It's me again with weird problems compiling Boost on the Mac! :-) I just converted my MacOS X code from CFM to Mach-O and I ran into another small compilation problem. This time, it is the thread code. Now that I am moved over to Mach-O, the _POSIX_THREADS flag is true, causing posix_features.hpp to set BOOST_HAS_PTHREADS to true. This seems to be causing all sorts of compiler errors. Probably due to the fact that, even though some of the posix headers are being included, I am using the MSL headers rather than the BSD headers, and my understanding is that none of that posix stuff will actually work until I eject the MSL in favor of the Unix C headers, which I am not prepared to do right now. That and the fact that since I am using Carbon, TARGET_CARBON is also true, therefore BOOST_HAS_MPTASKS is getting set to true. So anyway ... BOOST_HAS_PTHREADS and BOOST_HAS_MPTASKS are both getting defined. I would like to be able to control whether BOOST_HAS_PTHREADS gets defined, because I am actually wanting to use the MP libraries instead, despite _POSIX_THREADS being defined. It looks like how you handled this same problem with Windows was by adding a !defined(BOOST_HAS_WINTHREADS) to the condition as follows: # if defined(_POSIX_THREADS) && (_POSIX_THREADS+0 >= 0) && !defined(BOOST_HAS_WINTHREADS) # define BOOST_HAS_PTHREADS # endif One solution would be to add an additional check for MP Tasks as follows: # if defined(_POSIX_THREADS) && (_POSIX_THREADS+0 >= 0) && !defined(BOOST_HAS_WINTHREADS) && !defined(BOOST_HAS_MPTASKS) # define BOOST_HAS_PTHREADS # endif I did this in my local working copy and it seems to have fixed the problem. I had to add an additional "#define BOOST_HAS_MPTASKS" to my user.hpp to make sure that BOOST_HAS_MPTASKS got defined before the above check. I am not sure if this is the best way or if there is a better way to solve this problem. I suppose another approach would be to check for !defined(TARGET_CARBON) in the above check - if carbon is on, MP Tasks will get turned on. Or you could in the place where BOOST_HAS_MPTASKS gets defined, undef the BOOST_HAS_PTHREADS. But the way I solved it in my local copy (shown above) using !defined(BOOST_HAS_MPTASKS) seemed the cleanest to me, especially since it looks like it is how you solved the same problem for Windows. Anyway - I tried hard to find a way to make this compile without changing anything but my user.hpp but I failed. (If someone has any ideas I'd love to hear them.) -- Bobby --------------------------------------------------------------------- Bobby Thomale Senior Software Developer Inoveon Corporation http://www.inoveon.com/ ---------------------------------------------------------------------