1/* Language-level data type conversion for GNU C.
2 Copyright (C) 1987-2017 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free
8Software Foundation; either version 3, or (at your option) any later
9version.
10
11GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12WARRANTY; without even the implied warranty of MERCHANTABILITY or
13FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14for more details.
15
16You should have received a copy of the GNU General Public License
17along with GCC; see the file COPYING3. If not see
18<http://www.gnu.org/licenses/>. */
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 "system.h"
28#include "coretypes.h"
29#include "target.h"
30#include "c-tree.h"
31#include "convert.h"
32#include "langhooks.h"
33#include "ubsan.h"
34#include "stringpool.h"
35#include "attribs.h"
36#include "asan.h"
37
38/* Change of width--truncation and extension of integers or reals--
39 is represented with NOP_EXPR. Proper functioning of many things
40 assumes that no other conversions can be NOP_EXPRs.
41
42 Conversion between integer and pointer is represented with CONVERT_EXPR.
43 Converting integer to real uses FLOAT_EXPR
44 and real to integer uses FIX_TRUNC_EXPR.
45
46 Here is a list of all the functions that assume that widening and
47 narrowing is always done with a NOP_EXPR:
48 In convert.c, convert_to_integer.
49 In c-typeck.c, build_binary_op (boolean ops), and
50 c_common_truthvalue_conversion.
51 In expr.c: expand_expr, for operands of a MULT_EXPR.
52 In fold-const.c: fold.
53 In tree.c: get_narrower and get_unwidened. */
54
55/* Subroutines of `convert'. */
56
57
58
59/* Create an expression whose value is that of EXPR,
60 converted to type TYPE. The TREE_TYPE of the value
61 is always TYPE. This function implements all reasonable
62 conversions; callers should filter out those that are
63 not permitted by the language being compiled. */
64
65tree
66convert (tree type, tree expr)
67{
68 tree e = expr;
69 enum tree_code code = TREE_CODE (type);
70 const char *invalid_conv_diag;
71 tree ret;
72 location_t loc = EXPR_LOCATION (expr);
73
74 if (type == error_mark_node
75 || error_operand_p (expr))
76 return error_mark_node;
77
78 if ((invalid_conv_diag
79 = targetm.invalid_conversion (TREE_TYPE (expr), type)))
80 {
81 error (invalid_conv_diag);
82 return error_mark_node;
83 }
84
85 if (type == TREE_TYPE (expr))
86 return expr;
87 ret = targetm.convert_to_type (type, expr);
88 if (ret)
89 return ret;
90
91 STRIP_TYPE_NOPS (e);
92
93 if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr))
94 && (TREE_CODE (TREE_TYPE (expr)) != COMPLEX_TYPE
95 || TREE_CODE (e) == COMPLEX_EXPR))
96 return fold_convert_loc (loc, 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_loc (loc, type, e);
109
110 case INTEGER_TYPE:
111 case ENUMERAL_TYPE:
112 if (sanitize_flags_p (SANITIZE_FLOAT_CAST)
113 && current_function_decl != NULL_TREE
114 && TREE_CODE (TREE_TYPE (expr)) == REAL_TYPE
115 && COMPLETE_TYPE_P (type))
116 {
117 expr = save_expr (expr);
118 tree check = ubsan_instrument_float_cast (loc, type, expr);
119 expr = fold_build1 (FIX_TRUNC_EXPR, type, expr);
120 if (check == NULL_TREE)
121 return expr;
122 return fold_build2 (COMPOUND_EXPR, TREE_TYPE (expr), check, expr);
123 }
124 ret = convert_to_integer (type, e);
125 goto maybe_fold;
126
127 case BOOLEAN_TYPE:
128 return fold_convert_loc
129 (loc, type, c_objc_common_truthvalue_conversion (input_location, expr));
130
131 case POINTER_TYPE:
132 case REFERENCE_TYPE:
133 ret = convert_to_pointer (type, e);
134 goto maybe_fold;
135
136 case REAL_TYPE:
137 ret = convert_to_real (type, e);
138 goto maybe_fold;
139
140 case FIXED_POINT_TYPE:
141 ret = convert_to_fixed (type, e);
142 goto maybe_fold;
143
144 case COMPLEX_TYPE:
145 ret = convert_to_complex (type, e);
146 goto maybe_fold;
147
148 case VECTOR_TYPE:
149 ret = convert_to_vector (type, e);
150 goto maybe_fold;
151
152 case RECORD_TYPE:
153 case UNION_TYPE:
154 if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
155 return e;
156 break;
157
158 default:
159 break;
160
161 maybe_fold:
162 if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR)
163 ret = fold (ret);
164 return ret;
165 }
166
167 error ("conversion to non-scalar type requested");
168 return error_mark_node;
169}
170