On Wed, Oct 23, 2024 at 02:07:52PM -0700, Dan Williams wrote: > Andy Shevchenko wrote: > > On Fri, Oct 11, 2024 at 09:06:37AM +0800, Huang, Ying wrote: > > > David Hildenbrand <david@xxxxxxxxxx> writes: > > > > On 10.10.24 08:55, Huang Ying wrote: ... > > > > for ((_p) = (_root)->child; (_p); (_p) = next_resource_XXX(_root, _p)) > > > > > > Yes. This can improve code readability. > > > > > > A possible issue is that "_root" will be evaluated twice in above macro > > > definition. IMO, this should be avoided. > > > > Ideally, yes. But how many for_each type of macros you see that really try hard > > to achieve that? I believe we shouldn't worry right now about this and rely on > > the fact that root is the given variable. Or do you have an example of what you > > suggested in the other reply, i.e. where it's an evaluation of the heavy call? > > > > > Do you have some idea about > > > how to do that? Something like below? > > > > > > #define for_each_resource_XXX(_root, _p) \ > > > for (typeof(_root) __root = (_root), __p = (_p) = (__root)->child; \ > > > __p && (_p); (_p) = next_resource_XXX(__root, _p)) > > > > This is a bit ugly :-( I would avoid ugliness as long as we have no problem to > > solve (see above). > > Using a local defined variable to avoid double evaluation is standard > practice. I do not understand "avoid ugliness as long as we have no problem to > solve", the problem to solve will be if someone accidentally does > something like "for_each_resource_descendant(root++, res)". *That* will > be a problem when someone finally realizes that the macro is hiding a > double evaluation. Can you explain, why do we need __p and how can we get rid of that? I understand the part of the local variable for root. > So no, this proposal is not "ugly", it is a best practice. See the > definition of min_not_zero() for example. I know that there are a lot of macros that look uglier that this one. -- With Best Regards, Andy Shevchenko
