Hi Matt, Sean reported the same underlying problem against the operators library as <https://svn.boost.org/trac/boost/ticket/979>. I applied the fix as it was transparent for the users and also suggested a similar change for noncopyable on the mailing list - but there wasn't much interest IIRC. The problem with the approach you described is IMHO that if you allow noncopyable_<T> as an *alternative*, most people will likely ignore it. OTOH, a breaking change - turning the classic noncopyable into a template - might be too intrusive. Personally, I would not mind it, since the compiler will catch all uses of noncopyable without a template parameter and the required change is a no-brainer, so +1 for the change from my side. Let's see if more people like the idea this time :) Regards, Daniel On 13.06.2009, at 18:11, Matt Calabrese wrote:
Perhaps slightly off topic, but I seem to remember a couple of years ago Sean Parent pointing out that noncopyable might be better implemented with CRTP. Has this been forgotten? I think the rationale was that if you have one child which inherits from two or more bases that inherit from the current noncopyable, the empty base optimization can't be used since each of the noncopyable bases have to have different addresses, so your type's size grows with each additional base that inherits from noncopyable. As well, I believe that certain compilers were producing spurious warnings if you use such multiple inheritance, suggesting to the programmer that noncopyable may be better as a virtual base (which it clearly would not). Making a noncopyable template, perhaps called noncopyable_ so that the two can coexist, that is implemented the same way but whose intended use is to be instantiated with the child type fixes these problems by making certain that all noncopyable bases in a hierarchy have different types, meaning that EBO may be used and there are no duplicate noncopyable bases. -- -Matt Calabrese _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost