gcc/c-convert.c

   1 /* Language-level data type conversion for GNU C.
   2    Copyright (C) 1987, 1988, 1991, 1998 Free Software Foundation, Inc.
   3
   4 This file is part of GNU CC.
   5
   6 GNU CC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU CC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU CC; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 59 Temple Place - Suite 330,
  19 Boston, MA 02111-1307, USA.  */
  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 "tree.h"
  30 #include "flags.h"
  31 #include "convert.h"
  32 #include "toplev.h"
  33
  34 /* Change of width--truncation and extension of integers or reals--
  35    is represented with NOP_EXPR.  Proper functioning of many things
  36    assumes that no other conversions can be NOP_EXPRs.
  37
  38    Conversion between integer and pointer is represented with CONVERT_EXPR.
  39    Converting integer to real uses FLOAT_EXPR
  40    and real to integer uses FIX_TRUNC_EXPR.
  41
  42    Here is a list of all the functions that assume that widening and
  43    narrowing is always done with a NOP_EXPR:
  44      In convert.c, convert_to_integer.
  45      In c-typeck.c, build_binary_op (boolean ops), and truthvalue_conversion.
  46      In expr.c: expand_expr, for operands of a MULT_EXPR.
  47      In fold-const.c: fold.
  48      In tree.c: get_narrower and get_unwidened.  */
  49 \f
  50 /* Subroutines of `convert'.  */
  51
  52
  53 \f
  54 /* Create an expression whose value is that of EXPR,
  55    converted to type TYPE.  The TREE_TYPE of the value
  56    is always TYPE.  This function implements all reasonable
  57    conversions; callers should filter out those that are
  58    not permitted by the language being compiled.  */
  59
  60 tree
  61 convert (type, expr)
  62      tree type, expr;
  63 {
  64   register tree e = expr;
  65   register enum tree_code code = TREE_CODE (type);
  66
  67   if (type == TREE_TYPE (expr)
  68       || TREE_CODE (expr) == ERROR_MARK)
  69     return expr;
  70   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))
  71     return fold (build1 (NOP_EXPR, type, expr));
  72   if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
  73     return error_mark_node;
  74   if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
  75     {
  76       error ("void value not ignored as it ought to be");
  77       return error_mark_node;
  78     }
  79   if (code == VOID_TYPE)
  80     return build1 (CONVERT_EXPR, type, e);
  81 #if 0
  82   /* This is incorrect.  A truncation can't be stripped this way.
  83      Extensions will be stripped by the use of get_unwidened.  */
  84   if (TREE_CODE (expr) == NOP_EXPR)
  85     return convert (type, TREE_OPERAND (expr, 0));
  86 #endif
  87   if (code == INTEGER_TYPE || code == ENUMERAL_TYPE)
  88     return fold (convert_to_integer (type, e));
  89   if (code == POINTER_TYPE)
  90     return fold (convert_to_pointer (type, e));
  91   if (code == REAL_TYPE)
  92     return fold (convert_to_real (type, e));
  93   if (code == COMPLEX_TYPE)
  94     return fold (convert_to_complex (type, e));
  95
  96   error ("conversion to non-scalar type requested");
  97   return error_mark_node;
  98 }