Hi Jörn,
If I do
c_bh = kmalloc(blah);
err= -ENOMEM;
if (!c_bh)
goto error;
//here err = -ENOMEM
... do some stuff...
error:
return err;
It will return -ENOMEM, no? I mean I could set err back to 0 and do
something like:
c_bh = kmalloc(blah);
err= -ENOMEM;
if (!c_bh)
goto error;
err = 0;
... do some stuf...
error:
return err;
At first glance, at least for me, I'd be scratching my head when I
looked at that.
Also given that this error state is to be an exception not the rule,
if what Phillip suggests is correct, than it would actually be a tiney
be slower. So, all in all I'd rather leave it the way it is :-)
On 11/1/06, Phillip Susi <[email protected]> wrote:
I think this is getting into micro-optimization, which is usually bad.
Also moving the assignment of err outside the body of the if only
results in slightly faster code in the case where there is an error,
since you can test and _maybe_ conditionally jump directly to the error:
label if it is not very far away. With the assignment in the body, the
conditional jump must jump to the assignment followed by an
unconditional jump to the label.
In other words, the only time this micro optimization will be of benefit
is if you are erroring out most of the time rather than only under
exceptional conditions, AND the error label isn't too far away for a
conditional branch to reach. In other words, just don't do it ;)
Jörn Engel wrote:
> On Wed, 1 November 2006 13:02:12 -0500, Holden Karau wrote:
>> On 11/1/06, Jörn Engel <[email protected]> wrote:
>>> Result would be something like:
>>> c_bh = kmalloc(...
>>> err = -ENOMEM;
>>> if (!c_bh)
>>> goto error;
>> That wouldn't work so well since we always return err,
>
> I don't quite follow. If the branch is taken, err is -ENOMEM. If the
> branch is not taken, err is set to 0 with the next instruction.
>
> Both methods definitely work. Whether one is preferrable over the
> other is imo 90% taste and maybe 10% better code on some architecture.
> So just pick what you prefer.
>
> Jörn
>
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