gcc/c-convert.c

   1 /* Language-level data type conversion for GNU C.
   2    Copyright (C) 1987, 1988, 1991 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, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  19
  20
  21 /* This file contains the functions for converting C expressions
  22    to different data types.  The only entry point is `convert'.
  23    Every language front end must have a `convert' function
  24    but what kind of conversions it does will depend on the language.  */
  25
  26 #include "config.h"
  27 #include "tree.h"
  28 #include "flags.h"
  29 #include "convert.h"
  30
  31 /* Change of width--truncation and extension of integers or reals--
  32    is represented with NOP_EXPR.  Proper functioning of many things
  33    assumes that no other conversions can be NOP_EXPRs.
  34
  35    Conversion between integer and pointer is represented with CONVERT_EXPR.
  36    Converting integer to real uses FLOAT_EXPR
  37    and real to integer uses FIX_TRUNC_EXPR.
  38
  39    Here is a list of all the functions that assume that widening and
  40    narrowing is always done with a NOP_EXPR:
  41      In convert.c, convert_to_integer.
  42      In c-typeck.c, build_binary_op (boolean ops), and truthvalue_conversion.
  43      In expr.c: expand_expr, for operands of a MULT_EXPR.
  44      In fold-const.c: fold.
  45      In tree.c: get_narrower and get_unwidened.  */
  46 \f
  47 /* Subroutines of `convert'.  */
  48
  49
  50 \f
  51 /* Create an expression whose value is that of EXPR,
  52    converted to type TYPE.  The TREE_TYPE of the value
  53    is always TYPE.  This function implements all reasonable
  54    conversions; callers should filter out those that are
  55    not permitted by the language being compiled.  */
  56
  57 tree
  58 convert (type, expr)
  59      tree type, expr;
  60 {
  61   register tree e = expr;
  62   register enum tree_code code = TREE_CODE (type);
  63
  64   if (type == TREE_TYPE (expr)
  65       || TREE_CODE (expr) == ERROR_MARK)
  66     return expr;
  67   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))
  68     return fold (build1 (NOP_EXPR, type, expr));
  69   if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
  70     return error_mark_node;
  71   if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
  72     {
  73       error ("void value not ignored as it ought to be");
  74       return error_mark_node;
  75     }
  76   if (code == VOID_TYPE)
  77     return build1 (CONVERT_EXPR, type, e);
  78 #if 0
  79   /* This is incorrect.  A truncation can't be stripped this way.
  80      Extensions will be stripped by the use of get_unwidened.  */
  81   if (TREE_CODE (expr) == NOP_EXPR)
  82     return convert (type, TREE_OPERAND (expr, 0));
  83 #endif
  84   if (code == INTEGER_TYPE || code == ENUMERAL_TYPE)
  85     return fold (convert_to_integer (type, e));
  86   if (code == POINTER_TYPE)
  87     return fold (convert_to_pointer (type, e));
  88   if (code == REAL_TYPE)
  89     return fold (convert_to_real (type, e));
  90   if (code == COMPLEX_TYPE)
  91     return fold (convert_to_complex (type, e));
  92
  93   error ("conversion to non-scalar type requested");
  94   return error_mark_node;
  95 }