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‘length(<POSIXlt>) <- v’ is more careful about balancing, notably when ‘v’ is not integer, thanks to Suharto Anggono's remarks on the mailing list R-devel.
On Windows terminals ‘Ctrl-C’ now breaks out of waiting for keyboard input, fixing PR#18982.
C++ standard specifications (‘CXX_STD =’ in ‘src/Makevars*’ and in the ‘SystemRequirements’ field of the ‘DESCRIPTION’ file) are now checked more thoroughly. Invalid values are still ignored but now give a warning, as do contradictory specifications.