netbsd man page for __alignof__

__ALIGNOF__(3)						   BSD Library Functions Manual 					    __ALIGNOF__(3)

NAME
     __alignof__ -- GNU extension for alignment of an object

SYNOPSIS
     int
     __alignof__(void x);

DESCRIPTION
     The __alignof__() operator returns the alignment of its operand.  The operand can be a type or an expression.  If the operand is a 'lvalue',
     the return value represents the required alignment of the underlying type, not the actual alignment of the specified 'lvalue'.

     The returned value is specific to the architecture and the ABI.  If the architecture does not impose strict alignment requirements,
     __alignof__() returns the minimum required alignment.  If __aligned(3) is used to increase the alignment, __alignof__() returns the specified
     alignment.

EXAMPLES
     The syntax is comparable to the sizeof() operator.  If the architecture aligns integers along 32-bit address boundaries, the following should
     print the value 4.

	   (void)printf("%d
", __alignof__(int));

     On the other hand, the following example should print the value 1, even though this is unlikely to be the actual alignment of the structure
     member.

	   struct align {
		   int	x;
		   char y;
	   } a;

	   (void)printf("%d
", __alignof__(a.y));

SEE ALSO
     gcc(1), attribute(3), offsetof(3), typeof(3)

CAVEATS
     This is a non-standard, compiler-specific extension.

BSD
								 December 20, 2010							       BSD