1/* Language-level data type conversion for GNU C.
2 Copyright (C) 1987-2024 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.cc, convert_to_integer.
49 In c-typeck.cc, build_binary_op (boolean ops), and
50 c_common_truthvalue_conversion.
51 In expr.cc: expand_expr, for operands of a MULT_EXPR.
52 In fold-const.cc: fold.
53 In tree.cc: 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
68static tree
69c_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 (t: 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 (VOID_TYPE_P (TREE_TYPE (expr)))
103 {
104 error ("void value not ignored as it ought to be");
105 return error_mark_node;
106 }
107
108 {
109 tree false_value, true_value;
110 if (c_hardbool_type_attr (type, false_value: &false_value, true_value: &true_value))
111 {
112 bool save = in_late_binary_op;
113 in_late_binary_op = true;
114 expr = c_objc_common_truthvalue_conversion (input_location, expr);
115 in_late_binary_op = save;
116
117 return fold_build3_loc (loc, COND_EXPR, type,
118 expr, true_value, false_value);
119 }
120 }
121
122 switch (code)
123 {
124 case VOID_TYPE:
125 return fold_convert_loc (loc, type, e);
126
127 case ENUMERAL_TYPE:
128 if (ENUM_UNDERLYING_TYPE (type) != NULL_TREE
129 && TREE_CODE (ENUM_UNDERLYING_TYPE (type)) == BOOLEAN_TYPE)
130 goto convert_to_boolean;
131 gcc_fallthrough ();
132
133 case INTEGER_TYPE:
134 case BITINT_TYPE:
135 if (sanitize_flags_p (flag: SANITIZE_FLOAT_CAST)
136 && current_function_decl != NULL_TREE
137 && SCALAR_FLOAT_TYPE_P (TREE_TYPE (expr))
138 && COMPLETE_TYPE_P (type))
139 {
140 expr = save_expr (expr);
141 expr = c_fully_fold (expr, init_const, NULL);
142 tree check = ubsan_instrument_float_cast (loc, type, expr);
143 expr = fold_build1 (FIX_TRUNC_EXPR, type, expr);
144 if (check == NULL_TREE)
145 return expr;
146 return fold_build2 (COMPOUND_EXPR, TREE_TYPE (expr), check, expr);
147 }
148 ret = convert_to_integer (type, e);
149 goto maybe_fold;
150
151 case BOOLEAN_TYPE:
152 convert_to_boolean:
153 return c_objc_common_truthvalue_conversion (input_location, expr, type);
154
155 case POINTER_TYPE:
156 /* The type nullptr_t may be converted to a pointer type. The result is
157 a null pointer value. */
158 if (NULLPTR_TYPE_P (TREE_TYPE (e)))
159 {
160 /* To make sure that (void *)nullptr is not a null pointer constant,
161 build_c_cast will create an additional NOP_EXPR around the result
162 of this conversion. */
163 if (TREE_SIDE_EFFECTS (e))
164 ret = build2 (COMPOUND_EXPR, type, e, build_int_cst (type, 0));
165 else
166 ret = build_int_cst (type, 0);
167 goto maybe_fold;
168 }
169 gcc_fallthrough ();
170 case REFERENCE_TYPE:
171 ret = convert_to_pointer (type, e);
172 goto maybe_fold;
173
174 case NULLPTR_TYPE:
175 /* A null pointer constant or value of type nullptr_t may be
176 converted to nullptr_t. The latter case has already been
177 handled. build_c_cast will create an additional NOP_EXPR to
178 ensure the result of the conversion is not itself a null
179 pointer constant. */
180 if (null_pointer_constant_p (expr))
181 {
182 ret = build_int_cst (type, 0);
183 goto maybe_fold;
184 }
185 break;
186
187 case REAL_TYPE:
188 ret = convert_to_real (type, e);
189 goto maybe_fold;
190
191 case FIXED_POINT_TYPE:
192 ret = convert_to_fixed (type, e);
193 goto maybe_fold;
194
195 case COMPLEX_TYPE:
196 ret = convert_to_complex (type, e);
197 goto maybe_fold;
198
199 case VECTOR_TYPE:
200 if (gnu_vector_type_p (type)
201 || gnu_vector_type_p (TREE_TYPE (e))
202 /* Allow conversions between compatible non-GNU vector types
203 when -flax-vector-conversions is passed. The whole purpose
204 of the option is to bend the normal type rules and accept
205 nonconforming code. */
206 || (flag_lax_vector_conversions
207 && VECTOR_TYPE_P (TREE_TYPE (e))
208 && vector_types_convertible_p (t1: type, TREE_TYPE (e), emit_lax_note: false)))
209 {
210 ret = convert_to_vector (type, e);
211 goto maybe_fold;
212 }
213 break;
214
215 case RECORD_TYPE:
216 case UNION_TYPE:
217 if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
218 return e;
219 break;
220
221 default:
222 break;
223
224 maybe_fold:
225 if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR)
226 ret = init_const ? fold_init (ret) : fold (ret);
227 return ret;
228 }
229
230 /* If we are converting to nullptr_t, don't say "non-scalar type" because
231 the nullptr_t type is a scalar type. Only nullptr_t or a null pointer
232 constant shall be converted to nullptr_t. */
233 if (code == NULLPTR_TYPE)
234 {
235 error ("conversion from %qT to %qT", TREE_TYPE (e), type);
236 inform (input_location,
237 "only %qT or a null pointer constant can be converted to %qT",
238 type, type);
239 }
240 else
241 error ("conversion to non-scalar type requested");
242 return error_mark_node;
243}
244
245/* Create an expression whose value is that of EXPR, converted to type TYPE.
246 The TREE_TYPE of the value is always TYPE. This function implements all
247 reasonable conversions; callers should filter out those that are not
248 permitted by the language being compiled. */
249
250tree
251convert (tree type, tree expr)
252{
253 return c_convert (type, expr, init_const: false);
254}
255
256/* Create an expression whose value is that of EXPR, converted to type TYPE, in
257 a static initializer. The TREE_TYPE of the value is always TYPE. This
258 function implements all reasonable conversions; callers should filter out
259 those that are not permitted by the language being compiled. */
260
261tree
262convert_init (tree type, tree expr)
263{
264 return c_convert (type, expr, init_const: true);
265}
266

source code of gcc/c/c-convert.cc