I switched from master to next branches using git and did an acprep update to rebuild, the resultant binary failed (segfaulted I think) and I needed to do a make clean; acprep update to get a runnable program.
Switching branches should mark all affected libs and objects as out of date. Of course people will then complain that going from master to next and back to master without doing a build forces a complete rebuild when it is strictly not necessary but ...
