Proposed resolution:

This wording is relative to N5014.

1. Modify [hive.capacity] as indicated:

   void reserve(size_type n);
   

   -3- Effects: If n <= capacity() is `true`, there are no effects. Otherwise increases `capacity()` by allocating reserved blocks.

   -4- Postconditions: capacity() >= n is `true`.

   -5- Throws: `length_error` if `n` > max_size(), as well as any exceptions thrown by the allocator.

   -6- Complexity: It does not change the size of the sequence and takes at most linear time in the number of reserved blocks allocated and deallocated.

   -7- Remarks: All references, pointers, and iterators referring to elements in `*this`, as well as the past-the-end iterator, remain valid.

As noted by Arthur in issue 4379, `reserve(n)` could choose to deallocate some reserved (empty) blocks if in doing so it could then allocate blocks which brought `capacity()` closer to `n`.

For example if `capacity()` is `460`, `n` is `480`, the current-limits.min is `40` and there is a reserved block of capacity `70`, the latter could be deallocated and a new reserved block allocated of capacity `90`, bringing total capacity to `480`. As opposed to allocating a new reserved block at the min capacity of `40`, bringing the total capacity to `500`.

The implicit assumption in this issue is that we want `reserve()` to be able to deallocate. No-one has objected to this before, but if you want to, please speak up.

Anyway, the Complexity of `reserve()` does not presently reflect this ability.