On Sat, Dec 05, 2020 at 10:15:11AM -0500, Alan Stern wrote:
> On Sat, Dec 05, 2020 at 07:47:01PM +0700, Minh Bùi Quang wrote:
> > Vào Th 6, 4 thg 12, 2020 vào lúc 23:12 Alan Stern
> > <[email protected]> đã viết:
> > > Does this initialization end up using less memory than an explicit
> > > memset() call?
> >
> > You mean speed?
>
> No, I mean memory space.
>
> A memset call requires a certain amount of instruction space (to push
> the arguments and make the call) but no static data space.
> Initialization requires some instruction space (to copy the data) and
> static data space as well (to hold the data that is to be copied).
>
> Alan Stern
>
Thank you for your clarification, I didn't think about it before.
As I check when compiling the code, with MAX_NUM_UDC=32 the initialization
becomes
xor eax,eax
mov ecx,0x40
rep stos DWORD PTR es:[rdi],eax
With MAX_NUM_UDC=2, the initialization becomes
mov QWORD PTR [rbp-0x30],0x0
mov QWORD PTR [rbp-0x28],0x0
As I see, initialization does not require additional static data space.
Am I right?
Thanks,
Quang Minh
