Re: [PATCH] docs: printk-formats: Stop encouraging use of unnecessary %h[xudi] and %hh[xudi]

[Andy Shevchenko]

On Sat, Sep 7, 2019 at 9:15 PM Joe Perches <joe@xxxxxxxxxxx> wrote:
>
> Standard integer promotion is already done and %hx and %hhx is useless
> so do not encourage the use of %hh[xudi] or %h[xudi].
>
> As Linus said in:
> Link: https://lore.kernel.org/lkml/CAHk-=wgoxnmsj8GEVFJSvTwdnWm8wVJthefNk2n6+4TC=20e0Q@xxxxxxxxxxxxxx/
>
> It's a pointless warning, making for more complex code, and
> making people remember esoteric printf format details that have no
> reason for existing.
>
> The "h" and "hh" things should never be used. The only reason for them
> being used if if you have an "int", but you want to print it out as a
> "char" (and honestly, that is a really bad reason, you'd be better off
> just using a proper cast to make the code more obvious).
>
> So if what you have a "char" (or unsigned char) you should always just
> print it out as an "int", knowing that the compiler already did the
> proper type conversion.

> -               char                    %hhd or %hhx
> -               short int               %hd or %hx
> +               char                    %d or %x
> +               short int               %d or %x

> +               s8                      %d or %x
> +               s16                     %d or %x

This is incorrect. Integral promotions promotes also sign, which will
produce too many f:s.

-- 
With Best Regards,
Andy Shevchenko