1 /* Language-level data type conversion for GNU C.
2 Copyright (C) 1987, 1988, 1991, 1998, 2002 Free Software Foundation, Inc.
3
4 This file is part of GCC.
5
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 2, or (at your option) any later
9 version.
10
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING. If not, write to the Free
18 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
19 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 "c-common.h"
33 #include "toplev.h"
34
35 /* Change of width--truncation and extension of integers or reals--
36 is represented with NOP_EXPR. Proper functioning of many things
37 assumes that no other conversions can be NOP_EXPRs.
38
39 Conversion between integer and pointer is represented with CONVERT_EXPR.
40 Converting integer to real uses FLOAT_EXPR
41 and real to integer uses FIX_TRUNC_EXPR.
42
43 Here is a list of all the functions that assume that widening and
44 narrowing is always done with a NOP_EXPR:
45 In convert.c, convert_to_integer.
46 In c-typeck.c, build_binary_op (boolean ops), and
47 c_common_truthvalue_conversion.
48 In expr.c: expand_expr, for operands of a MULT_EXPR.
49 In fold-const.c: fold.
50 In tree.c: get_narrower and get_unwidened. */
51
52 /* Subroutines of `convert'. */
53
54
55
56 /* Create an expression whose value is that of EXPR,
57 converted to type TYPE. The TREE_TYPE of the value
58 is always TYPE. This function implements all reasonable
59 conversions; callers should filter out those that are
60 not permitted by the language being compiled. */
61
62 tree
convert(type,expr)63 convert (type, expr)
64 tree type, expr;
65 {
66 tree e = expr;
67 enum tree_code code = TREE_CODE (type);
68
69 if (type == TREE_TYPE (expr)
70 || TREE_CODE (expr) == ERROR_MARK
71 || code == ERROR_MARK || TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
72 return expr;
73
74 if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))
75 return fold (build1 (NOP_EXPR, type, expr));
76 if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
77 return error_mark_node;
78 if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
79 {
80 error ("void value not ignored as it ought to be");
81 return error_mark_node;
82 }
83 if (code == VOID_TYPE)
84 return build1 (CONVERT_EXPR, type, e);
85 #if 0
86 /* This is incorrect. A truncation can't be stripped this way.
87 Extensions will be stripped by the use of get_unwidened. */
88 if (TREE_CODE (expr) == NOP_EXPR)
89 return convert (type, TREE_OPERAND (expr, 0));
90 #endif
91 if (code == INTEGER_TYPE || code == ENUMERAL_TYPE)
92 return fold (convert_to_integer (type, e));
93 if (code == BOOLEAN_TYPE)
94 {
95 tree t = c_common_truthvalue_conversion (expr);
96 /* If it returns a NOP_EXPR, we must fold it here to avoid
97 infinite recursion between fold () and convert (). */
98 if (TREE_CODE (t) == NOP_EXPR)
99 return fold (build1 (NOP_EXPR, type, TREE_OPERAND (t, 0)));
100 else
101 return fold (build1 (NOP_EXPR, type, t));
102 }
103 if (code == POINTER_TYPE || code == REFERENCE_TYPE)
104 return fold (convert_to_pointer (type, e));
105 if (code == REAL_TYPE)
106 return fold (convert_to_real (type, e));
107 if (code == COMPLEX_TYPE)
108 return fold (convert_to_complex (type, e));
109 if (code == VECTOR_TYPE)
110 return fold (convert_to_vector (type, e));
111
112 error ("conversion to non-scalar type requested");
113 return error_mark_node;
114 }
115