gcc/cp/typeck.cc

/* Build expressions with type checking for C++ compiler.
   Copyright (C) 1987-2022 Free Software Foundation, Inc.
   Hacked by Michael Tiemann (tiemann@cygnus.com)

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.

GCC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */


/* 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 and C++ specific error
   checks, and some optimization.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "target.h"
#include "cp-tree.h"
#include "stor-layout.h"
#include "varasm.h"
#include "intl.h"
#include "convert.h"
#include "c-family/c-objc.h"
#include "c-family/c-ubsan.h"
#include "gcc-rich-location.h"
#include "stringpool.h"
#include "attribs.h"
#include "asan.h"
#include "gimplify.h"

static tree cp_build_addr_expr_strict (tree, tsubst_flags_t);
static tree cp_build_function_call (tree, tree, tsubst_flags_t);
static tree pfn_from_ptrmemfunc (tree);
static tree delta_from_ptrmemfunc (tree);
static tree convert_for_assignment (tree, tree, impl_conv_rhs, tree, int,
				    tsubst_flags_t, int);
static tree cp_pointer_int_sum (location_t, enum tree_code, tree, tree,
				tsubst_flags_t);
static tree rationalize_conditional_expr (enum tree_code, tree, 
					  tsubst_flags_t);
static bool comp_ptr_ttypes_real (tree, tree, int);
static bool comp_except_types (tree, tree, bool);
static bool comp_array_types (const_tree, const_tree, compare_bounds_t, bool);
static tree pointer_diff (location_t, tree, tree, tree, tsubst_flags_t, tree *);
static tree get_delta_difference (tree, tree, bool, bool, tsubst_flags_t);
static void casts_away_constness_r (tree *, tree *, tsubst_flags_t);
static bool casts_away_constness (tree, tree, tsubst_flags_t);
static bool maybe_warn_about_returning_address_of_local (tree, location_t = UNKNOWN_LOCATION);
static void error_args_num (location_t, tree, bool);
static int convert_arguments (tree, vec<tree, va_gc> **, tree, int,
                              tsubst_flags_t);
static bool is_std_move_p (tree);
static bool is_std_forward_p (tree);

/* Do `exp = require_complete_type (exp);' to make sure exp
   does not have an incomplete type.  (That includes void types.)
   Returns error_mark_node if the VALUE does not have
   complete type when this function returns.  */

tree
require_complete_type_sfinae (tree value, tsubst_flags_t complain)
{
  tree type;

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

  if (TREE_CODE (value) == OVERLOAD)
    type = unknown_type_node;
  else
    type = TREE_TYPE (value);

  if (type == error_mark_node)
    return error_mark_node;

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

  if (complete_type_or_maybe_complain (type, value, complain))
    return value;
  else
    return error_mark_node;
}

tree
require_complete_type (tree value)
{
  return require_complete_type_sfinae (value, tf_warning_or_error);
}

/* Try to complete TYPE, if it is incomplete.  For example, if TYPE is
   a template instantiation, do the instantiation.  Returns TYPE,
   whether or not it could be completed, unless something goes
   horribly wrong, in which case the error_mark_node is returned.  */

tree
complete_type (tree type)
{
  if (type == NULL_TREE)
    /* Rather than crash, we return something sure to cause an error
       at some point.  */
    return error_mark_node;

  if (type == error_mark_node || COMPLETE_TYPE_P (type))
    ;
  else if (TREE_CODE (type) == ARRAY_TYPE)
    {
      tree t = complete_type (TREE_TYPE (type));
      unsigned int needs_constructing, has_nontrivial_dtor;
      if (COMPLETE_TYPE_P (t) && !dependent_type_p (type))
	layout_type (type);
      needs_constructing
	= TYPE_NEEDS_CONSTRUCTING (TYPE_MAIN_VARIANT (t));
      has_nontrivial_dtor
	= TYPE_HAS_NONTRIVIAL_DESTRUCTOR (TYPE_MAIN_VARIANT (t));
      for (t = TYPE_MAIN_VARIANT (type); t; t = TYPE_NEXT_VARIANT (t))
	{
	  TYPE_NEEDS_CONSTRUCTING (t) = needs_constructing;
	  TYPE_HAS_NONTRIVIAL_DESTRUCTOR (t) = has_nontrivial_dtor;
	}
    }
  else if (CLASS_TYPE_P (type))
    {
      if (modules_p ())
	/* TYPE could be a class member we've not loaded the definition of.  */ 
	lazy_load_pendings (TYPE_NAME (TYPE_MAIN_VARIANT (type)));

      if (CLASSTYPE_TEMPLATE_INSTANTIATION (type))
	instantiate_class_template (TYPE_MAIN_VARIANT (type));
    }

  return type;
}

/* Like complete_type, but issue an error if the TYPE cannot be completed.
   VALUE is used for informative diagnostics.
   Returns NULL_TREE if the type cannot be made complete.  */

tree
complete_type_or_maybe_complain (tree type, tree value, tsubst_flags_t complain)
{
  type = complete_type (type);
  if (type == error_mark_node)
    /* We already issued an error.  */
    return NULL_TREE;
  else if (!COMPLETE_TYPE_P (type))
    {
      if (complain & tf_error)
	cxx_incomplete_type_diagnostic (value, type, DK_ERROR);
      note_failed_type_completion_for_satisfaction (type);
      return NULL_TREE;
    }
  else
    return type;
}

tree
complete_type_or_else (tree type, tree value)
{
  return complete_type_or_maybe_complain (type, value, tf_warning_or_error);
}


/* Return the common type of two parameter lists.
   We assume that comptypes has already been done and returned 1;
   if that isn't so, this may crash.

   As an optimization, free the space we allocate if the parameter
   lists are already common.  */

static tree
commonparms (tree p1, tree p2)
{
  tree oldargs = p1, newargs, n;
  int i, len;
  int any_change = 0;

  len = list_length (p1);
  newargs = tree_last (p1);

  if (newargs == void_list_node)
    i = 1;
  else
    {
      i = 0;
      newargs = 0;
    }

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

  n = newargs;

  for (i = 0; p1;
       p1 = TREE_CHAIN (p1), p2 = TREE_CHAIN (p2), n = TREE_CHAIN (n), i++)
    {
      if (TREE_PURPOSE (p1) && !TREE_PURPOSE (p2))
	{
	  TREE_PURPOSE (n) = TREE_PURPOSE (p1);
	  any_change = 1;
	}
      else if (! TREE_PURPOSE (p1))
	{
	  if (TREE_PURPOSE (p2))
	    {
	      TREE_PURPOSE (n) = TREE_PURPOSE (p2);
	      any_change = 1;
	    }
	}
      else
	{
	  if (simple_cst_equal (TREE_PURPOSE (p1), TREE_PURPOSE (p2)) != 1)
	    any_change = 1;
	  TREE_PURPOSE (n) = TREE_PURPOSE (p2);
	}
      if (TREE_VALUE (p1) != TREE_VALUE (p2))
	{
	  any_change = 1;
	  TREE_VALUE (n) = merge_types (TREE_VALUE (p1), TREE_VALUE (p2));
	}
      else
	TREE_VALUE (n) = TREE_VALUE (p1);
    }
  if (! any_change)
    return oldargs;

  return newargs;
}

/* Given a type, perhaps copied for a typedef,
   find the "original" version of it.  */
static tree
original_type (tree t)
{
  int quals = cp_type_quals (t);
  while (t != error_mark_node
	 && TYPE_NAME (t) != NULL_TREE)
    {
      tree x = TYPE_NAME (t);
      if (TREE_CODE (x) != TYPE_DECL)
	break;
      x = DECL_ORIGINAL_TYPE (x);
      if (x == NULL_TREE)
	break;
      t = x;
    }
  return cp_build_qualified_type (t, quals);
}

/* Merge the attributes of type OTHER_TYPE into the attributes of type TYPE
   and return a variant of TYPE with the merged attributes.  */

static tree
merge_type_attributes_from (tree type, tree other_type)
{
  tree attrs = targetm.merge_type_attributes (type, other_type);
  attrs = restrict_type_identity_attributes_to (attrs, TYPE_ATTRIBUTES (type));
  return cp_build_type_attribute_variant (type, attrs);
}

/* Return the common type for two arithmetic types T1 and T2 under the
   usual arithmetic conversions.  The default conversions have already
   been applied, and enumerated types converted to their compatible
   integer types.  */

static tree
cp_common_type (tree t1, tree t2)
{
  enum tree_code code1 = TREE_CODE (t1);
  enum tree_code code2 = TREE_CODE (t2);
  tree attributes;
  int i;


  /* In what follows, we slightly generalize the rules given in [expr] so
     as to deal with `long long' and `complex'.  First, merge the
     attributes.  */
  attributes = (*targetm.merge_type_attributes) (t1, t2);

  if (SCOPED_ENUM_P (t1) || SCOPED_ENUM_P (t2))
    {
      if (TYPE_MAIN_VARIANT (t1) == TYPE_MAIN_VARIANT (t2))
	return build_type_attribute_variant (t1, attributes);
      else
	return NULL_TREE;
    }

  /* FIXME: Attributes.  */
  gcc_assert (ARITHMETIC_TYPE_P (t1)
	      || VECTOR_TYPE_P (t1)
	      || UNSCOPED_ENUM_P (t1));
  gcc_assert (ARITHMETIC_TYPE_P (t2)
	      || VECTOR_TYPE_P (t2)
	      || UNSCOPED_ENUM_P (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
	= type_after_usual_arithmetic_conversions (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);
    }

  if (code1 == VECTOR_TYPE)
    {
      /* When we get here we should have two vectors of the same size.
	 Just prefer the unsigned one if present.  */
      if (TYPE_UNSIGNED (t1))
	return merge_type_attributes_from (t1, t2);
      else
	return merge_type_attributes_from (t2, t1);
    }

  /* 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);

  /* The types are the same; no need to do anything fancy.  */
  if (TYPE_MAIN_VARIANT (t1) == TYPE_MAIN_VARIANT (t2))
    return build_type_attribute_variant (t1, attributes);

  if (code1 != REAL_TYPE)
    {
      /* If one is unsigned long long, then convert the other to unsigned
	 long long.  */
      if (same_type_p (TYPE_MAIN_VARIANT (t1), long_long_unsigned_type_node)
	  || same_type_p (TYPE_MAIN_VARIANT (t2), long_long_unsigned_type_node))
	return build_type_attribute_variant (long_long_unsigned_type_node,
					     attributes);
      /* If one is a long long, and the other is an unsigned long, and
	 long long can represent all the values of an unsigned long, then
	 convert to a long long.  Otherwise, convert to an unsigned long
	 long.  Otherwise, if either operand is long long, convert the
	 other to long long.

	 Since we're here, we know the TYPE_PRECISION is the same;
	 therefore converting to long long cannot represent all the values
	 of an unsigned long, so we choose unsigned long long in that
	 case.  */
      if (same_type_p (TYPE_MAIN_VARIANT (t1), long_long_integer_type_node)
	  || same_type_p (TYPE_MAIN_VARIANT (t2), long_long_integer_type_node))
	{
	  tree t = ((TYPE_UNSIGNED (t1) || TYPE_UNSIGNED (t2))
		    ? long_long_unsigned_type_node
		    : long_long_integer_type_node);
	  return build_type_attribute_variant (t, attributes);
	}

      /* Go through the same procedure, but for longs.  */
      if (same_type_p (TYPE_MAIN_VARIANT (t1), long_unsigned_type_node)
	  || same_type_p (TYPE_MAIN_VARIANT (t2), long_unsigned_type_node))
	return build_type_attribute_variant (long_unsigned_type_node,
					     attributes);
      if (same_type_p (TYPE_MAIN_VARIANT (t1), long_integer_type_node)
	  || same_type_p (TYPE_MAIN_VARIANT (t2), long_integer_type_node))
	{
	  tree t = ((TYPE_UNSIGNED (t1) || TYPE_UNSIGNED (t2))
		    ? long_unsigned_type_node : long_integer_type_node);
	  return build_type_attribute_variant (t, attributes);
	}

      /* For __intN types, either the type is __int128 (and is lower
	 priority than the types checked above, but higher than other
	 128-bit types) or it's known to not be the same size as other
	 types (enforced in toplev.cc).  Prefer the unsigned type. */
      for (i = 0; i < NUM_INT_N_ENTS; i ++)
	{
	  if (int_n_enabled_p [i]
	      && (same_type_p (TYPE_MAIN_VARIANT (t1), int_n_trees[i].signed_type)
		  || same_type_p (TYPE_MAIN_VARIANT (t2), int_n_trees[i].signed_type)
		  || same_type_p (TYPE_MAIN_VARIANT (t1), int_n_trees[i].unsigned_type)
		  || same_type_p (TYPE_MAIN_VARIANT (t2), int_n_trees[i].unsigned_type)))
	    {
	      tree t = ((TYPE_UNSIGNED (t1) || TYPE_UNSIGNED (t2))
			? int_n_trees[i].unsigned_type
			: int_n_trees[i].signed_type);
	      return build_type_attribute_variant (t, attributes);
	    }
	}

      /* Otherwise prefer the unsigned one.  */
      if (TYPE_UNSIGNED (t1))
	return build_type_attribute_variant (t1, attributes);
      else
	return build_type_attribute_variant (t2, attributes);
    }
  else
    {
      if (same_type_p (TYPE_MAIN_VARIANT (t1), long_double_type_node)
	  || same_type_p (TYPE_MAIN_VARIANT (t2), long_double_type_node))
	return build_type_attribute_variant (long_double_type_node,
					     attributes);
      if (same_type_p (TYPE_MAIN_VARIANT (t1), double_type_node)
	  || same_type_p (TYPE_MAIN_VARIANT (t2), double_type_node))
	return build_type_attribute_variant (double_type_node,
					     attributes);
      if (same_type_p (TYPE_MAIN_VARIANT (t1), float_type_node)
	  || same_type_p (TYPE_MAIN_VARIANT (t2), float_type_node))
	return build_type_attribute_variant (float_type_node,
					     attributes);

      /* Two floating-point types whose TYPE_MAIN_VARIANTs are none of
	 the standard C++ floating-point types.  Logic earlier in this
	 function has already eliminated the possibility that
	 TYPE_PRECISION (t2) != TYPE_PRECISION (t1), so there's no
	 compelling reason to choose one or the other.  */
      return build_type_attribute_variant (t1, attributes);
    }
}

/* T1 and T2 are arithmetic or enumeration types.  Return the type
   that will result from the "usual arithmetic conversions" on T1 and
   T2 as described in [expr].  */

tree
type_after_usual_arithmetic_conversions (tree t1, tree t2)
{
  gcc_assert (ARITHMETIC_TYPE_P (t1)
	      || VECTOR_TYPE_P (t1)
	      || UNSCOPED_ENUM_P (t1));
  gcc_assert (ARITHMETIC_TYPE_P (t2)
	      || VECTOR_TYPE_P (t2)
	      || UNSCOPED_ENUM_P (t2));

  /* Perform the integral promotions.  We do not promote real types here.  */
  if (INTEGRAL_OR_ENUMERATION_TYPE_P (t1)
      && INTEGRAL_OR_ENUMERATION_TYPE_P (t2))
    {
      t1 = type_promotes_to (t1);
      t2 = type_promotes_to (t2);
    }

  return cp_common_type (t1, t2);
}

static void
composite_pointer_error (const op_location_t &location,
			 diagnostic_t kind, tree t1, tree t2,
			 composite_pointer_operation operation)
{
  switch (operation)
    {
    case CPO_COMPARISON:
      emit_diagnostic (kind, location, 0,
		       "comparison between "
		       "distinct pointer types %qT and %qT lacks a cast",
		       t1, t2);
      break;
    case CPO_CONVERSION:
      emit_diagnostic (kind, location, 0,
		       "conversion between "
		       "distinct pointer types %qT and %qT lacks a cast",
		       t1, t2);
      break;
    case CPO_CONDITIONAL_EXPR:
      emit_diagnostic (kind, location, 0,
		       "conditional expression between "
		       "distinct pointer types %qT and %qT lacks a cast",
		       t1, t2);
      break;
    default:
      gcc_unreachable ();
    }
}

/* Subroutine of composite_pointer_type to implement the recursive
   case.  See that function for documentation of the parameters.  And ADD_CONST
   is used to track adding "const" where needed.  */

static tree
composite_pointer_type_r (const op_location_t &location,
			  tree t1, tree t2, bool *add_const,
			  composite_pointer_operation operation,
			  tsubst_flags_t complain)
{
  tree pointee1;
  tree pointee2;
  tree result_type;
  tree attributes;

  /* Determine the types pointed to by T1 and T2.  */
  if (TYPE_PTR_P (t1))
    {
      pointee1 = TREE_TYPE (t1);
      pointee2 = TREE_TYPE (t2);
    }
  else
    {
      pointee1 = TYPE_PTRMEM_POINTED_TO_TYPE (t1);
      pointee2 = TYPE_PTRMEM_POINTED_TO_TYPE (t2);
    }

  /* [expr.type]

     If T1 and T2 are similar types, the result is the cv-combined type of
     T1 and T2.  */
  if (same_type_ignoring_top_level_qualifiers_p (pointee1, pointee2))
    result_type = pointee1;
  else if ((TYPE_PTR_P (pointee1) && TYPE_PTR_P (pointee2))
	   || (TYPE_PTRMEM_P (pointee1) && TYPE_PTRMEM_P (pointee2)))
    {
      result_type = composite_pointer_type_r (location, pointee1, pointee2,
					      add_const, operation, complain);
      if (result_type == error_mark_node)
	return error_mark_node;
    }
  else
    {
      if (complain & tf_error)
	composite_pointer_error (location, DK_PERMERROR,
				 t1, t2, operation);
      else
	return error_mark_node;
      result_type = void_type_node;
    }
  const int q1 = cp_type_quals (pointee1);
  const int q2 = cp_type_quals (pointee2);
  const int quals = q1 | q2;
  result_type = cp_build_qualified_type (result_type,
					 (quals | (*add_const
						   ? TYPE_QUAL_CONST
						   : TYPE_UNQUALIFIED)));
  /* The cv-combined type can add "const" as per [conv.qual]/3.3 (except for
     the TLQ).  The reason is that both T1 and T2 can then be converted to the
     cv-combined type of T1 and T2.  */
  if (quals != q1 || quals != q2)
    *add_const = true;
  /* If the original types were pointers to members, so is the
     result.  */
  if (TYPE_PTRMEM_P (t1))
    {
      if (!same_type_p (TYPE_PTRMEM_CLASS_TYPE (t1),
			TYPE_PTRMEM_CLASS_TYPE (t2)))
	{
	  if (complain & tf_error)
	    composite_pointer_error (location, DK_PERMERROR,
				     t1, t2, operation);
	  else
	    return error_mark_node;
	}
      result_type = build_ptrmem_type (TYPE_PTRMEM_CLASS_TYPE (t1),
				       result_type);
    }
  else
    result_type = build_pointer_type (result_type);

  /* Merge the attributes.  */
  attributes = (*targetm.merge_type_attributes) (t1, t2);
  return build_type_attribute_variant (result_type, attributes);
}

/* Return the composite pointer type (see [expr.type]) for T1 and T2.
   ARG1 and ARG2 are the values with those types.  The OPERATION is to
   describe the operation between the pointer types,
   in case an error occurs.

   This routine also implements the computation of a common type for
   pointers-to-members as per [expr.eq].  */

tree
composite_pointer_type (const op_location_t &location,
			tree t1, tree t2, tree arg1, tree arg2,
			composite_pointer_operation operation, 
			tsubst_flags_t complain)
{
  tree class1;
  tree class2;

  /* [expr.type]

     If one operand is a null pointer constant, the composite pointer
     type is the type of the other operand.  */
  if (null_ptr_cst_p (arg1))
    return t2;
  if (null_ptr_cst_p (arg2))
    return t1;

  /* We have:

       [expr.type]

       If one of the operands has type "pointer to cv1 void", then
       the other has type "pointer to cv2 T", and the composite pointer
       type is "pointer to cv12 void", where cv12 is the union of cv1
       and cv2.

    If either type is a pointer to void, make sure it is T1.  */
  if (TYPE_PTR_P (t2) && VOID_TYPE_P (TREE_TYPE (t2)))
    std::swap (t1, t2);

  /* Now, if T1 is a pointer to void, merge the qualifiers.  */
  if (TYPE_PTR_P (t1) && VOID_TYPE_P (TREE_TYPE (t1)))
    {
      tree attributes;
      tree result_type;

      if (TYPE_PTRFN_P (t2))
	{
	  if (complain & tf_error)
	    {
	      switch (operation)
		{
		case CPO_COMPARISON:
		  pedwarn (location, OPT_Wpedantic, 
			   "ISO C++ forbids comparison between pointer "
			   "of type %<void *%> and pointer-to-function");
		  break;
		case CPO_CONVERSION:
		  pedwarn (location, OPT_Wpedantic,
			   "ISO C++ forbids conversion between pointer "
			   "of type %<void *%> and pointer-to-function");
		  break;
		case CPO_CONDITIONAL_EXPR:
		  pedwarn (location, OPT_Wpedantic,
			   "ISO C++ forbids conditional expression between "
			   "pointer of type %<void *%> and "
			   "pointer-to-function");
		  break;
		default:
		  gcc_unreachable ();
		}
	    }
	  else
	    return error_mark_node;
        }
      result_type
	= cp_build_qualified_type (void_type_node,
				   (cp_type_quals (TREE_TYPE (t1))
				    | cp_type_quals (TREE_TYPE (t2))));
      result_type = build_pointer_type (result_type);
      /* Merge the attributes.  */
      attributes = (*targetm.merge_type_attributes) (t1, t2);
      return build_type_attribute_variant (result_type, attributes);
    }

  if (c_dialect_objc () && TYPE_PTR_P (t1)
      && TYPE_PTR_P (t2))
    {
      if (objc_have_common_type (t1, t2, -3, NULL_TREE))
	return objc_common_type (t1, t2);
    }

  /* if T1 or T2 is "pointer to noexcept function" and the other type is
     "pointer to function", where the function types are otherwise the same,
     "pointer to function" */
  if (fnptr_conv_p (t1, t2))
    return t1;
  if (fnptr_conv_p (t2, t1))
    return t2;

  /* [expr.eq] permits the application of a pointer conversion to
     bring the pointers to a common type.  */
  if (TYPE_PTR_P (t1) && TYPE_PTR_P (t2)
      && CLASS_TYPE_P (TREE_TYPE (t1))
      && CLASS_TYPE_P (TREE_TYPE (t2))
      && !same_type_ignoring_top_level_qualifiers_p (TREE_TYPE (t1),
						     TREE_TYPE (t2)))
    {
      class1 = TREE_TYPE (t1);
      class2 = TREE_TYPE (t2);

      if (DERIVED_FROM_P (class1, class2))
	t2 = (build_pointer_type
	      (cp_build_qualified_type (class1, cp_type_quals (class2))));
      else if (DERIVED_FROM_P (class2, class1))
	t1 = (build_pointer_type
	      (cp_build_qualified_type (class2, cp_type_quals (class1))));
      else
        {
          if (complain & tf_error)
	    composite_pointer_error (location, DK_ERROR, t1, t2, operation);
          return error_mark_node;
        }
    }
  /* [expr.eq] permits the application of a pointer-to-member
     conversion to change the class type of one of the types.  */
  else if (TYPE_PTRMEM_P (t1)
           && !same_type_p (TYPE_PTRMEM_CLASS_TYPE (t1),
			    TYPE_PTRMEM_CLASS_TYPE (t2)))
    {
      class1 = TYPE_PTRMEM_CLASS_TYPE (t1);
      class2 = TYPE_PTRMEM_CLASS_TYPE (t2);

      if (DERIVED_FROM_P (class1, class2))
	t1 = build_ptrmem_type (class2, TYPE_PTRMEM_POINTED_TO_TYPE (t1));
      else if (DERIVED_FROM_P (class2, class1))
	t2 = build_ptrmem_type (class1, TYPE_PTRMEM_POINTED_TO_TYPE (t2));
      else
        {
          if (complain & tf_error)
            switch (operation)
              {
              case CPO_COMPARISON:
                error_at (location, "comparison between distinct "
			  "pointer-to-member types %qT and %qT lacks a cast",
			  t1, t2);
                break;
              case CPO_CONVERSION:
                error_at (location, "conversion between distinct "
			  "pointer-to-member types %qT and %qT lacks a cast",
			  t1, t2);
                break;
              case CPO_CONDITIONAL_EXPR:
                error_at (location, "conditional expression between distinct "
			  "pointer-to-member types %qT and %qT lacks a cast",
			  t1, t2);
                break;
              default:
                gcc_unreachable ();
              }
          return error_mark_node;
        }
    }

  bool add_const = false;
  return composite_pointer_type_r (location, t1, t2, &add_const, operation,
				   complain);
}

/* Return the merged type of two types.
   We assume that comptypes has already been done and returned 1;
   if that isn't so, this may crash.

   This just combines attributes and default arguments; any other
   differences would cause the two types to compare unalike.  */

tree
merge_types (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 (original_type (t1) == original_type (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;

  /* Handle merging an auto redeclaration with a previous deduced
     return type.  */
  if (is_auto (t1))
    return t2;

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

  if (TYPE_PTRMEMFUNC_P (t1))
    t1 = TYPE_PTRMEMFUNC_FN_TYPE (t1);
  if (TYPE_PTRMEMFUNC_P (t2))
    t2 = TYPE_PTRMEMFUNC_FN_TYPE (t2);

  code1 = TREE_CODE (t1);
  code2 = TREE_CODE (t2);
  if (code1 != code2)
    {
      gcc_assert (code1 == TYPENAME_TYPE || code2 == TYPENAME_TYPE);
      if (code1 == TYPENAME_TYPE)
	{
          t1 = resolve_typename_type (t1, /*only_current_p=*/true);
	  code1 = TREE_CODE (t1);
	}
      else
	{
          t2 = resolve_typename_type (t2, /*only_current_p=*/true);
	  code2 = TREE_CODE (t2);
	}
    }

  switch (code1)
    {
    case POINTER_TYPE:
    case REFERENCE_TYPE:
      /* For two pointers, do this recursively on the target type.  */
      {
	tree target = merge_types (TREE_TYPE (t1), TREE_TYPE (t2));
	int quals = cp_type_quals (t1);

	if (code1 == POINTER_TYPE)
	  {
	    t1 = build_pointer_type (target);
	    if (TREE_CODE (target) == METHOD_TYPE)
	      t1 = build_ptrmemfunc_type (t1);
	  }
	else
	  t1 = cp_build_reference_type (target, TYPE_REF_IS_RVALUE (t1));
	t1 = build_type_attribute_variant (t1, attributes);
	t1 = cp_build_qualified_type (t1, quals);

	return t1;
      }

    case OFFSET_TYPE:
      {
	int quals;
	tree pointee;
	quals = cp_type_quals (t1);
	pointee = merge_types (TYPE_PTRMEM_POINTED_TO_TYPE (t1),
			       TYPE_PTRMEM_POINTED_TO_TYPE (t2));
	t1 = build_ptrmem_type (TYPE_PTRMEM_CLASS_TYPE (t1),
				pointee);
	t1 = cp_build_qualified_type (t1, quals);
	break;
      }

    case ARRAY_TYPE:
      {
	tree elt = merge_types (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_cplus_array_type
	  (elt, TYPE_DOMAIN (TYPE_DOMAIN (t1) ? t1 : t2));
	break;
      }

    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 = merge_types (TREE_TYPE (t1), TREE_TYPE (t2));
	tree p1 = TYPE_ARG_TYPES (t1);
	tree p2 = TYPE_ARG_TYPES (t2);
	tree parms;

	/* Save space: see if the result is identical to one of the args.  */
	if (valtype == TREE_TYPE (t1) && ! p2)
	  return cp_build_type_attribute_variant (t1, attributes);
	if (valtype == TREE_TYPE (t2) && ! p1)
	  return cp_build_type_attribute_variant (t2, attributes);

	/* Simple way if one arg fails to specify argument types.  */
	if (p1 == NULL_TREE || TREE_VALUE (p1) == void_type_node)
	  parms = p2;
	else if (p2 == NULL_TREE || TREE_VALUE (p2) == void_type_node)
	  parms = p1;
	else
	  parms = commonparms (p1, p2);

	cp_cv_quals quals = type_memfn_quals (t1);
	cp_ref_qualifier rqual = type_memfn_rqual (t1);
	gcc_assert (quals == type_memfn_quals (t2));
	gcc_assert (rqual == type_memfn_rqual (t2));

	tree rval = build_function_type (valtype, parms);
	rval = apply_memfn_quals (rval, quals);
	tree raises = merge_exception_specifiers (TYPE_RAISES_EXCEPTIONS (t1),
						  TYPE_RAISES_EXCEPTIONS (t2));
	bool late_return_type_p = TYPE_HAS_LATE_RETURN_TYPE (t1);
	t1 = build_cp_fntype_variant (rval, rqual, raises, late_return_type_p);
	break;
      }

    case METHOD_TYPE:
      {
	/* Get this value the long way, since TYPE_METHOD_BASETYPE
	   is just the main variant of this.  */
	tree basetype = class_of_this_parm (t2);
	tree raises = merge_exception_specifiers (TYPE_RAISES_EXCEPTIONS (t1),
						  TYPE_RAISES_EXCEPTIONS (t2));
	cp_ref_qualifier rqual = type_memfn_rqual (t1);
	tree t3;
	bool late_return_type_1_p = TYPE_HAS_LATE_RETURN_TYPE (t1);

	/* If this was a member function type, get back to the
	   original type of type member function (i.e., without
	   the class instance variable up front.  */
	t1 = build_function_type (TREE_TYPE (t1),
				  TREE_CHAIN (TYPE_ARG_TYPES (t1)));
	t2 = build_function_type (TREE_TYPE (t2),
				  TREE_CHAIN (TYPE_ARG_TYPES (t2)));
	t3 = merge_types (t1, t2);
	t3 = build_method_type_directly (basetype, TREE_TYPE (t3),
					 TYPE_ARG_TYPES (t3));
	t1 = build_cp_fntype_variant (t3, rqual, raises, late_return_type_1_p);
	break;
      }

    case TYPENAME_TYPE:
      /* There is no need to merge attributes into a TYPENAME_TYPE.
	 When the type is instantiated it will have whatever
	 attributes result from the instantiation.  */
      return t1;

    default:;
      if (attribute_list_equal (TYPE_ATTRIBUTES (t1), attributes))
	return t1;
      else if (attribute_list_equal (TYPE_ATTRIBUTES (t2), attributes))
	return t2;
      break;
    }

  return cp_build_type_attribute_variant (t1, attributes);
}

/* Return the ARRAY_TYPE type without its domain.  */

tree
strip_array_domain (tree type)
{
  tree t2;
  gcc_assert (TREE_CODE (type) == ARRAY_TYPE);
  if (TYPE_DOMAIN (type) == NULL_TREE)
    return type;
  t2 = build_cplus_array_type (TREE_TYPE (type), NULL_TREE);
  return cp_build_type_attribute_variant (t2, TYPE_ATTRIBUTES (type));
}

/* Wrapper around cp_common_type that is used by c-common.cc and other
   front end optimizations that remove promotions.  

   Return the common type for two arithmetic types T1 and T2 under the
   usual arithmetic conversions.  The default conversions have already
   been applied, and enumerated types converted to their compatible
   integer types.  */

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

  return cp_common_type (t1, t2);
}

/* Return the common type of two pointer types T1 and T2.  This is the
   type for the result of most arithmetic operations if the operands
   have the given two types.
 
   We assume that comp_target_types has already been done and returned
   nonzero; if that isn't so, this may crash.  */

tree
common_pointer_type (tree t1, tree t2)
{
  gcc_assert ((TYPE_PTR_P (t1) && TYPE_PTR_P (t2))
              || (TYPE_PTRDATAMEM_P (t1) && TYPE_PTRDATAMEM_P (t2))
              || (TYPE_PTRMEMFUNC_P (t1) && TYPE_PTRMEMFUNC_P (t2)));

  return composite_pointer_type (input_location, t1, t2,
				 error_mark_node, error_mark_node,
                                 CPO_CONVERSION, tf_warning_or_error);
}

/* Compare two exception specifier types for exactness or subsetness, if
   allowed. Returns false for mismatch, true for match (same, or
   derived and !exact).

   [except.spec] "If a class X ... objects of class X or any class publicly
   and unambiguously derived from X. Similarly, if a pointer type Y * ...
   exceptions of type Y * or that are pointers to any type publicly and
   unambiguously derived from Y. Otherwise a function only allows exceptions
   that have the same type ..."
   This does not mention cv qualifiers and is different to what throw
   [except.throw] and catch [except.catch] will do. They will ignore the
   top level cv qualifiers, and allow qualifiers in the pointer to class
   example.

   We implement the letter of the standard.  */

static bool
comp_except_types (tree a, tree b, bool exact)
{
  if (same_type_p (a, b))
    return true;
  else if (!exact)
    {
      if (cp_type_quals (a) || cp_type_quals (b))
	return false;

      if (TYPE_PTR_P (a) && TYPE_PTR_P (b))
	{
	  a = TREE_TYPE (a);
	  b = TREE_TYPE (b);
	  if (cp_type_quals (a) || cp_type_quals (b))
	    return false;
	}

      if (TREE_CODE (a) != RECORD_TYPE
	  || TREE_CODE (b) != RECORD_TYPE)
	return false;

      if (publicly_uniquely_derived_p (a, b))
	return true;
    }
  return false;
}

/* Return true if TYPE1 and TYPE2 are equivalent exception specifiers.
   If EXACT is ce_derived, T2 can be stricter than T1 (according to 15.4/5).
   If EXACT is ce_type, the C++17 type compatibility rules apply.
   If EXACT is ce_normal, the compatibility rules in 15.4/3 apply.
   If EXACT is ce_exact, the specs must be exactly the same. Exception lists
   are unordered, but we've already filtered out duplicates. Most lists will
   be in order, we should try to make use of that.  */

bool
comp_except_specs (const_tree t1, const_tree t2, int exact)
{
  const_tree probe;
  const_tree base;
  int  length = 0;

  if (t1 == t2)
    return true;

  /* First handle noexcept.  */
  if (exact < ce_exact)
    {
      if (exact == ce_type
	  && (canonical_eh_spec (CONST_CAST_TREE (t1))
	      == canonical_eh_spec (CONST_CAST_TREE (t2))))
	return true;

      /* noexcept(false) is compatible with no exception-specification,
	 and less strict than any spec.  */
      if (t1 == noexcept_false_spec)
	return t2 == NULL_TREE || exact == ce_derived;
      /* Even a derived noexcept(false) is compatible with no
	 exception-specification.  */
      if (t2 == noexcept_false_spec)
	return t1 == NULL_TREE;

      /* Otherwise, if we aren't looking for an exact match, noexcept is
	 equivalent to throw().  */
      if (t1 == noexcept_true_spec)
	t1 = empty_except_spec;
      if (t2 == noexcept_true_spec)
	t2 = empty_except_spec;
    }

  /* If any noexcept is left, it is only comparable to itself;
     either we're looking for an exact match or we're redeclaring a
     template with dependent noexcept.  */
  if ((t1 && TREE_PURPOSE (t1))
      || (t2 && TREE_PURPOSE (t2)))
    return (t1 && t2
	    && cp_tree_equal (TREE_PURPOSE (t1), TREE_PURPOSE (t2)));

  if (t1 == NULL_TREE)			   /* T1 is ...  */
    return t2 == NULL_TREE || exact == ce_derived;
  if (!TREE_VALUE (t1))			   /* t1 is EMPTY */
    return t2 != NULL_TREE && !TREE_VALUE (t2);
  if (t2 == NULL_TREE)			   /* T2 is ...  */
    return false;
  if (TREE_VALUE (t1) && !TREE_VALUE (t2)) /* T2 is EMPTY, T1 is not */
    return exact == ce_derived;

  /* Neither set is ... or EMPTY, make sure each part of T2 is in T1.
     Count how many we find, to determine exactness. For exact matching and
     ordered T1, T2, this is an O(n) operation, otherwise its worst case is
     O(nm).  */
  for (base = t1; t2 != NULL_TREE; t2 = TREE_CHAIN (t2))
    {
      for (probe = base; probe != NULL_TREE; probe = TREE_CHAIN (probe))
	{
	  tree a = TREE_VALUE (probe);
	  tree b = TREE_VALUE (t2);

	  if (comp_except_types (a, b, exact))
	    {
	      if (probe == base && exact > ce_derived)
		base = TREE_CHAIN (probe);
	      length++;
	      break;
	    }
	}
      if (probe == NULL_TREE)
	return false;
    }
  return exact == ce_derived || base == NULL_TREE || length == list_length (t1);
}

/* Compare the array types T1 and T2.  CB says how we should behave when
   comparing array bounds: bounds_none doesn't allow dimensionless arrays,
   bounds_either says than any array can be [], bounds_first means that
   onlt T1 can be an array with unknown bounds.  STRICT is true if
   qualifiers must match when comparing the types of the array elements.  */

static bool
comp_array_types (const_tree t1, const_tree t2, compare_bounds_t cb,
		  bool strict)
{
  tree d1;
  tree d2;
  tree max1, max2;

  if (t1 == t2)
    return true;

  /* The type of the array elements must be the same.  */
  if (strict
      ? !same_type_p (TREE_TYPE (t1), TREE_TYPE (t2))
      : !similar_type_p (TREE_TYPE (t1), TREE_TYPE (t2)))
    return false;

  d1 = TYPE_DOMAIN (t1);
  d2 = TYPE_DOMAIN (t2);

  if (d1 == d2)
    return true;

  /* If one of the arrays is dimensionless, and the other has a
     dimension, they are of different types.  However, it is valid to
     write:

       extern int a[];
       int a[3];

     by [basic.link]:

       declarations for an array object can specify
       array types that differ by the presence or absence of a major
       array bound (_dcl.array_).  */
  if (!d1 && d2)
    return cb >= bounds_either;
  else if (d1 && !d2)
    return cb == bounds_either;

  /* Check that the dimensions are the same.  */

  if (!cp_tree_equal (TYPE_MIN_VALUE (d1), TYPE_MIN_VALUE (d2)))
    return false;
  max1 = TYPE_MAX_VALUE (d1);
  max2 = TYPE_MAX_VALUE (d2);

  if (!cp_tree_equal (max1, max2))
    return false;

  return true;
}

/* Compare the relative position of T1 and T2 into their respective
   template parameter list.
   T1 and T2 must be template parameter types.
   Return TRUE if T1 and T2 have the same position, FALSE otherwise.  */

static bool
comp_template_parms_position (tree t1, tree t2)
{
  tree index1, index2;
  gcc_assert (t1 && t2
	      && TREE_CODE (t1) == TREE_CODE (t2)
	      && (TREE_CODE (t1) == BOUND_TEMPLATE_TEMPLATE_PARM
		  || TREE_CODE (t1) == TEMPLATE_TEMPLATE_PARM
		  || TREE_CODE (t1) == TEMPLATE_TYPE_PARM));

  index1 = TEMPLATE_TYPE_PARM_INDEX (TYPE_MAIN_VARIANT (t1));
  index2 = TEMPLATE_TYPE_PARM_INDEX (TYPE_MAIN_VARIANT (t2));

  /* Then compare their relative position.  */
  if (TEMPLATE_PARM_IDX (index1) != TEMPLATE_PARM_IDX (index2)
      || TEMPLATE_PARM_LEVEL (index1) != TEMPLATE_PARM_LEVEL (index2)
      || (TEMPLATE_PARM_PARAMETER_PACK (index1)
	  != TEMPLATE_PARM_PARAMETER_PACK (index2)))
    return false;

  /* In C++14 we can end up comparing 'auto' to a normal template
     parameter.  Don't confuse them.  */
  if (cxx_dialect >= cxx14 && (is_auto (t1) || is_auto (t2)))
    return TYPE_IDENTIFIER (t1) == TYPE_IDENTIFIER (t2);

  return true;
}

/* Heuristic check if two parameter types can be considered ABI-equivalent.  */

static bool
cxx_safe_arg_type_equiv_p (tree t1, tree t2)
{
  t1 = TYPE_MAIN_VARIANT (t1);
  t2 = TYPE_MAIN_VARIANT (t2);

  if (TYPE_PTR_P (t1)
      && TYPE_PTR_P (t2))
    return true;

  /* The signedness of the parameter matters only when an integral
     type smaller than int is promoted to int, otherwise only the
     precision of the parameter matters.
     This check should make sure that the callee does not see
     undefined values in argument registers.  */
  if (INTEGRAL_TYPE_P (t1)
      && INTEGRAL_TYPE_P (t2)
      && TYPE_PRECISION (t1) == TYPE_PRECISION (t2)
      && (TYPE_UNSIGNED (t1) == TYPE_UNSIGNED (t2)
	  || !targetm.calls.promote_prototypes (NULL_TREE)
	  || TYPE_PRECISION (t1) >= TYPE_PRECISION (integer_type_node)))
    return true;

  return same_type_p (t1, t2);
}

/* Check if a type cast between two function types can be considered safe.  */

static bool
cxx_safe_function_type_cast_p (tree t1, tree t2)
{
  if (TREE_TYPE (t1) == void_type_node &&
      TYPE_ARG_TYPES (t1) == void_list_node)
    return true;

  if (TREE_TYPE (t2) == void_type_node &&
      TYPE_ARG_TYPES (t2) == void_list_node)
    return true;

  if (!cxx_safe_arg_type_equiv_p (TREE_TYPE (t1), TREE_TYPE (t2)))
    return false;

  for (t1 = TYPE_ARG_TYPES (t1), t2 = TYPE_ARG_TYPES (t2);
       t1 && t2;
       t1 = TREE_CHAIN (t1), t2 = TREE_CHAIN (t2))
    if (!cxx_safe_arg_type_equiv_p (TREE_VALUE (t1), TREE_VALUE (t2)))
      return false;

  return true;
}

/* Subroutine in comptypes.  */

static bool
structural_comptypes (tree t1, tree t2, int strict)
{
  /* Both should be types that are not obviously the same.  */
  gcc_checking_assert (t1 != t2 && TYPE_P (t1) && TYPE_P (t2));

  /* Suppress typename resolution under spec_hasher::equal in place of calling
     push_to_top_level there.  */
  if (!comparing_specializations)
    {
      /* TYPENAME_TYPEs should be resolved if the qualifying scope is the
	 current instantiation.  */
      if (TREE_CODE (t1) == TYPENAME_TYPE)
	t1 = resolve_typename_type (t1, /*only_current_p=*/true);

      if (TREE_CODE (t2) == TYPENAME_TYPE)
	t2 = resolve_typename_type (t2, /*only_current_p=*/true);
    }

  if (TYPE_PTRMEMFUNC_P (t1))
    t1 = TYPE_PTRMEMFUNC_FN_TYPE (t1);
  if (TYPE_PTRMEMFUNC_P (t2))
    t2 = TYPE_PTRMEMFUNC_FN_TYPE (t2);

  /* Different classes of types can't be compatible.  */
  if (TREE_CODE (t1) != TREE_CODE (t2))
    return false;

  /* Qualifiers must match.  For array types, we will check when we
     recur on the array element types.  */
  if (TREE_CODE (t1) != ARRAY_TYPE
      && cp_type_quals (t1) != cp_type_quals (t2))
    return false;
  if (TREE_CODE (t1) == FUNCTION_TYPE
      && type_memfn_quals (t1) != type_memfn_quals (t2))
    return false;
  /* Need to check this before TYPE_MAIN_VARIANT.
     FIXME function qualifiers should really change the main variant.  */
  if (FUNC_OR_METHOD_TYPE_P (t1))
    {
      if (type_memfn_rqual (t1) != type_memfn_rqual (t2))
	return false;
      if (flag_noexcept_type
	  && !comp_except_specs (TYPE_RAISES_EXCEPTIONS (t1),
				 TYPE_RAISES_EXCEPTIONS (t2),
				 ce_type))
	return false;
    }

  /* 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 (TREE_CODE (t1) != ARRAY_TYPE
      && TYPE_MAIN_VARIANT (t1) == TYPE_MAIN_VARIANT (t2))
    goto check_alias;

  /* Compare the types.  Return false on known not-same. Break on not
     known.   Never return true from this switch -- you'll break
     specialization comparison.    */
  switch (TREE_CODE (t1))
    {
    case VOID_TYPE:
    case BOOLEAN_TYPE:
      /* All void and bool types are the same.  */
      break;

    case OPAQUE_TYPE:
    case INTEGER_TYPE:
    case FIXED_POINT_TYPE:
    case REAL_TYPE:
      /* With these nodes, we can't determine type equivalence by
	 looking at what is stored in the nodes themselves, because
	 two nodes might have different TYPE_MAIN_VARIANTs but still
	 represent the same type.  For example, wchar_t and int could
	 have the same properties (TYPE_PRECISION, TYPE_MIN_VALUE,
	 TYPE_MAX_VALUE, etc.), but have different TYPE_MAIN_VARIANTs
	 and are distinct types. On the other hand, int and the
	 following typedef

           typedef int INT __attribute((may_alias));

	 have identical properties, different TYPE_MAIN_VARIANTs, but
	 represent the same type.  The canonical type system keeps
	 track of equivalence in this case, so we fall back on it.  */
      if (TYPE_CANONICAL (t1) != TYPE_CANONICAL (t2))
	return false;

      /* We don't need or want the attribute comparison.  */
      goto check_alias;

    case TEMPLATE_TEMPLATE_PARM:
    case BOUND_TEMPLATE_TEMPLATE_PARM:
      if (!comp_template_parms_position (t1, t2))
	return false;
      if (!comp_template_parms
	  (DECL_TEMPLATE_PARMS (TEMPLATE_TEMPLATE_PARM_TEMPLATE_DECL (t1)),
	   DECL_TEMPLATE_PARMS (TEMPLATE_TEMPLATE_PARM_TEMPLATE_DECL (t2))))
	return false;
      if (TREE_CODE (t1) == TEMPLATE_TEMPLATE_PARM)
	break;
      /* Don't check inheritance.  */
      strict = COMPARE_STRICT;
      /* Fall through.  */

    case RECORD_TYPE:
    case UNION_TYPE:
      if (TYPE_TEMPLATE_INFO (t1) && TYPE_TEMPLATE_INFO (t2)
	  && (TYPE_TI_TEMPLATE (t1) == TYPE_TI_TEMPLATE (t2)
	      || TREE_CODE (t1) == BOUND_TEMPLATE_TEMPLATE_PARM)
	  && comp_template_args (TYPE_TI_ARGS (t1), TYPE_TI_ARGS (t2)))
	break;

      if ((strict & COMPARE_BASE) && DERIVED_FROM_P (t1, t2))
	break;
      else if ((strict & COMPARE_DERIVED) && DERIVED_FROM_P (t2, t1))
	break;

      return false;

    case OFFSET_TYPE:
      if (!comptypes (TYPE_OFFSET_BASETYPE (t1), TYPE_OFFSET_BASETYPE (t2),
		      strict & ~COMPARE_REDECLARATION))
	return false;
      if (!same_type_p (TREE_TYPE (t1), TREE_TYPE (t2)))
	return false;
      break;

    case REFERENCE_TYPE:
      if (TYPE_REF_IS_RVALUE (t1) != TYPE_REF_IS_RVALUE (t2))
	return false;
      /* fall through to checks for pointer types */
      gcc_fallthrough ();

    case POINTER_TYPE:
      if (TYPE_MODE (t1) != TYPE_MODE (t2)
	  || !same_type_p (TREE_TYPE (t1), TREE_TYPE (t2)))
	return false;
      break;

    case METHOD_TYPE:
    case FUNCTION_TYPE:
      /* Exception specs and memfn_rquals were checked above.  */
      if (!same_type_p (TREE_TYPE (t1), TREE_TYPE (t2)))
	return false;
      if (!compparms (TYPE_ARG_TYPES (t1), TYPE_ARG_TYPES (t2)))
	return false;
      break;

    case ARRAY_TYPE:
      /* Target types must match incl. qualifiers.  */
      if (!comp_array_types (t1, t2, ((strict & COMPARE_REDECLARATION)
				      ? bounds_either : bounds_none),
			     /*strict=*/true))
	return false;
      break;

    case TEMPLATE_TYPE_PARM:
      /* If T1 and T2 don't have the same relative position in their
	 template parameters set, they can't be equal.  */
      if (!comp_template_parms_position (t1, t2))
	return false;
      /* If T1 and T2 don't represent the same class template deduction,
         they aren't equal.  */
      if (CLASS_PLACEHOLDER_TEMPLATE (t1)
	  != CLASS_PLACEHOLDER_TEMPLATE (t2))
	return false;
      /* Constrained 'auto's are distinct from parms that don't have the same
	 constraints.  */
      if (!equivalent_placeholder_constraints (t1, t2))
	return false;
      break;

    case TYPENAME_TYPE:
      if (!cp_tree_equal (TYPENAME_TYPE_FULLNAME (t1),
			  TYPENAME_TYPE_FULLNAME (t2)))
	return false;
      /* Qualifiers don't matter on scopes.  */
      if (!same_type_ignoring_top_level_qualifiers_p (TYPE_CONTEXT (t1),
						      TYPE_CONTEXT (t2)))
	return false;
      break;

    case UNBOUND_CLASS_TEMPLATE:
      if (!cp_tree_equal (TYPE_IDENTIFIER (t1), TYPE_IDENTIFIER (t2)))
	return false;
      if (!same_type_p (TYPE_CONTEXT (t1), TYPE_CONTEXT (t2)))
	return false;
      break;

    case COMPLEX_TYPE:
      if (!same_type_p (TREE_TYPE (t1), TREE_TYPE (t2)))
	return false;
      break;

    case VECTOR_TYPE:
      if (gnu_vector_type_p (t1) != gnu_vector_type_p (t2)
	  || maybe_ne (TYPE_VECTOR_SUBPARTS (t1), TYPE_VECTOR_SUBPARTS (t2))
	  || !same_type_p (TREE_TYPE (t1), TREE_TYPE (t2)))
	return false;
      break;

    case TYPE_PACK_EXPANSION:
      return (same_type_p (PACK_EXPANSION_PATTERN (t1),
			   PACK_EXPANSION_PATTERN (t2))
	      && comp_template_args (PACK_EXPANSION_EXTRA_ARGS (t1),
				     PACK_EXPANSION_EXTRA_ARGS (t2)));

    case DECLTYPE_TYPE:
      if (DECLTYPE_TYPE_ID_EXPR_OR_MEMBER_ACCESS_P (t1)
          != DECLTYPE_TYPE_ID_EXPR_OR_MEMBER_ACCESS_P (t2))
	return false;
      if (DECLTYPE_FOR_LAMBDA_CAPTURE (t1) != DECLTYPE_FOR_LAMBDA_CAPTURE (t2))
	return false;
      if (DECLTYPE_FOR_LAMBDA_PROXY (t1) != DECLTYPE_FOR_LAMBDA_PROXY (t2))
	return false;
      if (!cp_tree_equal (DECLTYPE_TYPE_EXPR (t1), DECLTYPE_TYPE_EXPR (t2)))
        return false;
      break;

    case UNDERLYING_TYPE:
      if (!same_type_p (UNDERLYING_TYPE_TYPE (t1), UNDERLYING_TYPE_TYPE (t2)))
	return false;
      break;

    case TYPEOF_TYPE:
      if (!cp_tree_equal (TYPEOF_TYPE_EXPR (t1), TYPEOF_TYPE_EXPR (t2)))
	return false;
      break;

    default:
      return false;
    }

  /* If we get here, we know that from a target independent POV the
     types are the same.  Make sure the target attributes are also
     the same.  */
  if (!comp_type_attributes (t1, t2))
    return false;

 check_alias:
  if (comparing_dependent_aliases)
    {
      /* Don't treat an alias template specialization with dependent
	 arguments as equivalent to its underlying type when used as a
	 template argument; we need them to be distinct so that we
	 substitute into the specialization arguments at instantiation
	 time.  And aliases can't be equivalent without being ==, so
	 we don't need to look any deeper.  */
      tree dep1 = dependent_alias_template_spec_p (t1, nt_transparent);
      tree dep2 = dependent_alias_template_spec_p (t2, nt_transparent);
      if ((dep1 || dep2) && dep1 != dep2)
	return false;
    }

  return true;
}

/* Return true if T1 and T2 are related as allowed by STRICT.  STRICT
   is a bitwise-or of the COMPARE_* flags.  */

bool
comptypes (tree t1, tree t2, int strict)
{
  gcc_checking_assert (t1 && t2);

  /* TYPE_ARGUMENT_PACKS are not really types.  */
  gcc_checking_assert (TREE_CODE (t1) != TYPE_ARGUMENT_PACK
		       && TREE_CODE (t2) != TYPE_ARGUMENT_PACK);

  if (t1 == t2)
    return true;

  /* Suppress errors caused by previously reported errors.  */
  if (t1 == error_mark_node || t2 == error_mark_node)
    return false;

  if (strict == COMPARE_STRICT)
    {
      if (TYPE_STRUCTURAL_EQUALITY_P (t1) || TYPE_STRUCTURAL_EQUALITY_P (t2))
	/* At least one of the types requires structural equality, so
	   perform a deep check. */
	return structural_comptypes (t1, t2, strict);

      if (flag_checking && param_use_canonical_types)
	{
	  bool result = structural_comptypes (t1, t2, strict);
	  
	  if (result && TYPE_CANONICAL (t1) != TYPE_CANONICAL (t2))
	    /* The two types are structurally equivalent, but their
	       canonical types were different. This is a failure of the
	       canonical type propagation code.*/
	    internal_error 
	      ("canonical types differ for identical types %qT and %qT",
	       t1, t2);
	  else if (!result && TYPE_CANONICAL (t1) == TYPE_CANONICAL (t2))
	    /* Two types are structurally different, but the canonical
	       types are the same. This means we were over-eager in
	       assigning canonical types. */
	    internal_error 
	      ("same canonical type node for different types %qT and %qT",
	       t1, t2);
	  
	  return result;
	}
      if (!flag_checking && param_use_canonical_types)
	return TYPE_CANONICAL (t1) == TYPE_CANONICAL (t2);
      else
	return structural_comptypes (t1, t2, strict);
    }
  else if (strict == COMPARE_STRUCTURAL)
    return structural_comptypes (t1, t2, COMPARE_STRICT);
  else
    return structural_comptypes (t1, t2, strict);
}

/* Returns nonzero iff TYPE1 and TYPE2 are the same type, ignoring
   top-level qualifiers.  */

bool
same_type_ignoring_top_level_qualifiers_p (tree type1, tree type2)
{
  if (type1 == error_mark_node || type2 == error_mark_node)
    return false;
  if (type1 == type2)
    return true;

  type1 = cp_build_qualified_type (type1, TYPE_UNQUALIFIED);
  type2 = cp_build_qualified_type (type2, TYPE_UNQUALIFIED);
  return same_type_p (type1, type2);
}

/* Returns nonzero iff TYPE1 and TYPE2 are similar, as per [conv.qual].  */

bool
similar_type_p (tree type1, tree type2)
{
  if (type1 == error_mark_node || type2 == error_mark_node)
    return false;

  /* Informally, two types are similar if, ignoring top-level cv-qualification:
     * they are the same type; or
     * they are both pointers, and the pointed-to types are similar; or
     * they are both pointers to member of the same class, and the types of
       the pointed-to members are similar; or
     * they are both arrays of the same size or both arrays of unknown bound,
       and the array element types are similar.  */

  if (same_type_ignoring_top_level_qualifiers_p (type1, type2))
    return true;

  if ((TYPE_PTR_P (type1) && TYPE_PTR_P (type2))
      || (TYPE_PTRDATAMEM_P (type1) && TYPE_PTRDATAMEM_P (type2))
      || (TREE_CODE (type1) == ARRAY_TYPE && TREE_CODE (type2) == ARRAY_TYPE))
    return comp_ptr_ttypes_const (type1, type2, bounds_either);

  return false;
}

/* Helper function for layout_compatible_type_p and
   is_corresponding_member_aggr.  Advance to next members (NULL if
   no further ones) and return true if those members are still part of
   the common initial sequence.  */

bool
next_common_initial_seqence (tree &memb1, tree &memb2)
{
  while (memb1)
    {
      if (TREE_CODE (memb1) != FIELD_DECL
	  || (DECL_FIELD_IS_BASE (memb1) && is_empty_field (memb1)))
	{
	  memb1 = DECL_CHAIN (memb1);
	  continue;
	}
      if (DECL_FIELD_IS_BASE (memb1))
	{
	  memb1 = TYPE_FIELDS (TREE_TYPE (memb1));
	  continue;
	}
      break;
    }
  while (memb2)
    {
      if (TREE_CODE (memb2) != FIELD_DECL
	  || (DECL_FIELD_IS_BASE (memb2) && is_empty_field (memb2)))
	{
	  memb2 = DECL_CHAIN (memb2);
	  continue;
	}
      if (DECL_FIELD_IS_BASE (memb2))
	{
	  memb2 = TYPE_FIELDS (TREE_TYPE (memb2));
	  continue;
	}
      break;
    }
  if (memb1 == NULL_TREE && memb2 == NULL_TREE)
    return true;
  if (memb1 == NULL_TREE || memb2 == NULL_TREE)
    return false;
  if (DECL_BIT_FIELD_TYPE (memb1))
    {
      if (!DECL_BIT_FIELD_TYPE (memb2))
	return false;
      if (!layout_compatible_type_p (DECL_BIT_FIELD_TYPE (memb1),
				     DECL_BIT_FIELD_TYPE (memb2)))
	return false;
      if (TYPE_PRECISION (TREE_TYPE (memb1))
	  != TYPE_PRECISION (TREE_TYPE (memb2)))
	return false;
    }
  else if (DECL_BIT_FIELD_TYPE (memb2))
    return false;
  else if (!layout_compatible_type_p (TREE_TYPE (memb1), TREE_TYPE (memb2)))
    return false;
  if ((!lookup_attribute ("no_unique_address", DECL_ATTRIBUTES (memb1)))
      != !lookup_attribute ("no_unique_address", DECL_ATTRIBUTES (memb2)))
    return false;
  if (!tree_int_cst_equal (bit_position (memb1), bit_position (memb2)))
    return false;
  return true;
}

/* Return true if TYPE1 and TYPE2 are layout-compatible types.  */

bool
layout_compatible_type_p (tree type1, tree type2)
{
  if (type1 == error_mark_node || type2 == error_mark_node)
    return false;
  if (type1 == type2)
    return true;
  if (TREE_CODE (type1) != TREE_CODE (type2))
    return false;

  type1 = cp_build_qualified_type (type1, TYPE_UNQUALIFIED);
  type2 = cp_build_qualified_type (type2, TYPE_UNQUALIFIED);

  if (TREE_CODE (type1) == ENUMERAL_TYPE)
    return (TYPE_ALIGN (type1) == TYPE_ALIGN (type2)
	    && tree_int_cst_equal (TYPE_SIZE (type1), TYPE_SIZE (type2))
	    && same_type_p (finish_underlying_type (type1),
			    finish_underlying_type (type2)));

  if (CLASS_TYPE_P (type1)
      && std_layout_type_p (type1)
      && std_layout_type_p (type2)
      && TYPE_ALIGN (type1) == TYPE_ALIGN (type2)
      && tree_int_cst_equal (TYPE_SIZE (type1), TYPE_SIZE (type2)))
    {
      tree field1 = TYPE_FIELDS (type1);
      tree field2 = TYPE_FIELDS (type2);
      if (TREE_CODE (type1) == RECORD_TYPE)
	{
	  while (1)
	    {
	      if (!next_common_initial_seqence (field1, field2))
		return false;
	      if (field1 == NULL_TREE)
		return true;
	      field1 = DECL_CHAIN (field1);
	      field2 = DECL_CHAIN (field2);
	    }
	}
      /* Otherwise both types must be union types.
	 The standard says:
	 "Two standard-layout unions are layout-compatible if they have
	 the same number of non-static data members and corresponding
	 non-static data members (in any order) have layout-compatible
	 types."
	 but the code anticipates that bitfield vs. non-bitfield,
	 different bitfield widths or presence/absence of
	 [[no_unique_address]] should be checked as well.  */
      auto_vec<tree, 16> vec;
      unsigned int count = 0;
      for (; field1; field1 = DECL_CHAIN (field1))
	if (TREE_CODE (field1) == FIELD_DECL)
	  count++;
      for (; field2; field2 = DECL_CHAIN (field2))
	if (TREE_CODE (field2) == FIELD_DECL)
	  vec.safe_push (field2);
      /* Discussions on core lean towards treating multiple union fields
	 of the same type as the same field, so this might need changing
	 in the future.  */
      if (count != vec.length ())
	return false;
      for (field1 = TYPE_FIELDS (type1); field1; field1 = DECL_CHAIN (field1))
	{
	  if (TREE_CODE (field1) != FIELD_DECL)
	    continue;
	  unsigned int j;
	  tree t1 = DECL_BIT_FIELD_TYPE (field1);
	  if (t1 == NULL_TREE)
	    t1 = TREE_TYPE (field1);
	  FOR_EACH_VEC_ELT (vec, j, field2)
	    {
	      tree t2 = DECL_BIT_FIELD_TYPE (field2);
	      if (t2 == NULL_TREE)
		t2 = TREE_TYPE (field2);
	      if (DECL_BIT_FIELD_TYPE (field1))
		{
		  if (!DECL_BIT_FIELD_TYPE (field2))
		    continue;
		  if (TYPE_PRECISION (TREE_TYPE (field1))
		      != TYPE_PRECISION (TREE_TYPE (field2)))
		    continue;
		}
	      else if (DECL_BIT_FIELD_TYPE (field2))
		continue;
	      if (!layout_compatible_type_p (t1, t2))
		continue;
	      if ((!lookup_attribute ("no_unique_address",
				      DECL_ATTRIBUTES (field1)))
		  != !lookup_attribute ("no_unique_address",
					DECL_ATTRIBUTES (field2)))
		continue;
	      break;
	    }
	  if (j == vec.length ())
	    return false;
	  vec.unordered_remove (j);
	}
      return true;
    }

  return same_type_p (type1, type2);
}

/* Returns 1 if TYPE1 is at least as qualified as TYPE2.  */

bool
at_least_as_qualified_p (const_tree type1, const_tree type2)
{
  int q1 = cp_type_quals (type1);
  int q2 = cp_type_quals (type2);

  /* All qualifiers for TYPE2 must also appear in TYPE1.  */
  return (q1 & q2) == q2;
}

/* Returns 1 if TYPE1 is more cv-qualified than TYPE2, -1 if TYPE2 is
   more cv-qualified that TYPE1, and 0 otherwise.  */

int
comp_cv_qualification (int q1, int q2)
{
  if (q1 == q2)
    return 0;

  if ((q1 & q2) == q2)
    return 1;
  else if ((q1 & q2) == q1)
    return -1;

  return 0;
}

int
comp_cv_qualification (const_tree type1, const_tree type2)
{
  int q1 = cp_type_quals (type1);
  int q2 = cp_type_quals (type2);
  return comp_cv_qualification (q1, q2);
}

/* Returns 1 if the cv-qualification signature of TYPE1 is a proper
   subset of the cv-qualification signature of TYPE2, and the types
   are similar.  Returns -1 if the other way 'round, and 0 otherwise.  */

int
comp_cv_qual_signature (tree type1, tree type2)
{
  if (comp_ptr_ttypes_real (type2, type1, -1))
    return 1;
  else if (comp_ptr_ttypes_real (type1, type2, -1))
    return -1;
  else
    return 0;
}

/* Subroutines of `comptypes'.  */

/* Return true if two parameter type lists PARMS1 and PARMS2 are
   equivalent in the sense that functions with those parameter types
   can have equivalent types.  The two lists must be equivalent,
   element by element.  */

bool
compparms (const_tree parms1, const_tree parms2)
{
  const_tree t1, t2;

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

  for (t1 = parms1, t2 = parms2;
       t1 || t2;
       t1 = TREE_CHAIN (t1), t2 = TREE_CHAIN (t2))
    {
      /* If one parmlist is shorter than the other,
	 they fail to match.  */
      if (!t1 || !t2)
	return false;
      if (!same_type_p (TREE_VALUE (t1), TREE_VALUE (t2)))
	return false;
    }
  return true;
}


/* Process a sizeof or alignof expression where the operand is a type.
   STD_ALIGNOF indicates whether an alignof has C++11 (minimum alignment)
   or GNU (preferred alignment) semantics; it is ignored if OP is
   SIZEOF_EXPR.  */

tree
cxx_sizeof_or_alignof_type (location_t loc, tree type, enum tree_code op,
			    bool std_alignof, bool complain)
{
  gcc_assert (op == SIZEOF_EXPR || op == ALIGNOF_EXPR);
  if (type == error_mark_node)
    return error_mark_node;

  type = non_reference (type);
  if (TREE_CODE (type) == METHOD_TYPE)
    {
      if (complain)
	{
	  pedwarn (loc, OPT_Wpointer_arith,
		   "invalid application of %qs to a member function",
		   OVL_OP_INFO (false, op)->name);
	  return size_one_node;
	}
      else
	return error_mark_node;
    }
  else if (VOID_TYPE_P (type) && std_alignof)
    {
      if (complain)
	error_at (loc, "invalid application of %qs to a void type",
		  OVL_OP_INFO (false, op)->name);
      return error_mark_node;
    }

  bool dependent_p = dependent_type_p (type);
  if (!dependent_p)
    complete_type (type);
  if (dependent_p
      /* VLA types will have a non-constant size.  In the body of an
	 uninstantiated template, we don't need to try to compute the
	 value, because the sizeof expression is not an integral
	 constant expression in that case.  And, if we do try to
	 compute the value, we'll likely end up with SAVE_EXPRs, which
	 the template substitution machinery does not expect to see.  */
      || (processing_template_decl 
	  && COMPLETE_TYPE_P (type)
	  && TREE_CODE (TYPE_SIZE (type)) != INTEGER_CST))
    {
      tree value = build_min (op, size_type_node, type);
      TREE_READONLY (value) = 1;
      if (op == ALIGNOF_EXPR && std_alignof)
	ALIGNOF_EXPR_STD_P (value) = true;
      SET_EXPR_LOCATION (value, loc);
      return value;
    }

  return c_sizeof_or_alignof_type (loc, complete_type (type),
				   op == SIZEOF_EXPR, std_alignof,
				   complain);
}

/* Return the size of the type, without producing any warnings for
   types whose size cannot be taken.  This routine should be used only
   in some other routine that has already produced a diagnostic about
   using the size of such a type.  */
tree 
cxx_sizeof_nowarn (tree type)
{
  if (TREE_CODE (type) == FUNCTION_TYPE
      || VOID_TYPE_P (type)
      || TREE_CODE (type) == ERROR_MARK)
    return size_one_node;
  else if (!COMPLETE_TYPE_P (type))
    return size_zero_node;
  else
    return cxx_sizeof_or_alignof_type (input_location, type,
				       SIZEOF_EXPR, false, false);
}

/* Process a sizeof expression where the operand is an expression.  */

static tree
cxx_sizeof_expr (location_t loc, tree e, tsubst_flags_t complain)
{
  if (e == error_mark_node)
    return error_mark_node;

  if (instantiation_dependent_uneval_expression_p (e))
    {
      e = build_min (SIZEOF_EXPR, size_type_node, e);
      TREE_SIDE_EFFECTS (e) = 0;
      TREE_READONLY (e) = 1;
      SET_EXPR_LOCATION (e, loc);

      return e;
    }

  location_t e_loc = cp_expr_loc_or_loc (e, loc);
  STRIP_ANY_LOCATION_WRAPPER (e);

  /* To get the size of a static data member declared as an array of
     unknown bound, we need to instantiate it.  */
  if (VAR_P (e)
      && VAR_HAD_UNKNOWN_BOUND (e)
      && DECL_TEMPLATE_INSTANTIATION (e))
    instantiate_decl (e, /*defer_ok*/true, /*expl_inst_mem*/false);

  if (TREE_CODE (e) == PARM_DECL
      && DECL_ARRAY_PARAMETER_P (e)
      && (complain & tf_warning))
    {
      auto_diagnostic_group d;
      if (warning_at (e_loc, OPT_Wsizeof_array_argument,
		      "%<sizeof%> on array function parameter %qE "
		      "will return size of %qT", e, TREE_TYPE (e)))
	inform (DECL_SOURCE_LOCATION (e), "declared here");
    }

  e = mark_type_use (e);

  if (bitfield_p (e))
    {
      if (complain & tf_error)
	error_at (e_loc,
		  "invalid application of %<sizeof%> to a bit-field");
      else
        return error_mark_node;
      e = char_type_node;
    }
  else if (is_overloaded_fn (e))
    {
      if (complain & tf_error)
	permerror (e_loc, "ISO C++ forbids applying %<sizeof%> to "
		   "an expression of function type");
      else
        return error_mark_node;
      e = char_type_node;
    }
  else if (type_unknown_p (e))
    {
      if (complain & tf_error)
        cxx_incomplete_type_error (e_loc, e, TREE_TYPE (e));
      else
        return error_mark_node;
      e = char_type_node;
    }
  else
    e = TREE_TYPE (e);

  return cxx_sizeof_or_alignof_type (loc, e, SIZEOF_EXPR, false,
				     complain & tf_error);
}

/* Implement the __alignof keyword: Return the minimum required
   alignment of E, measured in bytes.  For VAR_DECL's and
   FIELD_DECL's return DECL_ALIGN (which can be set from an
   "aligned" __attribute__ specification).  STD_ALIGNOF acts
   like in cxx_sizeof_or_alignof_type.  */

static tree
cxx_alignof_expr (location_t loc, tree e, bool std_alignof,
		  tsubst_flags_t complain)
{
  tree t;

  if (e == error_mark_node)
    return error_mark_node;

  if (processing_template_decl)
    {
      e = build_min (ALIGNOF_EXPR, size_type_node, e);
      TREE_SIDE_EFFECTS (e) = 0;
      TREE_READONLY (e) = 1;
      SET_EXPR_LOCATION (e, loc);
      ALIGNOF_EXPR_STD_P (e) = std_alignof;

      return e;
    }

  location_t e_loc = cp_expr_loc_or_loc (e, loc);
  STRIP_ANY_LOCATION_WRAPPER (e);

  e = mark_type_use (e);

  if (!verify_type_context (loc, TCTX_ALIGNOF, TREE_TYPE (e),
			    !(complain & tf_error)))
    {
      if (!(complain & tf_error))
	return error_mark_node;
      t = size_one_node;
    }
  else if (VAR_P (e))
    t = size_int (DECL_ALIGN_UNIT (e));
  else if (bitfield_p (e))
    {
      if (complain & tf_error)
	error_at (e_loc,
		  "invalid application of %<__alignof%> to a bit-field");
      else
        return error_mark_node;
      t = size_one_node;
    }
  else if (TREE_CODE (e) == COMPONENT_REF
	   && TREE_CODE (TREE_OPERAND (e, 1)) == FIELD_DECL)
    t = size_int (DECL_ALIGN_UNIT (TREE_OPERAND (e, 1)));
  else if (is_overloaded_fn (e))
    {
      if (complain & tf_error)
	permerror (e_loc, "ISO C++ forbids applying %<__alignof%> to "
		   "an expression of function type");
      else
        return error_mark_node;
      if (TREE_CODE (e) == FUNCTION_DECL)
	t = size_int (DECL_ALIGN_UNIT (e));
      else
	t = size_one_node;
    }
  else if (type_unknown_p (e))
    {
      if (complain & tf_error)
        cxx_incomplete_type_error (e_loc, e, TREE_TYPE (e));
      else
        return error_mark_node;
      t = size_one_node;
    }
  else
    return cxx_sizeof_or_alignof_type (loc, TREE_TYPE (e),
				       ALIGNOF_EXPR, std_alignof,
                                       complain & tf_error);

  return fold_convert_loc (loc, size_type_node, t);
}

/* Process a sizeof or alignof expression E with code OP where the operand
   is an expression. STD_ALIGNOF acts like in cxx_sizeof_or_alignof_type.  */

tree
cxx_sizeof_or_alignof_expr (location_t loc, tree e, enum tree_code op,
			    bool std_alignof, bool complain)
{
  gcc_assert (op == SIZEOF_EXPR || op == ALIGNOF_EXPR);
  if (op == SIZEOF_EXPR)
    return cxx_sizeof_expr (loc, e, complain? tf_warning_or_error : tf_none);
  else
    return cxx_alignof_expr (loc, e, std_alignof,
			     complain? tf_warning_or_error : tf_none);
}

/*  Build a representation of an expression 'alignas(E).'  Return the
    folded integer value of E if it is an integral constant expression
    that resolves to a valid alignment.  If E depends on a template
    parameter, return a syntactic representation tree of kind
    ALIGNOF_EXPR.  Otherwise, return an error_mark_node if the
    expression is ill formed, or NULL_TREE if E is NULL_TREE.  */

tree
cxx_alignas_expr (tree e)
{
  if (e == NULL_TREE || e == error_mark_node
      || (!TYPE_P (e) && !require_potential_rvalue_constant_expression (e)))
    return e;
  
  if (TYPE_P (e))
    /* [dcl.align]/3:
       
	   When the alignment-specifier is of the form
	   alignas(type-id), it shall have the same effect as
	   alignas(alignof(type-id)).  */

    return cxx_sizeof_or_alignof_type (input_location,
				       e, ALIGNOF_EXPR,
				       /*std_alignof=*/true,
				       /*complain=*/true);
  
  /* If we reach this point, it means the alignas expression if of
     the form "alignas(assignment-expression)", so we should follow
     what is stated by [dcl.align]/2.  */

  if (value_dependent_expression_p (e))
    /* Leave value-dependent expression alone for now. */
    return e;

  e = instantiate_non_dependent_expr (e);
  e = mark_rvalue_use (e);

  /* [dcl.align]/2 says:

         the assignment-expression shall be an integral constant
	 expression.  */

  if (!INTEGRAL_OR_UNSCOPED_ENUMERATION_TYPE_P (TREE_TYPE (e)))
    {
      error ("%<alignas%> argument has non-integral type %qT", TREE_TYPE (e));
      return error_mark_node;
    }
  
  return cxx_constant_value (e);
}


/* EXPR is being used in a context that is not a function call.
   Enforce:

     [expr.ref]

     The expression can be used only as the left-hand operand of a
     member function call.

     [expr.mptr.operator]

     If the result of .* or ->* is a function, then that result can be
     used only as the operand for the function call operator ().

   by issuing an error message if appropriate.  Returns true iff EXPR
   violates these rules.  */

bool
invalid_nonstatic_memfn_p (location_t loc, tree expr, tsubst_flags_t complain)
{
  if (expr == NULL_TREE)
    return false;
  /* Don't enforce this in MS mode.  */
  if (flag_ms_extensions)
    return false;
  if (is_overloaded_fn (expr) && !really_overloaded_fn (expr))
    expr = get_first_fn (expr);
  if (DECL_NONSTATIC_MEMBER_FUNCTION_P (expr))
    {
      if (complain & tf_error)
	{
	  if (DECL_P (expr))
	    {
	      error_at (loc, "invalid use of non-static member function %qD",
			expr);
	      inform (DECL_SOURCE_LOCATION (expr), "declared here");
	    }
	  else
	    error_at (loc, "invalid use of non-static member function of "
		      "type %qT", TREE_TYPE (expr));
	}
      return true;
    }
  return false;
}

/* If EXP is a reference to a bit-field, and the type of EXP does not
   match the declared type of the bit-field, return the declared type
   of the bit-field.  Otherwise, return NULL_TREE.  */

tree
is_bitfield_expr_with_lowered_type (const_tree exp)
{
  switch (TREE_CODE (exp))
    {
    case COND_EXPR:
      if (!is_bitfield_expr_with_lowered_type (TREE_OPERAND (exp, 1)
					       ? TREE_OPERAND (exp, 1)
					       : TREE_OPERAND (exp, 0)))
	return NULL_TREE;
      return is_bitfield_expr_with_lowered_type (TREE_OPERAND (exp, 2));

    case COMPOUND_EXPR:
      return is_bitfield_expr_with_lowered_type (TREE_OPERAND (exp, 1));

    case MODIFY_EXPR:
    case SAVE_EXPR:
    case UNARY_PLUS_EXPR:
    case PREDECREMENT_EXPR:
    case PREINCREMENT_EXPR:
    case POSTDECREMENT_EXPR:
    case POSTINCREMENT_EXPR:
    case NEGATE_EXPR:
    case NON_LVALUE_EXPR:
    case BIT_NOT_EXPR:
      return is_bitfield_expr_with_lowered_type (TREE_OPERAND (exp, 0));

    case COMPONENT_REF:
      {
	tree field;
	
	field = TREE_OPERAND (exp, 1);
	if (TREE_CODE (field) != FIELD_DECL || !DECL_BIT_FIELD_TYPE (field))
	  return NULL_TREE;
	if (same_type_ignoring_top_level_qualifiers_p
	    (TREE_TYPE (exp), DECL_BIT_FIELD_TYPE (field)))
	  return NULL_TREE;
	return DECL_BIT_FIELD_TYPE (field);
      }

    case VAR_DECL:
      if (DECL_HAS_VALUE_EXPR_P (exp))
	return is_bitfield_expr_with_lowered_type (DECL_VALUE_EXPR
						   (CONST_CAST_TREE (exp)));
      return NULL_TREE;

    case VIEW_CONVERT_EXPR:
      if (location_wrapper_p (exp))
	return is_bitfield_expr_with_lowered_type (TREE_OPERAND (exp, 0));
      else
	return NULL_TREE;

    default:
      return NULL_TREE;
    }
}

/* Like is_bitfield_with_lowered_type, except that if EXP is not a
   bitfield with a lowered type, the type of EXP is returned, rather
   than NULL_TREE.  */

tree
unlowered_expr_type (const_tree exp)
{
  tree type;
  tree etype = TREE_TYPE (exp);

  type = is_bitfield_expr_with_lowered_type (exp);
  if (type)
    type = cp_build_qualified_type (type, cp_type_quals (etype));
  else
    type = etype;

  return type;
}

/* Perform the conversions in [expr] that apply when an lvalue appears
   in an rvalue context: the lvalue-to-rvalue, array-to-pointer, and
   function-to-pointer conversions.  In addition, bitfield references are
   converted to their declared types. Note that this function does not perform
   the lvalue-to-rvalue conversion for class types. If you need that conversion
   for class types, then you probably need to use force_rvalue.

   Although the returned value is being used as an rvalue, this
   function does not wrap the returned expression in a
   NON_LVALUE_EXPR; the caller is expected to be mindful of the fact
   that the return value is no longer an lvalue.  */

tree
decay_conversion (tree exp,
		  tsubst_flags_t complain,
		  bool reject_builtin /* = true */)
{
  tree type;
  enum tree_code code;
  location_t loc = cp_expr_loc_or_input_loc (exp);

  type = TREE_TYPE (exp);
  if (type == error_mark_node)
    return error_mark_node;

  exp = resolve_nondeduced_context_or_error (exp, complain);

  code = TREE_CODE (type);

  if (error_operand_p (exp))
    return error_mark_node;

  if (NULLPTR_TYPE_P (type) && !TREE_SIDE_EFFECTS (exp))
    {
      mark_rvalue_use (exp, loc, reject_builtin);
      return nullptr_node;
    }

  /* build_c_cast puts on a NOP_EXPR to make the result not an lvalue.
     Leave such NOP_EXPRs, since RHS is being used in non-lvalue context.  */
  if (code == VOID_TYPE)
    {
      if (complain & tf_error)
	error_at (loc, "void value not ignored as it ought to be");
      return error_mark_node;
    }
  if (invalid_nonstatic_memfn_p (loc, exp, complain))
    return error_mark_node;
  if (code == FUNCTION_TYPE || is_overloaded_fn (exp))
    {
      exp = mark_lvalue_use (exp);
      if (reject_builtin && reject_gcc_builtin (exp, loc))
	return error_mark_node;
      return cp_build_addr_expr (exp, complain);
    }
  if (code == ARRAY_TYPE)
    {
      tree adr;
      tree ptrtype;

      exp = mark_lvalue_use (exp);

      if (INDIRECT_REF_P (exp))
	return build_nop (build_pointer_type (TREE_TYPE (type)),
			  TREE_OPERAND (exp, 0));

      if (TREE_CODE (exp) == COMPOUND_EXPR)
	{
	  tree op1 = decay_conversion (TREE_OPERAND (exp, 1), complain);
	  if (op1 == error_mark_node)
            return error_mark_node;
	  return build2 (COMPOUND_EXPR, TREE_TYPE (op1),
			 TREE_OPERAND (exp, 0), op1);
	}

      if (!obvalue_p (exp)
	  && ! (TREE_CODE (exp) == CONSTRUCTOR && TREE_STATIC (exp)))
	{
	  if (complain & tf_error)
	    error_at (loc, "invalid use of non-lvalue array");
	  return error_mark_node;
	}

      /* Don't let an array compound literal decay to a pointer.  It can
	 still be used to initialize an array or bind to a reference.  */
      if (TREE_CODE (exp) == TARGET_EXPR)
	{
	  if (complain & tf_error)
	    error_at (loc, "taking address of temporary array");
	  return error_mark_node;
	}

      ptrtype = build_pointer_type (TREE_TYPE (type));

      if (VAR_P (exp))
	{
	  if (!cxx_mark_addressable (exp))
	    return error_mark_node;
	  adr = build_nop (ptrtype, build_address (exp));
	  return adr;
	}
      /* This way is better for a COMPONENT_REF since it can
	 simplify the offset for a component.  */
      adr = cp_build_addr_expr (exp, complain);
      return cp_convert (ptrtype, adr, complain);
    }

  /* Otherwise, it's the lvalue-to-rvalue conversion.  */
  exp = mark_rvalue_use (exp, loc, reject_builtin);

  /* If a bitfield is used in a context where integral promotion
     applies, then the caller is expected to have used
     default_conversion.  That function promotes bitfields correctly
     before calling this function.  At this point, if we have a
     bitfield referenced, we may assume that is not subject to
     promotion, and that, therefore, the type of the resulting rvalue
     is the declared type of the bitfield.  */
  exp = convert_bitfield_to_declared_type (exp);

  /* We do not call rvalue() here because we do not want to wrap EXP
     in a NON_LVALUE_EXPR.  */

  /* [basic.lval]

     Non-class rvalues always have cv-unqualified types.  */
  type = TREE_TYPE (exp);
  if (!CLASS_TYPE_P (type) && cv_qualified_p (type))
    exp = build_nop (cv_unqualified (type), exp);

  if (!complete_type_or_maybe_complain (type, exp, complain))
    return error_mark_node;

  return exp;
}

/* Perform preparatory conversions, as part of the "usual arithmetic
   conversions".  In particular, as per [expr]:

     Whenever an lvalue expression appears as an operand of an
     operator that expects the rvalue for that operand, the
     lvalue-to-rvalue, array-to-pointer, or function-to-pointer
     standard conversions are applied to convert the expression to an
     rvalue.

   In addition, we perform integral promotions here, as those are
   applied to both operands to a binary operator before determining
   what additional conversions should apply.  */

static tree
cp_default_conversion (tree exp, tsubst_flags_t complain)
{
  /* Check for target-specific promotions.  */
  tree promoted_type = targetm.promoted_type (TREE_TYPE (exp));
  if (promoted_type)
    exp = cp_convert (promoted_type, exp, complain);
  /* Perform the integral promotions first so that bitfield
     expressions (which may promote to "int", even if the bitfield is
     declared "unsigned") are promoted correctly.  */
  else if (INTEGRAL_OR_UNSCOPED_ENUMERATION_TYPE_P (TREE_TYPE (exp)))
    exp = cp_perform_integral_promotions (exp, complain);
  /* Perform the other conversions.  */
  exp = decay_conversion (exp, complain);

  return exp;
}

/* C version.  */

tree
default_conversion (tree exp)
{
  return cp_default_conversion (exp, tf_warning_or_error);
}

/* EXPR is an expression with an integral or enumeration type.
   Perform the integral promotions in [conv.prom], and return the
   converted value.  */

tree
cp_perform_integral_promotions (tree expr, tsubst_flags_t complain)
{
  tree type;
  tree promoted_type;

  expr = mark_rvalue_use (expr);
  if (error_operand_p (expr))
    return error_mark_node;

  type = TREE_TYPE (expr);

  /* [conv.prom]

     A prvalue for an integral bit-field (11.3.9) can be converted to a prvalue
     of type int if int can represent all the values of the bit-field;
     otherwise, it can be converted to unsigned int if unsigned int can
     represent all the values of the bit-field. If the bit-field is larger yet,
     no integral promotion applies to it. If the bit-field has an enumerated
     type, it is treated as any other value of that type for promotion
     purposes.  */
  tree bitfield_type = is_bitfield_expr_with_lowered_type (expr);
  if (bitfield_type
      && (TREE_CODE (bitfield_type) == ENUMERAL_TYPE
	  || TYPE_PRECISION (type) > TYPE_PRECISION (integer_type_node)))
    type = bitfield_type;

  gcc_assert (INTEGRAL_OR_ENUMERATION_TYPE_P (type));
  /* Scoped enums don't promote.  */
  if (SCOPED_ENUM_P (type))
    return expr;
  promoted_type = type_promotes_to (type);
  if (type != promoted_type)
    expr = cp_convert (promoted_type, expr, complain);
  else if (bitfield_type && bitfield_type != type)
    /* Prevent decay_conversion from converting to bitfield_type.  */
    expr = build_nop (type, expr);
  return expr;
}

/* C version.  */

tree
perform_integral_promotions (tree expr)
{
  return cp_perform_integral_promotions (expr, tf_warning_or_error);
}

/* Returns nonzero iff exp is a STRING_CST or the result of applying
   decay_conversion to one.  */

int
string_conv_p (const_tree totype, const_tree exp, int warn)
{
  tree t;

  if (!TYPE_PTR_P (totype))
    return 0;

  t = TREE_TYPE (totype);
  if (!same_type_p (t, char_type_node)
      && !same_type_p (t, char8_type_node)
      && !same_type_p (t, char16_type_node)
      && !same_type_p (t, char32_type_node)
      && !same_type_p (t, wchar_type_node))
    return 0;

  location_t loc = EXPR_LOC_OR_LOC (exp, input_location);

  STRIP_ANY_LOCATION_WRAPPER (exp);

  if (TREE_CODE (exp) == STRING_CST)
    {
      /* Make sure that we don't try to convert between char and wide chars.  */
      if (!same_type_p (TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (exp))), t))
	return 0;
    }
  else
    {
      /* Is this a string constant which has decayed to 'const char *'?  */
      t = build_pointer_type (cp_build_qualified_type (t, TYPE_QUAL_CONST));
      if (!same_type_p (TREE_TYPE (exp), t))
	return 0;
      STRIP_NOPS (exp);
      if (TREE_CODE (exp) != ADDR_EXPR
	  || TREE_CODE (TREE_OPERAND (exp, 0)) != STRING_CST)
	return 0;
    }
  if (warn)
    {
      if (cxx_dialect >= cxx11)
	pedwarn (loc, OPT_Wwrite_strings,
		 "ISO C++ forbids converting a string constant to %qT",
		 totype);
      else
	warning_at (loc, OPT_Wwrite_strings,
		    "deprecated conversion from string constant to %qT",
		    totype);
    }

  return 1;
}

/* Given a COND_EXPR, MIN_EXPR, or MAX_EXPR in T, return it in a form that we
   can, for example, use as an lvalue.  This code used to be in
   unary_complex_lvalue, but we needed it to deal with `a = (d == c) ? b : c'
   expressions, where we're dealing with aggregates.  But now it's again only
   called from unary_complex_lvalue.  The case (in particular) that led to
   this was with CODE == ADDR_EXPR, since it's not an lvalue when we'd
   get it there.  */

static tree
rationalize_conditional_expr (enum tree_code code, tree t,
                              tsubst_flags_t complain)
{
  location_t loc = cp_expr_loc_or_input_loc (t);

  /* For MIN_EXPR or MAX_EXPR, fold-const.cc has arranged things so that
     the first operand is always the one to be used if both operands
     are equal, so we know what conditional expression this used to be.  */
  if (TREE_CODE (t) == MIN_EXPR || TREE_CODE (t) == MAX_EXPR)
    {
      tree op0 = TREE_OPERAND (t, 0);
      tree op1 = TREE_OPERAND (t, 1);

      /* The following code is incorrect if either operand side-effects.  */
      gcc_assert (!TREE_SIDE_EFFECTS (op0)
		  && !TREE_SIDE_EFFECTS (op1));
      return
	build_conditional_expr (loc,
				build_x_binary_op (loc,
						   (TREE_CODE (t) == MIN_EXPR
						    ? LE_EXPR : GE_EXPR),
						   op0, TREE_CODE (op0),
						   op1, TREE_CODE (op1),
						   NULL_TREE,
						   /*overload=*/NULL,
						   complain),
                                cp_build_unary_op (code, op0, false, complain),
                                cp_build_unary_op (code, op1, false, complain),
                                complain);
    }

  tree op1 = TREE_OPERAND (t, 1);
  if (TREE_CODE (op1) != THROW_EXPR)
    op1 = cp_build_unary_op (code, op1, false, complain);
  tree op2 = TREE_OPERAND (t, 2);
  if (TREE_CODE (op2) != THROW_EXPR)
    op2 = cp_build_unary_op (code, op2, false, complain);

  return
    build_conditional_expr (loc, TREE_OPERAND (t, 0), op1, op2, complain);
}

/* Given the TYPE of an anonymous union field inside T, return the
   FIELD_DECL for the field.  If not found return NULL_TREE.  Because
   anonymous unions can nest, we must also search all anonymous unions
   that are directly reachable.  */

tree
lookup_anon_field (tree, tree type)
{
  tree field;

  type = TYPE_MAIN_VARIANT (type);
  field = ANON_AGGR_TYPE_FIELD (type);
  gcc_assert (field);
  return field;
}

/* Build an expression representing OBJECT.MEMBER.  OBJECT is an
   expression; MEMBER is a DECL or baselink.  If ACCESS_PATH is
   non-NULL, it indicates the path to the base used to name MEMBER.
   If PRESERVE_REFERENCE is true, the expression returned will have
   REFERENCE_TYPE if the MEMBER does.  Otherwise, the expression
   returned will have the type referred to by the reference.

   This function does not perform access control; that is either done
   earlier by the parser when the name of MEMBER is resolved to MEMBER
   itself, or later when overload resolution selects one of the
   functions indicated by MEMBER.  */

tree
build_class_member_access_expr (cp_expr object, tree member,
				tree access_path, bool preserve_reference,
				tsubst_flags_t complain)
{
  tree object_type;
  tree member_scope;
  tree result = NULL_TREE;
  tree using_decl = NULL_TREE;

  if (error_operand_p (object) || error_operand_p (member))
    return error_mark_node;

  gcc_assert (DECL_P (member) || BASELINK_P (member));

  /* [expr.ref]

     The type of the first expression shall be "class object" (of a
     complete type).  */
  object_type = TREE_TYPE (object);
  if (!currently_open_class (object_type)
      && !complete_type_or_maybe_complain (object_type, object, complain))
    return error_mark_node;
  if (!CLASS_TYPE_P (object_type))
    {
      if (complain & tf_error)
	{
	  if (INDIRECT_TYPE_P (object_type)
	      && CLASS_TYPE_P (TREE_TYPE (object_type)))
	    error ("request for member %qD in %qE, which is of pointer "
		   "type %qT (maybe you meant to use %<->%> ?)",
		   member, object.get_value (), object_type);
	  else
	    error ("request for member %qD in %qE, which is of non-class "
		   "type %qT", member, object.get_value (), object_type);
	}
      return error_mark_node;
    }

  /* The standard does not seem to actually say that MEMBER must be a
     member of OBJECT_TYPE.  However, that is clearly what is
     intended.  */
  if (DECL_P (member))
    {
      member_scope = DECL_CLASS_CONTEXT (member);
      if (!mark_used (member, complain) && !(complain & tf_error))
	return error_mark_node;

      if (TREE_UNAVAILABLE (member))
	error_unavailable_use (member, NULL_TREE);
      else if (TREE_DEPRECATED (member))
	warn_deprecated_use (member, NULL_TREE);
    }
  else
    member_scope = BINFO_TYPE (BASELINK_ACCESS_BINFO (member));
  /* If MEMBER is from an anonymous aggregate, MEMBER_SCOPE will
     presently be the anonymous union.  Go outwards until we find a
     type related to OBJECT_TYPE.  */
  while ((ANON_AGGR_TYPE_P (member_scope) || UNSCOPED_ENUM_P (member_scope))
	 && !same_type_ignoring_top_level_qualifiers_p (member_scope,
							object_type))
    member_scope = TYPE_CONTEXT (member_scope);
  if (!member_scope || !DERIVED_FROM_P (member_scope, object_type))
    {
      if (complain & tf_error)
	{
	  if (TREE_CODE (member) == FIELD_DECL)
	    error ("invalid use of non-static data member %qE", member);
	  else
	    error ("%qD is not a member of %qT", member, object_type);
	}
      return error_mark_node;
    }

  /* Transform `(a, b).x' into `(*(a, &b)).x', `(a ? b : c).x' into
     `(*(a ?  &b : &c)).x', and so on.  A COND_EXPR is only an lvalue
     in the front end; only _DECLs and _REFs are lvalues in the back end.  */
  if (tree temp = unary_complex_lvalue (ADDR_EXPR, object))
    {
      temp = cp_build_fold_indirect_ref (temp);
      if (!lvalue_p (object) && lvalue_p (temp))
	/* Preserve rvalueness.  */
	temp = move (temp);
      object = temp;
    }

  /* In [expr.ref], there is an explicit list of the valid choices for
     MEMBER.  We check for each of those cases here.  */
  if (VAR_P (member))
    {
      /* A static data member.  */
      result = member;
      mark_exp_read (object);

      if (tree wrap = maybe_get_tls_wrapper_call (result))
	/* Replace an evaluated use of the thread_local variable with
	   a call to its wrapper.  */
	result = wrap;

      /* If OBJECT has side-effects, they are supposed to occur.  */
      if (TREE_SIDE_EFFECTS (object))
	result = build2 (COMPOUND_EXPR, TREE_TYPE (result), object, result);
    }
  else if (TREE_CODE (member) == FIELD_DECL)
    {
      /* A non-static data member.  */
      bool null_object_p;
      int type_quals;
      tree member_type;

      if (INDIRECT_REF_P (object))
	null_object_p =
	  integer_zerop (tree_strip_nop_conversions (TREE_OPERAND (object, 0)));
      else
	null_object_p = false;

      /* Convert OBJECT to the type of MEMBER.  */
      if (!same_type_p (TYPE_MAIN_VARIANT (object_type),
			TYPE_MAIN_VARIANT (member_scope)))
	{
	  tree binfo;
	  base_kind kind;

	  /* We didn't complain above about a currently open class, but now we
	     must: we don't know how to refer to a base member before layout is
	     complete.  But still don't complain in a template.  */
	  if (!cp_unevaluated_operand
	      && !dependent_type_p (object_type)
	      && !complete_type_or_maybe_complain (object_type, object,
						   complain))
	    return error_mark_node;

	  binfo = lookup_base (access_path ? access_path : object_type,
			       member_scope, ba_unique, &kind, complain);
	  if (binfo == error_mark_node)
	    return error_mark_node;

	  /* It is invalid to try to get to a virtual base of a
	     NULL object.  The most common cause is invalid use of
	     offsetof macro.  */
	  if (null_object_p && kind == bk_via_virtual)
	    {
	      if (complain & tf_error)
		{
		  error ("invalid access to non-static data member %qD in "
			 "virtual base of NULL object", member);
		}
	      return error_mark_node;
	    }

	  /* Convert to the base.  */
	  object = build_base_path (PLUS_EXPR, object, binfo,
				    /*nonnull=*/1, complain);
	  /* If we found the base successfully then we should be able
	     to convert to it successfully.  */
	  gcc_assert (object != error_mark_node);
	}

      /* If MEMBER is from an anonymous aggregate, we have converted
	 OBJECT so that it refers to the class containing the
	 anonymous union.  Generate a reference to the anonymous union
	 itself, and recur to find MEMBER.  */
      if (ANON_AGGR_TYPE_P (DECL_CONTEXT (member))
	  /* When this code is called from build_field_call, the
	     object already has the type of the anonymous union.
	     That is because the COMPONENT_REF was already
	     constructed, and was then disassembled before calling
	     build_field_call.  After the function-call code is
	     cleaned up, this waste can be eliminated.  */
	  && (!same_type_ignoring_top_level_qualifiers_p
	      (TREE_TYPE (object), DECL_CONTEXT (member))))
	{
	  tree anonymous_union;

	  anonymous_union = lookup_anon_field (TREE_TYPE (object),
					       DECL_CONTEXT (member));
	  object = build_class_member_access_expr (object,
						   anonymous_union,
						   /*access_path=*/NULL_TREE,
						   preserve_reference,
						   complain);
	}

      /* Compute the type of the field, as described in [expr.ref].  */
      type_quals = TYPE_UNQUALIFIED;
      member_type = TREE_TYPE (member);
      if (!TYPE_REF_P (member_type))
	{
	  type_quals = (cp_type_quals (member_type)
			| cp_type_quals (object_type));

	  /* A field is const (volatile) if the enclosing object, or the
	     field itself, is const (volatile).  But, a mutable field is
	     not const, even within a const object.  */
	  if (DECL_MUTABLE_P (member))
	    type_quals &= ~TYPE_QUAL_CONST;
	  member_type = cp_build_qualified_type (member_type, type_quals);
	}

      result = build3_loc (input_location, COMPONENT_REF, member_type,
			   object, member, NULL_TREE);

      /* Mark the expression const or volatile, as appropriate.  Even
	 though we've dealt with the type above, we still have to mark the
	 expression itself.  */
      if (type_quals & TYPE_QUAL_CONST)
	TREE_READONLY (result) = 1;
      if (type_quals & TYPE_QUAL_VOLATILE)
	TREE_THIS_VOLATILE (result) = 1;
    }
  else if (BASELINK_P (member))
    {
      /* The member is a (possibly overloaded) member function.  */
      tree functions;
      tree type;

      /* If the MEMBER is exactly one static member function, then we
	 know the type of the expression.  Otherwise, we must wait
	 until overload resolution has been performed.  */
      functions = BASELINK_FUNCTIONS (member);
      if (TREE_CODE (functions) == FUNCTION_DECL
	  && DECL_STATIC_FUNCTION_P (functions))
	type = TREE_TYPE (functions);
      else
	type = unknown_type_node;
      /* Note that we do not convert OBJECT to the BASELINK_BINFO
	 base.  That will happen when the function is called.  */
      result = build3_loc (input_location, COMPONENT_REF, type, object, member,
			   NULL_TREE);
    }
  else if (TREE_CODE (member) == CONST_DECL)
    {
      /* The member is an enumerator.  */
      result = member;
      /* If OBJECT has side-effects, they are supposed to occur.  */
      if (TREE_SIDE_EFFECTS (object))
	result = build2 (COMPOUND_EXPR, TREE_TYPE (result),
			 object, result);
    }
  else if ((using_decl = strip_using_decl (member)) != member)
    result = build_class_member_access_expr (object,
					     using_decl,
					     access_path, preserve_reference,
					     complain);
  else
    {
      if (complain & tf_error)
	error ("invalid use of %qD", member);
      return error_mark_node;
    }

  if (!preserve_reference)
    /* [expr.ref]

       If E2 is declared to have type "reference to T", then ... the
       type of E1.E2 is T.  */
    result = convert_from_reference (result);

  return result;
}

/* Return the destructor denoted by OBJECT.SCOPE::DTOR_NAME, or, if
   SCOPE is NULL, by OBJECT.DTOR_NAME, where DTOR_NAME is ~type.  */

tree
lookup_destructor (tree object, tree scope, tree dtor_name,
		   tsubst_flags_t complain)
{
  tree object_type = TREE_TYPE (object);
  tree dtor_type = TREE_OPERAND (dtor_name, 0);
  tree expr;

  /* We've already complained about this destructor.  */
  if (dtor_type == error_mark_node)
    return error_mark_node;

  if (scope && !check_dtor_name (scope, dtor_type))
    {
      if (complain & tf_error)
	error ("qualified type %qT does not match destructor name ~%qT",
	       scope, dtor_type);
      return error_mark_node;
    }
  if (is_auto (dtor_type))
    dtor_type = object_type;
  else if (identifier_p (dtor_type))
    {
      /* In a template, names we can't find a match for are still accepted
	 destructor names, and we check them here.  */
      if (check_dtor_name (object_type, dtor_type))
	dtor_type = object_type;
      else
	{
	  if (complain & tf_error)
	    error ("object type %qT does not match destructor name ~%qT",
		   object_type, dtor_type);
	  return error_mark_node;
	}
      
    }
  else if (!DERIVED_FROM_P (dtor_type, TYPE_MAIN_VARIANT (object_type)))
    {
      if (complain & tf_error)
	error ("the type being destroyed is %qT, but the destructor "
	       "refers to %qT", TYPE_MAIN_VARIANT (object_type), dtor_type);
      return error_mark_node;
    }
  expr = lookup_member (dtor_type, complete_dtor_identifier,
			/*protect=*/1, /*want_type=*/false,
			tf_warning_or_error);
  if (!expr)
    {
      if (complain & tf_error)
	cxx_incomplete_type_error (dtor_name, dtor_type);
      return error_mark_node;
    }
  expr = (adjust_result_of_qualified_name_lookup
	  (expr, dtor_type, object_type));
  if (scope == NULL_TREE)
    /* We need to call adjust_result_of_qualified_name_lookup in case the
       destructor names a base class, but we unset BASELINK_QUALIFIED_P so
       that we still get virtual function binding.  */
    BASELINK_QUALIFIED_P (expr) = false;
  return expr;
}

/* An expression of the form "A::template B" has been resolved to
   DECL.  Issue a diagnostic if B is not a template or template
   specialization.  */

void
check_template_keyword (tree decl)
{
  /* The standard says:

      [temp.names]

      If a name prefixed by the keyword template is not a member
      template, the program is ill-formed.

     DR 228 removed the restriction that the template be a member
     template.

     DR 96, if accepted would add the further restriction that explicit
     template arguments must be provided if the template keyword is
     used, but, as of 2005-10-16, that DR is still in "drafting".  If
     this DR is accepted, then the semantic checks here can be
     simplified, as the entity named must in fact be a template
     specialization, rather than, as at present, a set of overloaded
     functions containing at least one template function.  */
  if (TREE_CODE (decl) != TEMPLATE_DECL
      && TREE_CODE (decl) != TEMPLATE_ID_EXPR)
    {
      if (VAR_P (decl))
	{
	  if (DECL_USE_TEMPLATE (decl)
	      && PRIMARY_TEMPLATE_P (DECL_TI_TEMPLATE (decl)))
	    ;
	  else
	    permerror (input_location, "%qD is not a template", decl);
	}
      else if (!is_overloaded_fn (decl))
	permerror (input_location, "%qD is not a template", decl);
      else
	{
	  bool found = false;

	  for (lkp_iterator iter (MAYBE_BASELINK_FUNCTIONS (decl));
	       !found && iter; ++iter)
	    {
	      tree fn = *iter;
	      if (TREE_CODE (fn) == TEMPLATE_DECL
		  || TREE_CODE (fn) == TEMPLATE_ID_EXPR
		  || (TREE_CODE (fn) == FUNCTION_DECL
		      && DECL_USE_TEMPLATE (fn)
		      && PRIMARY_TEMPLATE_P (DECL_TI_TEMPLATE (fn))))
		found = true;
	    }
	  if (!found)
	    permerror (input_location, "%qD is not a template", decl);
	}
    }
}

/* Record that an access failure occurred on BASETYPE_PATH attempting
   to access DECL, where DIAG_DECL should be used for diagnostics.  */

void
access_failure_info::record_access_failure (tree basetype_path,
					    tree decl, tree diag_decl)
{
  m_was_inaccessible = true;
  m_basetype_path = basetype_path;
  m_decl = decl;
  m_diag_decl = diag_decl;
}

/* If an access failure was recorded, then attempt to locate an
   accessor function for the pertinent field.
   Otherwise, return NULL_TREE.  */

tree
access_failure_info::get_any_accessor (bool const_p) const
{
  if (!was_inaccessible_p ())
    return NULL_TREE;

  tree accessor
    = locate_field_accessor (m_basetype_path, m_diag_decl, const_p);
  if (!accessor)
    return NULL_TREE;

  /* The accessor must itself be accessible for it to be a reasonable
     suggestion.  */
  if (!accessible_p (m_basetype_path, accessor, true))
    return NULL_TREE;

  return accessor;
}

/* Add a fix-it hint to RICHLOC suggesting the use of ACCESSOR_DECL, by
   replacing the primary location in RICHLOC with "accessor()".  */

void
access_failure_info::add_fixit_hint (rich_location *richloc,
				     tree accessor_decl)
{
  pretty_printer pp;
  pp_string (&pp, IDENTIFIER_POINTER (DECL_NAME (accessor_decl)));
  pp_string (&pp, "()");
  richloc->add_fixit_replace (pp_formatted_text (&pp));
}

/* If an access failure was recorded, then attempt to locate an
   accessor function for the pertinent field, and if one is
   available, add a note and fix-it hint suggesting using it.  */

void
access_failure_info::maybe_suggest_accessor (bool const_p) const
{
  tree accessor = get_any_accessor (const_p);
  if (accessor == NULL_TREE)
    return;
  rich_location richloc (line_table, input_location);
  add_fixit_hint (&richloc, accessor);
  inform (&richloc, "field %q#D can be accessed via %q#D",
	  m_diag_decl, accessor);
}

/* Subroutine of finish_class_member_access_expr.
   Issue an error about NAME not being a member of ACCESS_PATH (or
   OBJECT_TYPE), potentially providing a fix-it hint for misspelled
   names.  */

static void
complain_about_unrecognized_member (tree access_path, tree name,
				    tree object_type)
{
  /* Attempt to provide a hint about misspelled names.  */
  tree guessed_id = lookup_member_fuzzy (access_path, name,
					 /*want_type=*/false);
  if (guessed_id == NULL_TREE)
    {
      /* No hint.  */
      error ("%q#T has no member named %qE",
	     TREE_CODE (access_path) == TREE_BINFO
	     ? TREE_TYPE (access_path) : object_type, name);
      return;
    }

  location_t bogus_component_loc = input_location;
  gcc_rich_location rich_loc (bogus_component_loc);

  /* Check that the guessed name is accessible along access_path.  */
  access_failure_info afi;
  lookup_member (access_path, guessed_id, /*protect=*/1,
		 /*want_type=*/false, /*complain=*/false,
		 &afi);
  if (afi.was_inaccessible_p ())
    {
      tree accessor = afi.get_any_accessor (TYPE_READONLY (object_type));
      if (accessor)
	{
	  /* The guessed name isn't directly accessible, but can be accessed
	     via an accessor member function.  */
	  afi.add_fixit_hint (&rich_loc, accessor);
	  error_at (&rich_loc,
		    "%q#T has no member named %qE;"
		    " did you mean %q#D? (accessible via %q#D)",
		    TREE_CODE (access_path) == TREE_BINFO
		    ? TREE_TYPE (access_path) : object_type,
		    name, afi.get_diag_decl (), accessor);
	}
      else
	{
	  /* The guessed name isn't directly accessible, and no accessor
	     member function could be found.  */
	  error_at (&rich_loc,
		    "%q#T has no member named %qE;"
		    " did you mean %q#D? (not accessible from this context)",
		    TREE_CODE (access_path) == TREE_BINFO
		    ? TREE_TYPE (access_path) : object_type,
		    name, afi.get_diag_decl ());
	  complain_about_access (afi.get_decl (), afi.get_diag_decl (),
				 afi.get_diag_decl (), false, ak_none);
	}
    }
  else
    {
      /* The guessed name is directly accessible; suggest it.  */
      rich_loc.add_fixit_misspelled_id (bogus_component_loc,
					guessed_id);
      error_at (&rich_loc,
		"%q#T has no member named %qE;"
		" did you mean %qE?",
		TREE_CODE (access_path) == TREE_BINFO
		? TREE_TYPE (access_path) : object_type,
		name, guessed_id);
    }
}

/* This function is called by the parser to process a class member
   access expression of the form OBJECT.NAME.  NAME is a node used by
   the parser to represent a name; it is not yet a DECL.  It may,
   however, be a BASELINK where the BASELINK_FUNCTIONS is a
   TEMPLATE_ID_EXPR.  Templates must be looked up by the parser, and
   there is no reason to do the lookup twice, so the parser keeps the
   BASELINK.  TEMPLATE_P is true iff NAME was explicitly declared to
   be a template via the use of the "A::template B" syntax.  */

tree
finish_class_member_access_expr (cp_expr object, tree name, bool template_p,
				 tsubst_flags_t complain)
{
  tree expr;
  tree object_type;
  tree member;
  tree access_path = NULL_TREE;
  tree orig_object