1 /* Language-level data type conversion for GNU C.
2 Copyright (C) 1987-2023 Free Software Foundation, Inc.
4 This file is part of GCC.
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
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
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/>. */
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. */
28 #include "coretypes.h"
32 #include "langhooks.h"
34 #include "stringpool.h"
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.
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.
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. */
55 /* Subroutines of `convert'. */
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). */
69 c_convert (tree type
, tree expr
, bool init_const
)
72 enum tree_code code
= TREE_CODE (type
);
73 const char *invalid_conv_diag
;
75 location_t loc
= EXPR_LOCATION (expr
);
77 if (type
== error_mark_node
78 || error_operand_p (expr
))
79 return error_mark_node
;
81 if ((invalid_conv_diag
82 = targetm
.invalid_conversion (TREE_TYPE (expr
), type
)))
84 error (invalid_conv_diag
);
85 return error_mark_node
;
88 if (type
== TREE_TYPE (expr
))
90 ret
= targetm
.convert_to_type (type
, expr
);
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
)
104 error ("void value not ignored as it ought to be");
105 return error_mark_node
;
111 return fold_convert_loc (loc
, type
, e
);
114 if (ENUM_UNDERLYING_TYPE (type
) != NULL_TREE
115 && TREE_CODE (ENUM_UNDERLYING_TYPE (type
)) == BOOLEAN_TYPE
)
116 goto convert_to_boolean
;
120 if (sanitize_flags_p (SANITIZE_FLOAT_CAST
)
121 && current_function_decl
!= NULL_TREE
122 && TREE_CODE (TREE_TYPE (expr
)) == REAL_TYPE
123 && COMPLETE_TYPE_P (type
))
125 expr
= save_expr (expr
);
126 expr
= c_fully_fold (expr
, init_const
, NULL
);
127 tree check
= ubsan_instrument_float_cast (loc
, type
, expr
);
128 expr
= fold_build1 (FIX_TRUNC_EXPR
, type
, expr
);
129 if (check
== NULL_TREE
)
131 return fold_build2 (COMPOUND_EXPR
, TREE_TYPE (expr
), check
, expr
);
133 ret
= convert_to_integer (type
, e
);
138 return fold_convert_loc
139 (loc
, type
, c_objc_common_truthvalue_conversion (input_location
, expr
));
142 /* The type nullptr_t may be converted to a pointer type. The result is
143 a null pointer value. */
144 if (NULLPTR_TYPE_P (TREE_TYPE (e
)))
146 /* To make sure that (void *)nullptr is not a null pointer constant,
147 build_c_cast will create an additional NOP_EXPR around the result
148 of this conversion. */
149 if (TREE_SIDE_EFFECTS (e
))
150 ret
= build2 (COMPOUND_EXPR
, type
, e
, build_int_cst (type
, 0));
152 ret
= build_int_cst (type
, 0);
157 ret
= convert_to_pointer (type
, e
);
161 /* A null pointer constant or value of type nullptr_t may be
162 converted to nullptr_t. The latter case has already been
163 handled. build_c_cast will create an additional NOP_EXPR to
164 ensure the result of the conversion is not itself a null
166 if (null_pointer_constant_p (expr
))
168 ret
= build_int_cst (type
, 0);
174 ret
= convert_to_real (type
, e
);
177 case FIXED_POINT_TYPE
:
178 ret
= convert_to_fixed (type
, e
);
182 ret
= convert_to_complex (type
, e
);
186 if (gnu_vector_type_p (type
)
187 || gnu_vector_type_p (TREE_TYPE (e
))
188 /* Allow conversions between compatible non-GNU vector types
189 when -flax-vector-conversions is passed. The whole purpose
190 of the option is to bend the normal type rules and accept
191 nonconforming code. */
192 || (flag_lax_vector_conversions
193 && VECTOR_TYPE_P (TREE_TYPE (e
))
194 && vector_types_convertible_p (type
, TREE_TYPE (e
), false)))
196 ret
= convert_to_vector (type
, e
);
203 if (lang_hooks
.types_compatible_p (type
, TREE_TYPE (expr
)))
211 if (TREE_CODE (ret
) != C_MAYBE_CONST_EXPR
)
212 ret
= init_const
? fold_init (ret
) : fold (ret
);
216 /* If we are converting to nullptr_t, don't say "non-scalar type" because
217 the nullptr_t type is a scalar type. Only nullptr_t or a null pointer
218 constant shall be converted to nullptr_t. */
219 if (code
== NULLPTR_TYPE
)
221 error ("conversion from %qT to %qT", TREE_TYPE (e
), type
);
222 inform (input_location
,
223 "only %qT or a null pointer constant can be converted to %qT",
227 error ("conversion to non-scalar type requested");
228 return error_mark_node
;
231 /* Create an expression whose value is that of EXPR, converted to type TYPE.
232 The TREE_TYPE of the value is always TYPE. This function implements all
233 reasonable conversions; callers should filter out those that are not
234 permitted by the language being compiled. */
237 convert (tree type
, tree expr
)
239 return c_convert (type
, expr
, false);
242 /* Create an expression whose value is that of EXPR, converted to type TYPE, in
243 a static initializer. The TREE_TYPE of the value is always TYPE. This
244 function implements all reasonable conversions; callers should filter out
245 those that are not permitted by the language being compiled. */
248 convert_init (tree type
, tree expr
)
250 return c_convert (type
, expr
, true);