Building Rcpp package with external C library on Windows

Question

I am building a package with provides a wrapper around the cvode solver from the SUNDIALS ODE solving C library.

So far, I have been able to compile the package on my OS X machine by providing the source C files (taking inspiration from the Makevars from RcppCAF package) and making the static library on the fly and linking against it. The Makevars file can be found at the link below

https://github.com/sn248/Rcppsbmod/blob/master/src/Makevars

Earlier I was linking against static libraries on the system but now since I am making the static library (libsundials_all.a) on the fly when compiling the package, I believe users who don't have SUNDIALS installed on their system (at least on OS X) should be able to use this package also (Am I correct in thinking this?). I have checked the package compiled in such a way is able to integrate the a test ODE. Also, When I run a R CMD check (using Check option on RStudio, with --as-cran option), I get success, i.e.,

R CMD check results
0 errors | 0 warnings | 0 notes

However, I want users on Windows to be able to use this package, even if they don't have SUNDIALS installed on their machine, my questions are

1. Is this possible to do or Windows users need to have SUNDIALS installed?

2. Currently my Makevars.win is same as Makevars, so when I submit my package on R WinBuilder, I get the following message (which tells me that make is not able to find ar).

   make: ar: Command not found make: *** [../inst/libsundials_all.a] Error 127 Warning: running command 'make -f "Makevars.win" -f "D:/RCompile/recent/R-3.4.3/etc/i386/Makeconf" -f "D:/RCompile/recent/R-3.4.3/etc/i386/Makevars.site" -f "D:/RCompile/recent/R-3.4.3/share/make/winshlib.mk" SHLIB_LDFLAGS='$(SHLIB_CXXLDFLAGS)' SHLIB_LD='$(SHLIB_CXXLD)' SHLIB="Rcppsbmod.dll" ' had status 2 ERROR: compilation failed for package 'Rcppsbmod' * removing 'd:/RCompile/CRANguest/R-release/lib/Rcppsbmod' In R CMD INSTALL

Some searching revealed that RTools might not have ar,here but I don't think I am clear about what I should be doing to compile this package on Windows. I have looked a few Makevars.win files, but most of them are similar to Makevars. I feel I need to make a .dll (similar to libsundials_all.a, but I am not sure how to go about it at all.

Any suggestion here about how I can compile this package on Windows will be much appreciated!

Also, just for my curiosity, I often find code such (e.g., in Makevars.in of rcppgsl)

GSL_LIBS   = @GSL_LIBS@

I am not sure what @GSL_LIBS@ means and make tutorials didn't have this syntax either. Any explanation of this code will be very helpful.

Thanks!

Answer 1

Yes, it is possible to build a static library on Windows during package installation. I am doing that in the experimental windows branch of dqmagic:

PKG_CPPFLAGS = -I./libmagic -I./libgnurx -DHAVE_CONFIG_H
PKG_LIBS = -L. -lmagic -lregex -lshlwapi

all: $(SHLIB)
$(SHLIB): libmagic.a libregex.a

LIBMAGIC =libmagic/apprentice.o \ 
[... many object files ...]
libmagic.a: $(LIBMAGIC)

LIBREGEX = libgnurx/regex.o
libregex.a: $(LIBREGEX)

Note that I do not tell makehow to build a static library, leaving that to the automatic rules. That way there are no issues with ar missing. Note that the Linux/Mac OSX build uses a system installed library.

I think RcppGSL is not a good comparison in your case, since it uses an external library on all platforms. Reason is that with this package it has to be possible to compile and link with GSL after package installation. In your case, all the compilation and linking is done at installation time, right?