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From: =?utf-8?Q?Bj=C3=B8rn_Mork?= <bjorn@mork.no>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        Jonathan Corbet <corbet@lwn.net>,
        virtualization@lists.linux-foundation.org,
        Julia Lawall <julia.lawall@lip6.fr>,
        Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: [PATCH] CodingStyle: add some more error handling guidelines
Organization: m
References: <1471874251-7721-1-git-send-email-mst@redhat.com>
Date: Tue, 23 Aug 2016 13:03:15 +0200
In-Reply-To: <1471874251-7721-1-git-send-email-mst@redhat.com> (Michael
        S. Tsirkin's message of "Mon, 22 Aug 2016 16:57:46 +0300")
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"Michael S. Tsirkin" <mst@redhat.com> writes:

>                 foo = kmalloc(SIZE, GFP_KERNEL);
>                 if (!foo)
>                         goto err_foo;
>
>                 foo->bar = kmalloc(SIZE, GFP_KERNEL);
>                 if (!foo->bar)
>                         goto err_bar;
>                 ...
>
>                 kfree(foo->bar);
>         err_bar:
>
>                 kfree(foo);
>         err_foo:
>
>                 return ret;


I believe the CodingStyle already contain far too much personal style to
be useful as real style guide.  FWIW, I prefer a single error label, at
the "cost" of additional tests in the error path:


                 foo = kmalloc(SIZE, GFP_KERNEL);
                 if (!foo)
                         goto err;
                 foo->bar = kmalloc(SIZE, GFP_KERNEL);
                 if (!foo->bar)
                         goto err;
                 ...
 		 if (ret)
			goto err;
                 return 0;
      err:
                 if (foo)
                        kfree(foo->bar);
                 kfree(foo);
                 return ret;


The advantage is that I don't have to manage X different labels,
ensuring that they have the order is correct if some part of the
function is refactored etc.  That tends to get too complicated for my
simple brain. And since the error path is rarely tested, complicated
equals buggy.

My sample will of course trigger all those nice "optimizing the error
path" patches, but I ignore those anyway so that's not a big deal.


Bjørn