Re: Compiling the s390-ccw bios with clang (was: Re: s390-ccw: warning: writing 1 byte into a region of size 0)

[Cornelia Huck]

On Fri, 23 Apr 2021 09:57:08 +0200
Thomas Huth <thuth@redhat.com> wrote:

> On 23/04/2021 08.52, Christian Borntraeger wrote:
> [...]
> > We can of course discuss if we compile the BIOS for z10 instead of z900. TCG
> > in the mean time can handle up to z13 and z10 is now also 13 years old.  
> 
> I'd really like to see us supporting Clang in the s390-ccw bios, too, since 
> it provides additional useful compiler warnings ... but switching the -mz900 
> to -mz10 here also means that we could not boot VMs anymore that use a CPU 
> that is older than the z10...

We could still boot a kernel/initrd directly, couldn't we?

> 
> Is anybody still using such old CPUs? Should we maybe deprecate all CPUs 
> that are older than the z10 in QEMU? Alternatively, we could try to detect 
> Clang in the Makefile, and only use -mz10 in that case and continue to use 
> -mz900 in the other case...?

So, the issue with clang is that it compiles to at least a z10, right?
Any other issues we know about?