Repack Structures

Extra padding may be added to a structure by the compiler to meet alignment requirements as long and pointer fields grow to 64 bits for LP64. In the 64-bit environment on SPARC platforms, all types of structures are aligned to at least the size of the largest quantity within them. A simple rule for repacking a structure is to move the long and pointer fields to the beginning of the structure and rearrange the rest of the fields—usually, but not always, in descending order of size, depending on how well they can be packed. For example,

struct bar {
		int i;
		long j;
		int k;
		char *p;
};			/* sizeof (struct bar) = 32 */

For better results, use:

struct bar {
		char *p;
		long j;
		int i;
		int k;
};			/* sizeof (struct bar) = 24 */