linux-kernel - Re: [PATCH] powerpc: replace ternary operator with min()

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Date:   Mon, 24 Oct 2022 15:33:15 +1100
From:   Russell Currey <ruscur@...sell.cc>
To:     KaiLong Wang <wangkailong@...i.cn>, mpe@...erman.id.au,
        npiggin@...il.com, christophe.leroy@...roup.eu,
        farosas@...ux.ibm.com, mirq-linux@...e.qmqm.pl,
        dmitry.osipenko@...labora.com, kda@...ux-powerpc.org,
        naveen.n.rao@...ux.vnet.ibm.com
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc: replace ternary operator with min()

On Sun, 2022-10-23 at 20:44 +0800, KaiLong Wang wrote:
> Fix the following coccicheck warning:
> 
> arch/powerpc/xmon/xmon.c:2987: WARNING opportunity for min()
> arch/powerpc/xmon/xmon.c:2583: WARNING opportunity for min()
> 
> Signed-off-by: KaiLong Wang <wangkailong@...i.cn>

Hello,

This fails to compile on some platforms/compilers since n is a long and
16 is an int, expanding to:

r = __builtin_choose_expr(
	((!!(sizeof((typeof(n) *)1 == (typeof(16) *)1))) &&
	 ((sizeof(int) ==
	   sizeof(*(8 ? ((void *)((long)(n)*0l)) : (int *)8))) &&
	  (sizeof(int) ==
	   sizeof(*(8 ? ((void *)((long)(16) * 0l)) :
			(int *)8))))),
	((n) < (16) ? (n) : (16)), ({
		typeof(n) __UNIQUE_ID___x0 = (n);
		typeof(16) __UNIQUE_ID___y1 = (16);
		((__UNIQUE_ID___x0) < (__UNIQUE_ID___y1) ?
			 (__UNIQUE_ID___x0) :
			 (__UNIQUE_ID___y1));
	}));

Here's the full build failure as found by snowpatch:
https://github.com/ruscur/linux-ci/actions/runs/3308880562/jobs/5461579048#step:4:89

You should use min_t(long, n, 16) instead.

- Russell

> ---
>  arch/powerpc/xmon/xmon.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
> index f51c882bf902..a7751cd2cc9d 100644
> --- a/arch/powerpc/xmon/xmon.c
> +++ b/arch/powerpc/xmon/xmon.c
> @@ -2580,7 +2580,7 @@ static void xmon_rawdump (unsigned long adrs,
> long ndump)
>         unsigned char temp[16];
>  
>         for (n = ndump; n > 0;) {
> -               r = n < 16? n: 16;
> +               r = min(n, 16);
>                 nr = mread(adrs, temp, r);
>                 adrs += nr;
>                 for (m = 0; m < r; ++m) {
> @@ -2984,7 +2984,7 @@ prdump(unsigned long adrs, long ndump)
>         for (n = ndump; n > 0;) {
>                 printf(REG, adrs);
>                 putchar(' ');
> -               r = n < 16? n: 16;
> +               r = min(n, 16);
>                 nr = mread(adrs, temp, r);
>                 adrs += nr;
>                 for (m = 0; m < r; ++m) {