Is there anything that protected members or functions can be used for?
You cannot inherit from a union so there are no children that can access it. Does it provide a functional use or is just there because removing it was hassle?
Asked
Active
Viewed 497 times
13
-
2It'e there for completeness. – StoryTeller - Unslander Monica Nov 25 '13 at 15:06
-
@StoryTeller Elaborate! :-) – Grimm The Opiner Nov 25 '13 at 15:08
-
@user1158692, there's nothing to elaborate. It's the same sort of completeness that protected and private inheritance give you. It may be completely useless, but the formal language has a complete set of terms. – StoryTeller - Unslander Monica Nov 25 '13 at 15:10
-
@StoryTeller, are you saying that protected and private inheritance are completely useless? – Stefan Nov 25 '13 at 15:12
-
@Stefn, not quite. But if you find yourself inheriting privately, you may want to rethink your design to do composition instead. – StoryTeller - Unslander Monica Nov 25 '13 at 15:13
-
@StoryTeller, so they are not useless but are rarely required? That I agree with. I wanted to make sure it was not the same with the protected level in a union. – Stefan Nov 25 '13 at 15:16
-
@Stefan, I wouldn't say they are ever required, only not completely useless (which means they have their uses, but those uses have better alternatives). As for protected union members... I see no use whatsoever. – StoryTeller - Unslander Monica Nov 25 '13 at 15:18
1 Answers
12
protected in a union becomes completely equivalent to private, but this allowance does no harm and avoids extra special case handling and extra differences between union and struct/class (which are described all together in the standard).
Honestly, I think it's possible to use protected in a union just not to add the umteenth special case to the standard for the sake of it; maybe it didn't even come to mind to the standard committee to differentiate this behavior, since it's quite a bizarre corner case but does no harm as it's currently specified.
Matteo Italia
- 123,740
- 17
- 206
- 299
-
So it is just in there because it was more hassle than it was worth to remove it? – Stefan Nov 25 '13 at 15:32
-
@Stefan: I would say so; why bother with creating special cases? (ok, well, this is C++ and there are special cases and UB for everything, but the point stands) – Matteo Italia Nov 25 '13 at 15:34