[Dick] Nope, not sure at all. I overlooked "limited to linux on arm". (At any given time our "build" currently uses six instances of gcc - various PowerPC, x86 look-a-likes, DSPs, etc. - and I'll worry about those later.) Yes, your suggestion to put the test in libstdcpp3.hpp seems like it would work nicely. As a no-longer-lurking newbie, can I do something or do I sit back and wait for someone to add that test?
Well I can add the test, if you can tell me what defines identify Linux on arm.
[Dick] Once again I yelled before I was bit. I'm haven't been able to get bjam --v2 to pass BOOST_HAS_THREADS to the compiler so I ass-u-me-D it was some magic cookie that was being #undefD in preparation for use as a flag. Dumb. I'll go back to the boost.build list with this now. Thanks for the mentoring.
Using: bjam -sBUILD="<define>BOOST_HAS_THREADS=1" should do it. John.