linux-kernel - Re: [PATCH] treewide: remove redundent IS

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Date:   Tue, 7 Jan 2020 15:28:33 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Julia Lawall <julia.lawall@...6.fr>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        linux-crypto@...r.kernel.org,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        linux-i2c@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        Networking <netdev@...r.kernel.org>,
        ALSA Development Mailing List <alsa-devel@...a-project.org>,
        DTML <devicetree@...r.kernel.org>
Subject: Re: [PATCH] treewide: remove redundent IS_ERR() before error code check

On Tue, Jan 7, 2020 at 2:15 PM Eric Biggers <ebiggers@...nel.org> wrote:
>
> On Mon, Jan 06, 2020 at 01:58:33PM +0900, Masahiro Yamada wrote:
> > 'PTR_ERR(p) == -E*' is a stronger condition than IS_ERR(p).
> > Hence, IS_ERR(p) is unneeded.
> >
> > The semantic patch that generates this commit is as follows:
> >
> > // <smpl>
> > @@
> > expression ptr;
> > constant error_code;
> > @@
> > -IS_ERR(ptr) && (PTR_ERR(ptr) == - error_code)
> > +PTR_ERR(ptr) == - error_code
> > // </smpl>
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
>
> Any reason for not doing instead:
>
>         ptr == ERR_PTR(-error_code)
>
> ?

Because there is no reason to change

        PTR_ERR(ptr) == -error_code
to
        ptr == ERR_PTR(-error_code)



     if (PTR_ERR(ptr) == -error_code)
style seems to be used more often.

But, I think it is just a matter of preference after all.
Both work equally fine.



>  To me it seems weird to use PTR_ERR() on non-error pointers.  I even had to
> double check that it returns a 'long' and not an 'int'.  (If it returned an
> 'int', it wouldn't work...)
>
> - Eric



-- 
Best Regards
Masahiro Yamada