Messages in this thread | | | Date | Sun, 6 Dec 2020 18:24:05 +0700 | From | Bui Quang Minh <> | Subject | Re: [PATCH] USB: dummy-hcd: Fix uninitialized array use in init() |
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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 > > <stern@rowland.harvard.edu> 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
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