There doesn't appear to be an issue for this in Trac or any semblance of a discussion thread; however, the Mac OS SDK definition of 'nil' seems to cause Boost 1_39_0 (perhaps other versions) to emit a copious number of warning and error messages when included AFTER any OS X SDK header such as: #include <CoreFoundation/CoreFoundation.h> #include <IOKit/IOKitLib.h> #include <boost/accumulators/accumulators.hpp> #include <boost/accumulators/statistics/stats.hpp> #include <boost/accumulators/statistics/rolling_mean.hpp> using namespace boost; using namespace accumulators; As near as I can tell CoreServices/MacTypes.h is the source of the definition: #define nil NULL Fortunately, this can be resolved by reordering the include directives to include OS X headers AFTER Boost; however, it seems like these headers should play nicely together. Has Boost reserved 'nil' for some time or might something like 'nil_t' be used alternatively? Regards, Grant