1/* Language-level data type conversion for GNU C.
2   Copyright (C) 1987, 1988, 1991, 1998, 2002, 2003, 2004, 2005
3   Free Software Foundation, Inc.
4
5This file is part of GCC.
6
7GCC is free software; you can redistribute it and/or modify it under
8the terms of the GNU General Public License as published by the Free
9Software Foundation; either version 2, or (at your option) any later
10version.
11
12GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13WARRANTY; without even the implied warranty of MERCHANTABILITY or
14FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
15for more details.
16
17You should have received a copy of the GNU General Public License
18along with GCC; see the file COPYING.  If not, write to the Free
19Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
2002110-1301, USA.  */
21
22
23/* This file contains the functions for converting C expressions
24   to different data types.  The only entry point is `convert'.
25   Every language front end must have a `convert' function
26   but what kind of conversions it does will depend on the language.  */
27
28#include "config.h"
29#include "system.h"
30#include "coretypes.h"
31#include "tm.h"
32#include "tree.h"
33#include "flags.h"
34#include "convert.h"
35#include "c-common.h"
36#include "c-tree.h"
37#include "langhooks.h"
38#include "toplev.h"
39#include "target.h"
40
41/* Change of width--truncation and extension of integers or reals--
42   is represented with NOP_EXPR.  Proper functioning of many things
43   assumes that no other conversions can be NOP_EXPRs.
44
45   Conversion between integer and pointer is represented with CONVERT_EXPR.
46   Converting integer to real uses FLOAT_EXPR
47   and real to integer uses FIX_TRUNC_EXPR.
48
49   Here is a list of all the functions that assume that widening and
50   narrowing is always done with a NOP_EXPR:
51     In convert.c, convert_to_integer.
52     In c-typeck.c, build_binary_op (boolean ops), and
53	c_common_truthvalue_conversion.
54     In expr.c: expand_expr, for operands of a MULT_EXPR.
55     In fold-const.c: fold.
56     In tree.c: get_narrower and get_unwidened.  */
57
58/* Subroutines of `convert'.  */
59
60
61
62/* Create an expression whose value is that of EXPR,
63   converted to type TYPE.  The TREE_TYPE of the value
64   is always TYPE.  This function implements all reasonable
65   conversions; callers should filter out those that are
66   not permitted by the language being compiled.  */
67
68tree
69convert (tree type, tree expr)
70{
71  tree e = expr;
72  enum tree_code code = TREE_CODE (type);
73  const char *invalid_conv_diag;
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
90  if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))
91    return fold_convert (type, expr);
92  if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
93    return error_mark_node;
94  if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
95    {
96      error ("void value not ignored as it ought to be");
97      return error_mark_node;
98    }
99  if (code == VOID_TYPE)
100    return fold_convert (type, e);
101  if (code == INTEGER_TYPE || code == ENUMERAL_TYPE)
102    return fold (convert_to_integer (type, e));
103  if (code == BOOLEAN_TYPE)
104    return fold_convert (type, c_objc_common_truthvalue_conversion (expr));
105  if (code == POINTER_TYPE || code == REFERENCE_TYPE)
106    return fold (convert_to_pointer (type, e));
107  if (code == REAL_TYPE)
108    return fold (convert_to_real (type, e));
109  if (code == COMPLEX_TYPE)
110    return fold (convert_to_complex (type, e));
111  if (code == VECTOR_TYPE)
112    return fold (convert_to_vector (type, e));
113  if ((code == RECORD_TYPE || code == UNION_TYPE)
114      && lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
115      return e;
116
117  error ("conversion to non-scalar type requested");
118  return error_mark_node;
119}
120