1 /* $NetBSD: d_alignof.c,v 1.8 2022/06/22 19:23:18 rillig Exp $ */ 2 # 3 "d_alignof.c" 3 4 /* https://gcc.gnu.org/onlinedocs/gcc/Alignment.html */ 5 6 unsigned long 7 leading_and_trailing_alignof_type(void) 8 { 9 return __alignof__(short); 10 } 11 12 unsigned long 13 leading_alignof_type(void) 14 { 15 return __alignof(short); 16 } 17 18 unsigned long 19 plain_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 28 unsigned long 29 leading_and_trailing_alignof_expr(void) 30 { 31 return __alignof__ 3; 32 } 33 34 unsigned long 35 leading_alignof_expr(void) 36 { 37 return __alignof 3; 38 } 39 40 unsigned long 41 plain_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 */ 61 unsigned long 62 alignof_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