1/*	$NetBSD: expr_sizeof.c,v 1.18 2024/05/03 19:16:13 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
15void sink(unsigned long);
16
17struct {
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] */
26typedef 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] */
33typedef int sizeof_paren_zero[-(int)sizeof(0)];
34/* expect+1: error: negative array dimension (-4) [20] */
35typedef 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] */
41typedef int sizeof_global_var[-(int)sizeof s];
42/* expect+1: error: negative array dimension (-4) [20] */
43typedef 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] */
55typedef int sizeof_paren_global_struct_member[-(int)sizeof(s).member];
56/* expect+1: error: negative array dimension (-4) [20] */
57typedef int sizeof_paren_global_ptr_struct_member[-(int)sizeof(ps)->member];
58int arr[] = { 1, 2, 3 };
59/* expect+1: error: negative array dimension (-3) [20] */
60typedef 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] */
64void
65variable_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
78void
79bit_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 */
145void
146anonymous_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
168void
169sizeof_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: illegal 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 */
195struct s24 {
196	char c0;
197	double d8;
198	char c16;
199};
200/* expect+1: error: negative array dimension (-24) [20] */
201typedef int sizeof_s24[-(int)sizeof(struct s24)];
202
203void
204sizeof_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
218void
219sequence_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