Re: Build failure on ARM <5

[Rich Felker <dalias@libc.org>]

On Fri, Oct 20, 2017 at 05:26:14PM -0400, Rich Felker wrote:
> On Fri, Oct 20, 2017 at 09:36:45PM +0200, Szabolcs Nagy wrote:
> > * Reiner Herrmann <reiner@reiner-h.de> [2017-10-20 21:04:00 +0200]:
> > > Hi,
> > > 
> > > musl 1.1.17 fails to build [1] on arm versions <5 because
> > > of an unsupported clz instruction.
> > > The attached patch by Adrian Bunk [2] fixes this issue.
> > > 
> > 
> > this is my bug sorry,
> > 
> > > diff --git a/arch/arm/atomic_arch.h b/arch/arm/atomic_arch.h
> > > index a121010f..c5c56f81 100644
> > > --- a/arch/arm/atomic_arch.h
> > > +++ b/arch/arm/atomic_arch.h
> > > @@ -82,9 +82,13 @@ static inline void a_crash()
> > >  		: : : "memory");
> > >  }
> > >  
> > > +#if __ARM_ARCH >= 5
> > > +
> > 
> > this is not enough: v5t and v6 only supports clz in arm mode
> > v6t2 and v7 supports it in thumb mode too.
> 
> I don't think this matters yet because thumb1 is not supported at all.
> If we support it in the future it will matter, though.

After discussion on #musl, committed with additional notes on the
regression and limitations of the fix, and credit to the patch author.
Thanks.

Rich