1 /* Language-level data type conversion for GNU C.
2 Copyright (C) 1987-2016 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 3, 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 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
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(tree type,tree expr)63 convert (tree type, tree expr)
64 {
65 tree e = expr;
66 enum tree_code code = TREE_CODE (type);
67 const char *invalid_conv_diag;
68 tree ret;
69 location_t loc = EXPR_LOCATION (expr);
70
71 if (type == error_mark_node
72 || error_operand_p (expr))
73 return error_mark_node;
74
75 if ((invalid_conv_diag
76 = targetm.invalid_conversion (TREE_TYPE (expr), type)))
77 {
78 error (invalid_conv_diag);
79 return error_mark_node;
80 }
81
82 if (type == TREE_TYPE (expr))
83 return expr;
84 ret = targetm.convert_to_type (type, expr);
85 if (ret)
86 return ret;
87
88 STRIP_TYPE_NOPS (e);
89
90 if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr))
91 && (TREE_CODE (TREE_TYPE (expr)) != COMPLEX_TYPE
92 || TREE_CODE (e) == COMPLEX_EXPR))
93 return fold_convert_loc (loc, type, expr);
94 if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
95 return error_mark_node;
96 if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
97 {
98 error ("void value not ignored as it ought to be");
99 return error_mark_node;
100 }
101
102 switch (code)
103 {
104 case VOID_TYPE:
105 return fold_convert_loc (loc, type, e);
106
107 case INTEGER_TYPE:
108 case ENUMERAL_TYPE:
109 if (flag_sanitize & SANITIZE_FLOAT_CAST
110 && TREE_CODE (TREE_TYPE (expr)) == REAL_TYPE
111 && COMPLETE_TYPE_P (type)
112 && do_ubsan_in_current_function ())
113 {
114 if (in_late_binary_op)
115 expr = save_expr (expr);
116 else
117 {
118 expr = c_save_expr (expr);
119 expr = c_fully_fold (expr, false, NULL);
120 }
121 tree check = ubsan_instrument_float_cast (loc, type, expr);
122 expr = fold_build1 (FIX_TRUNC_EXPR, type, expr);
123 if (check == NULL_TREE)
124 return expr;
125 return fold_build2 (COMPOUND_EXPR, TREE_TYPE (expr), check, expr);
126 }
127 ret = convert_to_integer (type, e);
128 goto maybe_fold;
129
130 case BOOLEAN_TYPE:
131 return fold_convert_loc
132 (loc, type, c_objc_common_truthvalue_conversion (input_location, expr));
133
134 case POINTER_TYPE:
135 case REFERENCE_TYPE:
136 ret = convert_to_pointer (type, e);
137 goto maybe_fold;
138
139 case REAL_TYPE:
140 ret = convert_to_real (type, e);
141 goto maybe_fold;
142
143 case FIXED_POINT_TYPE:
144 ret = convert_to_fixed (type, e);
145 goto maybe_fold;
146
147 case COMPLEX_TYPE:
148 /* If converting from COMPLEX_TYPE to a different COMPLEX_TYPE
149 and e is not COMPLEX_EXPR, convert_to_complex uses save_expr,
150 but for the C FE c_save_expr needs to be called instead. */
151 if (TREE_CODE (TREE_TYPE (e)) == COMPLEX_TYPE)
152 {
153 if (TREE_CODE (e) != COMPLEX_EXPR)
154 {
155 tree subtype = TREE_TYPE (type);
156 tree elt_type = TREE_TYPE (TREE_TYPE (e));
157
158 if (in_late_binary_op)
159 e = save_expr (e);
160 else
161 e = c_save_expr (e);
162 ret
163 = fold_build2_loc (loc, COMPLEX_EXPR, type,
164 convert (subtype,
165 fold_build1 (REALPART_EXPR,
166 elt_type, e)),
167 convert (subtype,
168 fold_build1 (IMAGPART_EXPR,
169 elt_type, e)));
170 goto maybe_fold;
171 }
172 }
173 ret = convert_to_complex (type, e);
174 goto maybe_fold;
175
176 case VECTOR_TYPE:
177 ret = convert_to_vector (type, e);
178 goto maybe_fold;
179
180 case RECORD_TYPE:
181 case UNION_TYPE:
182 if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
183 return e;
184 break;
185
186 default:
187 break;
188
189 maybe_fold:
190 if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR)
191 ret = fold (ret);
192 return ret;
193 }
194
195 error ("conversion to non-scalar type requested");
196 return error_mark_node;
197 }
198