netdev - Re: [PATCH net-next 1/2] packet: clean up error variable assignments

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Message-ID: <1351011952.8609.2334.camel@edumazet-glaptop>
Date:	Tue, 23 Oct 2012 19:05:52 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Daniel Borkmann <dxchgb@...il.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/2] packet: clean up error variable
 assignments

On Tue, 2012-10-23 at 13:56 +0200, Daniel Borkmann wrote:
> This patch performs clean-ups of packet's err variables where appropriate.
> In particular, errnos are *only* assigned in error cases, which saves
> useless instructions in non-error cases and makes the code more readable
> in terms of which error type belongs to which evaluated error condition.
> Also, in some cases an errno was set, but not used until the next assignment.

I see no value in this patch.

Setting err before a test is a common way to handle error cases and
generates smaller code in linux kernel.

Better live with it than trying to change it ?

err = -ENOMEM;
match = kzalloc(xxxx);
if (!match)
	goto error;


is smaller (source code & generated code) than :

match = kzalloc(xxxx);
if (!match) {
	err = -ENOMEM;
	goto error;
}

An immediate load is basically free, but code size matters.


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