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A general description is here.
‘system()’ and ‘system2()’ no longer discard output from the command to stdout and stderr as often as they used to.
The MSI installer is now made by an R script, and there is now support for 64-bit builds.
It is now built using ‘WiX 3.0’ rather than ‘WiX 2.0’. (As a result it is about 25% smaller.)
The 32- and 64-bit distributions have been merged:
There is a combined installer (called ‘R-<version>-win.exe’). When used under 32-bit Windows this works as before and installs 32-bit R. When used under 64-bit Windows there are options to install either or both of 32- and 64-bit R: the default is to install both.
The default package type is ‘"win.binary"’ on both 32- and 64-bit builds: a single repository contains binary packages for both architectures. This is in place for CRAN, CRAN extras and BioC: ‘type = "win64.binary"’ can still be used for any repositories which follow the R 2.11.x convention. With the default filters (see ‘?available.packages’) packages will only be offered if they are available for the current architecture.
The default personal library, e.g. ‘~/R/win-library/2.12’ is now the same for both 32- and 64-bit R.
The recommended 64-bit toolchain has been changed to one that does not add leading underscores. See <URL: http://www.murdoch-sutherland.com/Rtools/> or <URL: http://www.stats.ox.ac.uk/pub/Rtools/>. Any static or import libraries for external software used in installing packages will need to be re-compiled for this toolchain, but the use of DLLs is unaffected.
‘system()’ (and hence ‘shell()’) did not always set the standard file handles properly, so some programs would not run.