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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