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

   Copyright (C) 1987, 1988, 1991, 1998, 2002, 2003, 2004, 2005

   Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under

the terms of the GNU General Public License as published by the Free

Software Foundation; either version 2, or (at your option) any later

version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY

WARRANTY; without even the implied warranty of MERCHANTABILITY or

FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

for more details.

You should have received a copy of the GNU General Public License

along with GCC; see the file COPYING.  If not, write to the Free

Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301, USA.  */

/* 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 "convert.h"

#include "c-common.h"

#include "c-tree.h"

#include "langhooks.h"

#include "toplev.h"

#include "target.h"

/* 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 (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.  */

/* Subroutines of `convert'.  */

/* Create an expression whose value is that of EXPR,

   converted to type TYPE.  The TREE_TYPE of the value

   is always TYPE.  This function implements all reasonable

   conversions; callers should filter out those that are

   not permitted by the language being compiled.  */

tree

convert (tree type, tree expr)

{

  tree e = expr;

  enum tree_code code = TREE_CODE (type);

  const char *invalid_conv_diag;

  if (type == error_mark_node

      || expr == error_mark_node

      || TREE_TYPE (expr) == error_mark_node)

    return error_mark_node;

  if ((invalid_conv_diag

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

    {

      error (invalid_conv_diag);

      return error_mark_node;

    }

  if (type == TREE_TYPE (expr))

    return expr;

  if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))

    return fold_build1 (NOP_EXPR, type, expr);

  if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)

    return error_mark_node;

  if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)

    {

      error ("void value not ignored as it ought to be");

      return error_mark_node;

    }

  if (code == VOID_TYPE)

    return build1 (CONVERT_EXPR, type, e);

#if 0

  /* This is incorrect.  A truncation can't be stripped this way.

     Extensions will be stripped by the use of get_unwidened.  */

  if (TREE_CODE (expr) == NOP_EXPR)

    return convert (type, TREE_OPERAND (expr, 0));

#endif

  if (code == INTEGER_TYPE || code == ENUMERAL_TYPE)

    return fold (convert_to_integer (type, e));

  if (code == BOOLEAN_TYPE)

    {

      tree t = c_objc_common_truthvalue_conversion (expr);

      if (TREE_CODE (t) == ERROR_MARK)

        return t;

      /* If it returns a NOP_EXPR, we must fold it here to avoid

         infinite recursion between fold () and convert ().  */

      if (TREE_CODE (t) == NOP_EXPR)

        return fold_build1 (NOP_EXPR, type, TREE_OPERAND (t, 0));

      else

        return fold_build1 (NOP_EXPR, type, t);

    }

  if (code == POINTER_TYPE || code == REFERENCE_TYPE)

    return fold (convert_to_pointer (type, e));

  if (code == REAL_TYPE)

    return fold (convert_to_real (type, e));

  if (code == COMPLEX_TYPE)

    return fold (convert_to_complex (type, e));

  if (code == VECTOR_TYPE)

    return fold (convert_to_vector (type, e));

  if ((code == RECORD_TYPE || code == UNION_TYPE)

      && lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))

      return e;

  error ("conversion to non-scalar type requested");

  return error_mark_node;

}