There's an example here: http://tinyurl.com/azrrh It's some kind of multiple definition problem. Perhaps a missing "inline" somewhere? ld: multiple definitions of symbol __ZN5boost9unit_test92_GLOBAL__N__ZGVZN5boost9unit_test9ut_detail24auto_ test_unit_registrar13curr_ts_storeEvE4inst13unit_test_logE /Volumes/scratch/dgregor/BoostRegressionTesting/results/bin/boost/ libs/test/build/libboost_test_exec_monitor.a/gcc-3_3-darwin/debug/ libboost_test_exec_monitor-gcc33-d-1_34.a(framework.o) definition of __ZN5boost9unit_test92_GLOBAL__N__ZGVZN5boost9unit_test9ut_detail24auto_ test_unit_registrar13curr_ts_storeEvE4inst13unit_test_logE in section (__DATA,__data) /Volumes/scratch/dgregor/BoostRegressionTesting/results/bin/boost/ libs/test/build/libboost_test_exec_monitor.a/gcc-3_3-darwin/debug/ libboost_test_exec_monitor-gcc33-d-1_34.a(results_collector.o) definition of __ZN5boost9unit_test92_GLOBAL__N__ZGVZN5boost9unit_test9ut_detail24auto_ test_unit_registrar13curr_ts_storeEvE4inst13unit_test_logE in section (__DATA,__data) ld: multiple definitions of symbol __ZN5boost9unit_test92_GLOBAL__N__ZGVZN5boost9unit_test9ut_detail24auto_ test_unit_registrar13curr_ts_storeEvE4inst17results_collectorE /Volumes/scratch/dgregor/BoostRegressionTesting/results/bin/boost/ libs/test/build/libboost_test_exec_monitor.a/gcc-3_3-darwin/debug/ libboost_test_exec_monitor-gcc33-d-1_34.a(framework.o) definition of __ZN5boost9unit_test92_GLOBAL__N__ZGVZN5boost9unit_test9ut_detail24auto_ test_unit_registrar13curr_ts_storeEvE4inst17results_collectorE in section (__DATA,__data) /Volumes/scratch/dgregor/BoostRegressionTesting/results/bin/boost/ libs/test/build/libboost_test_exec_monitor.a/gcc-3_3-darwin/debug/ libboost_test_exec_monitor-gcc33-d-1_34.a(results_collector.o) definition of __ZN5boost9unit_test92_GLOBAL__N__ZGVZN5boost9unit_test9ut_detail24auto_ test_unit_registrar13curr_ts_storeEvE4inst17results_collectorE in section (__DATA,__data) /Volumes/scratch/dgregor/BoostRegressionTesting/results/bin/boost/ libs/test/build/libboost_test_exec_monitor.a/gcc-3_3-darwin/debug/ libboost_test_exec_monitor-gcc33-d-1_34.a(results_reporter.o) definition of __ZN5boost9unit_test92_GLOBAL__N__ZGVZN5boost9unit_test9ut_detail24auto_ test_unit_registrar13curr_ts_storeEvE4inst17results_collectorE in section (__DATA,__data) /Volumes/scratch/dgregor/BoostRegressionTesting/results/bin/boost/ libs/test/build/libboost_test_exec_monitor.a/gcc-3_3-darwin/debug/ libboost_test_exec_monitor-gcc33-d-1_34.a(unit_test_suite.o) definition of __ZN5boost9unit_test92_GLOBAL__N__ZGVZN5boost9unit_test9ut_detail24auto_ test_unit_registrar13curr_ts_storeEvE4inst17results_collectorE in section (__DATA,__data) Doug