Andi Kleen wrote:
> On Thu, Aug 23, 2007 at 01:03:18PM +0100, Andy Whitcroft wrote:
>> It seems that this is a problem caused by the way we check for
>> compiler options in x86_64. Each compiler flag is checked for
>> individually and if available added to cflags-y, later that is
>> added to CFLAGS. However, this means that each flag is checked
>> in total isolation. On x86_64 (on this compiler at least) the
>> -mpreferred-stack-boundary and -m{32,64} flags are actually mutually
>> dependant, the alignment constraints vary based on the word size.
>> This leads to the compile failure:
>>
>> # gcc -mpreferred-stack-boundary=3 -S -xc /dev/null -o FOO
>> # echo $?
>> 0
>> # gcc -m64 -mpreferred-stack-boundary=3 -S -xc /dev/null -o FOO
>> /dev/null:1: error: -mpreferred-stack-boundary=3 is not between 4 and 12
>> # echo $?
>> 1
>>
>> In the main Makefile we always add each flag directly to CFLAGS
>> which means we check them all in combination, perhaps this is
>> prudent here also? Either way I suspect that changing the -m64
>> check to add itself directly to CFLAGS will fix this us.
>
> Ok that makes sense. Most people don't see it because they don't
> need -m64.
>
> I fixed it up with
> ftp://ftp.firstfloor.org/pub/ak/x86_64/quilt/patches/cflags-probe
> and then
> ftp://ftp.firstfloor.org/pub/ak/x86_64/quilt/patches/less-stack-alignment
> (replacement for the mm patch)
>
> Can you test?
Sure, will do that now and let you know.
-apw
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