Failures building glibc with mainline GCC

[Joseph Myers]

On Mon, 2 Aug 2021, Martin Sebor via Gcc wrote:

> On 7/30/21 2:52 PM, Joseph Myers wrote:
> > On Fri, 30 Jul 2021, Aldy Hernandez via Gcc wrote:
> > 
> > > There's a new jump threader in GCC which is much more aggressive, and
> > > may trigger latent problems with other warning passes, especially
> > > -Warray-bounds, -Woverflow, and -Wuninitialized.
> > > 
> > > Do your problems go away if you take out commit 2e96b5f14e?
> > 
> > Reverting that commit fixes all the glibc build failures except for
> > x86_64-linux-gnu, i686-gnu and powerpc64le-linux-gnu.
> > 
> 
> I just built Glibc for x86_64-linux-gnu with the top of trunk and
> got no unexpected warnings.  Can you please share the translation
> units for the files with the warnings?  (Or just open GCC bugs for
> them if you believe they're false positives.)

I still see the same error previously discussed for x86_64-linux-gnu.  
Compile the attached file with -O2 -Wall -Werror.

loadmsgcat.c: In function '_nl_load_domain':
loadmsgcat.c:770:22: error: array subscript 0 is outside array bounds of '__seg_fs struct pthread * __seg_fs[0]' [-Werror=array-bounds]

As discussed, this is a bug indicating that the code generating that 
warning fails to check targetm.addr_space.zero_address_valid to determine 
whether zero or small constant addresses are valid in the given address 
space.

-- 
Joseph S. Myers
joseph@codesourcery.com
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