1 /* $NetBSD: expr_sizeof.c,v 1.19 2025/04/12 15:49:49 rillig Exp $ */
2 # 3 "expr_sizeof.c"
3
4 /*
5 * C99 6.5.3.4 "The sizeof operator"
6 * C11 6.5.3.4 "The sizeof operator"
7 */
8
9 /* lint1-extra-flags: -X 351 */
10
11 /*
12 * A sizeof expression can either take a type name or an expression.
13 */
14
15 void sink(unsigned long);
16
17 struct {
18 int member;
19 } s, *ps;
20
21 /*
22 * In a sizeof expression taking a type name, the type name must be enclosed
23 * in parentheses.
24 */
25 /* expect+1: error: negative array dimension (-4) [20] */
26 typedef int sizeof_int[-(int)sizeof(int)];
27
28 /*
29 * In a sizeof expression taking an expression, the expression may or may not
30 * be enclosed in parentheses, like any other expression.
31 */
32 /* expect+1: error: negative array dimension (-4) [20] */
33 typedef int sizeof_paren_zero[-(int)sizeof(0)];
34 /* expect+1: error: negative array dimension (-4) [20] */
35 typedef int sizeof_zero[-(int)sizeof 0];
36
37 /*
38 * Even though 's' is not a constant expression, 'sizeof s' is.
39 */
40 /* expect+1: error: negative array dimension (-4) [20] */
41 typedef int sizeof_global_var[-(int)sizeof s];
42 /* expect+1: error: negative array dimension (-4) [20] */
43 typedef int sizeof_paren_global_var[-(int)sizeof(s)];
44
45 /*
46 * Even though 'sizeof(s)' may look like a function call expression, the
47 * parentheses around 's' are ordinary parentheses and do not influence the
48 * precedence.
49 *
50 * Therefore, the '.' following the '(s)' takes precedence over the 'sizeof'.
51 * Same for the '->' following the '(ps)'. Same for the '[0]' following the
52 * '(arr)'.
53 */
54 /* expect+1: error: negative array dimension (-4) [20] */
55 typedef int sizeof_paren_global_struct_member[-(int)sizeof(s).member];
56 /* expect+1: error: negative array dimension (-4) [20] */
57 typedef int sizeof_paren_global_ptr_struct_member[-(int)sizeof(ps)->member];
58 int arr[] = { 1, 2, 3 };
59 /* expect+1: error: negative array dimension (-3) [20] */
60 typedef int arr_count[-(int)sizeof(arr) / (int)sizeof(arr)[0]];
61
62 /* FIXME: 'n' is actually used, for the variable length array. */
63 /* expect+2: warning: parameter 'n' unused in function 'variable_length_array' [231] */
64 void
variable_length_array(int n)65 variable_length_array(int n)
66 {
67 int local_arr[n + 5];
68
69 /*
70 * Since the array length is not constant, it cannot be used in a
71 * typedef. Code like this is already rejected by the compiler. For
72 * simplicity, lint assumes that the array has length 1.
73 */
74 /* expect+1: error: negative array dimension (-4) [20] */
75 typedef int sizeof_local_arr[-(int)sizeof(local_arr)];
76 }
77
78 void
bit_fields(void)79 bit_fields(void)
80 {
81 struct {
82 _Bool flag0:1;
83 _Bool flag1:1;
84 _Bool flag2:1;
85 } flags;
86 /* expect+1: error: negative array dimension (-1) [20] */
87 typedef int sizeof_flags[-(int)sizeof(flags)];
88
89 struct {
90 struct {
91 _Bool flag0:1;
92 _Bool flag1:1;
93 _Bool flag2:1;
94 };
95 } anonymous_flags;
96 /* expect+1: error: negative array dimension (-1) [20] */
97 typedef int sizeof_anonymous_flags[-(int)sizeof(anonymous_flags)];
98
99 struct {
100 unsigned int bits0:16;
101 unsigned int bits1:16;
102 } same_storage_unit;
103 /* expect+1: error: negative array dimension (-4) [20] */
104 typedef int sizeof_same_storage_unit[-(int)sizeof(same_storage_unit)];
105
106 // Detect whether a bit-field can span multiple storage units.
107 // If so, the size is 12, if not, the size is 16.
108 struct {
109 unsigned int bits0:24;
110 unsigned int bits1:24;
111 unsigned int bits2:24;
112 unsigned int bits3:24;
113 } cross_storage_unit;
114 /* expect+1: error: negative array dimension (-16) [20] */
115 typedef int sizeof_cross_storage_unit[-(int)sizeof(cross_storage_unit)];
116
117 /*
118 * The bit-fields in a struct may be merged into the same storage
119 * units, even if their types differ. GCC 10, Clang 15 and lint all
120 * agree in packing the first group of bit-fields and the char into
121 * 4 bytes, even though their underlying types differ. The second
122 * group of bit-fields gets its own storage unit.
123 */
124 struct mixed {
125 _Bool flag0:1;
126 signed int signed0:1;
127 unsigned int unsigned0:1;
128 char ch[3];
129 _Bool flag1:1;
130 signed int signed1:1;
131 unsigned int unsigned1:1;
132 } mixed;
133 /* expect+1: error: negative array dimension (-8) [20] */
134 typedef int sizeof_mixed[-(int)sizeof(mixed)];
135 /* expect+3: error: negative array dimension (-1) [20] */
136 typedef int offsetof_mixed_ch[
137 -(int)__builtin_offsetof(struct mixed, ch)
138 ];
139 }
140
141 /*
142 * Ensure that anonymous structs and unions are handled correctly. They were
143 * added in C11, and lint did not properly support them until 2023.
144 */
145 void
anonymous_struct_and_union(void)146 anonymous_struct_and_union(void)
147 {
148 struct {
149 union {
150 unsigned char uc16[16];
151 unsigned char uc32[32];
152 };
153 } su_16_32;
154 /* expect+1: error: negative array dimension (-32) [20] */
155 typedef int sizeof_su_16_32[-(int)sizeof(su_16_32)];
156
157 union {
158 struct {
159 unsigned char uc16[16];
160 unsigned char uc32[32];
161 };
162 } us_16_32;
163 /* expect+1: error: negative array dimension (-48) [20] */
164 typedef int sizeof_us_16_32[-(int)sizeof(us_16_32)];
165 }
166
167
168 void
sizeof_errors(void)169 sizeof_errors(void)
170 {
171 /* expect+1: error: cannot take size/alignment of void [146] */
172 typedef int sizeof_void[-(int)sizeof(void)];
173
174 /*
175 * A 'void array' gets replaced with an 'int array' before
176 * type_size_in_bits gets to see it, thus the 256 * 4 = 1024.
177 */
178 /* expect+2: error: invalid use of 'void' [18] */
179 /* expect+1: error: negative array dimension (-1024) [20] */
180 typedef int sizeof_void_array[-(int)sizeof(void[256])];
181
182 /* expect+1: warning: enum 'incomplete_enum' never defined [235] */
183 enum incomplete_enum;
184 /* expect+2: warning: cannot take size/alignment of incomplete type [143] */
185 /* expect+1: error: negative array dimension (-4) [20] */
186 typedef int sizeof_incomplete_enum[-(int)sizeof(enum incomplete_enum)];
187 }
188
189
190 /*
191 * Due to the 'double' member, the alignment of this struct is 8, so the size
192 * has to be 24 (or at least divisible by 8), otherwise the 'double' member
193 * would not get the correct alignment in an array of this struct.
194 */
195 struct s24 {
196 char c0;
197 double d8;
198 char c16;
199 };
200 /* expect+1: error: negative array dimension (-24) [20] */
201 typedef int sizeof_s24[-(int)sizeof(struct s24)];
202
203 void
sizeof_array_parameter(short arr[12345])204 sizeof_array_parameter(short arr[12345])
205 {
206 // The size of an array parameter is the size of the decayed pointer.
207 // Subtracting 'sizeof(void *)' makes the test platform-independent.
208 typedef int sizeof_arr[-(int)(sizeof arr - sizeof(void *))];
209
210 // The 2 comes from 'sizeof(short)', as the type 'array[size] of elem'
211 // decays into the type 'pointer to elem', not 'pointer to array[size]
212 // of elem'.
213 /* expect+1: error: negative array dimension (-2) [20] */
214 typedef int sizeof_arr_elem[-(int)(sizeof *arr)];
215 }
216
217
218 void
sequence_of_structs(void)219 sequence_of_structs(void)
220 {
221 typedef unsigned char uint8_t;
222 typedef unsigned short uint16_t;
223 typedef unsigned int uint32_t;
224 typedef unsigned long long uint64_t;
225
226 union fp_addr {
227 uint64_t fa_64;
228 struct {
229 uint32_t fa_off;
230 uint16_t fa_seg;
231 uint16_t fa_opcode;
232 } fa_32;
233 } __packed _Alignas(4);
234
235 struct fpacc87 {
236 uint64_t f87_mantissa;
237 uint16_t f87_exp_sign;
238 } __packed _Alignas(2);
239
240 // FIXME: This otherwise unused struct declaration influences the
241 // offsets checked below. Without this struct, sizeof(struct save87)
242 // is calculated correctly as 108 below.
243 struct fpaccfx {
244 struct fpacc87 r _Alignas(16);
245 };
246
247 struct save87 {
248 uint16_t s87_cw _Alignas(4);
249 uint16_t s87_sw _Alignas(4);
250 uint16_t s87_tw _Alignas(4);
251 union fp_addr s87_ip;
252 union fp_addr s87_dp;
253 struct fpacc87 s87_ac[8];
254 };
255
256 /* expect+1: error: negative array dimension (-20) [20] */
257 typedef int o1[-(int)((unsigned long)(&(((struct save87 *)0)->s87_dp)))];
258 // FIXME: must be 28.
259 /* expect+1: error: negative array dimension (-32) [20] */
260 typedef int o2[-(int)((unsigned long)(&(((struct save87 *)0)->s87_ac)))];
261 // FIXME: must be 108.
262 /* expect+1: error: negative array dimension (-112) [20] */
263 typedef int reveal[-(int)sizeof(struct save87)];
264 }
265