gcc/c-convert.c

   1 /* Language-level data type conversion for GNU C.
   2    Copyright (C) 1987, 1988, 1991, 1998, 2002, 2003, 2004, 2005, 2007, 2008,
   3    2009 Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 3, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING3.  If not see
  19 <http://www.gnu.org/licenses/>.  */
  20
  21
  22 /* This file contains the functions for converting C expressions
  23    to different data types.  The only entry point is `convert'.
  24    Every language front end must have a `convert' function
  25    but what kind of conversions it does will depend on the language.  */
  26
  27 #include "config.h"
  28 #include "system.h"
  29 #include "coretypes.h"
  30 #include "tm.h"
  31 #include "tree.h"
  32 #include "flags.h"
  33 #include "convert.h"
  34 #include "c-common.h"
  35 #include "c-tree.h"
  36 #include "langhooks.h"
  37 #include "toplev.h"
  38 #include "target.h"
  39
  40 /* Change of width--truncation and extension of integers or reals--
  41    is represented with NOP_EXPR.  Proper functioning of many things
  42    assumes that no other conversions can be NOP_EXPRs.
  43
  44    Conversion between integer and pointer is represented with CONVERT_EXPR.
  45    Converting integer to real uses FLOAT_EXPR
  46    and real to integer uses FIX_TRUNC_EXPR.
  47
  48    Here is a list of all the functions that assume that widening and
  49    narrowing is always done with a NOP_EXPR:
  50      In convert.c, convert_to_integer.
  51      In c-typeck.c, build_binary_op (boolean ops), and
  52         c_common_truthvalue_conversion.
  53      In expr.c: expand_expr, for operands of a MULT_EXPR.
  54      In fold-const.c: fold.
  55      In tree.c: get_narrower and get_unwidened.  */
  56 \f
  57 /* Subroutines of `convert'.  */
  58
  59
  60 \f
  61 /* Create an expression whose value is that of EXPR,
  62    converted to type TYPE.  The TREE_TYPE of the value
  63    is always TYPE.  This function implements all reasonable
  64    conversions; callers should filter out those that are
  65    not permitted by the language being compiled.  */
  66
  67 tree
  68 convert (tree type, tree expr)
  69 {
  70   tree e = expr;
  71   enum tree_code code = TREE_CODE (type);
  72   const char *invalid_conv_diag;
  73   tree ret;
  74
  75   if (type == error_mark_node
  76       || expr == error_mark_node
  77       || TREE_TYPE (expr) == error_mark_node)
  78     return error_mark_node;
  79
  80   if ((invalid_conv_diag
  81        = targetm.invalid_conversion (TREE_TYPE (expr), type)))
  82     {
  83       error (invalid_conv_diag);
  84       return error_mark_node;
  85     }
  86
  87   if (type == TREE_TYPE (expr))
  88     return expr;
  89   ret = targetm.convert_to_type (type, expr);
  90   if (ret)
  91       return ret;
  92
  93   STRIP_TYPE_NOPS (e);
  94
  95   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))
  96     return fold_convert (type, expr);
  97   if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
  98     return error_mark_node;
  99   if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
 100     {
 101       error ("void value not ignored as it ought to be");
 102       return error_mark_node;
 103     }
 104
 105   switch (code)
 106     {
 107     case VOID_TYPE:
 108       return fold_convert (type, e);
 109
 110     case INTEGER_TYPE:
 111     case ENUMERAL_TYPE:
 112       ret = convert_to_integer (type, e);
 113       goto maybe_fold;
 114
 115     case BOOLEAN_TYPE:
 116       return fold_convert
 117         (type, c_objc_common_truthvalue_conversion (input_location, expr));
 118
 119     case POINTER_TYPE:
 120     case REFERENCE_TYPE:
 121       ret = convert_to_pointer (type, e);
 122       goto maybe_fold;
 123
 124     case REAL_TYPE:
 125       ret = convert_to_real (type, e);
 126       goto maybe_fold;
 127
 128     case FIXED_POINT_TYPE:
 129       ret = convert_to_fixed (type, e);
 130       goto maybe_fold;
 131
 132     case COMPLEX_TYPE:
 133       ret = convert_to_complex (type, e);
 134       goto maybe_fold;
 135
 136     case VECTOR_TYPE:
 137       ret = convert_to_vector (type, e);
 138       goto maybe_fold;
 139
 140     case RECORD_TYPE:
 141     case UNION_TYPE:
 142       if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
 143         return e;
 144       break;
 145
 146     default:
 147       break;
 148
 149     maybe_fold:
 150       if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR)
 151         ret = fold (ret);
 152       return ret;
 153     }
 154
 155   error ("conversion to non-scalar type requested");
 156   return error_mark_node;
 157 }