Add ccache

[krlmlr]

for regular compiles and for building packages.

• Define ccache package
  • upstream msys2 package works out of the box, perhaps remove man pages
• Install ccache
  • It seems necessary to install in both {mingw32,mingw64}/{bin,lib}; installing via pacman -U puts it into /usr/{bin,lib}, makepkg-mingw doesn't seem to pick it up from there
• Update makepkg*.conf
  • sed "/^BUILDENV/ s/!ccache/ccache/"
  • Add `PATH="/mingw{32,64}/lib/ccache/bin:${PATH}"
• Add /usr/lib/ccache/bin to $PATH
• Document how to turn off ccache (set CCACHE_DISABLE environment var)

Would you support that? How can I help?

[jeroen]

It seems necessary to install in both {mingw32,mingw64}/{bin,lib}; installing via pacman -U puts it into /usr/{bin,lib},

You are confusing mingw-packages with msys-packages. The latter are only used for the msys build environment itself, they are not useful for building native windows software like R.

You probably want to port this one: https://github.com/msys2/MINGW-packages/tree/master/mingw-w64-ccache

[krlmlr]

I successfully ported the mingw package you pointed to, happy to submit a PR. The package gets installed in /usr though, I believe we need it to live in /c/rtools40/{mingw32,mingw64} so that it is used by makepkg-mingw .

[jeroen]

If you build with makepkg-mingw it will be installed in /mingw{32,64}

[krlmlr]

Confirmed, I need to run pacman -U for both files created.

Will report with what is needed to enable ccache for building packages.

[krlmlr]

I have now successfully taught makepkg-mingw to use ccache -- need to set PATH in makepkg*.conf. The instructions in the ArchLinux documentation at https://wiki.archlinux.org/index.php/Ccache didn't work for me.

What's the best way to instruct R to use ccache for building R packages? Per https://github.com/r-windows/docs/blob/master/faq.md#how-does-r-find-compilers it won't be picked up from the $PATH. Should we tweak etc/*/Makeconf in R's installation, is there a better way?

An alternative way of running ccache is to replace gcc, g++ etc. with symlinks to the ccache binary. Need to ensure that the correct symlinks are restored when uninstalling ccache.

[jeroen]

You can override CC and CXX in your personal ~/.R/Makevars file. Maybe something like this:

CC=$(BINPREF)ccache $(BINPREF)gcc

Or from R:

dir.create("~/.R")
writeLines("CC=$(BINPREF)ccache $(BINPREF)gcc", "~/.R/Makevars")
writeLines("CXX=$(BINPREF)ccache $(BINPREF)g++", "~/.R/Makevars")
writeLines("CXX11=$(BINPREF)ccache $(BINPREF)g++", "~/.R/Makevars")
writeLines("CXX14=$(BINPREF)ccache $(BINPREF)g++", "~/.R/Makevars")
writeLines("CXX17=$(BINPREF)ccache $(BINPREF)g++", "~/.R/Makevars")

[krlmlr]

Thanks. Achieving great results with the following combo:

dir.create("~/.R")

vars <- c("CC", "CXX", "CXX11", "CXX14", "CXX17")
code <- paste0(vars, " := $(BINPREF)ccache $(", vars, ")")

writeLines(code, "~/.R/Makevars")

writeLines(
  c(
    'PATH="${RTOOLS40_HOME}\\usr\\bin;${PATH}"',
    paste0('MAKEFLAGS="-O -j', parallel::detectCores() + 1, '"')
  ),
  con = "~/.Renviron"
)

PR follows.

[krlmlr]

Can't install ccache on a fresh rtools40 install. pacman -Q doesn't list it. Any ideas?

[jeroen]

I haven't synced to CRAN yet. If you want to install now, edit the files c:/rtools40/etc/pacman.d/mingw{64,32}.conf and comment-out the cran mirrors, so that you use the bintray mirror, and then do pacman -Su.

[krlmlr]

When do you plan to sync next?