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Re: [RFC] libstdc++/8780

Joe Buck wrote:
I wrote:

The short answer is that, given
   std::vector<T>::iterator iter_T;


has type T* and points to the same object.  As the elements of a vector
must be contiguous, this works portably.

Martin writes:

Unfortunately, it will not work for an iterator pointing at the end
of a container.

You are of course correct that there are no guarantees that &*some_vector.end() will not produce a one-past-the-end pointer;
debugging implementations of vector<T>::iterator will very likely
throw an exception or abort.

Still, note that I said "has type T* and points to the same object":
in most cases, users that complain about this are trying to interface
data in a vector to a function that wants a pointer, and for them
the &*iter_T mechanism will do.

The most common case where I've needed to use the &* construction is to
pass data in a vector<T> to some function that wants a const T* and
perhaps a count.
Over a year ago, there was a discussion on
(see c++std-lib-7863) about adding vector::data() member function that
would be analogous to basic_string::data(). A function like that would
take care of the problem but, strangely, I don't see an issue about it
on the issues list or a formal proposal. Any takers? :)


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