d_alignof.c revision 1.6 
1/*	$NetBSD: d_alignof.c,v 1.6 2022/05/12 20:49:21 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	/* FIXME: the syntax error is wrong, this is perfectly valid */
69	/* expect+1: error: syntax error '->' [249] */
70	return __alignof__(ptr)->member + ptr->member;
71}
72/* expect-1: warning: function alignof_pointer_to_member falls off bottom without returning value [217] */
73