linux-kernel - Re: linux-next: build warning after merge of the akpm-current tree

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Message-Id: <20200401155831.24aa79ebbb14c654a2bee8c0@linux-foundation.org>
Date:   Wed, 1 Apr 2020 15:58:31 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Linux Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Longpeng <longpeng2@...wei.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Matthew Wilcox <willy@...radead.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: linux-next: build warning after merge of the akpm-current tree

On Tue, 31 Mar 2020 19:56:12 +1100 Stephen Rothwell <sfr@...b.auug.org.au> wrote:

> Hi all,
> 
> After merging the akpm-current tree, today's linux-next build (i386
> defconfig) produced this warning:
> 
> mm/hugetlb.c: In function 'huge_pte_offset':
> cc1: warning: function may return address of local variable [-Wreturn-local-addr]
> mm/hugetlb.c:5361:14: note: declared here
>  5361 |  pud_t *pud, pud_entry;
>       |              ^~~~~~~~~
> cc1: warning: function may return address of local variable [-Wreturn-local-addr]
> mm/hugetlb.c:5360:14: note: declared here
>  5360 |  p4d_t *p4d, p4d_entry;
>       |              ^~~~~~~~~
> 
> Introduced by commit
> 
>   826ddc88e2cf ("mm/hugetlb: fix a addressing exception caused by huge_pte_offset")

I can reproduce this (i386 defconfig, gcc-7.2.0).

I can see no way in which this makes any sense.  Hopefully it's a gcc
bug but it's hard to see how it could have messed up this fairly simple
code.