I just finished building a C++ extension using Rcpp on Mac OS X and
have a couple tips for anyone trying to do the same.
I used RcppTemplate as a starting point. When developing and testing,
it was easier to compile the extension by hand and use dyn.load() as
opposed to using the R packaging mechanism to rebuild the entire
package every time. In compiling RcppTemplate I ran into the following
difficulties on Mac OS X 10.5:
- ./configure is broken due to some missing environment vars. Use
"R_ARCH="/`arch`" R_SHARE_DIR=$R_HOME/share ./configure" instead.
- Marking a function RcppExport will cause the compile to fail
because __declspec(dllexport) is Windows-specific and not recognized
by the Apple compiler. Change the lines in Rcpp.hpp from
#ifdef BUILDING_DLL
#define RcppExport extern "C" __declspec(dllexport)
#else
#define RcppExport extern "C"
#endif
to
#if BUILDING_DLL && WIN32
#define RcppExport extern "C" __declspec(dllexport)
#else
#define RcppExport extern "C"
#endif
or if you don't care about cross-platform just write
#define RcppExport extern "C"
- Loading your compiled DLL using dyn.load() will complain about
not being able to find libRcpp. I think this is due to an improper
path-name being embedded in the library when it is compiled on your
machine.
$ otool -L /Library/Frameworks/R.framework/Resources/library/Rcpp/lib/
i386/libRcpp.dylib
/Library/Frameworks/R.framework/Resources/library/Rcpp/lib/i386/
libRcpp.dylib:
/Builds/Rdev-web/QA/Simon/packages/tiger-universal/Rlib/2.8/Rcpp/lib/
i386/libRcpp.dylib (compatibility version 0.0.0, current version 0.0.0)
For now you can fix this in your .dll using install_name_tool -- see
http://qin.laya.com/tech_coding_help/dylib_linking.html
for a good description of what needs to be done. A better solution
would be for the package maintainer to change the build process so
this gets generated correctly.
After I had the extension written and functioning properly, I used
package.skeleton to generate a tree, and then copied all of the source
files in the /src directory (including Rcpp.cpp and Rcpp.hpp) and
generated the proper firstlib.R file to load in my functions. After
this things went smoothly--'R CMD build' correctly compiled all of the
source files into a shared object file and I was able to build and
install the package with no further modifications.
It took me a little while to figure all of this out, so I figured I'd
post it to hopefully save someone else the time.
Jonathan
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