[ILUG] gcc compile options

[RenWei]

hi ,
 i want to know how "align" works in gcc .
i use this in my program, run in a X86 box, RedHat 6.2 full installed:

int a __attribute__ ((aligned(8)));

printf("size of a : %d \n", sizeof(a));

i want it's size be 8 bytes, by i get 4.
anyone can tell me how to use align in detail?
           
    thanks 
             renwei.