linux-kernel - Re: [PATCH] mm/mmap.c: silence variable 'new

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Date:   Wed, 24 Jul 2019 16:17:10 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Qian Cai <cai@....pw>
Cc:     YueHaibing <yuehaibing@...wei.com>, akpm@...ux-foundation.org,
        kirill.shutemov@...ux.intel.com, vbabka@...e.cz,
        yang.shi@...ux.alibaba.com, jannh@...gle.com, walken@...gle.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm/mmap.c: silence variable 'new_start' set but not used

On Wed 24-07-19 10:11:05, Qian Cai wrote:
> On Wed, 2019-07-24 at 22:07 +0800, YueHaibing wrote:
> > 'new_start' is used in is_hugepage_only_range(),
> > which do nothing in some arch. gcc will warning:
> > 
> > mm/mmap.c: In function acct_stack_growth:
> > mm/mmap.c:2311:16: warning: variable new_start set but not used [-Wunused-but-
> > set-variable]
> 
> Nope. Convert them to inline instead.

Agreed. Obfuscating the code is not really something we want.

> > Reported-by: Hulk Robot <hulkci@...wei.com>
> > Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> > ---
> >  mm/mmap.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/mm/mmap.c b/mm/mmap.c
> > index e2dbed3..56c2a92 100644
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -2308,7 +2308,7 @@ static int acct_stack_growth(struct vm_area_struct *vma,
> >  			     unsigned long size, unsigned long grow)
> >  {
> >  	struct mm_struct *mm = vma->vm_mm;
> > -	unsigned long new_start;
> > +	unsigned long __maybe_unused new_start;
> >  
> >  	/* address space limit tests */
> >  	if (!may_expand_vm(mm, vma->vm_flags, grow))

-- 
Michal Hocko
SUSE Labs