Re: [Qemu-devel] [PATCH 2/3] kvm-userspace: kvmppc: fix hostlonbits detection when cross compiling v2

[malc <av1474@comtv.ru>]

On Tue, 30 Sep 2008, ehrhardt@linux.vnet.ibm.com wrote:

> From: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
>
> *update*
> further debugging according to some requests revealed that ARCH_CFLAGS does
> not contain all CFLAGS that might be needed, especially those supplied via
> extra-cflags. Therefore people supplying things via extra-cflags instead of an
> environment variable might have had issues.

This part i don't get, there are few more checks before/after 
hostlongbits where no CFLAGS are added to the $cc argument list. What
makes hostlongbits selection "special"? Do people specify -m32/-m64 via
--extra-cflags?

>
> A recent kvm merge with qemu brought code for 64bit power that broke cross
> compilation. The issue is caused by configure trying to execute target
> architecture binaries where configure is executed.

Yes, i never thought about cross-compilation, my bad.

> I tried to change that detection so that it works with&without cross
> compilation with only a small change and especially without an addtional
> configure command line switch. Including the bits/wordsize.h header a platform
> usually can check its wordsize and by doing that configure can check the
> hostlongbits without executing the binary. Instead it now stops after
> preprocessing stage which resolved the __WORDSIZE constant and retrieves
> that value.
>
> I don't like my new check style, but it is at least less broken than before.
> Another approach that was suggested was that qemu might end up needing
> something like asm-offsets in the kernel to manage architecture sizes etc.
> Comments and other approaches welcome.
>

I think Hollis Blanchard's method is sound,

Thank you for bringing this up.

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