Re: [RFC] resource: Avoid unnecessary resource tree walking in __region_intersects()

From: Dan Williams
Date: Fri Oct 25 2024 - 11:19:56 EST


Andy Shevchenko wrote:
[..]
> > > but if you want to stick with your variant some improvements can be done:
> > >
> > > #define for_each_resource_XXX(_root, _p) \
> > > for (typeof(_root) __root = (_root), __p = _p = __root->child; \
> > > __p && _p; _p = next_resource_XXX(__root, _p))
> > >
> > >
> > > 1) no need to have local variable in parentheses;
> > > 2) no need to have iterator in parentheses, otherwise it would be crazy code
> > > that has put something really wrong there and still expect the thing to work.
> >
> > Why not:
> >
> > #define for_each_resource_XXX(_root, _p) \
> > for (typeof(_root) __root = (_root), __p = _p = __root->child; \
> > _p; _p = next_resource_XXX(__root, _p))
> >
> > The __p is only to allow for _p to be initialized in the first statement
> > without causing a new "_p" shadow to be declared.
>
> If people think this would be better than the existing patterns, okay. fine.

I think this case is different than the existing patterns in that the
iterator variable needs to be initiatlized from a declared variable, and
as Ying said, my proposal is busted.

To your point though, lets add a comment on why this macro is a bit
different to avoid people like me making bad cleanup suggestions.