Re: [PATCH] s390: Fix build warning with gcc6 in jmpbuf-unwind.h.

[Stefan Liebler <stli at linux dot vnet dot ibm dot com>]

On 07/23/2015 08:20 PM, Carlos O'Donell wrote:
> On 07/23/2015 05:11 AM, Andreas Schwab wrote:
> > Stefan Liebler <stli@linux.vnet.ibm.com> writes:
> >
> > > On 07/23/2015 10:30 AM, Andreas Schwab wrote:
> > > > Stefan Liebler <stli@linux.vnet.ibm.com> writes:
> > > >
> > > > > This patch casts _Unwind_GetCFA return to _Unwind_Ptr first
> > > >
> > > > How can a cast fix a truncated pointer value on s390x?
> > > >
> > > > Andreas.
> > > Why is the pointer truncated on s390x? All three types
> > > _Unwind_Word, _Unwind_Ptr and void * have a size of 4bytes on
> > > s390 and 8 bytes on s390x.
> >
> > Then why do you get a warning?
>
> Agreed.
>
> Why do you get a warning if the types are, as you claim, the same
> size?
>
> I don't disagree that they are the same size, since the code is
> generic and `typedef unsigned _Unwind_Word
> __attribute__((__mode__(__word__)));` should result in the values you
> quote.
>
> If it's a compiler defect then rather than a cast you need to file a
> bug and disable the warning with the glibc diagnostic macros and
> include rationale for that points at the gcc bug.
>
> Cheers, Carlos.
The used gcc-head was configured with "--with-mode=zarch". There is 
something broken in this mode. After the brasl to _Unwind_GetCFA,
it loads r2 with a value from stack. But r2 is normally used as return 
value after a function call. I'll forward this issue.

I've build glibc on s390-32 with gcc-head with esa mode and there is no 
warning. And here the value from stack is loaded to r3 and r2 is used as 
return value of _Unwind_GetCFA.

Please ignore this patch!
Thanks.

Bye Stefan