d_alignof.c revision 1.9 
1/*	$NetBSD: d_alignof.c,v 1.9 2023/06/30 09:21:52 rillig Exp $	*/
2# 3 "d_alignof.c"
3
4/* https://gcc.gnu.org/onlinedocs/gcc/Alignment.html */
5
6unsigned long
7leading_and_trailing_alignof_type(void)
8{
9	return __alignof__(short);
10}
11
12unsigned long
13leading_alignof_type(void)
14{
15	return __alignof(short);
16}
17
18unsigned long
19plain_alignof_type(void)
20{
21	/* The plain word 'alignof' is not recognized by GCC. */
22	/* expect+2: error: function 'alignof' implicitly declared to return int [215] */
23	/* expect+1: error: syntax error 'short' [249] */
24	return alignof(short);
25}
26/* expect-1: warning: function 'plain_alignof_type' falls off bottom without returning value [217] */
27
28unsigned long
29leading_and_trailing_alignof_expr(void)
30{
31	return __alignof__ 3;
32}
33
34unsigned long
35leading_alignof_expr(void)
36{
37	return __alignof 3;
38}
39
40unsigned long
41plain_alignof_expr(void)
42{
43	/* The plain word 'alignof' is not recognized by GCC. */
44	/* expect+2: error: 'alignof' undefined [99] */
45	/* expect+1: error: syntax error '3' [249] */
46	return alignof 3;
47}
48/* expect-1: warning: function 'plain_alignof_expr' falls off bottom without returning value [217] */
49
50
51/*
52 * As with 'sizeof', the keyword '__alignof__' doesn't require parentheses
53 * when followed by an expression.  This allows for the seemingly strange
54 * '->' after the parentheses, which in fact is perfectly fine.
55 *
56 * The NetBSD style guide says "We parenthesize sizeof expressions", even
57 * though it is misleading in edge cases like this.  The GCC manual says that
58 * '__alignof__' and 'sizeof' are syntactically the same, therefore the same
59 * reasoning applies to '__alignof__'.
60 */
61unsigned long
62alignof_pointer_to_member(void)
63{
64	struct s {
65		unsigned long member;
66	} var = { 0 }, *ptr = &var;
67
68	return __alignof__(ptr)->member + ptr->member;
69}
70
71void
72alignof_variants(void)
73{
74	/* expect+1: error: negative array dimension (-4) [20] */
75	typedef int array_int[-(int)__alignof(int[3])];
76
77	/* expect+1: error: negative array dimension (-8) [20] */
78	typedef int array_double[-(int)__alignof(double[3])];
79
80	/* expect+1: error: cannot take size/alignment of function type 'function(int) returning int' [144] */
81	typedef int func[-(int)__alignof(int(int))];
82
83	struct int_double {
84		int i;
85		double d;
86	};
87	/* expect+1: error: negative array dimension (-8) [20] */
88	typedef int struct_int_double[-(int)__alignof(struct int_double)];
89
90	struct chars {
91		char name[20];
92	};
93	/* expect+1: error: negative array dimension (-1) [20] */
94	typedef int struct_chars[-(int)__alignof(struct chars)];
95
96	/* expect+1: warning: struct 'incomplete_struct' never defined [233] */
97	struct incomplete_struct;
98	/* expect+1: error: cannot take size/alignment of incomplete type [143] */
99	typedef int incomplete_struct[-(int)__alignof(struct incomplete_struct)];
100
101	/* expect+1: warning: union 'incomplete_union' never defined [234] */
102	union incomplete_union;
103	/* expect+1: error: cannot take size/alignment of incomplete type [143] */
104	typedef int incomplete_union[-(int)__alignof(union incomplete_union)];
105
106	/* expect+1: warning: enum 'incomplete_enum' never defined [235] */
107	enum incomplete_enum;
108	/* expect+1: error: negative array dimension (-4) [20] */
109	typedef int incomplete_enum[-(int)__alignof(enum incomplete_enum)];
110
111	struct bit_fields {
112		_Bool bit_field:1;
113	};
114	/*
115	 * FIXME: This is not an attempt to initialize the typedef, it's the
116	 * initialization of a nested expression.
117	 */
118	/* expect+2: error: cannot initialize typedef '00000000_tmp' [25] */
119	/* expect+1: error: cannot take size/alignment of bit-field [145] */
120	typedef int bit_field[-(int)__alignof((struct bit_fields){0}.bit_field)];
121
122	/* expect+1: error: cannot take size/alignment of void [146] */
123	typedef int plain_void[-(int)__alignof(void)];
124}
125