Messages in this thread | | | From | Arnd Bergmann <> | Date | Thu, 1 Jul 2021 13:57:13 +0200 | Subject | Re: [PATCH 3/3 v2] sh: fix READ/WRITE redefinition warnings |
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On Thu, Jul 1, 2021 at 10:41 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote: > On Wed, Jun 30, 2021 at 9:36 PM John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de> wrote: > > On 6/30/21 9:33 PM, Randy Dunlap wrote: > > > On 6/30/21 2:36 AM, John Paul Adrian Glaubitz wrote: > > > 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)
I think I looked at this (or maybe a related sh driver) in the past and also gave up.
The best idea I have would be to manually expand the DECLARE_INTC_DESC() macros. It would be possible to add further variations of them for each combination of NULL/non-NULL arguments, but IMHO they don't actually add any readability over the expanded version in the first place.
Another option would be to change the definition from array/size to zero-terminated arrays and get rid of the sizeof hack.
Arnd
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