boost::uuids::name_generator::operator() is not const, as promised in the documentation

[lars.rohwedder@…]

The uuids::name_generator holds an internal state (detail::sha1 sha), which is resetted on every operator() call, hence the operator() cannot be const.

So the generators aren't reentrant and cannot be shared between threads. :-(

Solution:

Make the state a local variable in the operator(). So the operator() can be const (as documentation promises) and the class becomes reentrant.

[James E. King, III]

PR to resolve: ​https://github.com/boostorg/uuid/pull/23