cpp/io/ios base/xalloc

Returns a unique (program-wide) index value that can be used to access one and one  elements in the private storage of  by calling iword and pword. The call to does not allocate memory.

Effectively increments a private static data member of, as if by executing , if is the name of that static member

Parameters
(none)

Return value
Unique integer for use as pword/iword index.