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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 
      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 	/* 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