[vlc-devel] [PATCH 3/4] vlc_common.h: Ensure clip_uint8_vlc returns an uint8_t

[Rémi Denis-Courmont]

Le torstaina 22. lokakuuta 2020, 10.49.48 EEST Hugo Beauzée-Luyssen a écrit :
> Even though the modified branch is logically guaranteed to return a
> number that fits in an uint8, some compilers will complain that a signed
> 32 bits integer is returned

There are plenty of cases where we implicitly down-convert types. 
Realistically, you'll have to turn that warning off or ignore it.

> ---
>  include/vlc_common.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/vlc_common.h b/include/vlc_common.h
> index 323df74653..9742d2b943 100644
> --- a/include/vlc_common.h
> +++ b/include/vlc_common.h
> @@ -585,7 +585,7 @@ VLC_USED
>  static inline uint8_t clip_uint8_vlc( int32_t a )
>  {
>      if( a&(~255) ) return (-a)>>31;
> -    else           return a;
> +    else           return (uint8_t)a;
>  }
> 
>  /**

And the code is wrong with or without the patch. It overflows on INT32_MIN. 
Also I'm not sure if shifting a *signed* 32-bit value by 31 bits is defined.

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