[PATCH v2 1/1] arch/sh: avoid spurious sizeof-pointer-div warning

[PATCH v2 1/1] arch/sh: avoid spurious sizeof-pointer-div warning

[Michael Karcher]

Gcc warns about the pattern sizeof(void*)/sizeof(void), as it looks like
the abuse of a pattern to calculate the array size. This pattern appears
in the unevaluated part of the ternary operator in _INTC_ARRAY if the
parameter is NULL.

The replacement uses an alternate approach to return 0 in case of NULL
which does not generate the pattern sizeof(void*)/sizeof(void), but still
emits the warning if _INTC_ARRAY is called with a nonarray parameter.

This patch is required for successful compilation with -Werror enabled.

The idea to use _Generic for type distinction is taken from Comment #7
in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108483 by Jakub Jelinek

Signed-off-by: Michael Karcher <kernel@mkarcher.dialup.fu-berlin.de>
---
History:
v2:
   - improve title and remove mostly redundant first sentence of the
     description
   - adjust formatting of the _Generic construction

diff --git a/include/linux/sh_intc.h b/include/linux/sh_intc.h
index c255273b0281..98d1da0d8e36 100644
--- a/include/linux/sh_intc.h
+++ b/include/linux/sh_intc.h
@@ -97,7 +97,9 @@ struct intc_hw_desc {
      unsigned int nr_subgroups;
  };

-#define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(*a)
+#define _INTC_ARRAY(a) a, sizeof(a) / (_Generic(a, \
+                                       typeof(NULL):  (size_t)-1, \
+                                       default:       sizeof(*a)))

  #define INTC_HW_DESC(vectors, groups, mask_regs,    \
               prio_regs,    sense_regs, ack_regs)    \

Re: [PATCH v2 1/1] arch/sh: avoid spurious sizeof-pointer-div warning

[Randy Dunlap]

Hi,

On 1/22/23 08:27, Michael Karcher wrote:
> Gcc warns about the pattern sizeof(void*)/sizeof(void), as it looks like
> the abuse of a pattern to calculate the array size. This pattern appears
> in the unevaluated part of the ternary operator in _INTC_ARRAY if the
> parameter is NULL.
> 
> The replacement uses an alternate approach to return 0 in case of NULL
> which does not generate the pattern sizeof(void*)/sizeof(void), but still
> emits the warning if _INTC_ARRAY is called with a nonarray parameter.
> 
> This patch is required for successful compilation with -Werror enabled.
> 
> The idea to use _Generic for type distinction is taken from Comment #7
> in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108483 by Jakub Jelinek
> 
> Signed-off-by: Michael Karcher <kernel@mkarcher.dialup.fu-berlin.de>

There are lots of non-ASCII characters in the new patch. This is one example
from over 20,000 lines of warnings:

../include/linux/sh_intc.h:102:27: error: stray '\302' in program
  102 | <U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0> default:<U+00A0><U+00A0><U+00A0><U+00A0><U+00A0><U+00A0> sizeof(*a)))
      |                                                                                                                                                                                                                 ^~~~~~~~

With all of those changed to tabs or spaces:

Tested-by: Randy Dunlap <rdunlap@infradead.org> # build-tested

Thanks.

> ---
> History:
> v2:
>   - improve title and remove mostly redundant first sentence of the
>     description
>   - adjust formatting of the _Generic construction
> 
> diff --git a/include/linux/sh_intc.h b/include/linux/sh_intc.h
> index c255273b0281..98d1da0d8e36 100644
> --- a/include/linux/sh_intc.h
> +++ b/include/linux/sh_intc.h
> @@ -97,7 +97,9 @@ struct intc_hw_desc {
>      unsigned int nr_subgroups;
>  };
> 
> -#define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(*a)
> +#define _INTC_ARRAY(a) a, sizeof(a) / (_Generic(a, \
> +                                       typeof(NULL):  (size_t)-1, \
> +                                       default:       sizeof(*a)))
> 
>  #define INTC_HW_DESC(vectors, groups, mask_regs,    \
>               prio_regs,    sense_regs, ack_regs)    \
> 

-- 
~Randy