knit does not find xfun

[thule]

Hi,
I'm trying to knit an Rmd document to html in RStudio under Windows 10 (which I never had problems with before ...). Suddenly, RStudio keeps saying that an updated version of the package "xfun" has to be installed. Agreeing to that results in the following output:

---

There is a binary version available but the source version is later:
binary source needs_compilation
xfun 0.13 0.25 FALSE

installing the source package ‘xfun’

trying URL 'https://cran.rstudio.com/src/contrib/xfun_0.25.tar.gz'
Content type 'application/x-gzip' length 112755 bytes (110 KB)
downloaded 110 KB

• installing source package 'xfun' ...
  ** package 'xfun' successfully unpacked and MD5 sums checked
  ** libs

*** arch - i386
c:/Rtools/mingw_32/bin/gcc -I"C:/PROGRA~1/R/R-35~1.0/include" -DNDEBUG -O3 -Wall -std=gnu99 -mtune=generic -c base64.c -o base64.o
sh: line 1: c:/Rtools/mingw_32/bin/gcc: No such file or directory
make: *** [C:/PROGRA~1/R/R-35~1.0/etc/i386/Makeconf:208: base64.o] Error 127
ERROR: compilation failed for package 'xfun'

• removing 'C:/Users/Uwe/Documents/R/win-library/3.5/xfun'
• restoring previous 'C:/Users/Uwe/Documents/R/win-library/3.5/xfun'
  In R CMD INSTALL
  Warning in install.packages :
  installation of package ‘xfun’ had non-zero exit status

---

If I type "library(xfun)" the package is loaded. (I installed a binary version as RStudio notes).
I noticed that the file c:/Rtools/mingw_32/bin/gcc does not exist.
The correct path is C:\rtools40\mingw32\bin\gcc
How can I tell RStudio the correct path??

[andresrcs]

RTools40 is meant to be used with R >=4.0.0, you can't use it with R 3.5, you need to install a matching version of RTools, you can download older versions from here

https://cran.r-project.org/bin/windows/Rtools/history.html

Although, I would recommend updating your R version

[thule]

Thanks a lot, andresrcs, updating R (and RStudio) solved the problem.