cpp/io/ios base/pword

First, allocates or resizes the private storage (dynamic array of or another indexable data structure) sufficiently to make  a valid index, then returns a reference to the  element of the private storage with the index.

The reference may be invalidated by any operation on this object, including another call to, but the stored values are retained, so that reading from  with the same index later will produce the same value until the next call to std. The value can be used for any purpose. The index of the element must be obtained by xalloc, otherwise the behavior is undefined. New elements are initialized to a null pointer.

If the function fails (possibly caused by an allocation failure) and is a base class subobject of a  object or subobject, calls  which may throw std.

Return value
A reference to the element.

Exceptions
May throw std when setting the badbit.