Hi, I recently tried to build RevDB on OS X and the build failed because __thread isn't supported on OS X 10.6 which RPython specifies as the minimum supported version. I've updated DARWIN_VERSION_MIN to 10.7 in the reverse-debugger branch[1], because otherwise it doesn't build at all on OS X. Armin suggested that there would be a performance benefit to increasing DARWIN_VERSION_MIN for pypy as well (along with adding darwin to the SUPPORT__THREAD list). I would like to make this change, but I don't want to break pypy for anyone who may still need OS X 10.6 support. As far as I can tell, OS X 10.6 is unsupported (last release in 2011) but still available as a necessary upgrade step from older versions that don't support the app store to newer versions that are only available through the app store. I also have an old laptop running OS X 10.8, and several applications (including Chrome) have dropped support for that recently. [1] https://bitbucket.org/pypy/pypy/commits/a740348ea339c358601d9029bc6811f56c4d... Thanks, --jerith