Re: [PATCH v5 1/1] arch/sh: avoid spurious sizeof-pointer-div warning

Re: [PATCH v5 1/1] arch/sh: avoid spurious sizeof-pointer-div warning

[John Paul Adrian Glaubitz]

Hello!

On 1/23/23 21:05, 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
> inhttps://gcc.gnu.org/bugzilla/show_bug.cgi?id=108483  by Jakub Jelinek
> 
> Signed-off-by: Michael Karcher<kernel@mkarcher.dialup.fu-berlin.de>
> ---
> History:
> v5:
>    - Cleanly generated the patch
> v4:
>    - Put the case distinction into the numerator instead of the denominator
>    - Refactor the case disctinction into a second macro
> v3:
>    - I had a stern discussion with Thunderbird about not mangling the
>      space characters in my email, and I hope spaces get sent as standard
>      spaces now
> 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..37ad81058d6a 100644
> --- a/include/linux/sh_intc.h
> +++ b/include/linux/sh_intc.h
> @@ -97,7 +97,10 @@ struct intc_hw_desc {
>          unsigned int nr_subgroups;
>   };
> 
> -#define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(*a)
> +#define _INTC_SIZEOF_OR_ZERO(a) (_Generic(a,                 \
> +                                 typeof(NULL):  0,           \
> +                                 default:       sizeof(a)))
> +#define _INTC_ARRAY(a) a, _INTC_SIZEOF_OR_ZERO(a)/sizeof(*a)
> 
>   #define INTC_HW_DESC(vectors, groups, mask_regs,       \
>                       prio_regs, sense_regs, ack_regs)   \

Can anyone suggest which tree to pick this up through until we have established a
new linux-sh tree?

Shall this go through Andrew's tree?

Adrian

-- 
  .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
   `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

Re: [PATCH v5 1/1] arch/sh: avoid spurious sizeof-pointer-div warning

[Randy Dunlap]

On 1/24/23 00:11, John Paul Adrian Glaubitz wrote:
> Hello!
> 
> On 1/23/23 21:05, 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
>> inhttps://gcc.gnu.org/bugzilla/show_bug.cgi?id=108483  by Jakub Jelinek
>>
>> Signed-off-by: Michael Karcher<kernel@mkarcher.dialup.fu-berlin.de>
>> ---
>> History:
>> v5:
>>    - Cleanly generated the patch
>> v4:
>>    - Put the case distinction into the numerator instead of the denominator
>>    - Refactor the case disctinction into a second macro
>> v3:
>>    - I had a stern discussion with Thunderbird about not mangling the
>>      space characters in my email, and I hope spaces get sent as standard
>>      spaces now
>> 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..37ad81058d6a 100644
>> --- a/include/linux/sh_intc.h
>> +++ b/include/linux/sh_intc.h
>> @@ -97,7 +97,10 @@ struct intc_hw_desc {
>>          unsigned int nr_subgroups;
>>   };
>>
>> -#define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(*a)
>> +#define _INTC_SIZEOF_OR_ZERO(a) (_Generic(a,                 \
>> +                                 typeof(NULL):  0,           \
>> +                                 default:       sizeof(a)))
>> +#define _INTC_ARRAY(a) a, _INTC_SIZEOF_OR_ZERO(a)/sizeof(*a)
>>
>>   #define INTC_HW_DESC(vectors, groups, mask_regs,       \
>>                       prio_regs, sense_regs, ack_regs)   \
> 
> Can anyone suggest which tree to pick this up through until we have established a
> new linux-sh tree?
> 
> Shall this go through Andrew's tree?

I think Andrew or Arnd could merge it.

-- 
~Randy

[PATCH v5 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
inhttps://gcc.gnu.org/bugzilla/show_bug.cgi?id=108483  by Jakub Jelinek

Signed-off-by: Michael Karcher<kernel@mkarcher.dialup.fu-berlin.de>
---
(resend of the mail as plaintext only instead of multipart/alternative)
History:
v5:
   - Cleanly generated the patch
v4:
   - Put the case distinction into the numerator instead of the denominator
   - Refactor the case disctinction into a second macro
v3:
   - I had a stern discussion with Thunderbird about not mangling the
     space characters in my email, and I hope spaces get sent as standard
     spaces now
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..37ad81058d6a 100644
--- a/include/linux/sh_intc.h
+++ b/include/linux/sh_intc.h
@@ -97,7 +97,10 @@ struct intc_hw_desc {
         unsigned int nr_subgroups;
  };

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

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

Re: [PATCH v5 1/1] arch/sh: avoid spurious sizeof-pointer-div warning

[Randy Dunlap]

Hi--

On 1/24/23 13:48, 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
> inhttps://gcc.gnu.org/bugzilla/show_bug.cgi?id=108483  by Jakub Jelinek
> 
> Signed-off-by: Michael Karcher<kernel@mkarcher.dialup.fu-berlin.de>

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

Thanks.

> ---
> (resend of the mail as plaintext only instead of multipart/alternative)
> History:
> v5:
>   - Cleanly generated the patch
> v4:
>   - Put the case distinction into the numerator instead of the denominator
>   - Refactor the case disctinction into a second macro
> v3:
>   - I had a stern discussion with Thunderbird about not mangling the
>     space characters in my email, and I hope spaces get sent as standard
>     spaces now
> 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..37ad81058d6a 100644
> --- a/include/linux/sh_intc.h
> +++ b/include/linux/sh_intc.h
> @@ -97,7 +97,10 @@ struct intc_hw_desc {
>         unsigned int nr_subgroups;
>  };
> 
> -#define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(*a)
> +#define _INTC_SIZEOF_OR_ZERO(a) (_Generic(a,                 \
> +                                 typeof(NULL):  0,           \
> +                                 default:       sizeof(a)))
> +#define _INTC_ARRAY(a) a, _INTC_SIZEOF_OR_ZERO(a)/sizeof(*a)
> 
>  #define INTC_HW_DESC(vectors, groups, mask_regs,       \
>                      prio_regs, sense_regs, ack_regs)   \
> 
> 
> 

-- 
~Randy