This blog is updated daily.
A general description is here.
R on Windows by default uses ‘pkg-config’ for linking against external libraries. This makes it easier to test R and packages with alternative toolchains (such as from Msys2, e.g., testing with LLVM and possibly with sanitizers). It also allows more significant Rtools updates within a single R minor release.
The installer scripts for Windows have been tailored to Rtools45, an update of the Rtools44 toolchain. It is based on GCC 14. The experimental support for 64-bit ARM (‘aarch64’) CPUs is based on LLVM 19. R-devel and R 4.5.x are no longer maintained to be buildable using Rtools44 and it is advised to switch to Rtools45.
The ‘Writing R Extensions’ Texinfo source now contains very experimental annotations for more clearly identifying the API status of C entry points. These annotations are used to produce indices for API, experimental API, and embedded API entry points in the rendered versions. This is very preliminary and may be dropped if a better approach emerges.
Also for Fortran-callable entry points which are part of the API.