1 | /* Language-level data type conversion for GNU C. |
2 | Copyright (C) 1987-2023 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.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 | |
68 | static tree |
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 (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 | switch (code) |
109 | { |
110 | case VOID_TYPE: |
111 | return fold_convert_loc (loc, type, e); |
112 | |
113 | case ENUMERAL_TYPE: |
114 | if (ENUM_UNDERLYING_TYPE (type) != NULL_TREE |
115 | && TREE_CODE (ENUM_UNDERLYING_TYPE (type)) == BOOLEAN_TYPE) |
116 | goto convert_to_boolean; |
117 | gcc_fallthrough (); |
118 | |
119 | case INTEGER_TYPE: |
120 | case BITINT_TYPE: |
121 | if (sanitize_flags_p (flag: SANITIZE_FLOAT_CAST) |
122 | && current_function_decl != NULL_TREE |
123 | && SCALAR_FLOAT_TYPE_P (TREE_TYPE (expr)) |
124 | && COMPLETE_TYPE_P (type)) |
125 | { |
126 | expr = save_expr (expr); |
127 | expr = c_fully_fold (expr, init_const, NULL); |
128 | tree check = ubsan_instrument_float_cast (loc, type, expr); |
129 | expr = fold_build1 (FIX_TRUNC_EXPR, type, expr); |
130 | if (check == NULL_TREE) |
131 | return expr; |
132 | return fold_build2 (COMPOUND_EXPR, TREE_TYPE (expr), check, expr); |
133 | } |
134 | ret = convert_to_integer (type, e); |
135 | goto maybe_fold; |
136 | |
137 | case BOOLEAN_TYPE: |
138 | convert_to_boolean: |
139 | return fold_convert_loc |
140 | (loc, type, c_objc_common_truthvalue_conversion (input_location, expr)); |
141 | |
142 | case POINTER_TYPE: |
143 | /* The type nullptr_t may be converted to a pointer type. The result is |
144 | a null pointer value. */ |
145 | if (NULLPTR_TYPE_P (TREE_TYPE (e))) |
146 | { |
147 | /* To make sure that (void *)nullptr is not a null pointer constant, |
148 | build_c_cast will create an additional NOP_EXPR around the result |
149 | of this conversion. */ |
150 | if (TREE_SIDE_EFFECTS (e)) |
151 | ret = build2 (COMPOUND_EXPR, type, e, build_int_cst (type, 0)); |
152 | else |
153 | ret = build_int_cst (type, 0); |
154 | goto maybe_fold; |
155 | } |
156 | gcc_fallthrough (); |
157 | case REFERENCE_TYPE: |
158 | ret = convert_to_pointer (type, e); |
159 | goto maybe_fold; |
160 | |
161 | case NULLPTR_TYPE: |
162 | /* A null pointer constant or value of type nullptr_t may be |
163 | converted to nullptr_t. The latter case has already been |
164 | handled. build_c_cast will create an additional NOP_EXPR to |
165 | ensure the result of the conversion is not itself a null |
166 | pointer constant. */ |
167 | if (null_pointer_constant_p (expr)) |
168 | { |
169 | ret = build_int_cst (type, 0); |
170 | goto maybe_fold; |
171 | } |
172 | break; |
173 | |
174 | case REAL_TYPE: |
175 | ret = convert_to_real (type, e); |
176 | goto maybe_fold; |
177 | |
178 | case FIXED_POINT_TYPE: |
179 | ret = convert_to_fixed (type, e); |
180 | goto maybe_fold; |
181 | |
182 | case COMPLEX_TYPE: |
183 | ret = convert_to_complex (type, e); |
184 | goto maybe_fold; |
185 | |
186 | case VECTOR_TYPE: |
187 | if (gnu_vector_type_p (type) |
188 | || gnu_vector_type_p (TREE_TYPE (e)) |
189 | /* Allow conversions between compatible non-GNU vector types |
190 | when -flax-vector-conversions is passed. The whole purpose |
191 | of the option is to bend the normal type rules and accept |
192 | nonconforming code. */ |
193 | || (flag_lax_vector_conversions |
194 | && VECTOR_TYPE_P (TREE_TYPE (e)) |
195 | && vector_types_convertible_p (t1: type, TREE_TYPE (e), emit_lax_note: false))) |
196 | { |
197 | ret = convert_to_vector (type, e); |
198 | goto maybe_fold; |
199 | } |
200 | break; |
201 | |
202 | case RECORD_TYPE: |
203 | case UNION_TYPE: |
204 | if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr))) |
205 | return e; |
206 | break; |
207 | |
208 | default: |
209 | break; |
210 | |
211 | maybe_fold: |
212 | if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR) |
213 | ret = init_const ? fold_init (ret) : fold (ret); |
214 | return ret; |
215 | } |
216 | |
217 | /* If we are converting to nullptr_t, don't say "non-scalar type" because |
218 | the nullptr_t type is a scalar type. Only nullptr_t or a null pointer |
219 | constant shall be converted to nullptr_t. */ |
220 | if (code == NULLPTR_TYPE) |
221 | { |
222 | error ("conversion from %qT to %qT" , TREE_TYPE (e), type); |
223 | inform (input_location, |
224 | "only %qT or a null pointer constant can be converted to %qT" , |
225 | type, type); |
226 | } |
227 | else |
228 | error ("conversion to non-scalar type requested" ); |
229 | return error_mark_node; |
230 | } |
231 | |
232 | /* Create an expression whose value is that of EXPR, converted to type TYPE. |
233 | The TREE_TYPE of the value is always TYPE. This function implements all |
234 | reasonable conversions; callers should filter out those that are not |
235 | permitted by the language being compiled. */ |
236 | |
237 | tree |
238 | convert (tree type, tree expr) |
239 | { |
240 | return c_convert (type, expr, init_const: false); |
241 | } |
242 | |
243 | /* Create an expression whose value is that of EXPR, converted to type TYPE, in |
244 | a static initializer. The TREE_TYPE of the value is always TYPE. This |
245 | function implements all reasonable conversions; callers should filter out |
246 | those that are not permitted by the language being compiled. */ |
247 | |
248 | tree |
249 | convert_init (tree type, tree expr) |
250 | { |
251 | return c_convert (type, expr, init_const: true); |
252 | } |
253 | |