; we want to cover
     at least the cases that occur in legal static initializers.  */
  con0 = TREE_CODE (op0) == NOP_EXPR ? TREE_OPERAND (op0, 0) : op0;
  con1 = TREE_CODE (op1) == NOP_EXPR ? TREE_OPERAND (op1, 0) : op1;

  if (TREE_CODE (con0) == PLUS_EXPR)
    {
      lit0 = TREE_OPERAND (con0, 1);
      con0 = TREE_OPERAND (con0, 0);
    }
  else
    lit0 = integer_zero_node;

  if (TREE_CODE (con1) == PLUS_EXPR)
    {
      lit1 = TREE_OPERAND (con1, 1);
      con1 = TREE_OPERAND (con1, 0);
    }
  else
    lit1 = integer_zero_node;

  if (operand_equal_p (con0, con1, 0))
    {
      op0 = lit0;
      op1 = lit1;
    }


  /* First do the subtraction as integers;
     then drop through to build the divide operator.
     Do not do default conversions on the minus operator
     in case restype is a short type.  */

  op0 = build_binary_op (MINUS_EXPR, convert (restype, op0),
			 convert (restype, op1), 0);
  /* This generates an error if op1 is pointer to incomplete type.  */
  if (!COMPLETE_OR_VOID_TYPE_P (TREE_TYPE (TREE_TYPE (orig_op1))))
    error ("arithmetic on pointer to an incomplete type");

  /* This generates an error if op0 is pointer to incomplete type.  */
  op1 = c_size_in_bytes (target_type);

  /* Divide by the size, in easiest possible way.  */

  result = build (EXACT_DIV_EXPR, restype, op0, convert (restype, op1));

  folded = fold (result);
  if (folded == result)
    TREE_CONSTANT (folded) = TREE_CONSTANT (op0) & TREE_CONSTANT (op1);
  return folded;
}

/* Construct and perhaps optimize a tree representation
   for a unary operation.  CODE, a tree_code, specifies the operation
   and XARG is the operand.
   For any CODE other than ADDR_EXPR, FLAG nonzero suppresses
   the default promotions (such as from short to int).
   For ADDR_EXPR, the default promotions are not applied; FLAG nonzero
   allows non-lvalues; this is only used to handle conversion of non-lvalue
   arrays to pointers in C99.  */

tree
build_unary_op (enum tree_code code, tree xarg, int flag)
{
  /* No default_conversion here.  It causes trouble for ADDR_EXPR.  */
  tree arg = xarg;
  tree argtype = 0;
  enum tree_code typecode = TREE_CODE (TREE_TYPE (arg));
  tree val;
  int noconvert = flag;

  if (typecode == ERROR_MARK)
    return error_mark_node;
  if (typecode == ENUMERAL_TYPE || typecode == BOOLEAN_TYPE)
    typecode = INTEGER_TYPE;

  switch (code)
    {
    case CONVERT_EXPR:
      /* This is used for unary plus, because a CONVERT_EXPR
	 is enough to prevent anybody from looking inside for
	 associativity, but won't generate any code.  */
      if (!(typecode == INTEGER_TYPE || typecode == REAL_TYPE
	    || typecode == COMPLEX_TYPE))
	{
	  error ("wrong type argument to unary plus");
	  return error_mark_node;
	}
      else if (!noconvert)
	arg = default_conversion (arg);
      arg = non_lvalue (arg);
      break;

    case NEGATE_EXPR:
      if (!(typecode == INTEGER_TYPE || typecode == REAL_TYPE
	    || typecode == COMPLEX_TYPE
	    || typecode == VECTOR_TYPE))
	{
	  error ("wrong type argument to unary minus");
	  return error_mark_node;
	}
      else if (!noconvert)
	arg = default_conversion (arg);
      break;

    case BIT_NOT_EXPR:
      if (typecode == INTEGER_TYPE || typecode == VECTOR_TYPE)
	{
	  if (!noconvert)
	    arg = default_conversion (arg);
	}
      else if (typecode == COMPLEX_TYPE)
	{
	  code = CONJ_EXPR;
	  if (pedantic)
	    pedwarn ("ISO C does not support `~' for complex conjugation");
	  if (!noconvert)
	    arg = default_conversion (arg);
	}
      else
	{
	  error ("wrong type argument to bit-complement");
	  return error_mark_node;
	}
      break;

    case ABS_EXPR:
      if (!(typecode == INTEGER_TYPE || typecode == REAL_TYPE))
	{
	  error ("wrong type argument to abs");
	  return error_mark_node;
	}
      else if (!noconvert)
	arg = default_conversion (arg);
      break;

    case CONJ_EXPR:
      /* Conjugating a real value is a no-op, but allow it anyway.  */
      if (!(typecode == INTEGER_TYPE || typecode == REAL_TYPE
	    || typecode == COMPLEX_TYPE))
	{
	  error ("wrong type argument to conjugation");
	  return error_mark_node;
	}
      else if (!noconvert)
	arg = default_conversion (arg);
      break;

    case TRUTH_NOT_EXPR:
      if (typecode != INTEGER_TYPE
	  && typecode != REAL_TYPE && typecode != POINTER_TYPE
	  && typecode != COMPLEX_TYPE
	  /* These will convert to a pointer.  */
	  && typecode != ARRAY_TYPE && typecode != FUNCTION_TYPE)
	{
	  error ("wrong type argument to unary exclamation mark");
	  return error_mark_node;
	}
      arg = c_common_truthvalue_conversion (arg);
      return invert_truthvalue (arg);

    case NOP_EXPR:
      break;

    case REALPART_EXPR:
      if (TREE_CODE (arg) == COMPLEX_CST)
	return TREE_REALPART (arg);
      else if (TREE_CODE (TREE_TYPE (arg)) == COMPLEX_TYPE)
	return fold (build1 (REALPART_EXPR, TREE_TYPE (TREE_TYPE (arg)), arg));
      else
	return arg;

    case IMAGPART_EXPR:
      if (TREE_CODE (arg) == COMPLEX_CST)
	return TREE_IMAGPART (arg);
      else if (TREE_CODE (TREE_TYPE (arg)) == COMPLEX_TYPE)
	return fold (build1 (IMAGPART_EXPR, TREE_TYPE (TREE_TYPE (arg)), arg));
      else
	return convert (TREE_TYPE (arg), integer_zero_node);

    case PREINCREMENT_EXPR:
    case POSTINCREMENT_EXPR:
    case PREDECREMENT_EXPR:
    case POSTDECREMENT_EXPR:
      /* Handle complex lvalues (when permitted)
	 by reduction to simpler cases.  */

      val = unary_complex_lvalue (code, arg, 0);
      if (val != 0)
	return val;

      /* Increment or decrement the real part of the value,
	 and don't change the imaginary part.  */
      if (typecode == COMPLEX_TYPE)
	{
	  tree real, imag;

	  if (pedantic)
	    pedwarn ("ISO C does not support `++' and `--' on complex types");

	  arg = stabilize_reference (arg);
	  real = build_unary_op (REALPART_EXPR, arg, 1);
	  imag = build_unary_op (IMAGPART_EXPR, arg, 1);
	  return build (COMPLEX_EXPR, TREE_TYPE (arg),
			build_unary_op (code, real, 1), imag);
	}

      /* Report invalid types.  */

      if (typecode != POINTER_TYPE
	  && typecode != INTEGER_TYPE && typecode != REAL_TYPE)
	{
	  if (code == PREINCREMENT_EXPR || code == POSTINCREMENT_EXPR)
            error ("wrong type argument to increment");
          else
            error ("wrong type argument to decrement");

	  return error_mark_node;
	}

      {
	tree inc;
	tree result_type = TREE_TYPE (arg);

	arg = get_unwidened (arg, 0);
	argtype = TREE_TYPE (arg);

	/* Compute the increment.  */

	if (typecode == POINTER_TYPE)
	  {
	    /* If pointer target is an undefined struct,
	       we just cannot know how to do the arithmetic.  */
	    if (!COMPLETE_OR_VOID_TYPE_P (TREE_TYPE (result_type)))
	      {
		if (code == PREINCREMENT_EXPR || code == POSTINCREMENT_EXPR)
		  error ("increment of pointer to unknown structure");
		else
		  error ("decrement of pointer to unknown structure");
	      }
	    else if ((pedantic || warn_pointer_arith)
		     && (TREE_CODE (TREE_TYPE (result_type)) == FUNCTION_TYPE
			 || TREE_CODE (TREE_TYPE (result_type)) == VOID_TYPE))
              {
		if (code == PREINCREMENT_EXPR || code == POSTINCREMENT_EXPR)
		  pedwarn ("wrong type argument to increment");
		else
		  pedwarn ("wrong type argument to decrement");
	      }

	    inc = c_size_in_bytes (TREE_TYPE (result_type));
	  }
	else
	  inc = integer_one_node;

	inc = convert (argtype, inc);

	/* Handle incrementing a cast-expression.  */

	while (1)
	  switch (TREE_CODE (arg))
	    {
	    case NOP_EXPR:
	    case CONVERT_EXPR:
	    case FLOAT_EXPR:
	    case FIX_TRUNC_EXPR:
	    case FIX_FLOOR_EXPR:
	    case FIX_ROUND_EXPR:
	    case FIX_CEIL_EXPR:
	      pedantic_lvalue_warning (CONVERT_EXPR);
	      /* If the real type has the same machine representation
		 as the type it is cast to, we can make better output
		 by adding directly to the inside of the cast.  */
	      if ((TREE_CODE (TREE_TYPE (arg))
		   == TREE_CODE (TREE_TYPE (TREE_OPERAND (arg, 0))))
		  && (TYPE_MODE (TREE_TYPE (arg))
		      == TYPE_MODE (TREE_TYPE (TREE_OPERAND (arg, 0)))))
		arg = TREE_OPERAND (arg, 0);
	      else
		{
		  tree incremented, modify, value;
		  if (TREE_CODE (TREE_TYPE (arg)) == BOOLEAN_TYPE)
		    value = boolean_increment (code, arg);
		  else
		    {
		      arg = stabilize_reference (arg);
		      if (code == PREINCREMENT_EXPR || code == PREDECREMENT_EXPR)
			value = arg;
		      else
			value = save_expr (arg);
		      incremented = build (((code == PREINCREMENT_EXPR
					     || code == POSTINCREMENT_EXPR)
					    ? PLUS_EXPR : MINUS_EXPR),
					   argtype, value, inc);
		      TREE_SIDE_EFFECTS (incremented) = 1;
		      modify = build_modify_expr (arg, NOP_EXPR, incremented);
		      value = build (COMPOUND_EXPR, TREE_TYPE (arg), modify, value);
		    }
		  TREE_USED (value) = 1;
		  return value;
		}
	      break;

	    default:
	      goto give_up;
	    }
      give_up:

	/* Complain about anything else that is not a true lvalue.  */
	if (!lvalue_or_else (arg, ((code == PREINCREMENT_EXPR
				    || code == POSTINCREMENT_EXPR)
				   ? "invalid lvalue in increment"
				   : "invalid lvalue in decrement")))
	  return error_mark_node;

	/* Report a read-only lvalue.  */
	if (TREE_READONLY (arg))
	  readonly_error (arg,
			  ((code == PREINCREMENT_EXPR
			    || code == POSTINCREMENT_EXPR)
			   ? "increment" : "decrement"));

	if (TREE_CODE (TREE_TYPE (arg)) == BOOLEAN_TYPE)
	  val = boolean_increment (code, arg);
	else
	  val = build (code, TREE_TYPE (arg), arg, inc);
	TREE_SIDE_EFFECTS (val) = 1;
	val = convert (result_type, val);
	if (TREE_CODE (val) != code)
	  TREE_NO_UNUSED_WARNING (val) = 1;
	return val;
      }

    case ADDR_EXPR:
      /* Note that this operation never does default_conversion.  */

      /* Let &* cancel out to simplify resulting code.  */
      if (TREE_CODE (arg) == INDIRECT_REF)
	{
	  /* Don't let this be an lvalue.  */
	  if (lvalue_p (TREE_OPERAND (arg, 0)))
	    return non_lvalue (TREE_OPERAND (arg, 0));
	  return TREE_OPERAND (arg, 0);
	}

      /* For &x[y], return x+y */
      if (TREE_CODE (arg) == ARRAY_REF)
	{
	  if (!c_mark_addressable (TREE_OPERAND (arg, 0)))
	    return error_mark_node;
	  return build_binary_op (PLUS_EXPR, TREE_OPERAND (arg, 0),
				  TREE_OPERAND (arg, 1), 1);
	}

      /* Handle complex lvalues (when permitted)
	 by reduction to simpler cases.  */
      val = unary_complex_lvalue (code, arg, flag);
      if (val != 0)
	return val;

      /* Anything not already handled and not a true memory reference
	 or a non-lvalue array is an error.  */
      else if (typecode != FUNCTION_TYPE && !flag
	       && !lvalue_or_else (arg, "invalid lvalue in unary `&'"))
	return error_mark_node;

      /* Ordinary case; arg is a COMPONENT_REF or a decl.  */
      argtype = TREE_TYPE (arg);

      /* If the lvalue is const or volatile, merge that into the type
         to which the address will point.  Note that you can't get a
	 restricted pointer by taking the address of something, so we
	 only have to deal with `const' and `volatile' here.  */
      if ((DECL_P (arg) || TREE_CODE_CLASS (TREE_CODE (arg)) == 'r')
	  && (TREE_READONLY (arg) || TREE_THIS_VOLATILE (arg)))
	  argtype = c_build_type_variant (argtype,
					  TREE_READONLY (arg),
					  TREE_THIS_VOLATILE (arg));

      argtype = build_pointer_type (argtype);

      if (!c_mark_addressable (arg))
	return error_mark_node;

      {
	tree addr;

	if (TREE_CODE (arg) == COMPONENT_REF)
	  {
	    tree field = TREE_OPERAND (arg, 1);

	    addr = build_unary_op (ADDR_EXPR, TREE_OPERAND (arg, 0), flag);

	    if (DECL_C_BIT_FIELD (field))
	      {
		error ("attempt to take address of bit-field structure member `%s'",
		       IDENTIFIER_POINTER (DECL_NAME (field)));
		return error_mark_node;
	      }

	    addr = fold (build (PLUS_EXPR, argtype,
				convert (argtype, addr),
				convert (argtype, byte_position (field))));
	  }
	else
	  addr = build1 (code, argtype, arg);

	/* Address of a static or external variable or
	   file-scope function counts as a constant.  */
	if (staticp (arg)
	    && ! (TREE_CODE (arg) == FUNCTION_DECL
		  && !DECL_FILE_SCOPE_P (arg)))
	  TREE_CONSTANT (addr) = 1;
	return addr;
      }

    default:
      break;
    }

  if (argtype == 0)
    argtype = TREE_TYPE (arg);
  val = build1 (code, argtype, arg);
  return require_constant_value ? fold_initializer (val) : fold (val);
}

/* Return nonzero if REF is an lvalue valid for this language.
   Lvalues can be assigned, unless their type has TYPE_READONLY.
   Lvalues can have their address taken, unless they have DECL_REGISTER.  */

int
lvalue_p (tree ref)
{
  enum tree_code code = TREE_CODE (ref);

  switch (code)
    {
    case REALPART_EXPR:
    case IMAGPART_EXPR:
    case COMPONENT_REF:
      return lvalue_p (TREE_OPERAND (ref, 0));

    case COMPOUND_LITERAL_EXPR:
    case STRING_CST:
      return 1;

    case INDIRECT_REF:
    case ARRAY_REF:
    case VAR_DECL:
    case PARM_DECL:
    case RESULT_DECL:
    case ERROR_MARK:
      return (TREE_CODE (TREE_TYPE (ref)) != FUNCTION_TYPE
	      && TREE_CODE (TREE_TYPE (ref)) != METHOD_TYPE);

    case BIND_EXPR:
    case RTL_EXPR:
      return TREE_CODE (TREE_TYPE (ref)) == ARRAY_TYPE;

    default:
      return 0;
    }
}

/* Return nonzero if REF is an lvalue valid for this language;
   otherwise, print an error message and return zero.  */

int
lvalue_or_else (tree ref, const char *msgid)
{
  int win = lvalue_p (ref);

  if (! win)
    error ("%s", msgid);

  return win;
}

/* Apply unary lvalue-demanding operator CODE to the expression ARG
   for certain kinds of expressions which are not really lvalues
   but which we can accept as lvalues.  If FLAG is nonzero, then
   non-lvalues are OK since we may be converting a non-lvalue array to
   a pointer in C99.

   If ARG is not a kind of expression we can handle, return zero.  */

static tree
unary_complex_lvalue (enum tree_code code, tree arg, int flag)
{
  /* Handle (a, b) used as an "lvalue".  */
  if (TREE_CODE (arg) == COMPOUND_EXPR)
    {
      tree real_result = build_unary_op (code, TREE_OPERAND (arg, 1), 0);

      /* If this returns a function type, it isn't really being used as
	 an lvalue, so don't issue a warning about it.  */
      if (TREE_CODE (TREE_TYPE (arg)) != FUNCTION_TYPE && !flag)
	pedantic_lvalue_warning (COMPOUND_EXPR);

      return build (COMPOUND_EXPR, TREE_TYPE (real_result),
		    TREE_OPERAND (arg, 0), real_result);
    }

  /* Handle (a ? b : c) used as an "lvalue".  */
  if (TREE_CODE (arg) == COND_EXPR)
    {
      if (!flag)
	pedantic_lvalue_warning (COND_EXPR);
      if (TREE_CODE (TREE_TYPE (arg)) != FUNCTION_TYPE && !flag)
	pedantic_lvalue_warning (COMPOUND_EXPR);

      return (build_conditional_expr
	      (TREE_OPERAND (arg, 0),
	       build_unary_op (code, TREE_OPERAND (arg, 1), flag),
	       build_unary_op (code, TREE_OPERAND (arg, 2), flag)));
    }

  return 0;
}

/* If pedantic, warn about improper lvalue.   CODE is either COND_EXPR
   COMPOUND_EXPR, or CONVERT_EXPR (for casts).  */

static void
pedantic_lvalue_warning (enum tree_code code)
{
  switch (code)
    {
    case COND_EXPR:
      pedwarn ("use of conditional expressions as lvalues is deprecated");
      break;
    case COMPOUND_EXPR:
      pedwarn ("use of compound expressions as lvalues is deprecated");
      break;
    default:
      pedwarn ("use of cast expressions as lvalues is deprecated");
      break;
    }
}

/* Warn about storing in something that is `const'.  */

void
readonly_error (tree arg, const char *msgid)
{
  if (TREE_CODE (arg) == COMPONENT_REF)
    {
      if (TYPE_READONLY (TREE_TYPE (TREE_OPERAND (arg, 0))))
	readonly_error (TREE_OPERAND (arg, 0), msgid);
      else
	error ("%s of read-only member `%s'", _(msgid),
	       IDENTIFIER_POINTER (DECL_NAME (TREE_OPERAND (arg, 1))));
    }
  else if (TREE_CODE (arg) == VAR_DECL)
    error ("%s of read-only variable `%s'", _(msgid),
	   IDENTIFIER_POINTER (DECL_NAME (arg)));
  else
    error ("%s of read-only location", _(msgid));
}

/* Mark EXP saying that we need to be able to take the
   address of it; it should not be allocated in a register.
   Returns true if successful.  */

bool
c_mark_addressable (tree exp)
{
  tree x = exp;

  while (1)
    switch (TREE_CODE (x))
      {
      case COMPONENT_REF:
	if (DECL_C_BIT_FIELD (TREE_OPERAND (x, 1)))
	  {
	    error ("cannot take address of bit-field `%s'",
		   IDENTIFIER_POINTER (DECL_NAME (TREE_OPERAND (x, 1))));
	    return false;
	  }

	/* ... fall through ...  */

      case ADDR_EXPR:
      case ARRAY_REF:
      case REALPART_EXPR:
      case IMAGPART_EXPR:
	x = TREE_OPERAND (x, 0);
	break;

      case COMPOUND_LITERAL_EXPR:
      case CONSTRUCTOR:
	TREE_ADDRESSABLE (x) = 1;
	return true;

      case VAR_DECL:
      case CONST_DECL:
      case PARM_DECL:
      case RESULT_DECL:
	if (DECL_REGISTER (x) && !TREE_ADDRESSABLE (x)
	    && DECL_NONLOCAL (x))
	  {
	    if (TREE_PUBLIC (x) || TREE_STATIC (x) || DECL_EXTERNAL (x))
	      {
		error ("global register variable `%s' used in nested function",
		       IDENTIFIER_POINTER (DECL_NAME (x)));
		return false;
	      }
	    pedwarn ("register variable `%s' used in nested function",
		     IDENTIFIER_POINTER (DECL_NAME (x)));
	  }
	else if (DECL_REGISTER (x) && !TREE_ADDRESSABLE (x))
	  {
	    if (TREE_PUBLIC (x) || TREE_STATIC (x) || DECL_EXTERNAL (x))
	      {
		error ("address of global register variable `%s' requested",
		       IDENTIFIER_POINTER (DECL_NAME (x)));
		return false;
	      }

	    /* If we are making this addressable due to its having
	       volatile components, give a different error message.  Also
	       handle the case of an unnamed parameter by not trying
	       to give the name.  */

	    else if (C_TYPE_FIELDS_VOLATILE (TREE_TYPE (x)))
	      {
		error ("cannot put object with volatile field into register");
		return false;
	      }

	    pedwarn ("address of register variable `%s' requested",
		     IDENTIFIER_POINTER (DECL_NAME (x)));
	  }
	put_var_into_stack (x, /*rescan=*/true);

	/* drops in */
      case FUNCTION_DECL:
	TREE_ADDRESSABLE (x) = 1;
	/* drops out */
      default:
	return true;
    }
}

/* Build and return a conditional expression IFEXP ? OP1 : OP2.  */

tree
build_conditional_expr (tree ifexp, tree op1, tree op2)
{
  tree type1;
  tree type2;
  enum tree_code code1;
  enum tree_code code2;
  tree result_type = NULL;
  tree orig_op1 = op1, orig_op2 = op2;

  ifexp = c_common_truthvalue_conversion (default_conversion (ifexp));

  /* Promote both alternatives.  */

  if (TREE_CODE (TREE_TYPE (op1)) != VOID_TYPE)
    op1 = default_conversion (op1);
  if (TREE_CODE (TREE_TYPE (op2)) != VOID_TYPE)
    op2 = default_conversion (op2);

  if (TREE_CODE (ifexp) == ERROR_MARK
      || TREE_CODE (TREE_TYPE (op1)) == ERROR_MARK
      || TREE_CODE (TREE_TYPE (op2)) == ERROR_MARK)
    return error_mark_node;

  type1 = TREE_TYPE (op1);
  code1 = TREE_CODE (type1);
  type2 = TREE_TYPE (op2);
  code2 = TREE_CODE (type2);

  /* Quickly detect the usual case where op1 and op2 have the same type
     after promotion.  */
  if (TYPE_MAIN_VARIANT (type1) == TYPE_MAIN_VARIANT (type2))
    {
      if (type1 == type2)
	result_type = type1;
      else
	result_type = TYPE_MAIN_VARIANT (type1);
    }
  else if ((code1 == INTEGER_TYPE || code1 == REAL_TYPE
            || code1 == COMPLEX_TYPE)
           && (code2 == INTEGER_TYPE || code2 == REAL_TYPE
               || code2 == COMPLEX_TYPE))
    {
      result_type = common_type (type1, type2);

      /* If -Wsign-compare, warn here if type1 and type2 have
	 different signedness.  We'll promote the signed to unsigned
	 and later code won't know it used to be different.
	 Do this check on the original types, so that explicit casts
	 will be considered, but default promotions won't.  */
      if (warn_sign_compare && !skip_evaluation)
	{
	  int unsigned_op1 = TREE_UNSIGNED (TREE_TYPE (orig_op1));
	  int unsigned_op2 = TREE_UNSIGNED (TREE_TYPE (orig_op2));

	  if (unsigned_op1 ^ unsigned_op2)
	    {
	      /* Do not warn if the result type is signed, since the
		 signed type will only be chosen if it can represent
		 all the values of the unsigned type.  */
	      if (! TREE_UNSIGNED (result_type))
		/* OK */;
	      /* Do not warn if the signed quantity is an unsuffixed
		 integer literal (or some static constant expression
		 involving such literals) and it is non-negative.  */
	      else if ((unsigned_op2 && c_tree_expr_nonnegative_p (op1))
		       || (unsigned_op1 && c_tree_expr_nonnegative_p (op2)))
		/* OK */;
	      else
		warning ("signed and unsigned type in conditional expression");
	    }
	}
    }
  else if (code1 == VOID_TYPE || code2 == VOID_TYPE)
    {
      if (pedantic && (code1 != VOID_TYPE || code2 != VOID_TYPE))
	pedwarn ("ISO C forbids conditional expr with only one void side");
      result_type = void_type_node;
    }
  else if (code1 == POINTER_TYPE && code2 == POINTER_TYPE)
    {
      if (comp_target_types (type1, type2, 1))
	result_type = common_type (type1, type2);
      else if (integer_zerop (op1) && TREE_TYPE (type1) == void_type_node
	       && TREE_CODE (orig_op1) != NOP_EXPR)
	result_type = qualify_type (type2, type1);
      else if (integer_zerop (op2) && TREE_TYPE (type2) == void_type_node
	       && TREE_CODE (orig_op2) != NOP_EXPR)
	result_type = qualify_type (type1, type2);
      else if (VOID_TYPE_P (TREE_TYPE (type1)))
	{
	  if (pedantic && TREE_CODE (TREE_TYPE (type2)) == FUNCTION_TYPE)
	    pedwarn ("ISO C forbids conditional expr between `void *' and function pointer");
	  result_type = build_pointer_type (qualify_type (TREE_TYPE (type1),
							  TREE_TYPE (type2)));
	}
      else if (VOID_TYPE_P (TREE_TYPE (type2)))
	{
	  if (pedantic && TREE_CODE (TREE_TYPE (type1)) == FUNCTION_TYPE)
	    pedwarn ("ISO C forbids conditional expr between `void *' and function pointer");
	  result_type = build_pointer_type (qualify_type (TREE_TYPE (type2),
							  TREE_TYPE (type1)));
	}
      else
	{
	  pedwarn ("pointer type mismatch in conditional expression");
	  result_type = build_pointer_type (void_type_node);
	}
    }
  else if (code1 == POINTER_TYPE && code2 == INTEGER_TYPE)
    {
      if (! integer_zerop (op2))
	pedwarn ("pointer/integer type mismatch in conditional expression");
      else
	{
	  op2 = null_pointer_node;
	}
      result_type = type1;
    }
  else if (code2 == POINTER_TYPE && code1 == INTEGER_TYPE)
    {
      if (!integer_zerop (op1))
	pedwarn ("pointer/integer type mismatch in conditional expression");
      else
	{
	  op1 = null_pointer_node;
	}
      result_type = type2;
    }

  if (!result_type)
    {
      if (flag_cond_mismatch)
	result_type = void_type_node;
      else
	{
	  error ("type mismatch in conditional expression");
	  return error_mark_node;
	}
    }

  /* Merge const and volatile flags of the incoming types.  */
  result_type
    = build_type_variant (result_type,
			  TREE_READONLY (op1) || TREE_READONLY (op2),
			  TREE_THIS_VOLATILE (op1) || TREE_THIS_VOLATILE (op2));

  if (result_type != TREE_TYPE (op1))
    op1 = convert_and_check (result_type, op1);
  if (result_type != TREE_TYPE (op2))
    op2 = convert_and_check (result_type, op2);

  if (TREE_CODE (ifexp) == INTEGER_CST)
    return pedantic_non_lvalue (integer_zerop (ifexp) ? op2 : op1);

  return fold (build (COND_EXPR, result_type, ifexp, op1, op2));
}

/* Given a list of expressions, return a compound expression
   that performs them all and returns the value of the last of them.  */

tree
build_compound_expr (tree list)
{
  return internal_build_compound_expr (list, TRUE);
}

static tree
internal_build_compound_expr (tree list, int first_p)
{
  tree rest;

  if (TREE_CHAIN (list) == 0)
    {
      /* Convert arrays and functions to pointers when there
	 really is a comma operator.  */
      if (!first_p)
	TREE_VALUE (list)
	  = default_function_array_conversion (TREE_VALUE (list));

      /* Don't let (0, 0) be null pointer constant.  */
      if (!first_p && integer_zerop (TREE_VALUE (list)))
	return non_lvalue (TREE_VALUE (list));
      return TREE_VALUE (list);
    }

  rest = internal_build_compound_expr (TREE_CHAIN (list), FALSE);

  if (! TREE_SIDE_EFFECTS (TREE_VALUE (list)))
    {
      /* The left-hand operand of a comma expression is like an expression
         statement: with -Wextra or -Wunused, we should warn if it doesn't have
	 any side-effects, unless it was explicitly cast to (void).  */
      if (warn_unused_value
           && ! (TREE_CODE (TREE_VALUE (list)) == CONVERT_EXPR
                && VOID_TYPE_P (TREE_TYPE (TREE_VALUE (list)))))
        warning ("left-hand operand of comma expression has no effect");
    }

  /* With -Wunused, we should also warn if the left-hand operand does have
     side-effects, but computes a value which is not used.  For example, in
     `foo() + bar(), baz()' the result of the `+' operator is not used,
     so we should issue a warning.  */
  else if (warn_unused_value)
    warn_if_unused_value (TREE_VALUE (list));

  return build (COMPOUND_EXPR, TREE_TYPE (rest), TREE_VALUE (list), rest);
}

/* Build an expression representing a cast to type TYPE of expression EXPR.  */

tree
build_c_cast (tree type, tree expr)
{
  tree value = expr;

  if (type == error_mark_node || expr == error_mark_node)
    return error_mark_node;

  /* The ObjC front-end uses TYPE_MAIN_VARIANT to tie together types differing
     only in <protocol> qualifications.  But when constructing cast expressions,
     the protocols do matter and must be kept around.  */
  if (!c_dialect_objc () || !objc_is_object_ptr (type))
    type = TYPE_MAIN_VARIANT (type);

  if (TREE_CODE (type) == ARRAY_TYPE)
    {
      error ("cast specifies array type");
      return error_mark_node;
    }

  if (TREE_CODE (type) == FUNCTION_TYPE)
    {
      error ("cast specifies function type");
      return error_mark_node;
    }

  if (type == TYPE_MAIN_VARIANT (TREE_TYPE (value)))
    {
      if (pedantic)
	{
	  if (TREE_CODE (type) == RECORD_TYPE
	      || TREE_CODE (type) == UNION_TYPE)
	    pedwarn ("ISO C forbids casting nonscalar to the same type");
	}
    }
  else if (TREE_CODE (type) == UNION_TYPE)
    {
      tree field;
      value = default_function_array_conversion (value);

      for (field = TYPE_FIELDS (type); field; field = TREE_CHAIN (field))
	if (comptypes (TYPE_MAIN_VARIANT (TREE_TYPE (field)),
		       TYPE_MAIN_VARIANT (TREE_TYPE (value)), COMPARE_STRICT))
	  break;

      if (field)
	{
	  tree t;

	  if (pedantic)
	    pedwarn ("ISO C forbids casts to union type");
	  t = digest_init (type,
			   build_constructor (type,
					      build_tree_list (field, value)),
			   0);
	  TREE_CONSTANT (t) = TREE_CONSTANT (value);
	  return t;
	}
      error ("cast to union type from type not present in union");
      return error_mark_node;
    }
  else
    {
      tree otype, ovalue;

      /* If casting to void, avoid the error that would come
	 from default_conversion in the case of a non-lvalue array.  */
      if (type == void_type_node)
	return build1 (CONVERT_EXPR, type, value);

      /* Convert functions and arrays to pointers,
	 but don't convert any other types.  */
      value = default_function_array_conversion (value);
      otype = TREE_TYPE (value);

      /* Optionally warn about potentially worrisome casts.  */

      if (warn_cast_qual
	  && TREE_CODE (type) == POINTER_TYPE
	  && TREE_CODE (otype) == POINTER_TYPE)
	{
	  tree in_type = type;
	  tree in_otype = otype;
	  int added = 0;
	  int discarded = 0;

	  /* Check that the qualifiers on IN_TYPE are a superset of
	     the qualifiers of IN_OTYPE.  The outermost level of
	     POINTER_TYPE nodes is uninteresting and we stop as soon
	     as we hit a non-POINTER_TYPE node on either type.  */
	  do
	    {
	      in_otype = TREE_TYPE (in_otype);
	      in_type = TREE_TYPE (in_type);

	      /* GNU C allows cv-qualified function types.  'const'
		 means the function is very pure, 'volatile' means it
		 can't return.  We need to warn when such qualifiers
		 are added, not when they're taken away.  */
	      if (TREE_CODE (in_otype) == FUNCTION_TYPE
		  && TREE_CODE (in_type) == FUNCTION_TYPE)
		added |= (TYPE_QUALS (in_type) & ~TYPE_QUALS (in_otype));
	      else
		discarded |= (TYPE_QUALS (in_otype) & ~TYPE_QUALS (in_type));
	    }
	  while (TREE_CODE (in_type) == POINTER_TYPE
		 && TREE_CODE (in_otype) == POINTER_TYPE);

	  if (added)
	    warning ("cast adds new qualifiers to function type");

	  if (discarded)
	    /* There are qualifiers present in IN_OTYPE that are not
	       present in IN_TYPE.  */
	    warning ("cast discards qualifiers from pointer target type");
	}

      /* Warn about possible alignment problems.  */
      if (STRICT_ALIGNMENT && warn_cast_align
	  && TREE_CODE (type) == POINTER_TYPE
	  && TREE_CODE (otype) == POINTER_TYPE
	  && TREE_CODE (TREE_TYPE (otype)) != VOID_TYPE
	  && TREE_CODE (TREE_TYPE (otype)) != FUNCTION_TYPE
	  /* Don't warn about opaque types, where the actual alignment
	     restriction is unknown.  */
	  && !((TREE_CODE (TREE_TYPE (otype)) == UNION_TYPE
		|| TREE_CODE (TREE_TYPE (otype)) == RECORD_TYPE)
	       && TYPE_MODE (TREE_TYPE (otype)) == VOIDmode)
	  && TYPE_ALIGN (TREE_TYPE (type))