linux-kernel - Re: [PATCH] s390/time: Fix clk type in get_tod

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Message-ID: <CAKwvOdkLy9iKyJUqjgX8K8F98xS6Bz-O8OT_jdxZCzpSrfni8A@mail.gmail.com>
Date:   Sat, 8 Feb 2020 17:18:13 +0000
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        linux-s390 <linux-s390@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH] s390/time: Fix clk type in get_tod_clock

On Sat, Feb 8, 2020 at 3:10 PM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> Clang warns:
>
> In file included from ../arch/s390/boot/startup.c:3:
> In file included from ../include/linux/elf.h:5:
> In file included from ../arch/s390/include/asm/elf.h:132:
> In file included from ../include/linux/compat.h:10:
> In file included from ../include/linux/time.h:74:
> In file included from ../include/linux/time32.h:13:
> In file included from ../include/linux/timex.h:65:
> ../arch/s390/include/asm/timex.h:160:20: warning: passing 'unsigned char
> [16]' to parameter of type 'char *' converts between pointers to integer
> types with different sign [-Wpointer-sign]
>         get_tod_clock_ext(clk);
>                           ^~~
> ../arch/s390/include/asm/timex.h:149:44: note: passing argument to
> parameter 'clk' here
> static inline void get_tod_clock_ext(char *clk)
>                                            ^
>
> Change clk's type to just be char so that it matches what happens in
> get_tod_clock_ext.
>
> Fixes: 57b28f66316d ("[S390] s390_hypfs: Add new attributes")
> Link: https://github.com/ClangBuiltLinux/linux/issues/861
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>

First time I've seen a `typedef` in a function. I wonder if that makes
its definition have function scope? (re: get_tod_clock_ext())

> ---
>
> Alternatively, changing the clk type in get_tod_clock_ext to unsigned
> which is what it was in the early 2000s.

Yeah, it doesn't really matter for this case, it looks like. Either way,

Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

>
>  arch/s390/include/asm/timex.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/s390/include/asm/timex.h b/arch/s390/include/asm/timex.h
> index 670f14a228e5..6bf3a45ccfec 100644
> --- a/arch/s390/include/asm/timex.h
> +++ b/arch/s390/include/asm/timex.h
> @@ -155,7 +155,7 @@ static inline void get_tod_clock_ext(char *clk)
>
>  static inline unsigned long long get_tod_clock(void)
>  {
> -       unsigned char clk[STORE_CLOCK_EXT_SIZE];
> +       char clk[STORE_CLOCK_EXT_SIZE];
>
>         get_tod_clock_ext(clk);
>         return *((unsigned long long *)&clk[1]);
> --
> 2.25.0
>
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-- 
Thanks,
~Nick Desaulniers