...one of the most highly
regarded and expertly designed C++ library projects in the
world. — Herb Sutter and Andrei
The bugs to be fixed have come from several sources.
One type of bug which has been very difficult to understand has been that some test cases failed when compiled with optimisation and not without it. I now believe that this is related to the use of references in the arguments passed back, and I have one test where the cure is demonstrated, lazy_make_pair_tests.