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A general description is here.
‘on.exit()’ gains an optional argument ‘after’ with default ‘TRUE’. Using ‘after = FALSE’ with ‘add = TRUE’ adds an exit expression on top of any existing ones. This way the expressions are run in a first in last out fashion. From Lionel Henry.
‘sys.on.exit()’ is now always evaluated in the right frame. From Lionel Henry.
The order of selection of OpenMP flags has been changed: Oracle Developer Studio 12.5 accepts ‘-fopenmp’ and ‘-xopenmp’ but only the latter enables OpenMP so it is now tried first.