1 /* Language-level data type conversion for GNU C.
2 Copyright (C) 1987-2021 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 #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 INIT_CONST is true if the conversion is for arithmetic types for a static
65 initializer and folding must apply accordingly (discarding floating-point
66 exceptions and assuming the default rounding mode is in effect). */
67
68 static tree
c_convert(tree type,tree expr,bool init_const)69 c_convert (tree type, tree expr, bool init_const)
70 {
71 tree e = expr;
72 enum tree_code code = TREE_CODE (type);
73 const char *invalid_conv_diag;
74 tree ret;
75 location_t loc = EXPR_LOCATION (expr);
76
77 if (type == error_mark_node
78 || error_operand_p (expr))
79 return error_mark_node;
80
81 if ((invalid_conv_diag
82 = targetm.invalid_conversion (TREE_TYPE (expr), type)))
83 {
84 error (invalid_conv_diag);
85 return error_mark_node;
86 }
87
88 if (type == TREE_TYPE (expr))
89 return expr;
90 ret = targetm.convert_to_type (type, expr);
91 if (ret)
92 return ret;
93
94 STRIP_TYPE_NOPS (e);
95
96 if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr))
97 && (TREE_CODE (TREE_TYPE (expr)) != COMPLEX_TYPE
98 || TREE_CODE (e) == COMPLEX_EXPR))
99 return fold_convert_loc (loc, type, expr);
100 if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
101 return error_mark_node;
102 if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
103 {
104 error ("void value not ignored as it ought to be");
105 return error_mark_node;
106 }
107
108 switch (code)
109 {
110 case VOID_TYPE:
111 return fold_convert_loc (loc, type, e);
112
113 case INTEGER_TYPE:
114 case ENUMERAL_TYPE:
115 if (sanitize_flags_p (SANITIZE_FLOAT_CAST)
116 && current_function_decl != NULL_TREE
117 && TREE_CODE (TREE_TYPE (expr)) == REAL_TYPE
118 && COMPLETE_TYPE_P (type))
119 {
120 expr = save_expr (expr);
121 expr = c_fully_fold (expr, init_const, NULL);
122 tree check = ubsan_instrument_float_cast (loc, type, expr);
123 expr = fold_build1 (FIX_TRUNC_EXPR, type, expr);
124 if (check == NULL_TREE)
125 return expr;
126 return fold_build2 (COMPOUND_EXPR, TREE_TYPE (expr), check, expr);
127 }
128 ret = convert_to_integer (type, e);
129 goto maybe_fold;
130
131 case BOOLEAN_TYPE:
132 return fold_convert_loc
133 (loc, type, c_objc_common_truthvalue_conversion (input_location, expr));
134
135 case POINTER_TYPE:
136 case REFERENCE_TYPE:
137 ret = convert_to_pointer (type, e);
138 goto maybe_fold;
139
140 case REAL_TYPE:
141 ret = convert_to_real (type, e);
142 goto maybe_fold;
143
144 case FIXED_POINT_TYPE:
145 ret = convert_to_fixed (type, e);
146 goto maybe_fold;
147
148 case COMPLEX_TYPE:
149 ret = convert_to_complex (type, e);
150 goto maybe_fold;
151
152 case VECTOR_TYPE:
153 if (gnu_vector_type_p (type)
154 || gnu_vector_type_p (TREE_TYPE (e))
155 /* Allow conversions between compatible non-GNU vector types
156 when -flax-vector-conversions is passed. The whole purpose
157 of the option is to bend the normal type rules and accept
158 nonconforming code. */
159 || (flag_lax_vector_conversions
160 && VECTOR_TYPE_P (TREE_TYPE (e))
161 && vector_types_convertible_p (type, TREE_TYPE (e), false)))
162 {
163 ret = convert_to_vector (type, e);
164 goto maybe_fold;
165 }
166 break;
167
168 case RECORD_TYPE:
169 case UNION_TYPE:
170 if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
171 return e;
172 break;
173
174 default:
175 break;
176
177 maybe_fold:
178 if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR)
179 ret = init_const ? fold_init (ret) : fold (ret);
180 return ret;
181 }
182
183 error ("conversion to non-scalar type requested");
184 return error_mark_node;
185 }
186
187 /* Create an expression whose value is that of EXPR, converted to type TYPE.
188 The TREE_TYPE of the value is always TYPE. This function implements all
189 reasonable conversions; callers should filter out those that are not
190 permitted by the language being compiled. */
191
192 tree
convert(tree type,tree expr)193 convert (tree type, tree expr)
194 {
195 return c_convert (type, expr, false);
196 }
197
198 /* Create an expression whose value is that of EXPR, converted to type TYPE, in
199 a static initializer. The TREE_TYPE of the value is always TYPE. This
200 function implements all reasonable conversions; callers should filter out
201 those that are not permitted by the language being compiled. */
202
203 tree
convert_init(tree type,tree expr)204 convert_init (tree type, tree expr)
205 {
206 return c_convert (type, expr, true);
207 }
208