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A general description is here.
The behaviour of ‘unlink()’ for reparse points (including junctions and symbolic links) has changed. It no longer follow links (deleting the contents of the link target rather than the link), and it is able to delete the link itself (given sufficient permissions).
The 32-bit and 64-bit builds are now treated equally, as it is anticipated that 64-bit R will soon be (if not already) the more commonly used. This entails:
The ‘Rterm’ or ‘Rgui’ title mentions 32-bit as well as 64-bit.
The desktop icons are labelled ‘R i386’ and ‘R x64’.
‘R CMD INSTALL’ for a package with compiled code will fail if compilation fails for any of the installed sub-architectures: use ‘--no-multiarch’ to override this.
‘file.symlink()’ is now implemented on NTFS file systems on Vista or later, for accounts which have suitable permissions (and most will not). It can link existing directories, and existing-or-not files.
Using a prompt of more than 80 characters in ‘readline()’ could cause a buffer overflow in Rterm. (Reported by Henrik Bengtsson.)