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* [RFC: sound/i2c/cs8427] clang warns about cast to signed char
@ 2018-10-18 10:10 ` Philipp K
  0 siblings, 0 replies; 4+ messages in thread
From: Philipp K @ 2018-10-18 10:10 UTC (permalink / raw)
  Cc: kernelnewbies, linux-kernel, perex, tiwai, Lukas Bulwahn

Hi,

I tried compiling the cs8247 sound module with clang and hit the
following warning:

sound/i2c/cs8427.c:141:31: warning: implicit conversion from 'int' to
'char' changes value from 160 to -96 [-Wconstant-conversion]
        data[0] = CS8427_REG_AUTOINC | CS8427_REG_CORU_DATABUF;
                ~ ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

data is a char array, and CS8427_REG_AUTOINC is defined as 0x80 (dec
128) which is too big for a (signed) char.

Looking at other code in the same file, we usually use unsigned chars.

So is there a reason for data being signed in this case? Otherwise we
could just change data to unsigned char and be on the safe side.

If you want I can send in a patch.

Regards,
Philipp

^ permalink raw reply	[flat|nested] 4+ messages in thread

* [RFC: sound/i2c/cs8427] clang warns about cast to signed char
@ 2018-10-18 10:10 ` Philipp K
  0 siblings, 0 replies; 4+ messages in thread
From: Philipp K @ 2018-10-18 10:10 UTC (permalink / raw)
  To: kernelnewbies

Hi,

I tried compiling the cs8247 sound module with clang and hit the
following warning:

sound/i2c/cs8427.c:141:31: warning: implicit conversion from 'int' to
'char' changes value from 160 to -96 [-Wconstant-conversion]
        data[0] = CS8427_REG_AUTOINC | CS8427_REG_CORU_DATABUF;
                ~ ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

data is a char array, and CS8427_REG_AUTOINC is defined as 0x80 (dec
128) which is too big for a (signed) char.

Looking at other code in the same file, we usually use unsigned chars.

So is there a reason for data being signed in this case? Otherwise we
could just change data to unsigned char and be on the safe side.

If you want I can send in a patch.

Regards,
Philipp

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [RFC: sound/i2c/cs8427] clang warns about cast to signed char
  2018-10-18 10:10 ` Philipp K
@ 2018-10-18 10:13   ` Takashi Iwai
  -1 siblings, 0 replies; 4+ messages in thread
From: Takashi Iwai @ 2018-10-18 10:13 UTC (permalink / raw)
  To: Philipp K; +Cc: Lukas Bulwahn, kernelnewbies, perex, linux-kernel

On Thu, 18 Oct 2018 12:10:28 +0200,
Philipp K wrote:
> 
> Hi,
> 
> I tried compiling the cs8247 sound module with clang and hit the
> following warning:
> 
> sound/i2c/cs8427.c:141:31: warning: implicit conversion from 'int' to
> 'char' changes value from 160 to -96 [-Wconstant-conversion]
>         data[0] = CS8427_REG_AUTOINC | CS8427_REG_CORU_DATABUF;
>                 ~ ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
> 
> data is a char array, and CS8427_REG_AUTOINC is defined as 0x80 (dec
> 128) which is too big for a (signed) char.
> 
> Looking at other code in the same file, we usually use unsigned chars.
> 
> So is there a reason for data being signed in this case? Otherwise we
> could just change data to unsigned char and be on the safe side.

No any reason I know of.  It must be just an old convention.

> If you want I can send in a patch.

Yes, please.


thanks,

Takashi

^ permalink raw reply	[flat|nested] 4+ messages in thread

* [RFC: sound/i2c/cs8427] clang warns about cast to signed char
@ 2018-10-18 10:13   ` Takashi Iwai
  0 siblings, 0 replies; 4+ messages in thread
From: Takashi Iwai @ 2018-10-18 10:13 UTC (permalink / raw)
  To: kernelnewbies

On Thu, 18 Oct 2018 12:10:28 +0200,
Philipp K wrote:
> 
> Hi,
> 
> I tried compiling the cs8247 sound module with clang and hit the
> following warning:
> 
> sound/i2c/cs8427.c:141:31: warning: implicit conversion from 'int' to
> 'char' changes value from 160 to -96 [-Wconstant-conversion]
>         data[0] = CS8427_REG_AUTOINC | CS8427_REG_CORU_DATABUF;
>                 ~ ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
> 
> data is a char array, and CS8427_REG_AUTOINC is defined as 0x80 (dec
> 128) which is too big for a (signed) char.
> 
> Looking at other code in the same file, we usually use unsigned chars.
> 
> So is there a reason for data being signed in this case? Otherwise we
> could just change data to unsigned char and be on the safe side.

No any reason I know of.  It must be just an old convention.

> If you want I can send in a patch.

Yes, please.


thanks,

Takashi

^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2018-10-18 10:13 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-10-18 10:10 [RFC: sound/i2c/cs8427] clang warns about cast to signed char Philipp K
2018-10-18 10:10 ` Philipp K
2018-10-18 10:13 ` Takashi Iwai
2018-10-18 10:13   ` Takashi Iwai

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