linux-kernel - Re: [PATCH 3/3 v2] sh: fix READ/WRITE redefinition warnings

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Date:   Fri, 2 Jul 2021 11:25:19 +0200
From:   John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        Linux-sh list <linux-sh@...r.kernel.org>,
        Takashi YOSHII <takasi-y@....dti.ne.jp>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH 3/3 v2] sh: fix READ/WRITE redefinition warnings

Hi Geert!

On 7/1/21 10:41 AM, Geert Uytterhoeven wrote:
>>> OK. Thanks for all of the testing.
>>
>> I'll report back with the other patch applied that Geert mentioned from linux-next before this one.
> 
> FTR, I booted all three successfully on qemu/rts7751r2d and on physical landisk.

Good to know, thanks.

>> FWIW, there are some warnings when building the SH-7785LCR configuration:
>>
>> In file included from ./arch/sh/include/asm/hw_irq.h:6,
>>                  from ./include/linux/irq.h:591,
>>                  from ./include/asm-generic/hardirq.h:17,
>>                  from ./arch/sh/include/asm/hardirq.h:9,
>>                  from ./include/linux/hardirq.h:11,
>>                  from ./include/linux/interrupt.h:11,
>>                  from ./include/linux/serial_core.h:13,
>>                  from ./include/linux/serial_sci.h:6,
>>                  from arch/sh/kernel/cpu/sh4a/setup-sh7785.c:10:
>> ./include/linux/sh_intc.h:100:63: warning: division 'sizeof (void *) / sizeof (void)' does not compute the number of array elements [-Wsizeof-pointer-div]
>>   100 | #define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(*a)
>>       |                                                               ^
>> ./include/linux/sh_intc.h:107:9: note: in expansion of macro '_INTC_ARRAY'
>>   107 |         _INTC_ARRAY(sense_regs), _INTC_ARRAY(ack_regs), \
>>       |         ^~~~~~~~~~~
>> ./include/linux/sh_intc.h:124:15: note: in expansion of macro 'INTC_HW_DESC'
>>   124 |         .hw = INTC_HW_DESC(vectors, groups, mask_regs,                  \
>>       |               ^~~~~~~~~~~~
>> arch/sh/kernel/cpu/sh4a/setup-sh7785.c:478:8: note: in expansion of macro 'DECLARE_INTC_DESC'
>>   478 | static DECLARE_INTC_DESC(intc_desc, "sh7785", vectors, groups,
>>       |        ^~~~~~~~~~~~~~~~~
> 
> A while ago, I had a look into fixing them, but it was non-trivial.
> The issue is that the macros are sometimes used with NULL pointer arrays.
> The __same_type() check in
> 
>     #define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(*a)
> 
> is supposed to catch that, but modern compilers seem to evaluate the
> non-taken branch, too, leading to the warning.
> 
> Anyone with a suggestion? (CCing the multi-compiler guru)

Ah, thanks for the explanation.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@...ian.org
`. `'   Freie Universitaet Berlin - glaubitz@...sik.fu-berlin.de
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