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SubjectRe: [PATCH 3/3] x86: OLPC: speed up device tree creation during boot (v2)
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On Thu, 2010-11-18 at 09:34 +0100, Ingo Molnar wrote:
> * H. Peter Anvin <hpa@zytor.com> wrote:
>
> > On 11/14/2010 11:02 PM, Ingo Molnar wrote:
> > >
> > > * H. Peter Anvin <hpa@zytor.com> wrote:
> > >
> > >> What? What is wrong with static variables in functions? It really doesn't seem
> > >> to be a good idea to make them file-scope if they don't need to be.
> > >
> > > They are very easy to overlook and mix up with regular stack variables and i've seen
> > > (and introduced myself) a number of bugs due to them.
> > >
> > > They also often are used in buggy ways (with SMP not taken into consideration), so
> > > overlooking them during review compounds their negative effects. Putting them in
> > > front of the function isnt a big deal in exchange.
> > >
> > > There are people who never overlook them (like yourself), but my brain is wired up
> > > differently.
> > >
> >
> > However, I have to vehemently object to putting them in a wider scope
> > than is otherwise necessary. I agree that static variables should be
> > used sparsely if at all (there really are vary few uses of them that are
> > valid), but putting them in a larger scope screams "I'm used in more
> > than one function", and that is *not* a good thing.
>
> That's why we sometimes use the (imperfect) compromise to put them in front of that
> function, not at the top of the file.
>
> Look at the general balance of hardship: very little harm is done (it's not a big
> deal if a variable is only used in a single function) but having it with local
> variables can be _really_ harmful - for example i overlooked them when i reviewed
> this patch. I dont like important details obscured - i like them to be apparent.
> Again, this is something that some people can parse immediately on the visual level
> - me and many others cannot.

What about:

int foo(void)
{
static int bar;

struct thing_struct *thing;
int other_var;
char *p;

...
}

I think the visual wrongness of that formatting would be enough for me
to stop and look twice. Though I guess it doesn't work if you have few,
or no other variables other than the statics to declare.

cheers

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