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/* Language-level data type conversion for GNU C++.

   Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,

   1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009

   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 contains the functions for converting C++ expressions

   to different data types.  The only entry point is `convert'.

   Every language front end must have a `convert' function

   but what kind of conversions it does will depend on the language.  */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "tree.h"

#include "flags.h"

#include "cp-tree.h"

#include "intl.h"

#include "convert.h"

#include "toplev.h"

#include "decl.h"

#include "target.h"

static tree cp_convert_to_pointer (tree, tree);

static tree convert_to_pointer_force (tree, tree);

static tree build_type_conversion (tree, tree);

static tree build_up_reference (tree, tree, int, tree);

static void warn_ref_binding (tree, tree, tree);

/* Change of width--truncation and extension of integers or reals--

   is represented with NOP_EXPR.  Proper functioning of many things

   assumes that no other conversions can be NOP_EXPRs.

   Conversion between integer and pointer is represented with CONVERT_EXPR.

   Converting integer to real uses FLOAT_EXPR

   and real to integer uses FIX_TRUNC_EXPR.

   Here is a list of all the functions that assume that widening and

   narrowing is always done with a NOP_EXPR:

     In convert.c, convert_to_integer.

     In c-typeck.c, build_binary_op_nodefault (boolean ops),

        and c_common_truthvalue_conversion.

     In expr.c: expand_expr, for operands of a MULT_EXPR.

     In fold-const.c: fold.

     In tree.c: get_narrower and get_unwidened.

   C++: in multiple-inheritance, converting between pointers may involve

   adjusting them by a delta stored within the class definition.  */

/* Subroutines of `convert'.  */

/* if converting pointer to pointer

     if dealing with classes, check for derived->base or vice versa

     else if dealing with method pointers, delegate

     else convert blindly

   else if converting class, pass off to build_type_conversion

   else try C-style pointer conversion.  */

static tree

cp_convert_to_pointer (tree type, tree expr)

{

  tree intype = TREE_TYPE (expr);

  enum tree_code form;

  tree rval;

  if (intype == error_mark_node)

    return error_mark_node;

  if (MAYBE_CLASS_TYPE_P (intype))

    {

      intype = complete_type (intype);

      if (!COMPLETE_TYPE_P (intype))

        {

          error ("can't convert from incomplete type %qT to %qT",

                 intype, type);

          return error_mark_node;

        }

      rval = build_type_conversion (type, expr);

      if (rval)

        {

          if (rval == error_mark_node)

            error ("conversion of %qE from %qT to %qT is ambiguous",

                   expr, intype, type);

          return rval;

        }

    }

  /* Handle anachronistic conversions from (::*)() to cv void* or (*)().  */

  if (TREE_CODE (type) == POINTER_TYPE

      && (TREE_CODE (TREE_TYPE (type)) == FUNCTION_TYPE

          || VOID_TYPE_P (TREE_TYPE (type))))

    {

      if (TYPE_PTRMEMFUNC_P (intype)

          || TREE_CODE (intype) == METHOD_TYPE)

        return convert_member_func_to_ptr (type, expr);

      if (TREE_CODE (TREE_TYPE (expr)) == POINTER_TYPE)

        return build_nop (type, expr);

      intype = TREE_TYPE (expr);

    }

  if (expr == error_mark_node)

    return error_mark_node;

  form = TREE_CODE (intype);

  if (POINTER_TYPE_P (intype))

    {

      intype = TYPE_MAIN_VARIANT (intype);

      if (TYPE_MAIN_VARIANT (type) != intype

          && TREE_CODE (type) == POINTER_TYPE

          && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE

          && MAYBE_CLASS_TYPE_P (TREE_TYPE (type))

          && MAYBE_CLASS_TYPE_P (TREE_TYPE (intype))

          && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)

        {

          enum tree_code code = PLUS_EXPR;

          tree binfo;

          tree intype_class;

          tree type_class;

          bool same_p;

          intype_class = TREE_TYPE (intype);

          type_class = TREE_TYPE (type);

          same_p = same_type_p (TYPE_MAIN_VARIANT (intype_class),

                                TYPE_MAIN_VARIANT (type_class));

          binfo = NULL_TREE;

          /* Try derived to base conversion.  */

          if (!same_p)

            binfo = lookup_base (intype_class, type_class, ba_check, NULL);

          if (!same_p && !binfo)

            {

              /* Try base to derived conversion.  */

              binfo = lookup_base (type_class, intype_class, ba_check, NULL);

              code = MINUS_EXPR;

            }

          if (binfo == error_mark_node)

            return error_mark_node;

          if (binfo || same_p)

            {

              if (binfo)

                expr = build_base_path (code, expr, binfo, 0);

              /* Add any qualifier conversions.  */

              return build_nop (type, expr);

            }

        }

      if (TYPE_PTRMEMFUNC_P (type))

        {

          error ("cannot convert %qE from type %qT to type %qT",

                 expr, intype, type);

          return error_mark_node;

        }

      return build_nop (type, expr);

    }

  else if ((TYPE_PTRMEM_P (type) && TYPE_PTRMEM_P (intype))

           || (TYPE_PTRMEMFUNC_P (type) && TYPE_PTRMEMFUNC_P (intype)))

    return convert_ptrmem (type, expr, /*allow_inverse_p=*/false,

                           /*c_cast_p=*/false);

  else if (TYPE_PTRMEMFUNC_P (intype))

    {

      if (!warn_pmf2ptr)

        {

          if (TREE_CODE (expr) == PTRMEM_CST)

            return cp_convert_to_pointer (type,

                                          PTRMEM_CST_MEMBER (expr));

          else if (TREE_CODE (expr) == OFFSET_REF)

            {

              tree object = TREE_OPERAND (expr, 0);

              return get_member_function_from_ptrfunc (&object,

                                                       TREE_OPERAND (expr, 1));

            }

        }

      error ("cannot convert %qE from type %qT to type %qT",

             expr, intype, type);

      return error_mark_node;

    }

  if (integer_zerop (expr))

    {

      if (TYPE_PTRMEMFUNC_P (type))

        return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0,

                                 /*c_cast_p=*/false);

      if (TYPE_PTRMEM_P (type))

        {

          /* A NULL pointer-to-member is represented by -1, not by

             zero.  */

          expr = build_int_cst_type (type, -1);

        }

      else

        expr = build_int_cst (type, 0);

      return expr;

    }

  else if (TYPE_PTR_TO_MEMBER_P (type) && INTEGRAL_CODE_P (form))

    {

      error ("invalid conversion from %qT to %qT", intype, type);

      return error_mark_node;

    }

  if (INTEGRAL_CODE_P (form))

    {

      if (TYPE_PRECISION (intype) == POINTER_SIZE)

        return build1 (CONVERT_EXPR, type, expr);

      expr = cp_convert (c_common_type_for_size (POINTER_SIZE, 0), expr);

      /* Modes may be different but sizes should be the same.  There

         is supposed to be some integral type that is the same width

         as a pointer.  */

      gcc_assert (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (expr)))

                  == GET_MODE_SIZE (TYPE_MODE (type)));

      return convert_to_pointer (type, expr);

    }

  if (type_unknown_p (expr))

    return instantiate_type (type, expr, tf_warning_or_error);

  error ("cannot convert %qE from type %qT to type %qT",

         expr, intype, type);

  return error_mark_node;

}

/* Like convert, except permit conversions to take place which

   are not normally allowed due to access restrictions

   (such as conversion from sub-type to private super-type).  */

static tree

convert_to_pointer_force (tree type, tree expr)

{

  tree intype = TREE_TYPE (expr);

  enum tree_code form = TREE_CODE (intype);

  if (form == POINTER_TYPE)

    {

      intype = TYPE_MAIN_VARIANT (intype);

      if (TYPE_MAIN_VARIANT (type) != intype

          && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE

          && MAYBE_CLASS_TYPE_P (TREE_TYPE (type))

          && MAYBE_CLASS_TYPE_P (TREE_TYPE (intype))

          && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)

        {

          enum tree_code code = PLUS_EXPR;

          tree binfo;

          binfo = lookup_base (TREE_TYPE (intype), TREE_TYPE (type),

                               ba_unique, NULL);

          if (!binfo)

            {

              binfo = lookup_base (TREE_TYPE (type), TREE_TYPE (intype),

                                   ba_unique, NULL);

              code = MINUS_EXPR;

            }

          if (binfo == error_mark_node)

            return error_mark_node;

          if (binfo)

            {

              expr = build_base_path (code, expr, binfo, 0);

              if (expr == error_mark_node)

                 return error_mark_node;

              /* Add any qualifier conversions.  */

              if (!same_type_p (TREE_TYPE (TREE_TYPE (expr)),

                                TREE_TYPE (type)))

                expr = build_nop (type, expr);

              return expr;

            }

        }

    }

  return cp_convert_to_pointer (type, expr);

}

/* We are passing something to a function which requires a reference.

   The type we are interested in is in TYPE. The initial

   value we have to begin with is in ARG.

   FLAGS controls how we manage access checking.

   DIRECT_BIND in FLAGS controls how any temporaries are generated.

     If DIRECT_BIND is set, DECL is the reference we're binding to.  */

static tree

build_up_reference (tree type, tree arg, int flags, tree decl)

{

  tree rval;

  tree argtype = TREE_TYPE (arg);

  tree target_type = TREE_TYPE (type);

  gcc_assert (TREE_CODE (type) == REFERENCE_TYPE);

  if ((flags & DIRECT_BIND) && ! real_lvalue_p (arg))

    {

      /* Create a new temporary variable.  We can't just use a TARGET_EXPR

         here because it needs to live as long as DECL.  */

      tree targ = arg;

      arg = make_temporary_var_for_ref_to_temp (decl, TREE_TYPE (arg));

      /* Process the initializer for the declaration.  */

      DECL_INITIAL (arg) = targ;

      cp_finish_decl (arg, targ, /*init_const_expr_p=*/false, NULL_TREE,

                      LOOKUP_ONLYCONVERTING|DIRECT_BIND);

    }

  else if (!(flags & DIRECT_BIND) && ! lvalue_p (arg))

    return get_target_expr (arg);

  /* If we had a way to wrap this up, and say, if we ever needed its

     address, transform all occurrences of the register, into a memory

     reference we could win better.  */

  rval = cp_build_unary_op (ADDR_EXPR, arg, 1, tf_warning_or_error);

  if (rval == error_mark_node)

    return error_mark_node;

  if ((flags & LOOKUP_PROTECT)

      && TYPE_MAIN_VARIANT (argtype) != TYPE_MAIN_VARIANT (target_type)

      && MAYBE_CLASS_TYPE_P (argtype)

      && MAYBE_CLASS_TYPE_P (target_type))

    {

      /* We go through lookup_base for the access control.  */

      tree binfo = lookup_base (argtype, target_type, ba_check, NULL);

      if (binfo == error_mark_node)

        return error_mark_node;

      if (binfo == NULL_TREE)

        return error_not_base_type (target_type, argtype);

      rval = build_base_path (PLUS_EXPR, rval, binfo, 1);

    }

  else

    rval

      = convert_to_pointer_force (build_pointer_type (target_type), rval);

  return build_nop (type, rval);

}

/* Subroutine of convert_to_reference. REFTYPE is the target reference type.

   INTYPE is the original rvalue type and DECL is an optional _DECL node

   for diagnostics.

   [dcl.init.ref] says that if an rvalue is used to

   initialize a reference, then the reference must be to a

   non-volatile const type.  */

static void

warn_ref_binding (tree reftype, tree intype, tree decl)

{

  tree ttl = TREE_TYPE (reftype);

  if (!CP_TYPE_CONST_NON_VOLATILE_P (ttl))

    {

      const char *msg;

      if (CP_TYPE_VOLATILE_P (ttl) && decl)

        msg = G_("initialization of volatile reference type %q#T from "

                 "rvalue of type %qT");

      else if (CP_TYPE_VOLATILE_P (ttl))

        msg = G_("conversion to volatile reference type %q#T "

                 "from rvalue of type %qT");

      else if (decl)

        msg = G_("initialization of non-const reference type %q#T from "

                 "rvalue of type %qT");

      else

        msg = G_("conversion to non-const reference type %q#T from "

                 "rvalue of type %qT");

      permerror (input_location, msg, reftype, intype);

    }

}

/* For C++: Only need to do one-level references, but cannot

   get tripped up on signed/unsigned differences.

   DECL is either NULL_TREE or the _DECL node for a reference that is being

   initialized.  It can be error_mark_node if we don't know the _DECL but

   we know it's an initialization.  */

tree

convert_to_reference (tree reftype, tree expr, int convtype,

                      int flags, tree decl)

{

  tree type = TYPE_MAIN_VARIANT (TREE_TYPE (reftype));

  tree intype;

  tree rval = NULL_TREE;

  tree rval_as_conversion = NULL_TREE;

  bool can_convert_intype_to_type;

  if (TREE_CODE (type) == FUNCTION_TYPE

      && TREE_TYPE (expr) == unknown_type_node)

    expr = instantiate_type (type, expr,

                             (flags & LOOKUP_COMPLAIN)

                             ? tf_warning_or_error : tf_none);

  if (expr == error_mark_node)

    return error_mark_node;

  intype = TREE_TYPE (expr);

  gcc_assert (TREE_CODE (intype) != REFERENCE_TYPE);

  gcc_assert (TREE_CODE (reftype) == REFERENCE_TYPE);

  intype = TYPE_MAIN_VARIANT (intype);

  can_convert_intype_to_type = can_convert (type, intype);

  if (!can_convert_intype_to_type

      && (convtype & CONV_IMPLICIT) && MAYBE_CLASS_TYPE_P (intype)

      && ! (flags & LOOKUP_NO_CONVERSION))

    {

      /* Look for a user-defined conversion to lvalue that we can use.  */

      rval_as_conversion

        = build_type_conversion (reftype, expr);

      if (rval_as_conversion && rval_as_conversion != error_mark_node

          && real_lvalue_p (rval_as_conversion))

        {

          expr = rval_as_conversion;

          rval_as_conversion = NULL_TREE;

          intype = type;

          can_convert_intype_to_type = 1;

        }

    }

  if (((convtype & CONV_STATIC) && can_convert (intype, type))

      || ((convtype & CONV_IMPLICIT) && can_convert_intype_to_type))

    {

      if (flags & LOOKUP_COMPLAIN)

        {

          tree ttl = TREE_TYPE (reftype);

          tree ttr = lvalue_type (expr);

          if (! real_lvalue_p (expr))

            warn_ref_binding (reftype, intype, decl);

          if (! (convtype & CONV_CONST)

                   && !at_least_as_qualified_p (ttl, ttr))

            permerror (input_location, "conversion from %qT to %qT discards qualifiers",

                       ttr, reftype);

        }

      return build_up_reference (reftype, expr, flags, decl);

    }

  else if ((convtype & CONV_REINTERPRET) && lvalue_p (expr))

    {

      /* When casting an lvalue to a reference type, just convert into

         a pointer to the new type and deference it.  This is allowed

         by San Diego WP section 5.2.9 paragraph 12, though perhaps it

         should be done directly (jason).  (int &)ri ---> *(int*)&ri */

      /* B* bp; A& ar = (A&)bp; is valid, but it's probably not what they

         meant.  */

      if (TREE_CODE (intype) == POINTER_TYPE

          && (comptypes (TREE_TYPE (intype), type,

                         COMPARE_BASE | COMPARE_DERIVED)))

        warning (0, "casting %qT to %qT does not dereference pointer",

                 intype, reftype);

      rval = cp_build_unary_op (ADDR_EXPR, expr, 0, tf_warning_or_error);

      if (rval != error_mark_node)

        rval = convert_force (build_pointer_type (TREE_TYPE (reftype)),

                              rval, 0);

      if (rval != error_mark_node)

        rval = build1 (NOP_EXPR, reftype, rval);

    }

  else

    {

      rval = convert_for_initialization (NULL_TREE, type, expr, flags,

                                         "converting", 0, 0,

                                         tf_warning_or_error);

      if (rval == NULL_TREE || rval == error_mark_node)

        return rval;

      warn_ref_binding (reftype, intype, decl);

      rval = build_up_reference (reftype, rval, flags, decl);

    }

  if (rval)

    {

      /* If we found a way to convert earlier, then use it.  */

      return rval;

    }

  if (flags & LOOKUP_COMPLAIN)

    error ("cannot convert type %qT to type %qT", intype, reftype);

  return error_mark_node;

}

/* We are using a reference VAL for its value. Bash that reference all the

   way down to its lowest form.  */

tree

convert_from_reference (tree val)

{

  if (TREE_TYPE (val)

      && TREE_CODE (TREE_TYPE (val)) == REFERENCE_TYPE)

    {

      tree t = TREE_TYPE (TREE_TYPE (val));

      tree ref = build1 (INDIRECT_REF, t, val);

       /* We *must* set TREE_READONLY when dereferencing a pointer to const,

          so that we get the proper error message if the result is used

          to assign to.  Also, &* is supposed to be a no-op.  */

      TREE_READONLY (ref) = CP_TYPE_CONST_P (t);

      TREE_THIS_VOLATILE (ref) = CP_TYPE_VOLATILE_P (t);

      TREE_SIDE_EFFECTS (ref)

        = (TREE_THIS_VOLATILE (ref) || TREE_SIDE_EFFECTS (val));

      REFERENCE_REF_P (ref) = 1;

      val = ref;

    }

  return val;

}

/* Really perform an lvalue-to-rvalue conversion, including copying an

   argument of class type into a temporary.  */

tree

force_rvalue (tree expr)

{

  if (MAYBE_CLASS_TYPE_P (TREE_TYPE (expr)) && TREE_CODE (expr) != TARGET_EXPR)

    expr = ocp_convert (TREE_TYPE (expr), expr,

                        CONV_IMPLICIT|CONV_FORCE_TEMP, LOOKUP_NORMAL);

  else

    expr = decay_conversion (expr);

  return expr;

}

/* Fold away simple conversions, but make sure the result is an rvalue.  */

tree

cp_fold_convert (tree type, tree expr)

{

  return rvalue (fold_convert (type, expr));

}

/* C++ conversions, preference to static cast conversions.  */

tree

cp_convert (tree type, tree expr)

{

  return ocp_convert (type, expr, CONV_OLD_CONVERT, LOOKUP_NORMAL);

}

/* C++ equivalent of convert_and_check but using cp_convert as the

   conversion function.

   Convert EXPR to TYPE, warning about conversion problems with constants.

   Invoke this function on every expression that is converted implicitly,

   i.e. because of language rules and not because of an explicit cast.  */

tree

cp_convert_and_check (tree type, tree expr)

{

  tree result;

  if (TREE_TYPE (expr) == type)

    return expr;

  result = cp_convert (type, expr);

  if (c_inhibit_evaluation_warnings == 0

      && !TREE_OVERFLOW_P (expr)

      && result != error_mark_node)

    warnings_for_convert_and_check (type, expr, result);

  return result;

}

/* Conversion...

   FLAGS indicates how we should behave.  */

tree

ocp_convert (tree type, tree expr, int convtype, int flags)

{

  tree e = expr;

  enum tree_code code = TREE_CODE (type);

  const char *invalid_conv_diag;

  tree e1;

  if (error_operand_p (e) || type == error_mark_node)

    return error_mark_node;

  complete_type (type);

  complete_type (TREE_TYPE (expr));

  if ((invalid_conv_diag

       = targetm.invalid_conversion (TREE_TYPE (expr), type)))

    {

      error (invalid_conv_diag);

      return error_mark_node;

    }

  e = integral_constant_value (e);

  if (MAYBE_CLASS_TYPE_P (type) && (convtype & CONV_FORCE_TEMP))

    /* We need a new temporary; don't take this shortcut.  */;

  else if (same_type_ignoring_top_level_qualifiers_p (type, TREE_TYPE (e)))

    {

      if (same_type_p (type, TREE_TYPE (e)))

        /* The call to fold will not always remove the NOP_EXPR as

           might be expected, since if one of the types is a typedef;

           the comparison in fold is just equality of pointers, not a

           call to comptypes.  We don't call fold in this case because

           that can result in infinite recursion; fold will call

           convert, which will call ocp_convert, etc.  */

        return e;

      /* For complex data types, we need to perform componentwise

         conversion.  */

      else if (TREE_CODE (type) == COMPLEX_TYPE)

        return fold_if_not_in_template (convert_to_complex (type, e));

      else if (TREE_CODE (e) == TARGET_EXPR)

        {

          /* Don't build a NOP_EXPR of class type.  Instead, change the

             type of the temporary.  */

          TREE_TYPE (e) = TREE_TYPE (TARGET_EXPR_SLOT (e)) = type;

          return e;

        }

      else

        {

          /* We shouldn't be treating objects of ADDRESSABLE type as

             rvalues.  */

          gcc_assert (!TREE_ADDRESSABLE (type));

          return fold_if_not_in_template (build_nop (type, e));

        }

    }

  e1 = targetm.convert_to_type (type, e);

  if (e1)

    return e1;

  if (code == VOID_TYPE && (convtype & CONV_STATIC))

    {

      e = convert_to_void (e, /*implicit=*/NULL, tf_warning_or_error);

      return e;

    }

  if (INTEGRAL_CODE_P (code))

    {

      tree intype = TREE_TYPE (e);

      if (TREE_CODE (type) == ENUMERAL_TYPE)

        {

          /* enum = enum, enum = int, enum = float, (enum)pointer are all

             errors.  */

          if (((INTEGRAL_OR_ENUMERATION_TYPE_P (intype)

                || TREE_CODE (intype) == REAL_TYPE)

               && ! (convtype & CONV_STATIC))

              || TREE_CODE (intype) == POINTER_TYPE)

            {

              if (flags & LOOKUP_COMPLAIN)

                permerror (input_location, "conversion from %q#T to %q#T", intype, type);

              if (!flag_permissive)

                return error_mark_node;

            }

          /* [expr.static.cast]

             8. A value of integral or enumeration type can be explicitly

             converted to an enumeration type. The value is unchanged if

             the original value is within the range of the enumeration

             values. Otherwise, the resulting enumeration value is

             unspecified.  */

          if (TREE_CODE (expr) == INTEGER_CST && !int_fits_type_p (expr, type))

            warning (OPT_Wconversion,

                     "the result of the conversion is unspecified because "

                     "%qE is outside the range of type %qT",

                     expr, type);

        }

      if (MAYBE_CLASS_TYPE_P (intype))

        {

          tree rval;

          rval = build_type_conversion (type, e);

          if (rval)

            return rval;

          if (flags & LOOKUP_COMPLAIN)

            error ("%q#T used where a %qT was expected", intype, type);

          return error_mark_node;