Re: [PATCH] Re: [PATCH 4/4 v2] [RFC] UIO: generic platform driver

From: Hans J. Koch
Date: Mon Apr 14 2008 - 07:53:39 EST


On Mon, Apr 14, 2008 at 12:37:59PM +0100, Russell King - ARM Linux wrote:
> On Mon, Apr 14, 2008 at 01:20:21PM +0200, Uwe Kleine-KÃnig wrote:
> > [1] http://lkml.org/lkml/2008/4/11/81 or
> > http://thread.gmane.org/gmane.linux.kernel/665257
>
> In one of the mails, it was said:
> No. It's more important to see which variables are declared in the
> function and which are declared elsewhere. If you have to search the
> whole body of a function for possible declarations, this is BAD. And if
> it's not clear where a variable is used, the function is too long or has
> other style problems. Your function is short and clean, so where's the
> problem? Please move the declaration to the top of the function.
>
> I disagree with this statement. It's far better to limit the scope of
> variables so that you know they only have local use, and eg, not used
> inside a loop and then outside with possible unintended effects.
>
> If a variable is only used inside a loop, it should be declared _inside_
> that loop.
>
> The statement goes on to talk about the function being short and clean -
> that's not an argument to apply any particular point of view on this
> subject, since you can argue that because it's short and clean you can
> see that the variable is only used within the loop.
>
> So, please, keep the variable declaration inside the loop, and don't
> pollute the outer levels with unnecessary variable declarations.

OK, I'm finally convinced :-)
I knew this style from C++ where it makes sense, because a (class-)
variable declaration can implicitly call the constructor of that class
which you normally want to avoid if not needed. As this doesn't happen
in C, I found it unnecessary.
I agree now that there's also a readability argument. The limitation of
the scope is probably not that important as compilers will optimize that
anyway in a lot of cases.

Thanks,
Hans
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/