When installing a Rcpp package on Windows, you need to ensure that the package DLL is unloaded or you get a "Permission Denied" error when copying the new DLL. This means restarting R on every recompile, which is pretty annoying. Is there any way to unload the package DLL without killing R?
I've tried the detach("package:my_package", force=TRUE) command, but it doesnt unload the DLL.
If you want to do this in your main R session (without using RStudio, which makes reinstalling the package and reloading R very easy), you can use devtools:
library(devtools)
load_all("path/to/my/package")
Among other things, load_all will reload all your R code, and re-compile and reattach the DLL.
Opinions are divided on this. I often prefer to run the builds and test outside of my main R session(s), simply by chaining R CMD INSTALL with Rscript (or, on Linux, r calls from littler) to test the new build. If you use proper options to R CMD INSTALL ... to skip parts that may take extra time you get a quick turnaround AND are assured that you do get a fresh build.
And if you want the same behaviour by clicking a button, RStudio offers it too.
I guess you need to run library.dynam.unload to unload DLLs.
来源：https://stackoverflow.com/questions/14514672/can-rcpp-package-dlls-be-unloaded-without-restarting-r