[yocto] question about SDKMACHINE, SDK_ARCH and BUILD_ARCH

[Zhang, Jessica]

Richard Purdie wrote:
> On Thu, 2011-01-13 at 15:36 -0800, Zhang, Jessica wrote:
>> Hi Richard,
>> 
>> As I mentioned in IRC, we've noticed that bitbake behaves differently
>> on 64bit and 32bit machines from SDKMACHINE setup perspective.  It
>> never enforces SDKMACHINE to be set in local.conf for 64bit users but
>> for 32bit user, if you leave SDKMACHINE unset, the bitbake sanity
>> test will fail and prompts user to set the SDKMACHINE to i586.
>> 
>> It seems internally we really use SDK_ARCH which derived from
>> BUILD_ARCH that reflects the poky build machines arch.  And for
>> bitbake sanity check if it sees SDK_ARCH is i686, it will prompts
>> user to set SDKMACHINE to i586 since there's a known issue for this
>> case can't use the default build machine arch of i686.
>> 
>> Questions are:
>> 1. what  is the known issue for using i686?
> 
> (e)glibc will fail to build with some issues to do with architecture
> optimisations. I don't remember the details but the builds do fail and
> the warning is valid. The easy way to test is to disable the warning
> and try it!
> 
> Once, there were also conflicts between the native bits and the cross
> bits both being i686 but I think the problem was solved a long time
> ago. 
> 
> At some point it would be nice to fix this but as far as I know the
> problem remains and the sanity warning is still valid.
> 

Interestingly, by simply comment off the sanity check for SDK_ARCH == i686,
I successfully built meta-toolchain for i686-i586 and poky-image-sdk for x86
and didn't run into (e)glibc build errors.  I check my built toolchain and
sysroot, and everything looks right, as host as i686 and target as i586.  I
was able to use the cross toolchain to compile a simple c program.  Are
these enough test, if so, I'll submitted a patch ...

Thanks
Jessica
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