linux-kernel - Re: [PATCH] mtd: nand: Use ULL-suffix for big u64 constant

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Date:	Mon, 11 Aug 2014 12:06:44 -0700
From:	Brian Norris <computersforpeace@...il.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Boris BREZILLON <boris.brezillon@...e-electrons.com>,
	MTD Maling List <linux-mtd@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mtd: nand: Use ULL-suffix for big u64 constant

On Mon, Aug 11, 2014 at 08:51:51PM +0200, Geert Uytterhoeven wrote:
> On Mon, Aug 11, 2014 at 7:50 PM, Brian Norris
> <computersforpeace@...il.com> wrote:
> > On Sat, Aug 09, 2014 at 07:07:53PM +0200, Geert Uytterhoeven wrote:
> >> drivers/mtd/nand/nand_timings.c:45: warning: integer constant is too large for ‘long’ type
> >
> > On what compiler / static analyzer?
> 
> Any 32-bit version of gcc at the standard warning level, at least
> until gcc 4.4.7.
> With gcc 4.6 it's indeed gone.
> 
> >> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> >> ---
> >>  drivers/mtd/nand/nand_timings.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/mtd/nand/nand_timings.c b/drivers/mtd/nand/nand_timings.c
> >> index 8b36253420fa..e81470a8ac67 100644
> >> --- a/drivers/mtd/nand/nand_timings.c
> >> +++ b/drivers/mtd/nand/nand_timings.c
> >> @@ -42,7 +42,7 @@ static const struct nand_sdr_timings onfi_sdr_timings[] = {
> >>               .tRHZ_max = 200000,
> >>               .tRLOH_min = 0,
> >>               .tRP_min = 50000,
> >> -             .tRST_max = 250000000000,
> >> +             .tRST_max = 250000000000ULL,
> >
> > See [1] and [2]. I'm pretty sure it is a bug in your tool to warn about
> 
> Yes, I saw those, after I had created my patch. I decided to send it anyway ;-)
> 
> > this. The C standard seems pretty clear that the large literal constant
> > is automatically promoted to a sufficiently large type, so AIUI there
> > should be no need for such a warning. A standards-compliant compiler
> > will do the right thing.
> 
> Actually I didn't know there existed versions of gcc that did _not_ give
> this warning. This seems to be a recent thing on gcc for 32-bit targets.
> For 64-bit targets, apparently it only gives a warning if the constant
> is that large that it can no longer fit in a 64-bit signed integer.

I'm curious: do your broken compilers also generate broken code/data?
i.e., does gcc 4.4.7 give 250000000000 its proper ULL value still?

> > However, I could be convinced to apply this, if only to satisfy broken
> > tools and to avoid addressing this question over and over...
> 
> So please apply. Too many people are still using 32-bit targets and
> gcc < 4.6.

OK, you've convinced me ;) Applied to l2-mtd.git/next, with an editorial
comment.

Brian
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