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

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Message-ID: <20200107051521.GF705@sol.localdomain>
Date:   Mon, 6 Jan 2020 21:15:21 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Julia Lawall <julia.lawall@...6.fr>,
        linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-clk@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-gpio@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        netdev@...r.kernel.org, alsa-devel@...a-project.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH] treewide: remove redundent IS_ERR() before error code
 check

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)

?  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