When I simply allocate a two hundred byte array:
int main(void)
{
int myArray[50];
myArray[0] = 123;
myArray[6] = 456;
myArray[49] = 789;
return 0;
}
gcc allocates sixteen extra bytes:
main:
pushq %rbp
movq %rsp, %rbp
subq $88, %rsp
movl $123, -208(%rbp)
movl $456, -184(%rbp)
movl $789, -12(%rbp)
movl $0, %eax
leave
ret
Notice that it leaves 8 bytes "above" where the caller's rbp is stored
and the final 8 bytes of the red zone are unused. There seems to be an
8-byte buffer at both ends of the array. Why?
-- Bob
