The aligned variable attribute specifies a minimum alignment for the variable or structure field, measured in bytes.

/* aligns on 4 byte boundary for ARM */

short Variable_Attributes_aligned_1[3] __attribute__ ((aligned));

/* aligned on 16 byte boundary */

int Variable_Attributes_aligned_0 __attribute__ ((aligned (16)));

This makes sure that the variable is placed in 4 byte aligned boundary.

Source:

ARM RVCT Reference guide