Applying __align to static or global variables:
int __align(1024) varA; /* varA is aligned on a 1024-byte boundary main() and padded with 1020 bytes */ {...}static int __align(512) varB; /* varB is aligned on a 512-byte boundary and padded with 508 bytes */int __align(128) functionB( ); /* An error */typedef int __align(128) T; /* An error */__align enum C {a, b, c}; /* An error */
Applying __align to align and pad aggregate tags without affecting aggregate members:
__align(1024) struct structA {int i; int j;}; /* struct structA is aligned on a 1024-byte boundary with size including padding of 1024 bytes */__align(1024) union unionA {int i; int j;}; /* union unionA is aligned on a 1024-byte boundary with size including padding of 1024 bytes */
Applying __align to a structure or union, where the size and alignment of the aggregate using the structure or union is affected:
__align(128) struct S {int i;}; /* sizeof(struct S) == 128 */ struct S sarray[10]; /* sarray is aligned on 128-byte boundary with sizeof(sarray) == 1280 */ struct S __align(64) svar; /* error - alignment of variable is smaller than alignment of type */ struct S2 {struct S s1; int a;} s2; /* s2 is aligned on 128-byte boundary with sizeof(s2) == 256 */
Applying __align to an array:
AnyType __align(64) arrayA[10]; /* Only arrayA is aligned on a 64-byte boundary, and elements within that array are aligned according to the alignment of AnyType. Padding is applied after the back of the array and does not affect the size of the array member itself. */
Applying __align where the size of the variable alignment differs from the size of the type alignment:
__align(64) struct S {int i;}; struct S __align(32) s1; /* error, alignment of variable is smaller than alignment of type */ struct S __align(128) s2; /* s2 is aligned on 128-byte boundary */ struct S __align(16) s3[10]; /* error */int __align(1) s4; /* error */__align(1) struct S {int i;}; /* error */
Related information