* Linux kernel support -O0 optimization flag?
@ 2013-04-15 7:58 Ley Foon Tan
2013-04-15 11:16 ` richard -rw- weinberger
0 siblings, 1 reply; 4+ messages in thread
From: Ley Foon Tan @ 2013-04-15 7:58 UTC (permalink / raw)
To: linux-kernel; +Cc: Kenneth Chong Yin Tan
Change KBUILD_CFLAGS to -O0 in Makefile and got the compilation error as
below.
Is the Linux kernel support -O0 optimization flag?
Note, I have tried 2 architecture compilers and got the same error.
In function 'zap_pmd_range',
inlined from 'zap_pud_range' at mm/memory.c:1288:8,
inlined from 'unmap_page_range' at mm/memory.c:1313:8:
mm/memory.c:1243:23: error: call to '__build_bug_failed' declared with
attribute error: BUILD_BUG failed
make[1]: *** [mm/memory.o] Error 1
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: Linux kernel support -O0 optimization flag?
2013-04-15 7:58 Linux kernel support -O0 optimization flag? Ley Foon Tan
@ 2013-04-15 11:16 ` richard -rw- weinberger
2013-04-16 6:10 ` Ley Foon Tan
2013-04-24 8:29 ` Pavel Machek
0 siblings, 2 replies; 4+ messages in thread
From: richard -rw- weinberger @ 2013-04-15 11:16 UTC (permalink / raw)
To: Ley Foon Tan; +Cc: LKML, Kenneth Chong Yin Tan
On Mon, Apr 15, 2013 at 9:58 AM, Ley Foon Tan <lftan@altera.com> wrote:
>
>
> Change KBUILD_CFLAGS to -O0 in Makefile and got the compilation error as
> below.
> Is the Linux kernel support -O0 optimization flag?
No. If I'm not mistaken we need this to make sure that the compiler
inlines some functions.
In your case the compiler failed to compute the BUILD_BUG() macro correctly.
It depends also on optimization.
--
Thanks,
//richard
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Linux kernel support -O0 optimization flag?
2013-04-15 11:16 ` richard -rw- weinberger
@ 2013-04-16 6:10 ` Ley Foon Tan
2013-04-24 8:29 ` Pavel Machek
1 sibling, 0 replies; 4+ messages in thread
From: Ley Foon Tan @ 2013-04-16 6:10 UTC (permalink / raw)
To: richard -rw- weinberger; +Cc: LKML, Kenneth Chong Yin Tan
On Mon, 2013-04-15 at 13:16 +0200, richard -rw- weinberger wrote:
> No. If I'm not mistaken we need this to make sure that the compiler
> inlines some functions.
>
> In your case the compiler failed to compute the BUILD_BUG() macro correctly.
> It depends also on optimization.
>
Thank you.
So, the supported optimization flags are -O1, -O2, -O3 and -Os?
Regards
LFTAN
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Linux kernel support -O0 optimization flag?
2013-04-15 11:16 ` richard -rw- weinberger
2013-04-16 6:10 ` Ley Foon Tan
@ 2013-04-24 8:29 ` Pavel Machek
1 sibling, 0 replies; 4+ messages in thread
From: Pavel Machek @ 2013-04-24 8:29 UTC (permalink / raw)
To: richard -rw- weinberger; +Cc: Ley Foon Tan, LKML, Kenneth Chong Yin Tan
On Mon 2013-04-15 13:16:36, richard -rw- weinberger wrote:
> On Mon, Apr 15, 2013 at 9:58 AM, Ley Foon Tan <lftan@altera.com> wrote:
> >
> >
> > Change KBUILD_CFLAGS to -O0 in Makefile and got the compilation error as
> > below.
> > Is the Linux kernel support -O0 optimization flag?
>
> No. If I'm not mistaken we need this to make sure that the compiler
> inlines some functions.
>
> In your case the compiler failed to compute the BUILD_BUG() macro correctly.
> It depends also on optimization.
Actually... You probably could replace BUILD_BUG() with nop. Bugs are
not expected to happen, right? you'll probably hit something else...
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
^ permalink raw reply [flat|nested] 4+ messages in thread
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2013-04-15 7:58 Linux kernel support -O0 optimization flag? Ley Foon Tan
2013-04-15 11:16 ` richard -rw- weinberger
2013-04-16 6:10 ` Ley Foon Tan
2013-04-24 8:29 ` Pavel Machek
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